UNIVERSITY OF
ILLINOIS LIBRARY
AT URBANA-CHAMPAIGN
BIOLOGY
APR 9 1992
oology
NEW SERIES, NO. 60
The Birds of Mt. Isarog National Park, #
Southern Luzon, Philippines,
with Particular Reference
to Altitudinal Distribution
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Steven M. Goodman
Pedro C. Gonzales
September 28, 1990
Publication 1415
PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY
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Croat, T. B. 1978. Flora of Barro Colorado Island. Stanford University Press, Stanford, Calif., 943 pp.
Grubb, P. J., J. R. Lloyd, and T. D. Pennington. 1963. A comparison of montane and lowland rain forest in Ecuador
I. The forest structure, physiognomy, and floristics. Journal of Ecology. 51: 567-601.
Langdon, E. J. M. 1979. Yage among the Siona: Cultural patterns in visions, pp. 63-80. In Browman, D. L.,and R. A.
Schwarz, eds., Spirits, Shamans, and Stars. Mouton Publishers, The Hague, Netherlands.
Murra, J. 1946. The historic tribes of Ecuador, pp. 785-821. In Steward, J. H., ed., Handbook of South American
Indians. Vol. 2, The Andean Civilizations. Bulletin 143, Bureau of American Ethnology, Smithsonian
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FIELDIANA
Zoology
NEW SERIES, NO. 60
The Birds of Mt. Isarog National Park,
Southern Luzon, Philippines,
with Particular Reference
to Altitudinal Distribution
Steven M. Goodman
Museum of Zoology
University of Michigan
Ann Arbor. Michigan 48109
Present Address:
Department of Zoology
Field Museum of Natural History
Chicago, Illinois 60605-2496
Pedro C. Gonzales
Chief, Zoological Division
National Museum of the Philippines
Old Congress Building
Rizal Park
Manila, Philippines
Accepted July 25, 1989
Published September 28, 1990
Publication 1415
PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY
© 1990 Field Museum of Natural History
ISSN 0015-0754
PRINTED IN THE UNITED STATES OF AMERICA
Table of Contents
Abstract 1
Introduction 1
Study Site and Methods 2
Account of the 1988 Fieldwork 2
Vegetational and Ecological Types of Mt.
Isarog 2
Collections 6
Measurements 7
Netting 8
Observations 8
Systematic Order and Nomenclature 8
Species Accounts 8
Discussion 30
Altitudinal Overlap of Congeners 31
Densities of Birds Based on Netting 31
Altitudinal Distribution of Birds on Mt.
Isarog and Other Philippine Moun-
tains with Mossy Forest 33
Changes in the Resident Avifauna of Mt.
Isarog Between 1961 and 1988 36
The State of Mt. Isarog National Park .... 36
Acknowledgments 37
Literature Cited 38
List of Illustrations
2. View of western side of Mt. Isarog from
approximately 250 m 4
3. Partially cleared lowland forest at 900 m 5
4. Transitional lowland/montane forest at
about 1050 m 6
5. Mossy forest at 1 750 m 7
6. Graph comparing number of species oc-
curring in distinct ecological zones and at
various elevations on four mountains in
the Philippines 34
List of Tables
1 . Capture rate of Brachypteryx montana in
mammal snap-traps 21
2. Altitudinal distribution of resident bird
species on Mt. Isarog 24
3. Netting success on Mt. Isarog of resident
birds captured between 28 February and
30 May 1988 32
4. The species composition of mossy forest
avifaunas on four mountains in the Phil-
ippines 35
5. Differences in the number of resident
species found on Mt. Isarog in 1961 and
1988 37
1 . Map of southeastern Luzon and Mt. Isa-
rog 3
in
The Birds of Mt. Isarog National Park,
Southern Luzon, Philippines,
with Particular Reference
to Altitudinal Distribution
Abstract
Mt. Isarog National Park is located in south-
eastern Luzon, Philippines, on the Camarines Pen-
insula. The mountain is an old volcanic peak that
rises to 1966 m. The local climate is characterized
by the lack of a pronounced dry season. Four dis-
tinct vegetational zones occur on the mountain:
parang grassland (from the lowlands to 900 m),
lowland forest (from 450 to 900 m), montane for-
est (from 900 to 1 500 m), and mossy forest (from
1 500 m to the summit).
Information presented herein on the birds of Mt.
Isarog is based on the collections of D. S. Rabor,
obtained in the spring of 1961, and our own col-
lections and observations, made in the late winter
and spring of 1988. Our survey was conducted at
six focal points along an elevational transect of the
mountain. In the species accounts and discussion
sections particular attention is given to the alti-
tudinal distributions of the resident birds. We also
report measurements and weights of collected birds,
breeding data, stomach contents, some taxonomic
information, and general natural history obser-
vations.
A total of 135 bird species has been recorded
on Mt. Isarog: 1 16 residents and 19 migrants or
winter visitors. Species number and density de-
crease with altitude. Some of the factors that might
result in this relationship are analyzed. Three dis-
tinct patterns were found in the distribution of
congeners on the mountain: complete altitudinal
sympatry, broad elevational disjunction, and a
small amount of overlap with apparent species
replacement.
The distribution of the forest birds on Mt. Isa-
rog, based on the four vegetational zones, is com-
pared to three other mountains on Philippine is-
lands. In all cases the number of species on each
mountain decreases with altitude. The elevations
where different types of forest occurs varies be-
tween mountains. No species of mossy forest bird
is endemic to any one of these mountains, nor is
there a fleet of species limited to the mossy forest
zone.
Since Rabor visited Mt. Isarog in 1961, much
of the lowland forest has been cleared. By com-
paring his survey results with our 1988 informa-
tion it can be estimated that about 42% (27 of 64
species) of the lowland forest (between 450 and
900 m) birds have been locally extirpated. The
remaining tracts of forest within and outside the
park boundaries are still being cut, and the region
is severely threatened with deforestation. The de-
ployment of rangers in the area to enforce existing
laws against illegal logging, and a local education
program directed towards information about hab-
itat destruction and watershed management are
suggested as important steps in conserving the re-
maining undisturbed forests of Mt. Isarog.
Introduction
Although the island of Luzon, Philippines, has
been the site of numerous ornithological studies,
most of the information on the birds of that island
is contained in systematic reviews and descrip-
tions of new taxa. Only a few studies on regional
avifaunas of Luzon have been published; most of
these deal with the biogeographically distinct north
(e.g.,Ogilvie-Grant, 1 894; McGregor, 1904, 1924;
Morioka & Sakane, 1 979) and only a few deal with
the central and southern portions of the island
(Ogilvie-Grant, 1895; Wolfe, 1938;Gilliard, 1950).
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
Surprisingly, none of these studies contains quan-
tified information on the altitudinal distribution
of the resident montane avifauna on the island.
Also, to our knowledge no detailed bird list is
available for any montane Philippine national park.
This monograph reviews the bird species known
from Mt. Isarog National Park in southeastern Lu-
zon, describes their altitudinal distribution and
density, and compares these patterns with mon-
tane avifaunas on other islands in the Philippines.
Study Site and Methods
The southern end of Luzon is divided into the
large Camarines Peninsula (including the regions
Albay, Camarines, and Sorsogon) and the smaller
Bondoc Peninsula. The topography of southern
Luzon is dominated by several volcanic moun-
tains: Bulusan (1 560 m) in the extreme south, Ma-
yon (2421 m) and Isarog (1966 m) in the center,
and Labo (942 m) in the north. Mt. Isarog lies 5
km north and 20 km east of Naga City, at 1 3°40'N,
123°21'E.
The climate of the Camarines Sur Province near
Mt. Isarog is characterized by the lack of a pro-
nounced dry season, and a period of maximum
rainfall between November and January. The av-
erage annual rainfall at Naga City (ca. 20 m ele-
vation) is 280 cm and the temperature range is
approximately from 16 to 30° C (O'Brien, 1968).
Typhoons occur mostly in May and from Septem-
ber to November, principally along the Pacific
Ocean coast.
The Bicolanos are the main cultural group pres-
ently inhabiting southeastern Luzon (O'Brien,
1968). Formerly, non-Bicolano tribal peoples lived
on Mt. Isarog and surrounding lowland areas; their
cultural identities are ambiguous but they were
presumably a mixture of several different heritages
(Jagor, 1870, 1875; Miller, 1911; Lynch, 1948).
One of these groups were semi-nomadic forest
dwellers known as Agta. At the turn of the 20th
century the Agta lived on the lower slopes of Mt.
Isarog, where they subsisted as hunter-gatherers
and as agriculturalists (Miller, 1911). The subse-
quent fate of these people is not clear. We were
told in spring 1988 that the last of the "mountain
peoples" had left Mt. Isarog about 20 years before.
Account of the 1988 Field work
Heaney, on the distribution, systematics, and bio-
geography of Southeast Asian animals, particular-
ly mammals (Heaney, 1 986). The 1 988 survey was
a joint expedition between the Philippine National
Museum (pnm), the United States National Mu-
seum of Natural History (usnm), and Silliman
University.
On the morning of 27 February 1988 a recon-
naissance group went from Naga City to the Pani-
cuason Central Nursery, at about 450 m on the
western slope of Mt. Isarog (13°40'N, 123°20'E).
The nursery is located 4 km north and 1 8 km east
of Naga City. A local guide and Goodman spent
the next two days making a survey of the western
slopes of Mt. Isarog. On 1 March the balance of
the field team arrived at the nursery to commence
the survey.
From 3 to 3 1 March the field team (in various
combinations), along with several local people,
worked out of a series of five camps on the west
and northwest slopes of the mountain: camp 1 at
900 m, camp 2 at 1125 m, camp 3 at 1350 m,
camp 4 at 1550 m, and camp 5 at 1750 m (fig. 1).
These camps and the Panicuason Central Nursery
served as six focal points for an elevational tran-
sect. Two camps were often in simultaneous op-
eration, each by crews of 5-10 individuals. Be-
cause the primary focus of the expedition was
mammals, most efforts were devoted to rodent
trapping and bat netting. Gonzales and Goodman
represent exceptions to this focus. Their energies
were concentrated on a bird inventory, and they
were generally in different camps.
From 23 to 3 1 March Gonzales worked an area
of secondary forest at about 400 m. Specimens
were obtained at this site by netting and shooting.
Because of their close proximity and similarity in
habitat, data from this locality and the Panicuason
Central Nursery were combined.
From 17 April to 8 May 1988 a field team re-
turned to Mt. Isarog for further transect work. The
majority of effort was directed to trapping and
netting mammals and collecting plants, and no
systematic ornithological work was conducted. All
of the camps established on the first field trip were
reoccupied and a similar field procedure was fol-
lowed.
Vegetational and Ecological Types
of M t. Isarog
Our 1988 field trip to Mt. Isarog was part of a
long-term program, under the direction of L. R.
Following the definitions of Brown (1919) and
Whitmore (1984), four vegetational zones are rec-
FIELDIANA: ZOOLOGY
Curry #
Fig. 1 . Map of southeastern Luzon and Mount Isarog. The solid line surrounding the mountain represents the
reforestation project boundary. The positions of the Panicuason Central Nursery and our five transect points are
indicated on the west side of the mountain. The inset is of the southern portion of Luzon.
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
Fig. 2. View of the western side of Mt. Isarog from approximately 250 m. Note the grassland vegetation in the
foreground and the cleared areas on the lower slopes of the mountain. The upper zone is shrouded in clouds. (Photo
taken May 1988 by L. R. Heaney.)
ognized on Mt. Isarog: parang grassland, lowland
forest, montane forest, and mossy forest. Brown's
classification was developed for describing the
plants of Mt. Makiling (= Maquiling), central Lu-
zon, whereas Whitmore's is more generalized for
Southeast Asian tropical forests. The three types
of forest are not discrete ecological units with clear-
ly definable boundaries but grade into one another.
Parang (interspersed from the lowlands, in-
cluding the area around the Panicuason Central
Nursery, to camp 1 at 900 m)— This zone is not
a natural vegetation type of the area. It is the result
of the complete or partial removal of the original
forest (fig. 2). Areas of parang often consist of large
patches of grass, 1-3 m high (often cogon, Impera-
ta cylindrica), and disjunct lots of secondary forest.
In large tracts of land, particularly at the lower
foothills of Mt. Isarog where most of the rural
population resides, cleared areas were converted
directly from forest to tillable land or plantations.
Clearings of parang are regularly burned to thwart
secondary forest succession. Numerous small riv-
ers and streams that originate on the upper slopes
of Mt. Isarog course through this area. As of early
1988, on the west and northwest slopes of the
mountain areas, the parang extended up to 900 m.
Lowland Forest (in small patches from 450 to
900 m; synonym of Dipterocarp Forest sensu
Brown [1919])— The lower western slopes of Mt.
Isarog have been extensively cleared, but presum-
ably this forest type formerly extended to sea level.
As of spring 1988, most of the original lowland
forest on the west and northwest slopes below 450
m had been destroyed and much of it above 450
m had been extensively modified (fig. 3). When
Rabor visited Mt. Isarog in 1961 (see p. 36) he
found tracts of intact lowland forest down to ap-
proximately 450 m.
Small patches of forest, generally less than three
hectares, have been cleared by 'slash and burn'
agriculturalists. These openings are known as
kaingin, and such an agriculturalist is known as a
kainginero. Root crops and abaca (Musa textilis)
are the most commonly grown domestic plants in
these clearings. In spring 1988, the highest human
settlements on the west side of the mountain were
at about 650 m. Kaingin was a common feature
of the landscape up to 900 m, where it abruptly
FIELDIANA: ZOOLOGY
Fig. 3. Partially cleared lowland forest at 900 m. Note 1 2-m mist net in foreground. The view in the upper right
corner is northwest, towards San Miguel Bay. (Photo taken late March 1988 by S. M. Goodman.)
stopped because of a change in topography and
habitat (see below).
The remaining lowland forest had the charac-
teristic three-storied structure associated with this
ecological zone. The tallest trees were estimated
to be 30-45 m and in undisturbed areas they closed
off the canopy. Approximately 40% of the large
trees had buttressed bases. In selectively logged
areas of the forest it is these giants that are sought
after and removed. Strangler figs were relatively
common in both undisturbed and secondary low-
land forest. During March 1988 several types of
Fields spp. trees and shrubs were in flower and fruit.
The lower tiers of the intact lowland forest con-
sisted mostly of young trees and lianas. Epiphytes
were common and ground ferns and succulent herbs
rare. In most areas, rattan, a type of climbing spiny
palm (Calamus) used in commercial construction,
had been widely harvested from the forest by local
people.
The Panicuason Central Nursery is the local
headquarters of the Philippine Bureau of Forest
Development reforestation project on Mt. Isarog.
The main focus of this program is the replanting
of trees in large tracts of cleared lowland forest
between about 350 and 600 m. This is primarily
for watershed management and to a lesser extent
for selective logging. The oldest replanted stands
of forest on the west side of Mt. Isarog are about
20 years old. In virtually all replanted groves only
one or two species of trees have been introduced,
including Philippine mahogany (Vitex) and non-
native ipil-ipil (Leucaena). One edge of the nursery
lies along the national park boundary. Other hab-
itats near the Panicuason Central Nursery include
relatively large tracts of secondary lowland forest
with a few remaining large dipterocarps and dense
volunteer undergrowth; cleared areas used as tree
plantations; and, just outside the park, small set-
tlements surrounded by large agricultural fields.
Directly above the nursery the Yabo River courses
through several deep gorges, which are covered
with some undisturbed lowland forest.
Montane Forest (from approximately 900 to
1 500 m; synonym of Midmountain Forest sensu
Brown [191 9])— Directly behind camp 1 at 900 m
the mountain rose almost vertically for about 1 50
m. Between the bottom and the top of this steep
slope many characteristics of the forest changed.
Some of these differences appear diagnostic of the
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
Fig. 4. Transitional lowland/montane forest at about 1050 m. (Photo taken late March 1988 by S. M. Goodman.)
shift from lowland to montane forest (Brown,
1919). The trees were straighter, the structure of
the forest two-storied, and the canopy more open.
The understory at about 1050 m was denser than
in areas below, and various types of palms, ferns,
tree saplings, and bamboo were relatively com-
mon. Ficus spp. were rare (fig. 4). The first dense
growths of epiphytic ferns, pandans, and orchids
were noted here. Although rare, pitcher plants (Ne-
penthes), arborescent palms, and oaks (Lithocar-
pus) were found at this elevation. Vines of rattan
at least 40 mm in diameter were not uncommon.
As one moved up in elevation, to about 1500
m, epiphytes in the subcanopy and ground plants,
as well as a generally denser understory, became
more widespread. Within the montane forest there
was a noticeable change in the percentage of trees
with structural modifications: at 1125 m about
30% of the large trees had buttressed bases and at
1350 m between 10% and 15% had them. We
classify our camp 2 at 1 1 25 m as montane forest
with some transitional elements of lowland forest
and camp 3 as montane forest.
Mossy Forest (from approximately 1 500 m to
the summit at 1966 m; synonym of Upper Moun-
tain Rain Forest sensu Whitmore [1984])— The
transition zone from montane to mossy forest was
gradual. The area around our camp 4 at 1550 m
still had some characteristics of montane forest;
however, there was a noticeable reduction in tree
size and stature, vines became rare, strangler figs
completely dropped out, and there was a distinct
increase in moss cover on tree branches and trunks.
At about 1650 m the transition was more dra-
matic (fig. 5). The tallest trees were seldom over
10m and often were covered with luxuriant growths
of mosses, liverworts, orchids, and ferns (often up
to 25 cm thick). The locally high humidity and
regular rains kept the forest saturated with mois-
ture. No trees with buttressed bases were noted,
although some trees had support stilts. Pandans
were abundant, often covering the trunks of larger
trees. In some areas the ground debris was made
up largely of shed pandan leaves. This habitat con-
tinued up to the summit, where strong winds caused
the trees to become even more twisted and stunt-
ed. Near the summit there were patches of grass-
land, up to several hectares in size.
