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UNITED STATES DEPARTMENT OF AGRICULTURE

et ER POO

DEPARTMENT BULLETIN No. 1196

Washington, D. C. January, 1924

FOOD AND ECONOMIC RELATIONS OF NORTE AMERICAN GREBES.

By ALEXANDER WETMORE, Assistant Biologist, Division of Biological Investiga-
tions, Bureau of Biological Survey.

CONTENTS.

. Page. , Page
END DS 7 (es i, poVestern: erebe fo eo 2 eee : 5
Distribution and habits of grebes_ 1, Helboell grebe 2242 z= acter; eee 7
Breseraprien se = vn EES 2 Horned grebe_______ ey Ss) 2 10
Nests, eggs, and <A banal oa eee 20). Warned 2rebels 23) So) a eee 15
Economic relations_____ i Se 3 | Mexicam prebe.. 2-2. ==% Bee 18
| LOTTE RS io a re ns 4, .\"Pied-billed’ (grebe’=2_ 4. = "ee ee 19

4 Erercered Status = = 42-2. ts = 4 |

INTRODUCTION.

—_—

_ A knowledge of the feeding habits and general economic status of
| the species of grebes inhabiting the different sections of the United

States is of importance in connection with the relations of these birds
to the supply of food fishes. Living in ponds, lakes, and water-
courses, grebes have at times been suspected of being seriously detri-
mental to the continuance of certain valuable fishes. That this
| suspicion is without actual foundation in fact has been ascertained
in the investigations reported upon in this bulletin.

DISTRIBUTION AND HABITS OF GREBES.

Six species of grebes are found in North America north of the
Isthmus of Panama, all of them ranging within the limits of the
United States. These birds breed in the interior, but during their
migrations are found on salt water along our coasts as well as on
open ponds and streams throughout the country. Their almost
supernatural powers of diving to escape a shot are common knowl-
edge among hunters, from the boy armed with a small-bore rifle to

fe

1 Prepared by the author when a member of the present Division of Food Habits Re-
search.

Note.—This bulletin presents a detailed study of the food and feeding habits of the
six species of grebes that occur in the United States. It will serve as an index to the
economic status of these birds, and will be useful to naturalists, sportsmen, conservation-
ists, and others interested in waterfowl.

60230—23——-1
=

i

2 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

the sportsman with heavier equipment, and have earned for grebes
the common appellations of water-witch, hell-diver, and didapper.
In diving suddenly grebes spring forward and disappear head fore-
most, moving so quickly as to be below the surface before a charge
of shot can reach them. When not alarmed grebes often sink slowly
beneath the surface, and may remain for some time with only the
head projecting, maintaining their position through a lateral, rotary
motion of the strong, broadly lobed feet.

Under normal conditions grebes are quiet birds, spending their
time during most of the year, when not feeding, in swimming slowly
about, resting quietly, or in preening and caring for their plumage.

During the breeding period they become more active and exhibit | 1)

many pleasing habits and mannerisms unsuspected from their de-
meanor at other seasons. Several species have a peculiar “ dance ”
in which both birds, treading water and calling excitedly, stand bolt
upright on the surface in an attitude resembling miniature penguins.

DESCRIPTION.

The entire form of grebes has been modified in adaptation to their
watery habitat. The body is long, rather slender, and compressed,
the plumage close and dense, wholly impervious to moisture, and the
strong, heavy. legs are at practically the posterior end of the body.
The apparent position of the legs is accentuated by the form of the
tail, which is represented by only a few filamentous feathers, so that,
save on close examination, it appears to be absent.

The wings are short, and small in surface compared to the weight |

of the body, so that grebes prefer to trust to their marvelous agility
in diving to escape pursuit rather than attempt to fly. When flight
is necessary the birds rise in the air only after gaining momentum by
paddling with swiftly moving wings and feet for a hundred yards
or more along the surface of the water. When in the air they have
a direct, strongly sustained flight which carries them for long dis-
tances during their extended spring and fall migrations. In diving.
grebes usually hold the wings in closed position at the sides, but
they have also been observed to use them in swimming under water.

NESTS, EGGS, AND YOUNG.

The nests of grebes are made of masses of decaying vegetation
piled up in shallow water to form a mound that barely projects above
the surface. The eggs, laid in a depression on the summit of this
heap, lie almost in the water; they are often passed unnoted, as the
female invariably covers them carefully with some of the nest ma-
terial before leaving, unless frightened away by the sudden appear-
ance of an intruder.