Collections
Dioscoro S. Rabor visited Mt. Isarog between
23 March and 29 April 1961 and made a collection
FIELDIANA: ZOOLOGY
Fig. 5. Mossy forest at 1750 m. Note luxuriant growth of ground cover and moss. (Photo taken in late March
1988 by L. R. Heaney.)
of birds. His work on Mt. Isarog was part of a
broader survey of vertebrates inhabiting the
mountains in the provinces of Camarines Sur and
Sorsogon (Rabor, 1966). He worked the south-
eastern slopes of Mt. Isarog and used Curry as his
base station (fig. 1). Although we have no exact
information on how Rabor obtained specimens,
it is presumed he had mist nets, and on the basis
of wounds on several specimens, he also had fire-
arms. He acquired some birds from local hunters.
About 750 skins in the Rabor collection from Mt.
Isarog are deposited at the Field Museum of Nat-
ural History (fmnh) and another 94 at the College
of Forestry, University of Philippines at Los Ba-
nos. A portion of the fmnh material is cataloged
within the Conover Collection (cc). A few addi-
tional specimens from the 1 96 1 Rabor collection
were sent to the Delaware Museum of Natural
History and the University of Michigan Museum
of Zoology. All of this Rabor material has been
studied, but only specimens housed in the fmnh
have been used herein. This is because the other
collections are a subset of the material in the fmnh
in both species represented and altitudinal infor-
mation. Six new subspecies of birds were named
from this collection (Rand & Rabor, 1967). Rabor
also collected mammals at Mt. Isarog, including
the type specimens of the endemic genus and spe-
cies Archboldomys luzonensis (Musser, 1982) and
the species Rhynchomys isarogensis (Musser &
Freeman, 1981).
On our 1988 trip to Mt. Isarog, between 27
February and 31 March, birds were obtained in
mist nets, in mammal snap-traps, or by shooting
with air rifles; a few specimens were purchased
from local people. During this work 373 birds were
collected. Most of these animals were prepared as
skeletons or fluid-preserved specimens. On the
second 1988 trip to Mt. Isarog, between 17 April
and 8 May, an additional 60 bird specimens were
taken. The 1988 collections were divided between
the pnm and usnm. Including the 1961 Rabor ma-
terial in various museums and our own 1988 col-
lections, a total of 1 ,293 bird specimens have been
examined from Mt. Isarog.
Measurements
Because little quantified information is avail-
able in the literature on the measurements of Lu-
zon birds, particularly from the southern portion
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
of the island, summary statistics have been in-
cluded for most resident species taken on Mt. Isa-
rog. Unless explicitly noted, measurements are of
adults. For sample sizes (in parentheses) less than
four, the measurements for each individual are
listed. Measurements for larger samples are given
as mean ± standard deviation, followed by the
range.
Linear measurements were taken only from dried
skins; specimens saved in fluid or as skeletons are
not included in these summary statistics. Mea-
surements include (all in mm): Wing— measured
from the bend of the flattened wing at carpal joint
to longest primary tip. Tail— measured from the
point of insertion of central rectrices to distal tip.
Exposed culmen— measured from the base of the
feathering on the forehead to maxilla tip. Bill from
nostril— measured from anterior edge of nostril to
maxilla tip. Bill width— measured across the edges
of the bill rami at the level of the anterior edge of
nostril. Weights are given in grams. For many Ra-
bor specimens a range of altitudes was given on
the tag; for convenience, only the median is re-
ported here. The 1988 elevational information is
based primarily on altimeter readings.
Netting
A series of mist nets was operated at each tran-
sect site. All nets used were 2.6 m high, 36-mm
size mesh, and 12m long. A net left up for a 24-
hour period is termed a "net-day."
Nets were checked during daylight hours at least
once every two hours, and we generally never had
more than eight nets in operation at any one time
per transect zone. Nets were left up throughout the
night to catch bats and nocturnal birds. The bot-
tom edge of the lowest net panel was generally set
1 m above the ground. At each transect zone the
nets were placed in a variety of habitats, e.g., on
the rim of ridge tops, in parang, and in lanes in
thick understory growth.
Observations
6; and camp 5 at 1750 m— 4. Regular notes were
kept on the species observed or heard daily, the
elevation, and surrounding habitat. Both Gonzales
and Goodman carried altimeters, so precise details
of the elevational ranges of identified birds could
be worked out. In order to quantify this infor-
mation the following "abundance measures" have
been used: abundant— seen or heard numerous
times each day per transect zone, common— seen
or heard once each day per transect zone, uncom-
mon—seen or heard every two or three days per
transect zone, rare— seen or heard once or twice
for duration of stay in any transect zone.
Systematic Order and Nomenclature
We have generally followed the systematic ar-
rangement and common names used by Gonzales
and Rees (1988); in some cases alternative names
from Dickinson et al. (in press) have been pre-
sented in parentheses. An asterisk (*) at the start
of any species account indicates that at least one
specimen taken on Mt. Isarog of the respective
taxon has been examined. In cases when a bird
was only observed in the area and not collected,
the presumed subspecies has been inferred on
known patterns of geographic variation; this is de-
noted with the use of brackets ([ ]) surrounding the
subspecies name.
Species Accounts
Family Accipitridae
Aviceda jerdoni [magnirostris] Jerdon's Baza
This species was observed once. An adult was
noted on 14 March 1988 at 1550 m soaring over
the forest. According to duPont (1971) this sub-
species is endemic to the islands of Mindanao,
Palawan, and Samar, and although not previously
recorded on Luzon, it is presumably the form oc-
curring there.
In addition to collecting and netting specimens,
members of the 1988 expedition gathered obser-
vational information on birds. The cumulative
number of observer-days per transect zone was:
Panicuason Central Nursery (including 400 m
camp)— 14; camp 1 at 900 m— 14; camp 2 at 1 125
m— 7; camp 3 at 1350 m— 9; camp 4 at 1550 m—
*Pernis celebensis steerei Barred Honey Buzzard
The single record of this species on Mt. Isarog
is one Rabor collected on 1 9 April 1961 between
610 and 760 m.
Measurements— Immature female (1)— wing
385, tail 265, exposed culmen 32.8, weight 588.
FIELDIANA: ZOOLOGY
*Pernis apivorus philippensis
Buzzard
Crested Honey
An adult male collected on 20 April 1961 be-
tween 450 and 610 m is the only known record
for the mountain. duPont (1971) did not list this
species as occurring on Luzon. Stresemann and
Amadon (1979) include Luzon in its distribution,
but the basis for this was not stated.
Measurements— Male (1)— wing 414, tail 283,
exposed culmen 39.7, weight 1,004.
*Haliastur indus intermedius Brahminy Kite
The single record of this species on Mt. Isarog
is an immature bird obtained by Rabor on 1 9 April
1961 between 450 and 610 m. The bird was molt-
ing the wing and tail feathers.
*Spilornis holospilus Philippine Serpent Eagle
We occasionally observed pairs of Philippine
Serpent Eagles between 450 and 900 m soaring
over partially cleared areas and remaining patches
of forest. We did not note it at higher elevations.
Rabor collected four adults between 200 and
760 m.
Measurements— Wing— male (3) 357, 363, 368,
female (1) 369; tail-male (3) 232, 237, 241, fe-
male (1) 225; exposed culmen— male (3) 32.9, 35.3,
35.6, female (1) 35.8; weight-male (3) 656, 688,
858.
*Accipiter gularis gularis Japanese Sparrowhawk
An adult male (based on size, wing 172 and tail
111) was taken at approximately 380 m on 24
March 1961. This species is a winter visitor to the
Philippines (duPont, 1971).
WEiGHT-Male(l) 123.
*Accipiter virgatus confusus Besra
We have three records of this species on the
mountain. On 18 March 1988 an immature bird
was netted in primary forest at 1550 m, on 25
March 1988 an adult was captured in a heavily
disturbed area at 450 m, and on 24 April 1961 an
adult was taken at approximately 260 m. The 25
March bird was caught while chasing a pair of
Pachycephala philippinensis; the raptor had insect
and beetle remains in its stomach. The gizzard of
the immature bird was empty.
Measurements— Wing— male (2) 150, 166, im-
mature male (1) 159; tail— male (2) 109, 1 14, im-
mature male (1) 120; exposed culmen— male (2)
16.5, 16.6, immature male (1) 16.0; weight— male
(2) 94, 97, immature male (1) 120.
*Accipiter soloensis Chinese Goshawk
There are two records for Mt. Isarog of this mi-
grant from the Asian mainland. On 23 March 1 96 1
an immature bird and an adult female were col-
lected at approximately 260 m.
Weight— Female (1) 159, immature female (1)
160.
*Butastur indicus Grey-faced Buzzard
A Grey-faced Buzzard was collected by Rabor
on 23 April 1 96 1 at about 680 m. This is the only
known record for Mt. Isarog of this migrant from
the Asian mainland.
Weight— Immature female (1)418.
*Hieraaetus kienerii formosus
Eagle
Rufous-bellied
Records of this species include an adult male
taken on 29 March 1961 at 610 m and an im-
mature bird the following day at about 680 m.
Measurements— Wing— male (1) 346, imma-
ture unsexed (1)368; tail— male (1) 182, immature
unsexed (1) 195; exposed culmen— male (1) 33.9,
immature unsexed (1) 32.7; weight— male (1) 733,
immature unsexed (1) 932.
Family Falconidae
*Microhierax erythrogenys erythrogenys Philip-
pine Falconet
We found this species only in the vicinity of 900
m, where adults were netted on 9 and 10 March.
On 1 1 March an immature bird was noted in a
partially cleared area hawking insects from a tree
perch about 1 5 m above the ground. Rabor col-
lector six adults between 450 and 760 m.
Measurements— Wing— male (5) 107.0 ± 1.26,
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
106-109, female (3) 109, 1 13, 1 16; tail-male (5)
58.8 ± 2.93, 55-63, female (3) 64, 64, 67; exposed
culmen-male(5) 11.9 ± 0.11, 11.7-12.1, female
(3) 12.3, 12.5, 12.5; weight-male (5) 42.3 ± 2.27,
38.0-44.0, female (2) 55.8, 61.5.
Family Phasianidae
Gallus gallus [gallus] Red Junglefowl
Recorded only once. The distinctive call of this
species was heard at dusk from a tract of primary
forest above the 900 m camp. The nearest known
human habitation with domestic chickens was
about 400 m below in elevation and Vi km distant
from this site. Other records of this species in
southeastern Luzon include a female (fmnh cc
23359) "with several young chicks" taken between
100 and 300 m at Tugas, Matnog, Sorsogon Prov-
ince, on 19 May 1961 and two females (fmnh cc
23358, 23360) obtained between 760 and 910 m
at Mt. Bulusan, Sorsogon Province, in mid-May
1961.
Family Rallidae
*Amaurornis olivacens olivaceus Plain Swamp-
hen (Bush-hen)
An adult male and female were taken by Rabor
on 20 April 1961 between 450 and 610 m. These
are the only known records for the mountain.
Family Scolopacidae
*Actitis hypoleucos Common Sandpiper
The only record for Mt. Isarog of this winter
visitor to the Philippines is one taken on 24 April
1961 at about 250 m.
Weight— Female (1) 58.4.
Family Columbidae
*Treron pompadora axillaris Pompadour Green
Pigeon
The only record of this species from Mt. Isarog
is a female collected by Rabor on 25 March 1961
between 450 and 610 m. The bird had an enlarged
ovary.
Measurements— Female (1)— wing 159, tail 86,
exposed culmen 18.7, weight 219.
*Phapitreron leucotis leucotis White-eared Brown
Dove
This species was widely distributed up the slopes
of Mt. Isarog. It was distinctly more common be-
tween 450 and 1125m than in the vicinity of 1 350
m, and was not recorded above the latter zone. It
seemed primarily confined to dipterocarp and low-
er montane forest. At 900 m it was sympatric with
P. amethystina.
One female collected on 26 March 1988 at 450
m had ovarian follicles measuring up to 5 mm;
towards the end of the month White-eared Brown
Doves were heard singing, and this species may
have been about to commence breeding. All of the
five birds obtained by Rabor in the first half of
April 1961 were in or approaching breeding con-
dition. Specimens we took at 450 m and 900 m
had fig seeds in their stomachs. On several occa-
sions this species was noted near the 1350m camp
feeding on Lithocarpus acorns.
Measurements— Wing— male (2) 135, 141, fe-
male (4) 129.5 ± 1.50, 127-131; tail-male (2)
83, 89, female (4) 82.0 ± 3.16, 78-86; exposed
culmen -male (2) 14.4, 15.6, female (3) 14.4, 15.2,
15.9; weight-male (2) 120, 144, female (4) 146.8
± 27.7, 106-184.
*Phapitreron amethystina amethystina Amethyst
Brown Dove
We found the Amethyst Brown Dove only in
the vicinity of the 900 m camp, where it was un-
common. This species appears to be restricted to
undisturbed areas of lowland forest on Mt. Isarog.
Rabor collected 10 specimens between 450 and
1060 m, including several adults in breeding con-
dition between late March and mid- April and three
fledglings in the first half of April.
Measurements— Wing— male (1) 151, female
(5) 145.8 ± 3.76, 141-151; tail-male (1) 93, fe-
male (4) 88.8 ± 5.26, 80-94; exposed culmen-
male (1) 23.5, female (5) 22.8 ± 0.48, 21.9-23.2;
weight-male (1) 149, female (5) 141.8 ± 8.74,
130-155.
*Ptilinopus occipitalis Yellow-breasted Fruit
Dove
We did not record this species on Mt. Isarog.
Rabor collected 1 3 specimens in late March and
10
FIELDIANA: ZOOLOGY
April 1 96 1 between 300 and 1 060 m; several were
in or approaching breeding condition.
Measurements— Wing— male (8) 161.9 ± 3.37,
157-167, female (5) 156.4 ±3.07, 153-161; tail-
male (6) 102.0 ± 3.37, 98-107, female (5) 97.7 ±
3.20, 94-103; exposed culmen— male (8) 16.1 ±
0.35, 15.4-16.5, female (4) 15.58 ± 0.49, 15.0-
16.3; weight-male (7) 244.3 ± 15.38, 224-271,
female (5) 234.8 ± 9.28, 225-252.
*Ptilinopus leclancheri leclancheri
Fruit Dove
Black-chinned
The only known records of this species from
Mt. Isarog are a male collected between 450 and
610 m on 29 April 1961 and a female at 700 m
on 3 April 1961.
each transect zone, except at 1350 m. It appeared
to be less common at lower altitudes, particularly
in disturbed and replanted tracts of forest. This
may have in part been related to relatively heavy
hunting pressure on doves and pigeons by kain-
gineros living on the lower slopes of the mountain.
This species' distinctive call could occasionally be
heard at the higher altitudes, generally at dusk and
dawn. A specimen taken on 30 March 1 988 at 450
m had slightly enlarged ovarian follicles and an-
other on 3 1 March 1961 at approximately 840 m
had a shelled egg in the oviduct.
Measurements— Wing— male (3) 183, 185, 186,
female (3) 178, 180, 180; tail-male (3) 176, 177,
188, female (3) 173, 175, 180; exposed culmen -
male (3) 15.6, 15.9, 16.1, female (2) 14.7, 15.3;
weight- male (3) 157, 183, 191, female (2) 191
(with egg), 177.
Ducula aenea [aenea] Green Imperial Pigeon
We noted this species on several occasions at
450 m and 1 125 m. A flock of three was observed
at the latter altitude feeding on acorns.
Chalcophaps indica [indica] Emerald Dove
We have a single observation of this species in
late March 1988 at 450 m.
*Ducula poliocephala poliocephala
Imperial Pigeon
Pink-bellied
We observed this species once in the forest at
900 m and twice in the primary forest at 1350 m.
Rabor collected one adult female (with an enlarged
ovary) on 6 April 1961 at 610 m.
Measurements— Female (1)— wing 227, tail
147, exposed culmen 19.7, weight 622.
*Gallicolumba luzonica luzonica
Bleeding-heart Pigeon
Luzon
We observed a Luzon Bleeding-heart Pigeon at
450 m and Rabor collected an adult female at
approximately 700 m.
Measurements— Female (1)— wing 143, tail 90,
exposed culmen 16.2, weight 133.
*Columba vitiensis griseogularis Metallic Wood
Pigeon
We observed the Metallic Wood Pigeon once at
900 m and twice at 1350 m, among the lower
branches of forest trees. Two adult males were
collected by Rabor in the first half of April 1 96 1
at approximately 1 140 and 1670 m, one of which
had slightly enlarged gonads.
Measurements— Male (2)— wing 245, 246; tail
149, 155; exposed culmen 21.7, 22.1; weight 508.
Family Psittacidae
Cacatua haematuropygia Philippine (Red-
vented) Cockatoo
A group of two or three was observed at about
1 100 m flying over the forest. The distinctive white
plumage, parrot-like flight, and harsh cry were di-
agnostic. One of our Bicolano guides mentioned
that this species was occasionally observed on Mt.
Isarog.
*Macropygia phasianella tenuirostris
billed (Brown) Cuckoo Dove
Slender- *Bolbopsittacus lunulatus lunulatus Guaiabero
This species was sparsely distributed along our
transect survey of Mt. Isarog. We recorded it in
Guaiabero were noted a few times at about 450
m. They were seen singly or in groups of up to
three in partially cleared forest or at the edge of
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
11
fields. Rabor collected six specimens between 450
and 760 m. The only record above this zone is
one netted in 1988 at 900 m in a disturbed area.
A bird taken on 9 March 1988 at 450 m had a
slightly thickened oviduct and egg follicles mea-
suring up to 5 mm. The stomachs of two birds
obtained at 450 m contained fig seeds and fruits.
Measurements — Wing— male (7) 100.3 ±
1.01, 98-103, female (2) 103, 103; tail-male (7)
36.1 ± 1.81, 34-^0, female (1) 35; exposed cul-
men-male(6) 18.5 ± 1.03, 17.2-20.0, female (1)
20.1; weight- male (7) 66.6 ± 6.32, 60-80, female
(3)61,72, 77.
*Loriculus philippensis philippensis Philippine
Hanging Parakeet (Colasisi)
We noted this species a few times in the vicinity
of 450 m, where it was uncommon. Rabor ob-
tained one between 450 and 760 m on 25 April
1961.
Measurements— Immature male (1)— wing 97,
tail 42, exposed culmen 15.6.
Family Cuculidae
*Cuculus fugax pectoralis Hodgson's Hawk
Cuckoo
We recorded this species twice on Mt. Isarog:
single adults were netted at 450 m and 1 125 m.
way & Wells, 1976) two males obtained at about
610 m on 5 and 17 April are referable to C. s.
horsfieldi (wing 216 and 212, respectively); a fe-
male obtained on 7 April between 1060 and 1220
m (wing 195) and a male on 1 5 April between 450
and 610 m (wing 186) cannot be confidently iden-
tified to subspecies.
Weight- Male (2) 73, 103; female (1) 81.
*Cacomantis variolosus sepulcralis Brush Cuckoo
We found the Brush Cuckoo to be common be-
tween 450 and 1125 m, uncommon at 1350 m,
and rare at 1 550 m. Rabor collected 1 1 specimens
between about 6 1 and 1 220 m. Throughout March
1988 this species was regularly heard vocalizing
in the early morning hours from tree perches in
the forest and at the edge of clearings. Specimens
taken in late March and early April had enlarged
gonads, including a female on 1 April 1 96 1 with
a "ripe egg." Two immature females were ob-
tained on 1 1 and 1 8 April 1961. Stomach contents
of several individuals contained insect remains.
We found no evidence for the occurrence of Ca-
comantis merulinus on Mt. Isarog.
Measurements— Wing— male (7) 1 15.7 ± 0.70,
115-117, female (2) 1 14, 1 15; tail-male (7) 120.0
± 5.07, 113-130, female (1) 115; exposed cul-
men-male(7) 16.8 ± 0.49, 16.0-17.7, female (2)
15.8, 16.9; weight-male (7) 32.0 ± 1.51, 30-34,
female (2) 30, 33.
*Cuculus micropterus micropterus Indian Cuckoo
Two adults were taken by Rabor: a male on 1 4
April 1961 at approximately 530 m and a female
the following day at about 840 m. duPont (1971)
considered this species a straggler in the Philip-
pines to Mindoro and Negros. In addition to the
Mt. Isarog specimens, other Luzon records include
a male taken on 15 April 1960 in Cagayan Prov-
ince (fmnh 258836), and one netted in 1967 and
two in 1970 at Dalton Pass, Nueva Vizcaya Prov-
ince (McClure & Leelavit, 1972).
*Cuculns saturatus horsfieldi Oriental Cuckoo
Four specimens of this migrant from the Asian
mainland were taken by Rabor on Mt. Isarog in
1961. On the basis of wing measurements (Med-
*Chrysococcyx xanthorhynchus amethystinus
Violet Cuckoo
The only record of this species for Mt. Isarog is
an adult female taken on 4 April 1961 at 760 m
containing a "ripe egg."
Measurements— Female (1)— wing 105, tail 65,
exposed culmen 15.7, weight 21.2.
*Surniculus lugubris chalybaeus Drongo Cuckoo
We recorded this species once on Mt. Isarog. A
single bird was observed and heard calling at sun-
rise on 2 March 1988 at 450 m. Rabor collected
three adult specimens in 1961 between 610 and
680 m.
Measurements— Wing— male (2) 128, 133, fe-
male (1) 124; tail -male (2) 105, 99, female (1)
12
FIELDIANA: ZOOLOGY
103; exposed culmen— male (2) 19.3, 19.9, female
(1) 19.6; weight- male (2) 33, 35, female (1) 36.
*Eudynamys scolopacea mindanensis
Koel
Common
155-1 77, female (13) 162.9 ± 4.27, 155-171; tail-
male (9) 2 1 5.7 ± 6.36, 205-227, female ( 1 3) 2 1 2.8
±8.31, 195-227; exposed culmen- male (9) 36.0
± 1.54, 34.3-39.8, female (13) 34.8 ± 1.29, 32.9-
36.6; weight- male (9) 179.8 ± 13.03, 160-204,
female (13) 169.2 ±21.7, 121-207.
There are three records from the area. One was
heard calling near the 1550 m camp during the
night of 12-13 March and one was observed at
1125 m on 21 March 1988. Rabor collected a
female with an enlarged ovary on 26 April 1961
at approximately 380 m.
Measurements— Female (1)— wing 203, tail
186, exposed culmen 30.6, weight 223.
* Phaenicophaeus superciliosus superciliosus Red-
crested Malkoha
We found this species only in the vicinity of 450
m where it was uncommon and locally sympatric
with Phaenicophaeus cumingi. Rabor collected 2 1
Red-crested Malkohas between approximately 300
and 760 m; these included fledglings and nestlings
in the first half of April and adult females in breed-
ing condition in the second half of April. A female
taken on 24 March was just molting from subadult
to adult plumage.
Measurements— Wing— male (6) 161.2 ± 5.05,
15 5- 170, female (10) 158.3 ± 2.65, 153-163; tail-
male (6)21 1.8 ± 2.91, 208-2 1 5, female ( 1 0) 2 1 2.4
± 1 1.44, 191-224; exposed culmen— male (5) 34.5
± 0.95, 33.1-35.6, female (10) 33.8 ± 0.99, 32.3-
35.1; weight-male (5) 121.6 ± 4.27, 118-130,
female (8) 123.4 ± 10.31, 105-138.
*Centropus viridis viridis Philippine Coucal
We found this species only in the vicinity of 450
m, where it was uncommon. Rabor collected seven
specimens between late March and late April 1 96 1
between approximately 300 and 700 m, including
several adults (in or approaching breeding con-
dition) and two nestlings. An adult male collected
on 28 March 1988 had enlarged testes. The stom-
achs of two specimens contained insects.
Measurements— Wing— male (4) 153.5 ± 4.39,
150-161, female (3) 170, 172, 176; tail-male (4)
222.3 ± 9.60, 212-238, female (3) 227, 228, 253;
exposed culmen— male (4) 27.2 ± 0.56, 26.4-27.9,
female (2) 27.8, 30.0; weight- male (3) 124, 126,
140, female (3) 152, 153, 157.
*Centropus unirufus Rufous Coucal
There are two records of this species. In early
April 1 96 1 Rabor collected an adult female and
an adult male between 550 and 760 m. The male
had enlarged testes.
Measurements— Wing— male (1) 161, female
( 1 ) 1 64; tail— male ( 1 ) 222, female (1)210; exposed
culmen— male (1) 34.9, female (1) 38.3; weight-
male (1) 146, female (1)215.
* Phaenicophaeus cumingi
koha
Scale-feathered Mal-
We noted this species with some regularity and
heard it vocalizing in patches of undisturbed forest
and replanted areas from 450 to 900 m. One bird
was caught in a mammal snap-trap placed on the
ground. Rabor collected 23 specimens between 300
and 760 m.
A female taken on 8 March 1988 had enlarged
ovarian follicles. The stomach of one bird ob-
tained at about 650 m contained seven caterpil-
lars, measuring up to 100 mm. Another one from
900 m had numerous insect parts and two cater-
pillars, the largest about 1 1 mm in length.
Measurements— Wing— male (9) 163.2 ± 6.92,
Family Strigidae
*Otus longicornis Luzon Scops Owl
This species was found from 450 m to the upper
reaches of the mountain. It was noted calling dur-
ing the night a few times at the 1 125 m camp.
Near the 1 350 and 1 550 m camps it was generally
heard every night. One bird was captured in a
mammal snap-trap placed on the ground. Adult
specimens collected in the second half of March
1988 were in various reproductive states, from
having small to greatly enlarged gonads. The stom-
achs from several birds contained insects, includ-
ing Coleoptera and Orthoptera. We follow Mar-
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
13
shall (1978) in considering this bird specifically
distinct from Otus scops.
Measurements— Wing— male (4) 144.8 ± 2.49,
141-147, female (1) 148; tail-male (4) 67.3 ±
1 .79, 65-70, female (1) 69; exposed culmen— male
(3) 16.5, 17.2, 17.8, female (1) 16.7; weight -male
(8) 72.3 ± 3.53, 69-78, female (1) 95.
*Otus megalotis Philippine Scops Owl
The Philippine Scops Owl was found to be wide-
ly distributed on the slopes of Mt. Isarog. It was
regularly heard calling at night at 450 and 900 m,
was rare from 1 125 to 1550 m, and appeared to
be absent at 1750 m. Several males taken in the
first half of March 1988 were in or approaching
breeding condition. We follow Marshall (1978) in
considering this owl specifically distinct from Otus
bakkamoena. The Mt. Isarog specimens all have
heavy tarsi, feathered down to the proximal por-
tion of the toes.
Measurements— Male (3) wing— 168, 173, 173;
tail— 75, 78, 81; exposed culmen— 22.0, 22.5, 23.9;
weight- 159, 165, 182.
*Ninox philippensis philippensis Philippine
(Boobook) Hawk Owl
This species was common at 450 m and 900 m;
birds were regularly heard calling or captured in
mist nets at night. It was uncommon at 1 125 m
and not recorded above this altitude. Several birds
collected in March 1988 were in or approaching
breeding condition. Insects, mostly beetles, were
found in the stomachs of specimens.
Measurements— Wing— male (10) 171.6 ±
5.30, 163-179; tail-male (10) 79.6 ± 4.48, 72-
86; exposed culmen-male (7) 19.0 ± 0.98, 17.4-
19.9; weight-male (11) 115.7 ± 8.1, 110-135,
female (1) 141.
*Ninox scutulata randi Brown (Boobook) Hawk
Owl
The only records we have for Mt. Isarog are two
adult females taken by Rabor in April 1961 be-
tween 450 and 610 m.
Measurements— Female (2)— wing 217, 221;
tail 117, 117; weight 195,205.
Family Podargidae
*Batrachostomus septimus microrhynchus Phil-
ippine Frogmouth
Rabor collected a male Philippine Frogmouth
at approximately 530 m. duPont (1971) noted that
this species' distribution on Luzon was restricted
to the northern portion of the island, where the
endemic form B. s. microrhynchus occurred. The
Mt. Isarog specimen matches birds from northern
Luzon in plumage coloration and size. A female
taken at Mt. Bulusan, San Roque, Sorsogon Prov-
ince, southeastern Luzon (fmnh 265627), is the
palest in plumage coloration of any Philippine B.
septimus in the fmnh collection and has a short
wing (128 mm).
Measurements— Male (1)— wing 137, weight
69.
Family Caprimulgidae
*Eurostopodus macrotis macrotis Great Eared
Nightjar
This species was regularly seen at dusk near 450
m taking to the air and foraging for insects. The
stomach of the single specimen was empty except
for a few beetle parts.
Family Apodidae
Collocalia cf. vanikorensis Island Swiftlet
Flocks of aerial-foraging swiftlets were observed
on Mt. Isarog from 450 m to the summit. On the
basis of size and plumage coloration some of the
swiftlets were tentatively identified as C. vaniko-
rensis (sensu Dickinson, 1989); however, no spec-
imens of this species have been collected on Mt.
Isarog. Swiftlets comparable to C vanikorensis were
distinctly less common at 1550 m and 1750 m
than at lower altitudes. Above 1550 m they were
generally noted towards the latter portion of the
afternoon, particularly on cloudy and rainy days,
and on occasion in mixed flocks with at least Col-
localia esculenta.
* Collocalia esculenta marginata Glossy (White-
bellied) Swiftlet
Flocks of Glossy Swiftlets were commonly not-
ed flying above the slopes of the mountain. At
lower elevations they regularly flew among Island
Swiftlets, but above 1550 m the two species ap-
peared segregated. The rump feathers of the single
14
FIELDIANA: ZOOLOGY
Mt. Isarog specimen are distinctly edged with white,
characteristic of C. e. margi nata (duPont, 1971).
Measurements— Male (1)— wing 103, tail 43,
weight 7.0.
Family Trogonidae
*Harpactes ardens luzoniensis
Trogon
Philippine
A single bird was noted in early March 1988 at
900 m near the transition zone between diptero-
carp and lower montane forest. In 1961, Rabor
collected 1 1 specimens between about 450 and
1060 m. These include females on 30 March and
20 April with enlarged ovaries, and a male on 29
March molting from subadult to adult plumage.
Measurements— Wing— male (2) 134, 140, fe-
male (8) 140.4 ± 3.67, 134-145; tail-male (2)
150, 161, female (8) 155.9 ± 6.94, 150-169; ex-
posed culmen— male (2) 18.2, 19.0, female (6) 19.5
± 0.67, 18.6-20.7; weight-male (2) 80, 87, fe-
male (8) 85.8 ± 4.44, 80-92.
Family Alcedinidae
*Alcedo cyanopectus cyanopectus
Kingfisher
Dwarf River
We recorded this species once; a female was
collected on 26 March 1988 along a river at about
450 m. The specimen's stomach contained insect
remains.
Measurements— Female (1)— wing 62, tail 24,
exposed culmen 35.1, weight 21.5.
*Ceyx melanurus melanurus
(Jungle) Kingfisher
Philippine Forest
The only record for the area is a female (with
an enlarged ovary) taken by Rabor on 5 April 1 96 1
at about 610 m.
Measurements— Female (1)— wing 57, tail 18,
exposed culmen 32.7, weight 22.
*Halcyon chloris chloris Collared Kingfisher
A female collected by Rabor on 2 1 April 1 96 1
between 450 and 6 10 m is the only known record
for the mountain.
*Halcyon smyrnensis gularis
Kingfisher
White-throated
We observed the White-throated Kingfisher
several times at 450 m, generally near streams or
rivers. Rabor took an adult female, with an en-
larged ovary, on 3 April 1961 between 300 and
450 m.
* Halcyon lindsayi lindsayi
fisher
Spotted Wood King-
The Spotted Wood Kingfisher was encountered
every day in the 450 to 900 m zone and on two
days at 1350 m. At 900 m this species' character-
istic rattle-like call was heard each morning before
sunrise and on several occasions birds were cap-
tured in mist nets during the predawn hours. Ra-
bor collected nine specimens between 450 and 6 1
m. A female taken on 25 March 1 988 had a shelled
egg in the oviduct and other ova measuring 35 x
26 and 16x16 mm, and another bird obtained
on 20 April 1961 had an enlarged ovary. The
stomach contents of collected birds consisted of
insects, including larvae and beetles.
Measurements— Wing— male (10) 113.3 ±
4.47, 108-124, female (5) 112.4 ± 2.06, 109-115;
tail -male (10) 84.7 ± 1.90, 82-88, female (5) 85.0
± 2.61, 81-89; exposed culmen-male (8) 40.78
± 1.85, 37.5-44.3, female (5) 4 1.56 ± 1.35,40.0-
43.7; weight-male (10) 83.7 ± 6.76, 72-96; fe-
male (3) 95, 96, 117.
Family Coraciidae
*Eurystomus orientalis cyanocollis Dollarbird
The only record of the Dollarbird on Mt. Isarog
is a male collected by Rabor on 4 April 1 96 1 at
about 610 m.
Measurements— Male (1)— wing 185, tail 101,
exposed culmen 27.5, weight 129.
Family Bucerotidae
*Penelopides panini manilloe Tarictic Hornbill
This species was uncommon at 450 and 900 m.
It was often observed in pairs, moving along stream
channels, river beds, or at the edge of the forest.
One was collected from a tree standing in grass-
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
15
land. Ten specimens were taken by Rabor in 1961
between 300 and 760 m. Several individuals ob-
tained in late March 1988 and early April 1961
were in breeding condition, including a female on
6 April with a "ripe egg." Birds collected at 450
m had Ficus fruit and seeds in their stomachs.
Measurements— Wing— male (11) 235.5 ±
4.79, 224-241, female (2) 224, 229; tail-male (1 1)
193.3 ± 5.78, 181-202, female (2) 184, 186; ex-
posed culmen-male (1 1) 92.7 ± 3.64, 88. 1-99.5,
female (2) 78.9, 80.9; weight- male (9) 450.2 ±
26.6, 400-479, female (2) 470, 475.
*Buceros hydrocorax hydrocorax Rufous Horn-
bill
An adult male obtained by Rabor on 20 April
1961 between 610 and 760 m is the only known
record of this species on Mt. Isarog.
Measurements— Male (1)— wing 420, tail 314,
weight 1,824.
Family Capitonidae
*Megalaima haemacephala haemacephala
Crimson-breasted (Coppersmith) Barbet
This species was uncommon at 450 m in dis-
turbed areas and secondary forest. We did not
record it above this zone. Rabor collected two
specimens, one of which had slightly enlarged tes-
tes, on 8 and 9 April 1 96 1 between 300 and 610m.
Family Picidae
*Mulleripicus funebris funebris
pecker
Sooty Wood-
We found the Sooty Woodpecker to be uncom-
mon in the vicinity of 450 m. In 1961 Rabor re-
corded it between 300 and 600 m and collected
four birds, including a female on 23 March with
an enlarged ovary.
Measurements— Wing— male (3) 160, 160, 164,
female (1) 152; tail-male (3) 125, 131, 137, fe-
male (1) 125; exposed culmen— male (3) 35.5, 36.7,
37.4, female (1) 36.5; weight-male (3) 164, 164,
170, female (1) 161.
We recorded this species once on Mt. Isarog.
An adult was observed at 450 m in a section of
relatively undisturbed forest near the Yabo Falls.
Two adults were collected by Rabor on 1 8 April
1961 between 450 and 610 m.
Measurements— Wing— male (1) 205, female
( 1 ) 208; tail— male ( 1 ) 1 5 1 , female ( 1 ) 1 50; exposed
culmen— male (1) 51.5, female (1) 50.2; weight-
male (1) 250, female (1) 243.