On hatching, the down-covered young birds swim readily, with
the foreneck and breast submerged, so that only the head and
posterior portion of the back project above the water. They tire
easily, however, and with plaintive whistles approach the mother,
who depresses her back, allowing the young to scramble up on this
living raft, where they take refuge under the long inner feathers
of her wings while she swims slowly away. (See fig. 4, p. 19.) In
a few days the young become more expert in the water and hide

5 a 3 PN IE ER, ge APS 6 he
— » iy, >

NORTH AMERICAN GREBES. a

among the growths of aquatic vegetation, so that until they are at
least two-thirds grown it is difficult to observe them. After the
_ young are well grown, the adults disappear for a time in order to
molt, resorting for the purpose to dense growths of rushes, where
_ they remain in seclusion for a period of three or four weeks. Like
_ ducks and geese, they shed all the wing feathers simultaneously
- and are then unable to fly.

ECONOMIC RELATIONS.

The food of the grebes, as would be expected, is made up largely
of aquatic organisms belonging to a variety of groups. Of these,
_ fishes are perhaps of greatest importance in establishing the economic

status of these peculiar birds. The western and Holboell grebes,
the largest of the six forms of the family found within our limits,
_ take more fishes than do the smaller species, but on the whole they
- can not be considered actually injurious, as the kinds eaten are in
most cases of little or no value to man.
| From the basis of the present studies it can not be said that any
_ species of grebe is directly inimical to the fishing industry. Grebes
which alight during migration in ponds at fish hatcheries may do
serious damage, and in such places it is advisable to drive them away
_ or destroy them if Federal and State laws permit.? This stricture
applies in the main, however, to only one species, the pied-billed
grebe, as only occasionally do the other forms appear in such locali-
ties. ‘The sacrifice of the few pied-billed grebes which it may be
necessary to kill for this reason can have little or no effect upon the
abundance of these widely distributed birds.
_ With the exception of the large western grebe (which so far as
_ known at present feeds only upon fishes), all of our grebes feed
_ extensively upon crustaceans, and when more material is available
_ for study it is possible that this species also may be found to eat
this kind of food. The Holboell grebe takes many marine crusta-
eeans, as do the horned and eared grebes. The two last mentioned
_and the pied-billed grebe destroy also many crawfishes. The feeding
of the pied-billed grebe is especially beneficial in this manner in
localities where crawfishes are destructive to crops.

Aquatic Coleoptera (beetles) and Heteroptera (bugs) figure
largely in the food of the smaller grebes, and that of the pied-
billed grebe shows that the birds prey extensively upon giant water-
bugs and predacious water beetles, insects that are reputed to be
_ seriously destructive at times to the small fry of fishes. Eared
and horned grebes in summer often act the part of scavenger in
_ feeding upon the masses of miscellaneous insects found floating on
the water. During the flights that occur as these forms emerge in
the adult state, frequently bays and ponds are covered with the
bodies of such of these creatures as have attempted to alight, only
to be entrapped by the water and drowned. From this source
these grebes secure a greatly varied insect fare, but one, however, of
no particular economic significance.

*For a summary of the provisions of Federal, State, and Provincial game laws, see

_ the latest annual Farmers’ Bulletin on the subject (that for the season 1923-24, Farmers
_ Bulletin No. 1375, U. S. Department of Agriculture).

4 BULLETIN 119, U. S. DEPARTMENT OF AGRICULTURE.

FEATHER EATING.

All of our species of grebes have the peculiar habit of eating
quantities of their own feathers, masses of which were found in
practically every stomach opened. This fact has been recognized
' by naturalists for many years, though in numerous instances the
feather remains have been mistaken for miscellaneous substances,
ranging from the hair of mammals to silky vegetable fibers. Why
these feathers are eaten and what part they may play in the economy
of the bird are points on which we have no definite knowledge. The
feathered covering of grebes is dense and abundant, and the writer
on various occasions has observed the birds preening and arranging
their plumage. Feathers loosened during this process are sometimes
discarded and sometimes dabbled in the water, to be moistened and
then swallowed.

The stomach of the grebe has a small accessory chamber (a
pyloric lobe) in which the opening into the small intestine is found.
This lobe is almost invariably plugged with a ball of feathers, even
though feathers are absent in the main chamber.

It is noticed that feathers occur in greatest abundance and most
commonly in stomachs containing remains of fishes and hard-bodied
insects, and that they are less abundant (or are even occasionally
absent) in gizzards containing soft-bodied larvae or crustaceans
that are easy of digestion and assimilation. It may be suggested
that the feathers act as a strainer to prevent the passage of fish
bones or large fragments of chitin into the intestine until they
have been reduced to a proper size and condition by the process of
digestion. In this way injury to the intestinal walls from these
hard fragments may be avoided.