*Dendrocopos maculatus validirostris Philippine
Pygmy Woodpecker
This species was observed each day we were
camped at 450, 900, and 1 125 m, in both primary
and secondary forests. It was uncommon at 1350
m and not recorded above this altitude. A male
taken by Rabor between 910 and 1060 m on 29
March 1961 had enlarged testes.
Measurements— Wing— male (2) 84, 88, fe-
male (2) 82, 86; tail-male (2) 37, 37, female (2)
36, 40; exposed culmen— male (2) 17.9, 18.3, fe-
male (2) 18.4, 19.0; weight- male (2) 24, 25, fe-
male (1) 25.
'Chrysocolaptes lucidus haematribon
(Flameback) Goldenback
Greater
We found this species to be uncommon in both
primary and secondary forest at 900 and 1 125 m,
and rare at 450 m. On 23 March 1988, three adults
were observed calling and moving about the forest
just above our 1125m camp. The following morn-
ing one was found nearby excavating a hole in a
dead tree about 15 m above the ground. Rabor
collected 16 Greater Goldenbacks in 1961 be-
tween 210 and 1060 m, including a male on 1
April with enlarged testes.
Measurements— Wing— male (8) 144.0 ±3.16,
139-1 50, female (8) 142.3 ± 4.63, 135-148; tail-
male (8) 82.9 ± 3.79, 76-89, female (8) 79.6 ±
3.64, 75-86; exposed culmen— male (8) 39.03 ±
1.88, 36.4-42.4, female (8) 34.8 ± 1.44, 32.6-
36.4; weight-male (8) 130.9 ± 8.01, 123-145,
female (7) 126.4 ± 9.60, 110-143.
Family Pittidae
*Dryocopus javensis confusus
Woodpecker
White-bellied *Pitta erythrogaster erythrogaster Red-breasted
Pitta
16
FIELDIANA: ZOOLOGY
The only record of this species for Mt. Isarog is
an adult female collected by Rabor on 5 April 1 96 1
at about 610 m.
Measurements— Female (1)— wing 100, tail 33,
exposed oilmen 20.5, weight 66.
Pitta kochi Koch's (Whiskered) Pitta
Koch's Pitta was observed once on Mt. Isarog.
On 19 March 1988 a single bird was watched for
about three minutes foraging on the ground at a
distance of up to 5 m. The salient plumage char-
acteristics of the Koch's Pitta were clearly dis-
cernable. According to duPont (1971), this species
is restricted to northern Luzon; however, single
birds were captured in 1 967 at Dalton Pass, Nueva
Vizcaya Province, and in 1964 at Balian, Laguna
Province (McClure & Leelavit, 1972).
Family Campephagidae
*Coracina striata striata Bar-bellied Cuckoo-
shrike
Three specimens of the Bar-bellied Cuckoo-
shrike were collected by Rabor in 1 96 1 between
450 and 610m. One of the birds was an immature.
*Coracina coerulescens coerulescens Black
Cuckoo-shrike
*Lalage nigra chilensis Pied Triller
We found the Pied Triller to be uncommon at
450, 900, and 1 550 m. It is not clear if this species'
altitudinal distribution on Mt. Isarog is continu-
ous. In all cases it was observed in clearings, both
natural and man-made. Rabor collected three adult
specimens— two at 150 m and one between 450
and 610 m.
Measurements— Male— wing (2) 93, 94; tail (3)
all in molt; exposed culmen (3) 13.8, 14.2, 14.4;
weight (2) 26.5, 27.6.
*Pericrocotus divaricatus divaricatus Ashy Min-
ivet
The only known records on Mt. Isarog for this
migrant from the Asian mainland are a pair of
adult males taken by Rabor on 3 April 1961 at
610 m.
*Pericrocotus flammeus novus Scarlet Mini vet
Specimens from Mt. Isarog include an adult male
with enlarged testes taken on 24 March 1961 be-
tween 300 and 450 m and another adult male with
slightly enlarged testes obtained on 1 April 1 96 1
between 610 and 760 m.
Measurements— Male (2)— wing 78, 85; tail 80,
86; exposed culmen 12.3, 12.4; weight 16.5, 18.0.
Seventeen Black Cuckoo-shrikes were taken by
Rabor in 1961 between 300 and 760 m. These
included adults in late March and early April with
enlarged gonads. The 1988 expedition did not re-
cord either Coracina species.
Measurements— Wing— male (9) 136.2 ± 4.89,
128-143, female (6) 130.8 ± 6.87, 127-146; tail-
male (10) 111.5 ± 3.23, 1 05-1 1 7, female (7) 1 06.3
± 2.91, 103-1 1 1; exposed culmen-male (9) 22.2
± 0.75, 21.3-23.6, female (7) 21.4 ± 0.47, 20.5-
22.0; weight-male (8) 65.5 ± 3.04, 6 1-70, female
(7) 60.3 ± 4.62, 53-69.
*Lalage melanoleuca melanoleuca Black and
White Triller
An adult female with an enlarged ovary and an
immature bird were collected by Rabor on 23
March 1961 between 450 and 610 m.
Family Paridae
*Parus elegans elegans Elegant Tit
Single birds or groups of up to three were seen
daily in areas between 450 and 900 m. They were
often observed in tracts of undisturbed forest, and
occasionally in areas with secondary and replanted
forest. This species was uncommon at 1125m and
not recorded higher on the mountain. Fifteen spec-
imens were collected by Rabor in 1 96 1 , 12 of these
were taken below 900 m and 3 at about 1 140 m.
The majority of the Rabor birds had enlarged go-
nads. One fledgling was found at about 6 1 m on
6 April 1961. The stomachs of collected birds in-
variably contained parts of small insects.
A Parus elegans was noted on 4 March 1988 at
900 m in a mixed species foraging flock with Sitta
frontalis and Rhabdornis mystacalis. The Rhab-
dornis moved at the front of the flock lifting up
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
17
bark and leaves, probing into crevices, and up-
rooting small epiphytes; the tit and nuthatch fol-
lowed and gleaned small insects from spots visited
by the Rhabdornis.
Measurements— Wing— male (12) 65.5 ± 1.19,
64-68, female (6) 65.7 ± 2.29, 63-70; tail-male
(12) 38.0 ± 1.15, 36^0, female (6) 37.3 ± 0.75,
36-38; exposed culmen-male (12) 10.1 ± 0.28,
9.8-10.6, female (5) 9.3 ± 0.65, 8.2-9.9; weight-
male (12) 13.5 ± 1.31, 10.5-15.9, female (7) 12.2
± 1.07, 11.4-13.4.
Family Sittidae
*Sitta frontalis isarog Velvet-fronted Nuthatch
The Velvet-fronted Nuthatch was common in
the vicinity of 900 m, and uncommon at 450 m
and 1350 m. There are 1 3 specimens in the Rabor
collection taken in 1961 between 450 and 1220
m. We found single birds or groups of up to four
foraging together, occasionally in mixed species
flocks, in both primary and secondary forest. Be-
tween 4 and 7 March 1988 we observed a pair
gathering moss for nesting material and carrying
it to a hole excavated in a dead snag about 7 m
off" the ground. Insects were the only food item
found in the stomachs of specimens. The type lo-
cality of S. f. isarog is Mt. Isarog (Rand & Rabor,
1967).
On 17 March 1988 a mixed species foraging
flock of single Sitta frontalis, Rhipidura cyaniceps,
and Pachycephala plateni was observed at 1350
m. The nuthatch moved through the forest picking
at and tearing open bark and small epiphytes, after
which the flycatchers would sally forth and glean
insects. (See under Parus elegans for another in-
cident of Sitta involved in a mixed species foraging
flock.)
Measurements— Wing— male (6) 77.0 ± 1.15,
76-79, female (8) 76.6 ± 1.58, 76-80; tail-male
(6) 39.3 ± 0.94, 38-41, female (8) 39.6 ± 1.80,
37-43; exposed culmen— male (6) 15.0 ± 0.65,
14.3-16.3, female (8) 14.4 ± 0.70, 13.5-15.4;
weight-male (6) 16.8 ± 0.56, 16.0-17.4, female
(8) 16.3 ± 0.73, 15.5-17.9.
Family Rhabdornithidae
We found the Stripe-headed Rhabdornis only
in the zone between 450 and 900 m, where it was
uncommon in primary and secondary forest. In
1 96 1 Rabor collected 1 3 specimens between 300
and 910 m; 2 taken in late March had enlarged
gonads. On 29 February 1988 a Stripe-headed
Rhabdornis was observed entering an excavated
hole in a tree, about 5 m above the ground, with
food in its bill.
This species was noted on two occasions in mixed
species foraging flocks. On 4 March 1988, one was
observed moving through the forest at 900 m rip-
ping up debris on trees, followed by three Phyl-
loscopus cebuensis. (See under Parus elegans for a
description of another mixed species foraging flock
incident.)
Measurements— Wing— male (9) 84.1 ± 1.20,
82-86, female (4) 82.5 ± 1.66, 81-85; tail-male
(9) 47.4 ± 1.64, 44-50, female (4) 45.5 ± 0.50,
45^46; exposed culmen— male (9) 21.3 ± 0.98,
20.0-23.2, female (4) 20.5 ± 0.28, 20.0-20.7;
weight-male (8) 27.8 ± 2.07, 23.5-30.9, female
(4)29.6 ± 0.71,28.5-30.3.
Family Timaliidae
*Napothera rabori sorsogonensis Luzon (Ra-
bor's) Wren Babbler
This species was obtained twice on Mt. Isarog.
One was captured in a mammal snap-trap placed
on the ground in primary forest at 900 m and
another at an unknown elevation. These speci-
mens were compared to the type of N. r. sorso-
gonensis taken in the Sorsogon Province, southern
Luzon, and they match the plumage characters
that distinguish this form (Rand & Rabor, 1967;
duPont, 1 97 1). A third individual was noted above
the 900 m camp foraging on the ground. The bird
was watched for a few minutes as it flipped over
leaf and wood debris while slowly walking across
the forest floor. Although the bird was never ac-
tually observed swallowing food, it appeared to be
eating invertebrates picked up from the ground.
Measurements— Wing— male (1) 91, unsexed
(1) 85; tail— male (1) 71, unsexed (1) in molt; bill
from nostril— male (1) 14.2; exposed culmen-
male (1) 21.1; weight— male (1) 65, unsexed (1)
57.
*Rhabdornis mystacalis mystacalis Stripe-
headed Rhabdornis
*Stachyris capitalis affinis Rusty-crowned Tree
Babbler
18
FIELDIANA: ZOOLOGY
Five specimens were taken by Rabor on Mt.
I sarog in 1 96 1 — four between 300 and 610m and
one at about 1 140 m. Birds taken on 25 March
and 1 9 April 1 96 1 had enlarged gonads.
Measurements— Wing— male (4) 70.5 ± 2.06,
67-72, female (1) 70; tail -male (4) 59.8 ± 2.27,
56-62, female (1) 60; exposed culmen— male (3)
14.5, 14.8, 15.4, female (1) 15.4; weight -male (4)
14.9 ± 0.90, 13.4-15.8, female (1) 15.6.
*Stachyris whiteheadi sorsogonensis Whitehead's
(Chestnut-faced) Tree Babbler
This species is one of the most common and
widely distributed birds on the slopes of Mt. Isa-
rog. Its abundance increased between 900 m and
the summit. Single individuals or flocks of up to
1 5 birds were regularly heard calling and moving
about in the forest above 1550 m. At the upper
altitudes the netting success of this species was the
highest of any bird (see p. 31). In the vicinity of
900 m it was uncommon and virtually all of the
records from this elevation are of netted individ-
uals.
On the basis of gonad size, the majority of spec-
imens we obtained in March 1988 were not in
reproductive condition, although a few, mostly
males, had slightly enlarged gonads; perhaps this
species was about to commence breeding. We ob-
served some apparent courtship begging and feed-
ing displays by adults. A substantial number of
the birds obtained by Rabor in April 1961 had
enlarged gonads, which would give credence to a
late spring/summer breeding season. On several
occasions this species was observed drinking water
held in pitcher plants (Nepenthes sp.).
Measurements— Wing— male (61)69.6 ± 1.54,
65-74, female (68) 67.7 ± 1.40, 63-71; tail-male
(60) 55.7 ± 1.24, 53-60, female (66) 54.6 ± 1.31,
50-58; exposed culmen— male (58) 15.21 ± 0.55,
14.0-16.1, female (65) 14.65 ± 0.58, 13.0-15.9;
weight-male(32)22.8 ± 1.96, 18.0-26.7, female
(35)21.0 ± 2.10, 17.0-26.2.
Family Pycnonotidae
*Pycnonotus urostictus urostictus Wattled Bul-
bul
The Wattled Bulbul was apparently confined to
areas near and below 900 m. Single birds were
collected on 10 March 1 988 at 900 m and 1 1 April
1961 at 450 m.
Measurements— Male (2)— wing 81, 83; tail 70,
74; exposed culmen 13.2, 13.6; weight 24, 27.
* Pycnonotus goiavier goiavier Yellow-vented
Bulbul
We found this species to be common in areas
with secondary growth at and below 450 m. Twen-
ty-two specimens were taken in 1961 by Rabor,
20 from below 380 m, and single birds from about
530 and 700 m. On the basis of gonad size, spec-
imens taken in late March and April were ap-
proaching breeding condition. Immature birds were
collected on 24 March and 24 April 1961. We
regularly noted small groups of Yellow-vented
Bulbuls in fig trees feeding on ripening fruits, a
food that on the basis of gizzard analysis (N = 12)
made up the predominant portion of their diet.
One stomach also contained insect parts.
Measurements— Wing— male (10) 85.1 ± 1.76,
83-88, female (13) 82.7 ± 3.14, 80-87; tail -male
(10) 78.0 ± 2.28, 75-81, female (13) 76.5 ± 1.94,
74-80; exposed culmen— male (9) 15.1 ± 0.45,
14.4-15.7, female (12) 14.8 ± 0.50, 14.0-15.4;
weight-male (7) 29.3 ± 1.28, 27-31, female (1 1)
29.3 ± 1.21, 27-31.
*Hypsipetes philippinus philippinus Philippine
Bulbul
The Philippine Bulbul was one of the most com-
mon birds on Mt. Isarog in areas up to 900 m;
neither Rabor nor our group found it any higher.
Birds were generally observed in secondary forest
or heavily disturbed areas. Specimens taken in both
March 1961 and 1988 and April 1961 had en-
larged gonads. A nestling was obtained on 24 March
and a fledgling on 9 April 1 96 1 .
Near 450 m, groups of up to five birds were
noted in Ficus trees feeding on ripening fruits, and
fig seeds were common in most examined stom-
achs. This species' diet is largely frugivorous, al-
though insects were found in gizzards of several
birds.
Measurements— Wing— male (17) 99.9 ± 2.04,
95-102, female (18) 95.0 ± 2.94, 89-100; tail-
male ( 1 6) 86.0 ±2.12, 82-90, female (18) 81.8 rb
2.85, 77-87; exposed culmen— male (17) 20.7 ±
0.78, 19.0-22.2, female (17) 19.6 ± 2.68, 19.4-
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
19
21.8; weight-male (19) 38.3 ± 2.66, 35-43, fe-
male (19) 36.9 ± 3.75, 31^8.
Family Irenidae
*Irena cyanogaster cyanogaster Philippine Fairy
Bluebird
The distinctive call of the Philippine Fairy Blue-
bird was heard daily, often as part of the dawn
chorus, in the vicinity of our 900 and 1125m
camps. At 450 m and 1350 m (the highest point
it was noted) this species was uncommon. Rabor
collected 17 specimens on Mt. Isarog, all of which
were from below 1060 m. Birds taken from late
March through April were in or approaching
breeding condition. The stomach of one specimen
was empty and another contained a few insect
parts.
Measurements— Wing— male (8) 136.8 ± 3.46,
131-142, female (9) 133.9 ± 3.38, 128-138; tail-
male (8) 104.6 ± 1.32, 103-107, female (9) 101.3
± 2.26, 98-104; exposed culmen— male (7) 25.8
± 1.09, 24.0-26.7, female (9) 26.2 ± 0.83, 24.6-
27.0; weight-male (9) 79.6 ± 3.72, 75-87, female
(9)77.4 ± 6.16,71-90.
Family Turdidae
*Brachypteryx montana andersoni White-browed
Short wing
The White-browed Shortwing was a character-
istic bird of areas with undisturbed forest. It was
uncommon at 900 m, common from 1 125 to 1350
m, and abundant from 1 550 m to the summit. We
did not record this species below 900 m. Rabor
obtained 1 5 specimens on the mountain, all above
1000 m, with the exception of a single female col-
lected at 610 m.
This species was regularly captured in snap-traps
placed on the ground for small mammals. The trap
success rate of Brachypteryx was highest on the
upper portion of the mountain (table 1), which
concurs with our estimates of altitudinal abun-
dance based on sight records.
This species was regularly heard singing on our
March 1988 trip during the predawn and dawn
chorus. Males would vocalize from the forest floor
or perches up to 1 m off the ground. Most adults
taken in March 1961 and 1988 and April 1961
had enlarged gonads. Immatures were obtained on
17 and 21 April 1961. Food remains in the stom-
achs of collected birds consisted of small insect
parts and occasionally land snails. The type lo-
cality of B. m. andersoni is Mt. Isarog (Rand &
Rabor, 1967).
Measurements— Wing— male (1 1) 66.9 ± 1.31,
65-70, female (12) 65.8 ± 2.27, 62-70; tail-male
(1 1) 44.5 ± 0.89, 43-46, female (1 1) 43.5 ± 2.53,
38^*8; exposed culmen-male (11) 12.9 ± 0.66,
11.7-14.0, female (11) 13.1 ± 0.51, 12.7-14.0;
weight- male (15) 16.9 ± 1.89, 13.0-20.0, female
(17) 18.5 ± 1.29, 16.0-21.0.
*Copsychus luzoniensis luzoniensis
browed Shama
White-
Rabor collected two adult male White-browed
Shama in mid- April 1961 between 450 and 610
m, one of which had slightly enlarged testes.