Whatever the use of feathers, they can not be held to have any
considerable food value, even though they are constantly ground
up and passed on into the intestinal tract. In the accounts of the
individual species, therefore, though the presence of feathers in these
stomachs has in each case been estimated as a matter of interest,
this item has been discarded before the actual food content is ap-
portioned on the basis of 100 per cent.

PROTECTED STATUS.

Prior to 1903 many thousands of grebes were killed by hunters
for the sake of their beautiful breast feathers, which attracted atten-
tion in commerce. The western grebe especially suffered heavily
from the whim of feminine fashion, as this species, like the eared
grebe, congregated in large colonies during the breeding season.
Held to one locality by the instinct that drew them to their nests
and young, the birds were slaughtered in these colonies with ease
until their numbers were greatly reduced. One hunter in Oregon told
of killing 135 grebes on one occasion, and on the large shallow lakes
in the Great Basin region many thousands in all were shot for their
skins. Fortunately, in 1903 the market for grebe skins was closed,
and slaughter by professional hunters practically ceased. With in-
creased protection during recent years the birds have regained some-
thing of their former abundance. |

A serious factor affecting grebes, as well as many other species
of water birds, is the reclamation of extensive marshes and shallow

NORTH AMERICAN GREBES. 5

lakes in the West, projects which have reduced the areas where these
birds may find suitable breeding grounds. As grebes are not con-
sidered game and are thus protected by Federal law at all seasons,
they should maintain their present numbers. |

Although the meat of the grebe is edible if properly prepared, it
is relatively small in quantity and is not of the best quality. The
bulk of it is found on the strong thighs and legs, where in adult
birds the muscles are quite likely to be tough and stringy. When
cooked, the flesh is very dark and at times is unpleasant in taste and
odor, so that it does not meet with general favor.

WESTERN GREBE.

(Aechmophorus occidentalis.)

The western grebe, the largest member of its family found in North
American waters, ranges in the western portion of the continent,

B1332M

Fic. 1.—Western grebe.

where it breeds from British Columbia and Manitoba south to north-
ern California, Utah, and North Dakota. During the winter season a
part of these birds remain in the North wherever there is sufficient
open water for their needs, but others at this time extend their range
as far south as the State of Jalisco in central Mexico. Western
grebes are found on the larger rivers and lakes, and in the summer
season frequent the great marshy, tule-grown lakes common through-
out their breeding range. In winter they often occur on the ocean
or on salt-water lagoons and bays.
The large body, long slender neck, and elongate, sharp-pointed
bill serve to distinguish these grebes from any of the other diving
_ birds found in company with them. (See fig. 1.) To these char-
_ acters may be added a dark gray or blackish coloration above and
pure snowy white beneath, with a brilliant red eye, which may be
_ noted upon close approach.

6 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

Like other grebes, the present species usually depends upon its
skill in diving to escape pursuers, but when encountered in shallow
channels choked with growths of aquatic vegetation it occasionally
takes wing, when with long neck and large feet outstretched, and on
small, rapidly beating wings, it presents a most curious appearance.

Western grebes nest in colonies, building up large, rounded piles
of aquatic vegetation to form mounds that barely project from the
water. The eggs, usually two or three in number (sets of five are
reported), are laid in a slight depression on the top of this mass.
The down-covered gray young take to the water as soon as hatched
and swim readily with the fore part of the body submerged. When
tired they clamber upon the mother’s back under her arching wings,
and are carried along with their heads projecting through her
feathers.

The loud, stirring calls of the adults, one of the pleasant sounds
of the great western marshes, come to mind whenever the birds
themselves are considered.

FOOD.

Nineteen stomachs of the western grebe, from California, Oregon,
Utah, and British Columbia, were available for examination in the
study of its food. These were collected in January, March, April,
May, September, October, November, and December. Like all other
grebe stomachs, these, without exception, contained masses of feath-
ers from the bodies of the birds themselves, and in four, feathers were
present to the exclusion of all other material.

Fish remains were present in all but one of the 15 stomachs that
contained food and, disregarding the feathers universally found,
made up practically the entire food (100 per cent) of the birds ex-
amined. A few remains of water boatmen (Corixidae) in one
stomach, amounting to a mere trace, constituted the only other ani-
mal food. One individual had eaten a small mass of rootlets, but
the presence of this vegetable matter, forming only 2 per cent of the
contents of the single stomach in which it occurred, is considered
accidental.

One bird from Okanogan Lake, British Columbia, had eaten two
Columbia chubs (d/ylochetlus caurinus) about 5 inches long. These
fishes are said to frequent the spawning beds of salmon in order to
devour their eggs. Another individual had eaten two other small
fishes belonging to the same family, the carps (Cyprinidae), but
these were too far advanced in digestion to allow more certain identi-
fication. A bird taken near the mouth of Bear River, Utah, had
eaten two small carp (Cyprinus carpio) and a sucker known locally as
“mullet” (Catostomus ardens). Another stomach from the same
locality contained four small carp entire and the remains of four
more, while in a third were four chubs (Leuciscus lineatus), one of
which was 4} inches long.

A grebe from Netarts Bay, Oreg., contained fragments of seven or
more little smelts(Atherinops affinas) ,and another from near Wilming-
ton, Calif., had eaten a small California smelt (Atherinopsis cali-
forniensis). Both of these fishes occur in large schools in shallow
bays, and when grown have some value as human food. What few
of the small fry are eaten by western grebes can have no particular

NORTH AMERICAN GREBES. 7

economic significance, as these small fishes are present in great
_ schools and the grebes are few in number. Other stomachs con-
tained merely a few bones of fishes that were too far advanced in
digestion to be identified. J. Macoun, of the Canadian Geological
Survey, has reported finding a large salamander (Ambystoma) in
the stomach of one of these birds. ~

SUMMARY.

‘
,
;

The material available is scanty, but seems to show that the west-
ern grebe depends almost entirely upon fishes as a source of food.
Those taken, however, are seemingly of little importance. The
species inhabiting the streams and shallow lakes upon which this
grebe has its summer home are, as a rule, of little economic value.
In other regions the grebes do not occur in sufficient numbers to
make them a factor of any moment in the continuance or abundance
of any species of food fish. Their feeding is confined to the numer-
ous smaller fry, and the destruction of a few is of no economic
significance. The brief survey that it has been possible to make of
its food indicates that the western grebe is worthy of protection as
an interesting form of life, having no traits that may be marked
as, Injurious.

‘ ES ae Papas, 5 PP Mey

" ci

HOLBOELL GREBE.
(Colymbus holboelli.)

The Holboell, or red-necked, grebe has a range extending over
most of the northern part of North America and eastern Asia. In
our continent it breeds from northern Alaska and Ungava (North-
west Territories) south to the northern border of the United States
from Washington to southwestern Minnesota. In winter it passes
in migration south as far as California, Colorado, the Ohio Valley,
and North Carolina, and occurs north to British Columbia, Wiscon-
sin, and Maine wherever there is suitable water free from ice.

During the winter season these grebes frequent the bays and open
ocean along our coasts, and large lakes and streams inland. Their
habit of remaining in the North on the open water of large lakes
during winter often leads to their destruction, as many cases are
known in which the birds have been caught during severe weather
and frozen into the ice. Grebes usually are unable to rise in flight
from a hard surface, and require a considerable start in order to
gain momentum for ‘flight from the water. When caught by en-
croaching ice, therefore, they may be unable to escape unless they
chance upon a permanent air hole, where they may live until the re-
turn of milder weather.

On their breeding grounds the Holboell grebes are reputed to be
very shy, and, though found in the open during much of the re-
mainder of the year, they are perhaps as little known generally as
any of our grebes except the pygmy Mexican grebe, which barely
enters our boundaries from Mexico.

FOOD.

’ The material available for the detailed study of the food of this
__ bird consists of 46 stomachs, representing all the months of the year

8 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

but June. These were collected in British Columbia, Alberta,
Oregon, North Dakota, Wisconsin, Michigan, Pennsylvania, New
York, Connecticut, Massachusetts, and North Carolina. The months
of September, October, and November are best represented, while for
the summer season there is very little material. —

All the stomachs of the Holboell grebes examined contained feath-
ers from the birds themselves, and in 10, feathers alone composed the
contents. (See fig. 2.) In tabulating the food items it was found
that in the remaining 36 stomachs feathers made up 70 per cent of
the total. Although these feathers are ground up and passed out
through the intestine, they are not considered as having a distinct
nutritive value, as is explained in the introductory paragraphs of

BI269M

Fic. 2.—Stomach contents of the Holboell grebe (Colymbus holboelli), showing the large
numbers of feathers normally present in stomachs of grebes. The larger mass comes
from the stomach proper, the smaller from the pyloric lobe.

this paper. For this reason they are not considered in the following
computation, and the food items remaining are taken as representing
100 per cent. Of this, 97 per cent is animal and 3 per cent vege-
table food.