Measurements— Male (2)— wing 77, 80; tail 75,
76; exposed culmen 14.6, 15.5; weight 22.8, 25.3.
*Monticola solitarins philippensis Blue Rock-
thrush
Adult male specimens of the Blue Rockthrush
collected on Mt. Isarog include one with enlarged
gonads taken on 29 March 1961 between 1060
and 1 125 m and another on 1 April 1961 between
610 and 760 m. This species is a migrant to the
Philippines from the Asian mainland.
*Zoothera andromedae Sunda Thrush
This species was recorded only once on Mt. Isa-
rog. A male was netted on 14 March 1988 at 1 500
m; it had enlarged gonads.
Measurements— Male (1)— wing 125, tail 66,
exposed culmen 23.5, weight 81.
*Zoothera dauma aurea Scaly Thrush
The Scaly Thrush, a winter visitor to Luzon
from the Asian mainland, was recorded on a few
occasions at 450 m. Without exception it was not-
ed foraging on the ground, generally in undis-
turbed areas of forest. One bird was taken in a
mammal snap-trap placed on the forest floor.
20
FIELDIANA: ZOOLOGY
* Turdus poliocephalus mayonensis Island Thrush
The Island Thrush is one of the more widely
distributed forest birds on Mt. Isarog. We found
this species to be common at elevations at and
above 1 125 m. It was generally seen singly or in
pairs. It was one of the common songsters of the
predawn and early morning chorus.
The plumage coloration of Mt. Isarog birds is
similar to specimens of T. p. mayonensis taken in
the Albay Province of southern Luzon. This spe-
cies was regularly seen foraging on the forest floor,
and several birds were captured in mammal snap-
traps. The gonads of several specimens collected
in March 1988 and April 1961 were enlarged.
Measurements— Wing— male (10) 124.3 ±
2.24, 121-128, female (3) 117, 121, 127; tail-
male (10) 93.3 ± 2.15, 90-97, female (3) 88, 91,
96; exposed culmen- male (9) 19.8 ± 0.91, 18.5-
21.0, female (3) 19.1, 19.3, 20.4; weight- male (6)
70.5 ± 4.72, 64-77, female (3) 69, 77, 78.
Table 1 . Capture rate of Brachypteryx montana in
mammal snap-traps.
Transect
Total
point
Brachypteryx
Total
% Trap
(m)
taken
trap-nights
success
900
1
111
0.13%
1125
2
455
0.44%
1350
3
945
0.32%
1550
8
848
0.94%
1750
13
759
1.71%
*Megalurus palustris forbesi Striated Grassbird
This species was common in cleared and cul-
tivated areas with grass thickets at and below 450
m. Rabor collected an adult female on 23 March
1961 between 150 and 300 m.
*Megalurus timoriensis [tweeddalei] Tawny
Grassbird
*Turdus chrysolaus chrysolaus
Thrush
Brown-headed
Two Brown-headed Thrushes were netted on 9
March 1988 at 450 m. We did not otherwise ob-
serve this species on Mt. Isarog. It appears to be
a rare winter visitor to the lower elevations.
Weight- Unsexed (2) 57, 59.
We found the Tawny Grassbird to be uncom-
mon at about 450 m, where it was locally sym-
patric with M. palustris. Rabor did not collect this
species on Mt. Isarog, but he obtained two at Mt.
Bulusan, Sorsogon Province, southeastern Luzon,
on 1 May 1961 between 610 and 760 m.
*Cisticola exilis semirufa
headed) Cisticola
Bright-capped (Golden-
*Turdus obscurus Eye-browed Thrush
There are two records of this mainland Asian
migrant on Mt. Isarog. On 7 March 1988 an adult
was netted at 900 m and on 29 March 1 96 1 an-
other was taken between 910 and 1060 m.
WEiGH-rs-Male (2) 65, 85.
Family Sylviidae
*Cettia diphone canturians Japanese Bush War-
bler
An adult female Japanese Bush Warbler taken
on 7 April 1961 between 450 and 610 m is the
only known record of this mainland Asian migrant
from Mt. Isarog.
There is a single record of this species on Mt.
Isarog. An adult male with enlarged testes was
taken by Rabor on 3 1 March 1 96 1 at about 790 m.
*Phylloscopus trivirgatus nigrorum
Leaf Warbler
Mountain
The Mountain Leaf Warbler was common on
Mt. Isarog between 1 350 m and the summit. From
900 to 1 125 m it was uncommon, and we did not
record it lower. The exceptions are birds taken by
Rabor on 2 April between 610 and 760 m and on
12 April 1961 between 760 and 910 m. It was
generally observed singly or in groups of up to four
individuals, which tended to forage in the upper
portion of the canopy. Several birds taken in March
1988 and April 1961 had enlarged gonads. This
bird was noted in a mixed species foraging flock
(see under Rhipidura cyaniceps). There was essen-
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
21
tially no altitudinal overlap on the mountain be-
tween this species and P. cebuensis (table 2).
Measurements— Wing— male (14) 55.8 ± 1.32,
53-58, female (11) 53.5 ± 1.67, 52-57; tail-male
(14) 38.8 ± 1.08, 37-41, female (11) 37.1 ± 1.24,
35-38; exposed culmen— male (13) 9.6 ± 0.34,
9.0-10.5, female (9) 9.2 ± 0.48, 8.3-10.2; weight-
male (7) 7.3 ± 0.97, 6.0-9.4, female (6) 7.5 ±
1.08, 6.0-8.9.
observed moving through a patch of secondary
forest at about 870 m. According to Watson et al.
(1986) this form is the only one known from Luzon
and is restricted to the northern portion of the
island. A Mountain Tailorbird was captured in
1967 at Balian, Laguna Province, central Luzon
(McClure & Leelavit, 1972) and a male and female
of this species were collected on 22 March 1926
at Lucban, Tayabas, central Luzon (Baud, 1978).
*Phylloscopus cebuensis sorsogonensis Dubois'
(Lemon-throated) Leaf Warbler
We found this species uncommon at 450 m and
rare at 900 m. Rabor obtained 1 1 specimens: 3
between 300 and 450 m, 5 between 450 and 610
m, 1 between 610 and 760 m, and 2 between 910
and 1060 m. Virtually all of the specimens taken
in late March and April had enlarged gonads. Our
general impression was that this species forages at
a lower vertical level in the forest than P. trivir-
gatus.
P. cebuensis was noted on two occasions in mixed
species foraging flocks. (See the accounts of Rhab-
dornis mystacalis and Prionochilus olivaceus.)
Measurements -Wing -male (9) 58.0 ± 1.89,
55-61, female (3) 52, 53, 54; tail-male (9) 45.2
± 1.31, 43^*7, female (2) 38, 43; exposed cul-
men-male(9) 11.1 ± 0.26, 10.5-11.2, female (2)
10.6, 10.6; weight-male (9) 9.00 ± 0.39, 8.4-9.6,
female (3) 7.9, 8.8, 10.5.
*Orthotomus derbianus Grey-backed Tailorbird
We found the Grey-backed Tailorbird only in
the vicinity of 450 m, where it was uncommon in
grassy areas in and around secondary patches of
forest. Rabor collected eight specimens between
approximately 2 1 and 760 m, including a nestling
on 25 March 1961. The stomachs of two birds
contained small insects.
Measurements— Wing— male (5) 53.0 ± 0.89,
52-54, female (5) 50.6 ± 2.87, 46-54; tail-male
(3) 47, 52, 54, female (4) 45.8 ± 4.44, 40-51;
exposed culmen— male (5) 15.8 ± 0.43, 15.2-16.3,
female (5) 15.12 ± 0.89, 14.3-16.7; weight- male
(5) 10.9 ± 1.32, 9.0-12.4, female (5) 10.5 ± 0.55,
10.0-11.5.
Family Muscicapidae
*Ficedula hyperythra luzoniensis
Flycatcher
Snowy-browed
*Phylloscopus borealis cf. borealis Arctic War-
bler
Five specimens of the Arctic Warbler, a winter
visitor to the Philippines from Asia, were taken
on Mt. Isarog. All the material was collected be-
tween early March and mid- April 1988 in lowland
areas between 300 and 610 m. The plumage char-
acters used to distinguish among the potential
forms wintering on Luzon are not easily discern-
able and these specimens are tentatively assigned
to nominate borealis.
WEiGHT-Male (2) 8.5, 9.2; female (2) 8.5, 8.8.
We found this species to be uncommon at 1 125
and 1350m and rare at 1 550 m. One was captured
at 1350 m in a mammal snap-trap placed on the
ground. Rabor obtained males at 1060 m and be-
tween 760 and 910m; one taken on 1 1 April 1 96 1
had enlarged testes.
Measurements— Wing— male (3) 61, 62, 62;
tail— male (3) 43, 43, 46; exposed culmen— male
(3) 9.5, 11.1, 11.1; weight-male (3) 8.5, 10.0,
10.5, female (2) 9.5, 9.6.
*Ficedula westermanni westermanni
Flycatcher
Little Pied
Orthotomus cucullatus [philippinus]
Tailorbird
Mountain
There is only one record of this species from the
area. On 28 February 1988 a group of four was
The Little Pied Flycatcher was distinctly more
common between 1550 and 1750 m than between
1 1 25 and 1 350 m. The only record of it below this
latter zone is one collected by Rabor in 1961 at
about 1050 m. Single individuals were noted for-
22
FIELDIANA: ZOOLOGY
aging in the upper portion of the forest canopy.
On the basis of gonad size, only one of the spec-
imens collected was in or approaching breeding
condition; the exception was a female taken on 30
March 1 96 1 with an enlarged ovary. The stomachs
of two birds contained small insects.
Measurements— Wing— male (6) 60.0 ± 1.15,
59-62, female (4) 58.0 ± 1.87, 56-61; tail-male
(7) 41.1 ± 0.99, 40-43, female (4) 40.0 ± 0.71,
39—41 ; exposed culmen— male (7) 9.7 ± 0.60,9.0-
10.4, female (4) 10.0 ± 0.52, 9.1-10.3; weight-
male (4) 8.1 ± 0.56, 7.5-9.0, female (2) 8.0, 9.7.
erable variation was found in the bill length and
width of this species, which does not appear re-
lated to sexual dimorphism.
Measurements— Wing— male (8) 77.3 ± 2.49,
71-79, female (4) 77.5 ± 1.12, 76-79; tail-male
(8) 63.3 ± 1.92, 59-66, female (4) 60.5 ± 0.50,
60-61; exposed culmen— male (7) 10.8 ± 0.39,
10.0-11.3, female (4) 10.4 ± 0.46, 9.8-10.9; bill
from nostril-male (8) 7.6 ± 0.37, 6.9-8.2, female
(4) 7.4 ± 0.32, 6.9-7.7; bill width- male (6) 5.1
± 0.38, 4.5-5.8, female (4) 5.2 ± 0.22, 4.9-5.5;
weight-male (6) 17.4 ± 2.05, 14.0-18.7, female
(2) 18.9, 24.5.
*Cyornis herioti camarinensis Blue-breasted Fly-
catcher
Rabor collected a single Blue-breasted Flycatch-
er on Mt. Isarog between 300 and 450 m; this
specimen is the type of C. h. camarinensis (Rand
& Rabor, 1967). The bird was an adult male with
enlarged testes. He also obtained two individuals
of this form at Mt. Bulusan, Sorsogon Province,
southeastern Luzon, in early May 1961 between
450 and 990 m.
Measurements— Male— wing (2) 76, 76; tail (2)
57, 56; exposed culmen (2) 15.0, 14.2; bill from
nostril (2) 1 1 .4, 1 1 .2; bill width (2) 5.8, 5.8; weight
(1)21.4.
Muscicapa griseisticta Grey-streaked Flycatcher
We observed a single Grey-streaked Flycatcher
on 4 March 1 988 at 900 m in a thicket surrounded
by a partially cleared area of forest. Rabor col-
lected five females in the second half of April 1 96 1
between 450 and 910 m.
Weight -Female (3) 14.4, 15.6, 15.7.
Family Monarchidae
*Hypothymis azurea azurea Black-naped Mon-
arch
The only records from Mt. Isarog are an adult
female taken on 30 March 1 96 1 between 300 and
450 m and another female (with an enlarged ovary)
taken on 24 April 1961 between 210 and 300 m.
Measurements— Female— wing (2) 69, 70; tail
(2) 65, 70; exposed culmen (2) 12.4, 13.2; weight
(1)11.8.
Hypothymis helenae [helenae] Short-crested
Monarch
The Short-crested Monarch was rare and only
found in the vicinity of 900 m. A single male was
heard calling and observed two or three times in
the forest canopy near our camp.
*Rhipidura cyaniceps cyaniceps Blue-headed
Fantail
*Muscicapa (Eumyias) panayensis nigrimentalis
Philippine Verditer (Island Flycatcher)
We found this species to be uncommon across
a relatively broad zone on Mt. Isarog, from 900
to 1550 m. Rabor collected 10 specimens: 2 at
about 760 m, 1 between 760 and 9 1 m, 4 between
1060 and 1220 m, and 3 at 1670 m. Several birds
taken in late March 1 96 1 and 1 988 and April 1 96 1
had enlarged gonads. Singing Philippine Verditer
were noted on several occasions near our 900 m
camp, and two were observed feeding in a fig tree
on insects attracted to the ripening fruit. Consid-
The Blue-headed Fantail was one of the most
common and widely distributed birds and was re-
corded between 450 and 1550 m. It was found in
a variety of habitats ranging from heavily dis-
turbed secondary forest to virgin primary forest.
This species was regularly heard singing during our
March 1988 stay on the mountain. The gonads of
individuals collected in March 1 96 1 and 1 988 and
April 1961 were enlarged. Food remains in the
stomachs of several birds consisted exclusively of
insect remains.
This fantail was noted on two occasions in mixed
species foraging flocks. On 19 March 1988, one
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
23
Table 2. Altitudinal distribution of resident bird species on Mt. Isarog. 1
Elevation
450 m
Species
or below
900 m
1125 m
1350 m
1550 m
1750 m
Aviceda jerdoni
_
—
_
_
R
_
Pernis celebensis 2
—
*
—
—
—
—
Pernis apivorus 3
•
—
—
—
—
—
Haliastur indus 3
*
—
—
—
—
—
Spilornis holospilus
U
U
—
—
—
—
Accipiter virgatus
R
—
—
—
R
—
Hieraaetus kieneri*
*
—
—
—
—
—
Microhierax erythrogenys
*
u
—
—
—
—
Gallus gallus
—
R
—
—
—
—
Amaurornis olivaceus 3
*
—
—
—
—
—
Treron pompadora 3
*
—
—
—
—
—
Phapitreron leucotis
C
C
C
U/R
—
—
Phapitreron amethyst ina
•
u
—
—
—
—
Ptilinopus occipitalis 5
*
*
—
—
—
—
Ptilinopus leclancheri 6
*
*
—
—
—
—
Ducula aenea
u
—
u
—
—
—
Ducula poliocephala 3
*
—
—
R
—
—
Columba vitiensis 1
—
R
*
R
*
—
Macropygia phasianella
R
*
u
—
U
U
Chalcophaps indica
R
—
—
—
—
—
Gallicolumba luzonica 6
R
*
—
—
—
—
Cacatua haematuropygia
—
—
R
—
—
—
Bolbopsittacus lunulatus
U
R
—
—
—
—
Loriculus philippensis 2
u
•
—
—
—
—
Cuculusfugax
R
—
R
—
—
—
Cacomantis variolosus
C
C
C
U
R
—
Chrysococcyx xanthorhynchus 2
—
*
—
—
—
—
Surniculus lugubris 4
R
—
—
—
—
—
Eudynamys scolopacea
*
—
R
—
R
—
Phaenicophaeus superciliosus 2
U
*
—
—
—
—
Phaenicophaeus cumingi
U
u
—
—
—
—
Centropus viridis 6
u
*
—
—
—
—
Centropus unirufus 2
*
*
—
—
—
—
Otus longicornis
R
—
U/R
u
U
u
Otus megalotis
u
u
R
R
R
—
Ninox philippensis
c
c
U
—
—
—
Ninox scutulata 3
*
—
—
—
—
—
Batrachostomus septimus
*
—
—
—
—
—
Eurostopodus macrotis
c
—
—
—
—
—
[Collocalia vanikorensis]
c
c
C
C
U
u
Collocalia esculenta
c
c
c
c
c
c
Harpactes ardens 5
*
R
—
—
—
—
Ceyx cyanopectus
R
—
—
—
—
—
Ceyx melanurus 3
*
—
—
—
—
—
Halcyon chloris 3
*
—
—
—
—
—
Halcyon smyrnensis
u
—
—
—
—
—
Halcyon lindsayi
c
c
—
R
—
—
Eurystomus orientalis 3
*
—
—
—
—
—
Penelopides panini
u
u
—
—
—
—
Buceros hydrocorax 2
*
—
—
—
—
—
Megalaima haemacephala 3
u
—
—
—
—
—
Mulleripicus funebris
u
—
—
—
—
—
Dryocopus javensis
R
—
—
—
—
—
Dendrocopos maculatus
C
c
c
u
—
—
Chrysocolaptes lucidus
R
u
u
—
—
—
Pitta erythrogaster 3
*
—
—
—
—
—
Pitta kochi
—
—
—
R
—
—
Coracina striata 3
*
—
—
—
—
—
Coracina coerulescens 2
*
-
-
—
—
—
1 Records obtained from 1961 Rabor collection from Mt. Isarog = *. Records from 1988 expedition to the area:
A = abundant, C = common, U = uncommon, R = rare. See Materials and Methods for definitions of terms.
2 Specimen(s) taken up to 760 m.
3 Specimen(s) taken at or up to 610 m.
24
FIELDIANA: ZOOLOGY
Table 2. Continued
Elevation
450 m
Species
or below
900m
1125
m 1350 m
1550 m
1750 m
Lalage melanoleuca?
•
_
_
—
—
—
Lalage nigra
U
U
—
—
U
—
Pericrocotus flammeus 2
*
*
—
—
—
—
Dicrurus balicassius
c
u
—
—
—
—
Oriolus chinensis 2
u
*
—
—
—
—
Corvus macrorhynchos
c
—
—
—
—
—
Parus elegans
c
c
U
—
—
—
Sitta frontalis
u
c
*
U
—
—
Rhabdornis mystacalis
u
u
—
—
—
—
Napothera rabori
—
R
—
—
—
—
Stachyris capitalist
*
—
*
—
—
—
Stachyris whiteheadi
—
u
c
c
A
A
Pycnonotus urostictus
—
u
—
—
—
—
Pycnonotus goiavier 6
c
*
—
—
—
—
Hypsipetes philippinus
A
A
—
—
—
—
Irena cyanogaster
u
C
c
R
—
—
Brachypteryx montana*
*
U
c
C
A
A
Copsychus luzoniensis*
*
—
—
—
—
—
Zoothera andromedae
—
—
—
—
R
—
Turdus poliocephalus
—
—
c
c
C
C
Megalurus palustris
c
—
—
—
—
—
Megalurus timoriensis
u
—
—
—
—
—
Cisticola exilis*
—
*
—
—
—
—
Phylloscopus trivirgatus
—
u
u
c
C
c
Phylloscopus cebuensis
u
R
—
—
—
—
Orthotomus cucullatus
—
R
—
—
—
—
Orthotomus derbianus 2
u
*
—
—
—
—
Rhipidura cyaniceps
c
C
c
c
c
—
Ficedula hyperythra 2
—
*
u
u
R
—
Ficedula westermanni
—
—
u
u
C
c
Cyornis herioti
4i
—
—
—
—
—
Muscicapa panayensis
—
u
u
u
u
—
Hypothymis azurea
*
—
—
—
—
—
Hypothymis helenae
—
R
—
—
—
—
Pachycephala plateni
—
C
c
A
c
—
Pachycephala philippinensis 9
u
u
*
—
—
—
Anthus novaeseelandiae
*
—
—
—
—
—
Artamus leucorhynchus
*
R
-
—
—
—
Aplonis panayensis 3
*
—
—
—
—
—
Sarcops calms
c
R
—
—
—
—
Anthreptes malacensis*
*
—
—
—
—
—
Nectarinia sperata?
*
—
—
—
—
—
Nectarinia jugularis
*
—
—
—
—
—
Aethopyga flagrans
*
*
—
—
—
—
Aethopyga pulcherrima 2
—
*
u
c
u
—
Arachnothera clarae
R
—
—
—
—
—
Prionochilus olivaceus
U
R
—
—
—
—
Dicaeum bicolor
*
C
*
u
—
—
Dicaeum australe
c
—
—
—
—
—
Dicaeum trigonostigma 6
*
*
—
—
—
—
Dicaeum hypoleucum
c
R
—
—
—
—
Dicaeum pygmaeum
R
—
—
—
—
—
Zosterops nigrorum
C
U
—
—
—
—
Passer montanus
C
—
—
—
—
—
Erythrura hyperythra
—
R
—
—
—
—
Lonchura leucogastra 2
R
—
—
—
—
—
Lonchura malaccd i
*
—
—
—
—
—
Total number of species
95
64
31
24
22
9
4 Specimen(s) taken between 610 and 680 m.
5 Specimen(s) taken up to 1060 m.
6 Specimen(s) taken up to 700 m.
7 Specimen(s) taken up to 1 670 m.
8 Specimen taken at 790 m.
9 Specimen(s) taken between 1060 and 1220 m.
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
25
was observed moving through the forest at 1350
m, probing under and flipping over leaves. It was
followed within 20 m by one Phylloscopus trivir-
gatus and one Pachycephala plateni. (See under
Sitta frontalis for another mixed species foraging
flock incident.)
Measurements— Wing— male (9) 78.9 ± 2.81,
75-84, female (6) 76.0 ± 2.58, 71-79; tail-male
(9) 83.0 ± 2.79, 78-88, female (6) 79.2 ± 2.48,
74-81; exposed culmen— male (8) 11.2 ± 1.08,
10.0-12.6, female (6) 11.0 ± 0.62, 10.0-11.8;
weight- male (12) 13.6 ± 1.21, 12.0-15.6, female
(8) 13.5 ± 0.47, 13.0-14.1.
Family Pachycephalidae
* Pachycephala plateni crissalis Philippine Whis-
tler
We found the Philippine Whistler to be com-
mon or abundant between 900 and 1550 m. In
1961 Rabor collected 1 8 specimens on the moun-
tain, 1 1 of which were taken at 1670 m. This spe-
cies was observed in both secondary and primary
forest, and at the edge of cleared areas. There ap-
pears to be a small zone of altitudinal overlap on
the mountain between this species and P. philip-
pinensis (table 2).
The breeding season of the Philippine Whistler
seems to be variable from year to year. The gonads
of most adults collected in March 1 988 were small,
and this species was not breeding. Several im-
mature birds and recent fledglings were observed
and netted. This is in contrast to 1961 when the
majority of birds collected by Rabor between late
March and late April had enlarged gonads.
This whistler was noted on two occasions as a
member of mixed species foraging flocks. (See un-
der Rhipidura cyaniceps and Sitta frontalis.)
Measurements— Wing— male (16) 82.1 ± 1.36,
80-85, female (13) 80.4 ± 1.08, 78-82; tail-male
(16) 65.6 ± 1.97, 63-70, female (13) 65.2 ± 1.70,
63-68; exposed culmen— male (16) 14.7 ± 0.51,
13.9-15.8, female (12) 13.6 ± 2.91, 12.5-15.4;
weight-male (10) 21.2 ± 6.0, 19.0-25.2, female
(13)22.1 ± 1.84, 17.5-24.5.
*Pachycephala philippinensis philippinensis
Yellow-bellied Whistler
In the spring of 1988 the Yellow-bellied Whis-
tler was uncommon at 450 m and 900 m; it was
not recorded above this zone. Rabor obtained 14
specimens on the mountain in 1961, all of which
were taken below 760 m; the only exceptions were
nestlings obtained on 6 and 22 April between 1060
and 1 220 m. Several birds collected in late March
and April had enlarged gonads and appeared to
be in breeding condition. One specimen had beetle
remains in its stomach.
Measurements— Wing— male (6) 86.2 ± 3.02,
83-90, female (8) 82.6 ± 1.87, 79-85; tail-male
(6) 65.7 ± 0.75, 65-67, female (8) 62.5 ± 2.12,
58-66; exposed culmen— male (6) 15.6 ± 0.35,
15.0-16.1, female (8) 15.0 ± 0.84, 13.7-16.1;
weight-male (5) 23.7 ± 2.60, 21.0-27.3, female
(7)24.3 ± 1.95,21.0-26.9.
Family Motacillidae
*Motacillaflava simillima Yellow Wagtail
Two specimens were collected by Rabor on 24
April 1961 between 210 and 300 m. This species
is a winter visitor to Luzon from mainland Asia.
*Motacilla cinerea robusta Grey Wagtail
We found this species, a migrant to the Phil-
ippines from the Asian mainland, to be common
at 450 m near the Panicuason Central Nursery in
the vicinity of cleared areas and irrigated planting
beds. Rabor collected five females below 450 m;
his latest spring record was 24 April 1961.
WEiGHT-Female (5) 16.9 ± 2.26, 13.5-20.2.
* Ant hits novaeseelandiae lugubris Richard's
(Common) Pipit
The Rabor collection contains five birds taken
at Mt. Isarog on 23 and 24 April 1961, all below
300 m.
*Anthns gustavi gustavi Petchora Pipit
A pair of Petchora Pipits was obtained on 1
April 1961 between 610 and 760 m. This species
is a winter visitor to the Philippines from the Asian
mainland.
WEiGHT-Male (1) 23.1, female (1) 17.7.
26
FIELDIANA: ZOOLOGY
*Anthus hodgsoni hodgsoni Olive Tree Pipit
The single record of this mainland Asian mi-
grant on Mt. Isarog was a female taken on 28
March 1961 between 910 and 1220 m.
Family Laniidae
*Lanius cristatus lucionensis Brown Shrike
We found the Brown Shrike, a winter visitor to
the Philippines from the Asian mainland, to be
uncommon at 450 and 900 m. One was taken by
Rabor on 21 April 1961 at about 1 140 m. They
were generally observed perched in trees at the
edge of parang or heavily disturbed areas. The
stomachs of two birds contained insect remains.
WEiGHT-Male (8) 34.2 ± 4.20, 28.5^1.5, fe-
male (6) 32.3 ±3.31, 26.9-36.3.
Family Sturnidae
*Aplonis panayensis panayensis Philippine
Glossy Starling
The single record of this species on Mt. Isarog
is one obtained by Rabor on 29 March 1961 at
610 m.
Measurements— Female— wing 106, tail 68,
exposed culmen 17.0, weight 48.6.
*Sturnus philippensis Chestnut-cheeked Starling
The only record of the Chestnut-cheeked Star-
ling, a winter visitor to Luzon from Japan, is a
female taken on 4 April 1961 between 300 and
450 m.
Weight- Female (1) 28.8.
*Sarcops calvus calms Coleto
We found this species to be common in heavily
disturbed areas between 450 and 600 m, and it
was observed once at 900 m. It could often be seen
perched in dead trees in cleared fields or parang.
A pair collected in late March 1988 at 450 m had
slightly enlarged gonads and appeared to be ap-
proaching breeding condition. Rabor obtained
seven specimens in 1961, all below 760 m, in-
cluding a male with enlarged testes on 19 April
and a juvenile male on 25 April. The stomachs of
two birds contained small fruits and fig seeds.
Measurements— Wing— male (5) 130.6 ± 3.32,
124-133, female (3) 131, 134, 136; tail -male (5)
112.2 ± 2.71, 108-115, female (3) 108, 109, 115;
exposed culmen— male (5) 27.2 ± 0.68, 26.2-28.3,
female (3) 26.7, 26.7, 29.0; weight-male (5) 143.8
± 6.24, 133-150, female (2) 149, 160.
Family Nectariniidae
*Anthreptes malacensis birgitae
Sunbird
Brown-throated
The single record of this species on Mt. Isarog
is a female taken by Rabor on 26 April 1 96 1 be-
tween 450 and 610 m.
Measurements— Female (1)— wing 61, tail 35,
exposed culmen 18.5, weight 1 1.9.
*Nectarinia sperata sperata
Sunbird
Purple-throated
Two adult males were found by Rabor in late
March 1961 between 300 and 610 m. One had
enlarged gonads.
Measurements— Male (2)— wing 53, 56; tail 31,
31; exposed culmen 14.0, 15.7; weight 6.4, 8.2.
*Nectarinia jugularis jugularis
Sunbird
Olive-backed
Three male Olive-backed Sunbirds were ob-
tained by Rabor on 25 March 1961 between 150
and 300 m. These are the only known records of
this species for Mt. Isarog.
Measurements— Male— wing (3) 58, 59, 60; tail
(2) 38, 39; exposed culmen (2) 18.3, 18.6; weight
(3) 8.0, 9.9, 9.9.
*Aethopyga jlagrans jlagrans Flaming Sunbird
In 1961 Rabor obtained seven individuals of
this species on Mt. Isarog between 300 and 910
m. A male obtained on 1 1 April 1 96 1 had enlarged
testes.
Measurements— Wing— male (3) 50, 5 1, 52, fe-
male (4) 47.5 ± 1.12, 46-49; tail-male (3) 28,
28, 31, female (4) 25.3 ± 1.30, 24-27; exposed
culmen -male (2) 17.9, 18.2, female (4) 16.3 ±
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
27
0.39, 15.9-16.9; weight-male (3) 6.4, 6.5, 7.0,
female (3) 6.5, 6.5, 7.3.
female (2) 8.0, 8.6; weight-male (3) 10.0, 10.0,
10.0, female (2) 8.5, 9.0.
*Aethopyga pulcherrima jefferyi
(Metallic-winged) Sunbird
Mountain
We noted the Mountain Sunbird in the zone
between 1 125 and 1550 m. It was most common
at 1350 m, where males were regularly observed
singing and displaying, often from canopy perches.
Rabor obtained five specimens from elevations
between 610 and 1670 m, including a male on 18
April 1 96 1 with enlarged gonads. This species was
often found feeding on the contents of a red trum-
pet flower, a plant most abundant near 1350 m.
Measurements— Wing— male (2) 51, 52, fe-
male (3) 47, 48, 48; tail-male (2) 28, 29, female
(3) 24, 26, 26; exposed culmen— male (2) 21.5,
21.5, female (3) 16.3, 17.9, 18.5; weight-male (1)
6.2, female (2) 5.0, 6.3.
Arachnothera clarae [luzonensis] Naked-faced
Spiderhunter
This species was noted once in the area. On 29
February 1988, one was observed at the edge of a
relatively undisturbed patch of forest at 450 m.
Family Dicaeidae
*Prionochilus olivaceus parsonsi Olive-backed
Flowerpecker
This species occurs on the lower slopes of Mt.
Isarog. It was found to be uncommon at 450 m in
both secondary and primary forest and was ob-
served once at 900 m. Males taken on 25 March
1988 and 19 April 1961 were in or approaching
breeding condition. Several individuals were not-
ed at 450 m in a fig tree picking off and eating
flower buds; they were followed by two Phyllos-
copus cebuensis gleaning insects from the dis-
turbed vegetation. The stomach of one Olive-
backed Flowerpecker contained both insect and
plant remains. Mt. Isarog specimens are similar
in size and plumage coloration to material of P.
o. parsonsi taken in northern Luzon.
Measurements— Wing— male (3) 57, 59, 60, fe-
male (2) 50, 52; tail-male (3) 26, 27, 28, female
(2) 23, 24; exposed culmen— male (3) 8.5, 8.5, 9.5,
*Dicaeum bicolor inexpectatum Bicolored Flow-
erpecker
In 1988 the Bicolored Flowerpecker was com-
mon at 900 m and uncommon at 1 350 m. We did
not record it anywhere else on the mountain. In-
dividuals were seldom noted in the forest, and
most observations were of groups feeding in fruit-
ing trees. Thus, there was the impression that they
move some distance in search of food. Rabor ob-
tained 13 specimens in 1961 from altitudes be-
tween 450 and 1 220 m.
The breeding season of this species seems vari-
able from year to year. In March 1988 a few adults
had slightly enlarged gonads and the organs seemed
to be regressing; we also noted fledglings being fed
by adults. Most birds taken by Rabor in April 1 96 1
were in breeding condition, including a female on
8 April with a "ripe egg." He also obtained seven
fledglings in the last third of April.
This bird seems largely frugivorous. During ear-
ly March 1 988 a fig tree in a clearing at 900 m was
in fruit. Up to 20 Bicolored Flowerpeckers were
observed in the tree at any one time feeding on
ripening figs. The lack of other frugivores in the
area seemed odd; this species was the only fruit-
eating bird noted in the tree over the course of six
days.
Measurements— Wing— male (5) 53.2 ± 1.17,
52-55, female (3) 53, 53, 54; tail-male (5) 23.4
± 1.02, 22-25, female (3) 23, 23, 24; exposed
culmen-male (5) 8.0 ± 0.42, 7.2-8.4, female (2)
7.6, 8.5; weight-male (7) 9.3 ± 0.43, 8.7-10.0,
female (2) 8.8, 10.0.
*Dicaeum australe australe Philippine (Red-
striped) Flowerpecker
This species was common at 450 m. It was nol
recorded at any higher elevation. A female taken
on 25 March 1988 had enlarged ovarian follicles
and probably would have laid eggs within a fe\*
weeks. A male obtained on 26 March 1961 hac
enlarged testes. One bird had small insects in it;
stomach.
Measurements— Wing— male (2) 55, 57, fe
male (1) 53; tail-male (2) 27, 28, female (1) 25
exposed culmen— male (2) 10.0, 10.3, female (1
9.7; weight-male (2) 7.3, 8.0.
28
FIELDIANA: ZOOLOGY
*Dicaeum trigonostigma xanthopygium
bellied Flowerpecker
Orange-
Rabor obtained three adult males, all with en-
larged testes, on 24 March and 6 and 16 April
1961 between 300 and 700 m.
Measurements— Wing— male (3) 53, 53, 54;
tail— male (3) 24, 24, 25; exposed culmen— male
(3) 9.8, 9.9, 10.0; weight-male (3) 6.4, 6.7, 7.6.
*Dicaeum hypoleucum obscurum
(Buzzing) Flowerpecker
White-bellied
The White-bellied Flowerpecker was common
in the vicinity of 450 m and rare near 900 m. It
seemed most common in areas of disturbed forest.
Many individuals taken in late March 1961 and
1988 and late April 1961 were in or approaching
breeding condition. Some variation was found in
the foods consumed— stomachs contained small
buds and/or insects.
Measurements— Wing— male (8) 52.5 ± 1.66,
51-56, female (4) 52.0 ±0.71, 51-53; tail-male
(8) 21.8 ± 0.97, 20-23, female (4) 21.5 ± 0.87,
21-23; exposed culmen— male (8) 11.1 ± 0.35,
10.6-11.6, female (4) 10.9 ± 0.29, 10.6-11.3;
weight-male (8) 7.6 ± 0.60, 7.0-8.4, female (3)
7.0, 8.7, 9.0.
*Dicaeum pygmaeum pygmaeum
erpecker
Pygmy Flow-
The single specimen from the mountain, an adult
male in breeding condition, was netted on 30 March
1988 at 450 m.
Measurements— Male (1)— wing 46, tail 20,
exposed culmen 8.7, weight 4.0.
Family Zosteropidae
*Zosterops nigrorum luzonica Yellow White-eye
This species was found on the lower slopes of
Mt. Isarog. At 450 m it was common and flocks
of up to 20 were often seen feeding on swarms of
small insects. Single birds or pairs were occasion-
ally noted at 900 m where it was uncommon; we
have no records above this altitude. Two birds
taken in late March 1 96 1 had enlarged testes. One
taken in 1988 had small insects in its stomach.
Measurements— Wing— male (4) 52.8 ± 1.30,
51-54, female (2) 48, 51; tail-male (4) 35.0 ±
0.0, 35-35, female (2) 32, 35; exposed culmen—
male (4) 10.5 ±0.18, 10.2-10.7, female (2) 9.7,
10.2; weight-male (3) 8.0, 8.0, 9.2, female (2) 7.0,
8.7.
Family Ploceidae
*Passer montanus saturatus Eurasian Tree Spar-
row
This introduced species was abundant in areas
below 350 m, surrounding the mountain. Rabor
collected several adults in breeding condition,
fledglings, and immatures between late March and
late April 1 96 1 . The Mt. Isarog material was com-
pared to a series of P. m. saturatus from Japan
and P. m. malaccensis from Malaca. The crown,
wings, back, and rump color of Mt. Isarog birds
are distinctly pale and similar to saturatus.
Family Estrildidae
*Erythrura hyperythra brunneiventris Tawny-
breasted Parrotfinch
On 9 March 1988 an adult female, not in breed-
ing condition, was netted at 900 m in a partially
logged area. Its stomach was empty. The specimen
fits the description of E. h. brunneiventris given
by duPont (1971). A comparison of the bird with
specimens taken elsewhere in the Philippines
showed no plumage differences.
Measurements— Female (1)— wing 59, tail 32,
exposed culmen 9.5, weight 12.
*Lonchura leucogastra everetti
Munia
White-bellied
Records of the White-bellied Munia on Mt. Isa-
rog include one netted at 450 m on 5 March 1988
in a partially cleared area and one taken between
610 and 760 m on 2 April 1961. The latter bird
had enlarged gonads. Presumably this species and
the next are common in lowland agricultural areas.
*Lonchura malacca jagori Chestnut Munia
Rabor found this species in the zone between
450 and 6 1 m. A male collected on 1 6 April 1 96 1
had enlarged testes.
GOODMAN & GONZALES. BIRDS OF MT. ISAROG NATIONAL PARK
29
Measurements— Wing— male (2) 54, 57, fe-
male (3) 54, 55, 55; tail-male (2) 35, 36, female
(3) 33, 34, 36; exposed culmen— male (2) 11.1,
1 1.2, female (3) 10.2, 1 1.3, 1 1.6; weight-male (2)
11.7, 11.7, female (2) 10.1, 11.4.
Family Oriolidae
*Oriolus chinensis chinensis Black-naped Oriole
We found the Black-naped Oriole to be uncom-
mon and restricted to the area near 450 m. There
are 19 specimens of this bird in the Rabor collec-
tion, all of which were taken below 530 m, with
the exception of an adult male and female from
between 610 and 760 m. At least half of the birds
taken by Rabor were in or approaching breeding
condition. His collection also includes one fledg-
ling from 100 m and three from about 530 m, all
obtained in the second half of April 1961.
Measurements— Wing— male (9) 156.4 ± 4.79,
15 1-1 63, female (4) 157.5 ± 2.87, 153-160; tail-
male (9) 101.7 ± 2.11, 98-105, female (4) 104.0
± 1.87, 102-107; exposed culmen— male (8) 35.2
± 1.07, 33.6-36.5, female (3) 35.6 ± 0.78, 34.7-
36.6; weight-male (7) 94.0 ± 1 .77, 92-97, female
(3)98, 101, 101.
Family Dicruridae
*Dicrurus balicassius balicassius Balicassiao
The Balicassiao is a characteristic bird of the
lower elevations of Mt. Isarog. They were common
at 450 m and regularly seen singly or in groups of
up to five. This species was noted a few times at
the edge of the forest near the 900 m camp, but
not at any higher elevation. Rabor obtained 32
specimens of the Balicassiao on Mt. Isarog, none
of which were taken above 760 m. About half of
the specimens collected in late March 1961 and
1988 and April 1961 were in breeding condition.
The stomach contents of these birds consisted of
arthropods, including mantids, beetles, and spi-
ders.
Measurements— Wing— male (20) 142.3 ±
2.62, 138-147, female (16) 142.6 ± 2.71, 138-
147; tail-male (20) 112.9 ± 3.89, 106-120, fe-
male (16) 114.6 ± 3.37, 109-122; bill from nos-
tril-male (20) 20.5 ± 0.74, 18.9-21.6, female (16)
19.6 ± 4.98, 18.4-22.0; weight- male (16) 71.6
± 3.67, 63.3-78.8, female (14) 73.0 ± 4.28, 65-
80.
Family Artamidae
*Artamus leucorhynchus leucorhynchus White-
breasted Wood Swallow
We observed a single bird at about 800 m flying
over a clearing surrounded by secondary forest. In
1961 Rabor obtained eight specimens, including
four fledglings on 25 April, all from areas below
450 m.
Measurements— Wing— male (3) 132, 136, 136,
female (1) 133; tail-male (2) 59, 60, female (1)
57; exposed culmen— male (3) 17.7, 19.2, 20.0,
female (1) 19.0; weight- male (1) 41.6, female (1)
42.9.
Family Corvidae
*Corvus macrorhynchos philippinns Large-billed
Crow
This species was common at and below 450 m.
We generally noted it near cultivated lands and
rarely in forested areas. Rabor collected a nestling
between 240 and 300 m on 22 April 1961.
Discussion
On the basis of the combined information from
the 1961 and 1988 expeditions, a total of 1 16 res-
ident bird species have been recorded on Mt. Isa-
rog. Of these, 95 species were recorded at or below
450 ± 50 m, 64 at 900 ± 50 m, 31 at 1 125 ± 50
m, 24 at 1350 ± 50 m, 22 at 1550 ± 50 m, and
9 at 1750 ± 50 m. An additional 19 species of
migrants and winter visitors were also document-
ed. When the pattern of altitudinal distribution of
the resident birds was examined, several interest-
ing points and patterns emerged.
It needs to be stated that our work on Mt. Isarog
was not exhaustive and that aspects of the local
avifauna still remain unknown, particularly sea-
sonal movements and the distribution of rare and
secretive birds. The comparison of the Mt. Isarog
information with data sets from various moun-
tains in the Philippines gathered by other research-
30
FIELDIANA: ZOOLOGY
ers in a nonstandard manner presents further
problems. However, because there has not been
any published review of the altitudinal distribu-
tion of Philippine birds, we feel that even given
these potential problems the comparisons made
in the discussion section allow general trends to
be pointed out.
Altitudinal Overlap of Congeners
Of the 87 genera of resident birds on Mt. Isarog,
25 locally contain more than one species (range
from two to five). The elevational distribution
of these birds was analyzed by dividing the moun-
tain into the following zones: (1) parang and low-
land forest, approximately 200 to 900 m; (2) mon-
tane forest, 1 125 to 1350 m; and (3) mossy forest,
1 550 to 1 750 m. Among these 25 congeneric groups
three distinct patterns were found: complete alti-
tudinal sympatry, broad elevational disjunction,
or a small amount of overlap with apparent species
replacement.
Twelve of 25 (48%) congeneric groups occur in
parang and lowland forest and have completely
overlapping altitudinal ranges; these are Pernis,
Ptilinopus, Phaenicophaeus, Centropus, Ceyx,
Coracina, Pycnonotus, Megalurus, Orthotomus,
Hypothymis, Nectarinia, and Lonchura. We have
no information on finer level habitat preferences
of the members of any of these groups and it is
possible that some ecological segregation exists.
In 8 of 25 (32%) cases at least one species of a
congeneric group was confined to parang and low-
land forest and at least one other member occurred
sympatrically and also in montane forest. For ex-
ample, Phapitreron leucotis was found from pa-
rang to montane forest (up to 1350 m) and P.
amethystina only in parang and lowland forest.
Other congeneric groups showing a similar pattern
were Ninox, Halcyon, Lalage, Phylloscopus, Ae-
thopyga, and Dicaeum. Within a few of these groups
more than one species fits the pattern. Halcyon
chloris and H. smyrnensis were restricted to areas
at or below 450 m, while H. lindsayii occurred in
the same areas as well as up to 1 350 m. In lowland
areas five species of Dicaeum were sympatric, but
the range of only one, D. bicolor, extended up to
montane forest. The altitudinal distributions of
the Ducula and Pitta species groups were not suf-
ficiently well documented to clarify their range on
the mountain.
In the third distinctive pattern found, congeners
had broad distributions up the mountain and often
replaced one another within a narrow altitudinal
zone. Three of the 25 (12%) congeneric groups fit
this category. For example, Otus megalotis was
uncommon in parang and lowland forest, while
O. longicornis was rare in these areas and uncom-
mon in montane and mossy forest. The congeneric
groups of Ficedula and Pachycephala showed a
similar replacement pattern.
There is no single recognizable pattern in the
altitudinal ranges of congeneric groups on Mt. Isa-
rog; considerable variation was found within and
between genera. This is presumably related to the
ways different types of birds, whether closely re-
lated or not, respond to varying aspects of the
environment. Perhaps even more importantly,
subtle differences in the use of resources by con-
geners are difficult to quantify. Thus, our ability
to understand the role of competition (Terborgh,
1971) in molding these bird distributions is se-
verely hampered, but the apparent commonness
of elevational replacement of congeners was not
present on Mt. Isarog. A similar pattern has been
found in mainland Southeast Asian forests (Med-
way, 1972).
Densities of Birds Based on Netting
We used mist nets to assess densities of ground
dwelling and lower understory birds within the six
transect zones (Karr, 1981). Of the total 378 net-
days accrued between 3 and 31 March 1988, 97
were at 450 m, 54 were at 900 m, 56 were at 1 125
m, 79 were at 1350 m, 66 were at 1550 m, and
26 were at 1750 m (table 3). The number of birds
captured and the success rate per transect zone (=
total captured/total number of net-days) were 76
and 0.78, 44 and 0.81, 24 and 0.43, 51 and 0.65,
97 and 1.47, and 28 and 1.08, respectively. It is
important to note that the number of net-days per
transect zone was relatively low, particularly at the
1750 m camp, and the conclusions drawn from
this information should be considered tentative.
There does not appear to be any clear linear
relationship between bird density and altitude. The
highest density was found in the mossy forest zone,
where Stachyris whiteheadi was particularly com-
mon. This species accounted for 74 of 97 birds
netted at the 1 550 m camp and 23 of 28 netted at
the 1750 m camp. The lowest bird density was
found in the midsection of the montane forest at
1125 m and 1350 m. Moderate densities were
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
31
Table 3. Netting success on Mt. Isarog of resident birds captured between 28 February and 30 May 1988.
Elevation (Total net-days)
450 m
900 m
1125 m
1350 m
1550 m
1750 m
Species
(97)
(54)
(56)
(79)
(66)
(26)
Accipiter virgatus
1/0.01
_
_
1/0.02
Accipiter sp.
1/0.01
—
—
—
—
—
Microhierax erythrogenys
—
2/0.04
—
—
—
—
Phapitreron leucotis
—
1/0.02
—
—
—
—
Bolbopsittacus lunulatus
—
1/0.02
—
—
—
—
Cuculusfugax
—
—
1/0.02
—
—
—
Cacomantis variolosus
—
1/0.02
—
1/0.01
—
—
Otus longicornis
1/0.01
—
4/0.07
2/0.03
2/0.03
1/0.04
Otus megalotis
2/0.02
2/0.03
—
—
1/0.02
—
Ninox philippensis
5/0.05
3/0.06
—
—
—
—
Collocalia esculenta
—
1/0.02
—
—
—
—
Halcyon lindsayi
7/0.07
—
—
—
—
—
Dendrocopos maculatus
1/0.01
—
—
—
—
—
Dicrurus balicassius
8/0.08
—
—
—
—
—
Pants elegans
5/0.05
5/0.09
—
—
—
—
Sitta frontalis
—
2/0.03
—
—
—
—
Stachyris whiteheadi
—
6/0.11
3/0.05
30/0.38
74/1.12
23/0.88
Pycnonotus urostictus
—
1/0.02
—
—
—
—
Hypsipetes philippinus
17/0.18
7/0.13
—
—
—
—
Irena cyanogaster
—
1/0.02
—
—
—
—
Brachypteryx montana
—
—
1/0.02
5/0.06
4/0.06
1/0.04
Zoothera andromedae
—
—
—
—
1/0.02
—
Turdus poliocephalus
—
—
1/0.02
2/0.03
7/0.11
1/0.04
Phylloscopus trivirgatus
—
—
1/0.02
1/0.01
1/0.02
1/0.04
Phylloscopus cebuensis
1/0.01
—
—
—
—
—
Orthotomns derbianus
2/0.02
—
—
—
—
—
Rhipidura cyaniceps
6/0.06
4/0.07
3/0.05
2/0.03
1/0.02
—
Ficedula hyperythra
—
—
2/0.04
1/0.01
1/0.02
—
Ficedula westermanni
—
—
1/0.02
—
—
1/0.04
Cyornis herioti
1/0.01
—
—
—
—
—
Muscicapa panayensis
—
1/0.02
1/0.02
—
—
—
Pachycephala plateni
—
1/0.02
6/0.11
7/0.09
4/0.06
—
Pachycephala philippinensis
2/0.02
—
—
—
—
—
Prionochilus olivaceus
4/0.04
—
—
—
—
—
Dicaeum bicolor
—
3/0.05
—
—
—
—
Dicaeum australe
1/0.01
—
—
—
—
—
Dicaeum hypoleucum
10/0.10
1/0.02
—
—
—
—
Erythrura hyperythra
—
1/0.02
—
—
—
—
Lonchura leucogastra
1/0.01
—
—
—
—
—
Total success rate
76/0.78
44/0.81
24/0.43
51/0.65
97/1.47
28/1.08
Total success rate excluding
Stachyris whiteheadi
76/0.78
38/0.70
21/0.38
21/0.27
23/0.35
5/0.19
Total number of species
19
19
11
9
11
6
1 Entry given as total number captured per transect zone/netting success rate.
found in the lowland forest at 450 m and lower
montane forest at 900 m.
There was considerable variation in the range
and density of various groups on the mountain.
Owls were the most evenly distributed family.
Combining the data on the two Otus and one Ni-
nox (the main food of which is large invertebrates)
the rate of netting success was 0.07 at 450 m, 0.09
at 900 m, 0.07 at 1 125 m, 0.04 at 1350 m, 0.05
at 1550 m, and 0.04 at 1750 m. The flycatcher
guild (including Rhipidura and Pachycephala) ap-
peared to be more common at middle elevations
than at lower or upper zones. This is compared to
warblers, another group of insectivores, which were
sparsely distributed across the mountain. Flow-
erpeckers were netted with some frequency at 450
m (0. 1 5 netting success) and at 900 m (0.07 netting
success), but not at any higher elevation.
32
FIELDIANA: ZOOLOGY
A It it udinal Distribution of Birds on Mt. Isarog
and Other Philippine Mountains
with Mossy Forest
From our 1988 observations and the combined
1 96 1 and 1 988 collections, it is clear that the num-
ber of resident bird species on Mt. Isarog declines
with increasing altitude. We recorded 95 species
at or below 450 m, 64 at 900 m, 31 at 1 125 m,
24 at 1350 m, 22 at 1550 m, and 9 at 1750 m
(correlation of log-transformed data, P = 0.01, r
= 0.92, N = 6) (table 2). Similar patterns have
been described for montane avifaunas elsewhere
in the Philippines (see below) and in tropical areas
on other continents (Chapman, 1917; Terborgh,
1971, 1977; Diamond & LeCroy, 1979). Philip-
pine fruit bats show a parallel pattern of decreasing
density and species diversity with increasing al-
titude (Heaney et al., 1989). This pattern presum-
ably is related to decreasing habitat complexity
and usable primary productivity with altitude
(MacArthur et al., 1966; Orians, 1969; Kikkawa
& Williams, 1971).
For comparison with the pattern found on Mt.
Isarog, information on the altitudinal distribution
of birds on Mt. Malindang (2420 m), western Min-
danao, was tabulated from Rand and Rabor ( 1 960);
Mt. Halcon (2580 m), Mindoro, from Ripley and
Rabor (1958) and Morioka and Sison (1987); and
Canlaon Volcano (2500 m), Negros, from Ripley
and Rabor (1956). The taxa collected near Mt.
Halcon at Alcate, Makatok, and Lake Naujan
(Ripley & Rabor, 1958) have not been used in the
tabulation of species occurring on the mountain.
In order to put the ecology of these mountains in
context, particularly with respect to the habitats
on Mt. Isarog, the various altitudinal zones on
each will be briefly described.
On Mt. Malindang, 5 1 resident bird species were
collected between 600 and 1065 m, 49 between
1065 and 1370 m, 38 between 1370 and 1670 m,
22 between 1670 and 1975 m, and 18 between
1975 and 2420 m (correlation of log-transformed
data, P = 0.03, r = 0.9 1 , N = 5) (fig. 6). Rand and
Rabor ( 1 960) classified the habitats on the moun-
tain as: (1) cultivation, grassland, or second-growth
from sea level to 750 m (a small amount of original
lowland forest was interspersed in this zone up to
1065 m); (2) transitional lowland and montane
forest from 1065 to 1520 m; (3) montane forest
from 1520 to 1975 m; and (4) mossy forest from
1975 to 2420 m.
Fifty-three bird species have been documented
(mostly specimens, a few observations) on Mt.
Halcon between sea level and 750 m, 29 between
750 and 1065 m, 31 between 1065 and 1370 m,
26 between 1370 and 1670 m, 17 between 1670
and 1975 m, and 7 between 1975 and 2580 m
(correlation of log-transformed data, P = 0.03, r
= 0.86, N = 6) (fig. 6). The vegetation on the
mountain was classified by Ripley and Rabor
(1958) as: (1) lowland forest from sea level to 460
m (apparently when they visited the area in 1954
this section of forest had not been extensively
cleared); (2) transitional lowland and montane for-
est from 460 to 760 m; (3) montane forest from
760 to 1370 m; and (4) disjunct and interspersed
climbing bamboo and mossy forest from 1 220 to
2280 m. The summit of Mt. Halcon is covered
with clumps of short grasses and herbs, a few
shrubs, and no trees (Morioka & Sison, 1987).
On Canlaon Volcano, 68 resident birds were
collected between 760 and 1370 m, 14 between
1370 and 1975 m, and 1 1 between 1975 and 2490
m (correlation of log-transformed data, P = 0.18,
r = 0.96, N = 3) (fig. 6). The habitats were classified
by Ripley and Rabor (1956) as: (1) transitional
lowland and montane forest between 760 and 1 370
m; some cultivation and second growth was found
in this zone up to 1065 m; (2) montane forest
between 1370 and 1975 m; and (3) mossy forest
between 1 975 and 2500 m. The summit was most-
ly bare rock with some clumps of grasses.
In all cases the number of resident species on
each of these four mountains drops off with in-
creasing altitude (fig. 6). However, the rate of de-
crease, particularly at lower altitudes, and fluctu-
ations in the number of species as a function of
elevation, vary among mountains. A greater num-
ber of resident species occurs on the lower slopes
of Mt. Isarog than on any of the other three moun-
tains; this is at least in part an artifact, because
the lowest transect point on any of the four peaks
is on Mt. Isarog at 450 m. Further, Mt. Isarog is
the only mountain of the four on which obser-
vational information was used in the species tab-
ulations. There are few localities in the Luzon is-
land group where the lowland resident avifauna is
well known, at least in a parallel way to Mt. Isarog.
Probably the best comparison that can be made
is to Catanduanes Island, which lies 85 km from
Mt. Isarog (directly off southeastern Luzon) and
rises in elevation to just under 900 m. The number
of resident species occurring in the lowland forest
or parang on Catanduanes is 108 (Manuel, 1937;
Gonzales, 1983; Goodman & Gonzales, 1989),
compared to 1 1 1 at or below 900 m on Mt. Isarog
(table 2). These figures are presumably typical of
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
33
112
96 -
.2 80
O
<u
D-
<*-. 64
O
Vh
<u
.o
B 48
55
13
-32
H
16 -
Mt. Isarog,
Luzon\
Mossy Forest ^^
Montane Forest <S^
Trans. Montane / Lowland Forest CIZ>
Lowland Forest CZ^>
«—>..-— Mt. Canlaon, Negros
Mt. Halcon, \
Mindoro \_ \
■□;••
•. N N ^ Mt. Malindang,
'•. E3 Mindanao
V£
400
800
1200
1600
2000
2400
Elevation (m)
Fig. 6. Graph comparing the number of species occurring in distinct ecological zones and at various elevations
on four mountains in the Philippines. Data for Mt. Canlaon, Negros, are from Ripley and Rabor (1956); Mt. Halcon,
Mindoro, from Ripley and Rabor (1958) and Morioka and Sison (1987); and Mt. Malindang, Mindanao, from Rand
and Rabor (1960).
the number of resident birds found in comparable
types of lowland habitat throughout this portion
of the Philippines. The number occurring in the
lowland forest of Mt. Malindang, Mindanao, seems
low, and this may be an artifact of incomplete
information.
At middle to high elevations the number of res-
ident birds on the four mountains is similar. Al-
though the actual altitude of mossy forest varies
on these mountains, each appears to hold a rela-
tively similar number of resident birds in this zone
(altitude of mossy forest in parentheses): Mt. Isa-
rog(1550-1966 m)-7 species, Mt. Halcon (1975-
2580 m)-7 species, Canlaon Volcano (1975-2230
m)— 10 species, and Mt. Malindang (1975-2420
m)— 18 species (table 4).
Given these patterns, two questions may be
asked: ( 1 ) Is there a distinct set of species or genera
that tend to occur in the mossy forest of these
mountains? and (2) Is there a high degree of en-
demism among the resident birds of this distinct
ecological zone? When the number of species oc-
curring in the mossy forest zone of Mt. Isarog was
compared to those found in the mossy forest zones
of the other three mountains several interesting
patterns emerged: 3 of 7 species (43%) also occur
on Mt. Halcon, 5 of 1 (50%) also occur on Can-
laon Volcano, and 1 of 1 8 (6%) also occurs on Mt.
Malindang (table 4). Thus, there is considerable
variation between mountains and no distinct set
of species forms the mossy forest resident avifau-
na. Moreover, there is considerable variation in
the habitat preference of certain species between
the four mountains.
The only species that occurs in the mossy forest
of all four mountains is Phylloscopus trivirgatus.
Turdus poliocephalus and Brachypteryx montana
are found in this zone on three of the four moun-
tains, the exception being Mt. Malindang. Of the
30 species listed in Table 4, 19 are found on at
least two of the four mountains, but not necessarily
in the same ecological zones. For example, Bra-
chypteryx montana on Mt. Malindang was re-
stricted to transitional lowland/montane forest and
montane forest, but on Mt. Isarog it was found
from lowland forest to mossy forest. Parus elegans
on Canlaon Volcano and Mt. Halcon is a mossy
forest bird, but on Mt. Isarog it is common at low
34
FIELDIANA: ZOOLOGY
Table 4. The species composition of mossy forest avifaunas on four mountains in the Philippines.
Mt. Malindang,
Canlaon Volcano,
Mt. 1 1 a Uon.
Mt. Isarog,
Mindanao
Negros
Mindoro
Luzon
Species
(1975-2420 m)
(1975-2230 m)
(1975-2580 m)
(1550-1966 m)
Gallus gallus
X
+
+
+
Phapitreron amethystina
X
+
+
+
Macropygia phasianella
+
X
+
X
Cuculus fugax
X
+
+
+
Otus longicornis
X
Chrysocolaptes lucidus
X
+
+
Coracina ostenta
X
Coracina mcgregori
X
Parus elegans
+
X
X
+
Stachyris whiteheadi
X
Brachypteryx montana
+
X
X
X
Zoothera andromedae
X
+
+
Turdus poliocephalus
+
X
X
X
Bradypterus caudal us
X
Phylloscopus trivirgatus
X
X
X
X
Rhipidura nigrocinnamomea
X
Ficedula hyperythra
X
X
+
+
Ficedula westermanni
+
X
X
Muscicapa panayensis
X
+
+
+
Pachycephala philippensis
X
+
Pachycephala plateni
X
+
+
Lanius validirostris
+
X
Dicaeum nigrilore
X
Aethopyga boltoni
X
Aethopyga pulcherrima
+
+
Zosterops montanus
X
X
X
Zosterops nigrorum
+
X
+
Lophozosterops goodfellowi
X
Hypocryptadius cinnamomens
X
Pyrrhula leucogenys
X
Total/mountain
Number shared with Mt. Isarog
Number species shared with Mt. Isarog
but occurring at lower elevations
18
1
10
5
1 This table does not include altitudinally roaming species such as swifts, x = present in mossy forest, + = present
on respective mountain but not in mossy forest. A blank indicates that the species is unknown from that mountain.
and uncommon at lower middle elevations. This
pattern is opposite that found in other high-moun-
tain tropical avifaunas, such as the Andes (Haffer,
1987), areas of peninsular Malaysia (Medway &
Wells, 1976), New Guinea (Beehler, 1981), and
widely disjunct mountain ranges in Africa (Mo-
reau, 1966; Dowsett, 1986), where many bird spe-
cies have altitudinally limited, yet geographically
extensive ranges.
What about species restricted or endemic to
mossy forest? Eleven of the 30 (37%) species found
in mossy forest on the four mountains (table 4)
occur on only one of the four mountains. Two of
these species are restricted to Luzon: Otus longi-
cornis is found at all elevations of Mt. Isarog and
at other localities, and Stachyris whiteheadi occurs
at lower elevations on Mt. Isarog and on numerous
other mountains (duPont, 1971). The latter species
shows a considerable amount of geographical vari-
ation on Luzon, which may be related to differ-
entiation on nonconnected mountain chains
(Goodman & Gonzales, unpubl.). Coracina osten-
ta was the only 1 of the 1 1 species that was re-
stricted to Canlaon Volcano. However, this bird
is also known from the islands of Panay and Gui-
maras (duPont, 1971); these two islands were con-
nected to Negros in the late Pleistocene (Heaney,
1 986). No bird species was restricted to the mossy
forest on Mt. Halcon. The situation on Mt. Malin-
dang is distinctly different; of the 1 1 species in the
sample that are restricted to a single mountain, 8
were found only on Mt. Malindang. Of these, six
are Mindanao endemics: Coracina mcgregori,
Rhipidura nigrocinnamomea, Dicaeum nigrilore,
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
35
Aethopyga boltoni, Lophozosterops goodfellowi, and
Hyprocryptadius cinnamomous. Three of the six
(Rhipidura, Aethopyga, and Lophozosterops) show
geographical variation among several Mindanao
mountains, while the other three are distributed
across the island but have no recognized subspe-
cies (duPont, 1971). Thus, although restricted to
the island, none of these six birds is endemic to a
single mountain. The remaining two of the eight
Mindanao mossy forest birds are Bradypterus cau-
datus, which has three distinct geographical forms
occurring on Mt. Malindang and Mt. Apo (Min-
danao) and northern Luzon, and Pyrrhula leuco-
gonys, which has two distinct subspecies, one on
Mindanao and the other in northern Luzon.
There is no known bird species exclusively en-
demic to the mossy forest of any of these four
mountains. Many of the taxa listed in Table 4
show great variability among mountains in their
preferred habitat and altitudinal range. Thus, it
appears that a substantial number of mossy forest
birds found on these peaks are drawn from a pool
of species adapted to a range of habitats rather
than from an endemic and/or geographically re-
stricted set of mossy forest taxa. The exception is
Mt. Malindang, or more precisely Mindanao, an
island that shows a higher degree of endemism;
however, these endemics are not restricted to the
mossy forest zone of any single peak. All six Min-
danao mossy forest endemics discussed are mem-
bers of different bird families and clearly are not
the result of a single invasion and subsequent ra-
diation.
Changes in the Resident Avifauna of
Mt. Isarog Between 1961 and 1988
Although we have no quantifiable data on the
amount of time that members of the 1961 expe-
dition to Mt. Isarog spent at each elevational zone,
it is clear from their collections that the complete
altitudinal range of the mountain was surveyed.
Information associated with the preferred eco-
types of many of the birds collected and inscrip-
tions (particularly elevation) on the specimen la-
bels allow some inference to be made about the
condition of the Mt. Isarog lowland forest in 1961.
When Rabor conducted the 1961 survey, the
area of Mt. Isarog below 450 m was probably to
a large extent already cleared of the original forest
and composed of large tracts of agricultural lands
and parang (essentially as we found it in 1988).
Below 450 m, he collected a long series of species
associated with parang and modified areas and few
specimens of birds characteristic of typically un-
disturbed woodland. In 1 96 1 the forest from about
450 to 900 m was presumably largely intact except
for relatively small clearings made by shifting sub-
sistence agriculturalists. Since 1 96 1 this zone has
been subjected to extensive logging and partial
clear-cutting. The evidence for this is based on
differences between the species collected in 1961
and 1988 (see below). In 1988 we found no tracts
of undisturbed lowland forest between 450 and
900 m larger than a few hectares. The forest above
900 m remains relatively intact, and the only clear
disturbance is the extensive cutting of rattan.
A combined total of 1 1 6 resident birds was found
on the mountain by the 1961 and 1988 surveys.
Of these, 95 occurred at or below 450 m, 64 be-
tween 450 and 900 m, and 30 above 900 m. When
these data are analyzed as the number of species
found in a given zone by one survey and not the
other, a startling pattern emerges. With one ex-
ception, differences between the 1961 and 1988
surveys in the number of species collected in any
of these altitudinal zones varied from about 6 to
1 3% (table 5). This degree of variation is presumed
to be largely sampling variation in the total num-
ber of species recorded per zone by each survey
(relative to the other) and/or some aspect of spe-
cies turnover. The only exception was the area
between 450 and 900 m, where the 1961 survey
found 27 species (42% of the total known from
this zone) not recorded by the 1988 workers. This
dramatic change is in exactly the habitat that has
undergone the greatest ecological degradation in
the past few decades. Thirty-four species (29%)
collected on Mt. Isarog in 1961 were not found in
1988, and are presumed to be locally extirpated.
Of these 34 species, 21 (62%) were recorded by
Rabor only at or below 610 m and 28 (82%) only
at or below 760 m. Further, of these 34 species,
10 (29%) are relatively large (> 100 g), 4 (12%) are
predators, and 5 (15%) are considered particularly
good for eating. Local human-caused extinction
of birds resulting from the clearing of forest and
to a limited extent by hunting, has most severely
impacted large, raptorial, and good-tasting birds.
It is clear that when the forest is destroyed species
are locally extirpated, and that hunting can have
a significant impact.
The State of Mt. Isarog National Park
Mt. Isarog National Park was established 20
July 1938 by governmental proclamation no. 293.
36
FIELDIANA: ZOOLOGY
Table 5. Differences in the number of resident species found on Mt. Isarog in 1961 and 1988.
At or
below 450 m
(95)'
Between
450 and 900 m
(64)
Above 900
(30)
Total
(116)
Collected in 1961 but not in 1988
Collected in 1988 but not in 1961
7 (7.4%)
6 (6.3%)
27 (42.2%)
4 (6.3%)
2 (6.7%)
4(13.3%)
34 (29.3%)
9 (7.8%)
Number in parentheses is the total number of species recorded for the column heading.
It comprises an area of about 10,110 hectares (Parks
and Wildlife Office, 1968). The park has been not-
ed as a health resort with spectacular canyons,
gorges, ravines, and waterfalls, and as a game ref-
uge.
We have no specific information on the area
from its establishment as a national park to the
early 1960s. As discussed on p. 36, when Rabor
visited the park in spring 1 96 1 some undisturbed
tracts of lowland forest still remained in the zone
between 450 and 900 m. During the past few dec-
ades there have been continuous logging activities
in the area. In 1977 the Bicol area (Region 5),
composed of the Catanduanes, Camarines Norte,
Camarines Sur, Albay, Masbate, and Sorsogon
provinces, had an estimated 144,085 hectares of
virgin forest; by 1988 this had been reduced to
16,885 hectares. Thus, on the average of 12,720
hectares of virgin forest were lost each year during
this period (Principe, 1988). Although the 1977
figure may have been exaggerated, the extent of
logging in the area has been ecologically devas-
tating. In August 1983 the government posed a
complete logging ban in the region, apparently to
no avail. At present, only about 1 ,000 hectares are
being reforested annually with important timber
trees. Even some of the reforested areas are being
invaded by kaingineros and laid to waste.
During our spring 1988 field season, the drone
of chain saws could be heard from before sunrise
to after sunset in forested areas within the national
park boundaries. With alarming frequency we
could feel the ground tremble as the remaining
large dipterocarps came crashing down. These il-
legal, large-scale cutting operations were not con-
ducted independently by slash and burn agricul-
turalists, but rather by well-financed commercial
operators.
In 1975 it was estimated that 250 settlers lived
within the Mt. Isarog National Park (IUCN Trop-
ical Forest Programme, 1988). During our 1988
visit it was clear that this number had increased.
There were several settlements just outside the
park boundaries. Because of the steep topography
and the few large dipterocarp trees, the area above
900 m appears to be relatively safe from forest
clearing. Rattan is regularly gathered from the zone;
however, this activity presumably has a negligible
effect on the local forest. Our impression was that
the majority of forest clearing within the park
boundaries below 900 m had been initiated by
large-scale operations for lumber and not slash and
burn agriculturalists for crop lands. Once the pri-
mary forest had been removed, the kaingineros
further cleared, maintained, and planted the area.
Thus, the greatest current threat to the Mt. Isarog
National Park is the illegal commercial logging
operations.
The remaining tracts of undisturbed forest in
the Mt. Isarog National Park are in immediate
need of protection. This could be accomplished
by the deployment of rangers in the area to enforce
existing laws against illegal logging, strict legal
prosecution against offenders, and the establish-
ment of a local education program directed toward
information about habitat destruction and water-
shed management. We are aware that these sug-
gestions would only provide short-term relief; the
real solution for the Philippines and many other
places in the world will only come after extensive
social reforms to alter present economic systems
that are based on the exploitation of natural and
human resources.
Acknowledgments
Other participants in the 1988 Mt. Isarog sur-
vey included Arcinio Batal, Renato Fernandez,
Lawrence Heaney, Fernando Jumalon, Myrissa
Lepiten, Maylene Laranjo, Jacinto Ramos, Eric
Rickart, Douglas Samson, David Schmidt, Leo-
ning Tag-at, and Ruth Utzurrum. Many local peo-
ple living in the Mt. Isarog area provided assist-
ance. Officials of the Philippine Bureau of Forestry
Development allowed us access to the facilities at
the Panicuason Central Nursery. Messrs. Narvaja
GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
37
and Basmayor and officials of the Bicol University,
College of Fisheries, Tabaco, Albay, provided
transportation and helped in numerous ways. The
ornithological work could not have been accom-
plished without the gracious help of all of these
people; to all we extend our warmest thanks. A
grant from the Thomas J. Dee Fund, Field Mu-
seum of Natural History, Chicago, allowed SMG
to study the 1 96 1 Rabor collection from Mt. Is-
arog. Gene Hess, Delaware Museum of Natural
History; Julio Leuterio, College of Forestry, Uni-
versity of Philippines at Los Baiios; and David
Willard, Field Museum of Natural History, kindly
allowed us access to material in their care. We
acknowledge financial support from the Philippine
National Museum, the Smithsonian Institution,
and the U.S. National Science Foundation (BSR-
85 14223 to L. R. Heaney). Mr. BritGriswald kindly
drafted Figures 1 and 6. For comments on an ear-
lier draft of this paper we are grateful to Drs. L.
R. Heaney, R. S. Kennedy, E. A. Rickart, R. W.
Storer, and an anonymous reviewer.
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GOODMAN & GONZALES: BIRDS OF MT. ISAROG NATIONAL PARK
39
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