Fish forms the most important single item in the food of the Hol-
boell grebe, as in 36 stomachs it made 55.5 per cent of the total. Fish
remains occurred in 23 stomachs, or half the total number examined,
and made the sole food items in 14. Two birds taken on Barkley
Sound, Vancouver Island, during the winter season had eaten sev-
eral Alaska sticklebacks (Gasterosteus cataphractus), a salt-water
species belonging to a family noted for its destructiveness to the
spawn and young fry of other fishes. One grebe taken at Nahant,

NORTH AMERICAN GREBES. 9

Mass., in April, had eaten a sculpin (Myoxocephalus aeneus), while
three others secured near Shelter Island, N. Y., in February and
_ March had eaten, respectively, 2, 14, and 18 fishes of the same species.

_ Another had taken an eel (Anguilla chrysypa) and a top minnow of

_ the genus Fundulus. Fragments of fishes belonging to the group con-
taining the perches were found in grebes from Okanogan Lake
(British Columbia), North Dakota, and Currituck Sound, N. C.,
while in one other individual were remains of a minnow of the
family Cyprinidae. Eleven stomachs contained fragments of bony
fishes that were too far along in digestion to be identified. |

Crustaceans, found in 9 stomachs, form one-fifth of the total food,
or 20 per cent. One bird from near Staten Island, N. Y., taken in
March, had eaten 5 mud lobsters (Upogebia affinis) with about 50
other stalk-eyed crustaceans, mainly common shrimps (Crago vul-
garis) and a few prawns (Palaemonetes vulgaris). Another from
the same locality had 75 per cent of the stomach contents made up
of a mass of remains of the common shrimp. A bird from Pennsyl-
vania had taken a crawfish of the genus Cambarus, while 4 from
‘Okanogan Lake, British Columbia, had eaten crawfishes of another
group, Potamobius. Two others contained remains of crustaceans
that were not definitely identified.

Insects form 21.5 per cent of the food and occurred in 13 stomachs
of the Holboell grebes examined. One bird had eaten many larvae
of a caddisfly. Predacious diving beetles, both in the adult and
larval stages, were found in 4 stomachs, and a whirligig beetle
(Dineutes) in 1. One stomach contained several adult dragonflies,
another fragments of water boatmen (Corixidae), and still another
back-swimmers (Votonecta). Water scavenger-beetles (Hydro-
-philidae) were encountered once. These are all aquatic in habit
and might be expected to be the prey of the water-loving grebes.
Other miscellaneous food from the group of insects consisted of re-
mains of flies (family Muscidae), wasps, ants, and other Hymenop-
tera, a stink bug (Pentatomidae), lamellicorn beetles (Scarabaeidae),
ground beetles (Carabidae), billbugs (Calandridae), and indetermi-
nate remains of Coleoptera.

Certain of the insect remains were accompanied by bones of small
predatory fishes in such a way that it seemed probable that the insects
originally had been contained in the stomachs of the fishes, and for
this reason they were not estimated as part of the true food of the
grebe. In other cases they appeared alone. It is probable that the
Holboell grebes secure these miscellaneous insects by picking up in-
dividuals floating on the water. An aquatic bird could not be con-
sidered as an active enemy of living individuals of these terrestrial
species. Other than these insects, a single jaw of a large sea worm
(Nereis) was the only item of miscellaneous animal food encoun-
tered.

Vegetable substances (3 per cent of the total bulk) were found in
4 stomachs. These have no significance as food and may have been
- secured during the eager chase of active prey or in some cases may
have been released from the stomachs of herbivorous fishes during
their digestion.

60230—24——_2

10 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

SUMMARY.

From this survey of the food of the Holboell grebe it appears
that though fish formed slightly more than half the sustenance
of the individuals examined, this fact is of small significance,
as the species taken are in the main of little commercial value.
These birds have no special predilection for food fishes valuable to
man, but are merely in search of something to satisfy hunger, so that
to them a sculpin is as valuable as a species.considered more edible
by man. As these common forms of little worth are found in abun-
dance, they often furnish a ready supply of food. It can not be con-
sidered, therefore, that this grebe is in any true sense an enemy of
the fishing industry, while it is probable that, when more material is
available for the summer months, when the birds are in the shallow
fresh-water inland lakes, insects and crustaceans will be found to
furnish a much larger proportion of the food than is indicated above.

GEE
LZ LEELA

7iphive
Ze8|

Z

Fig. 3.—Horned grebe. BI63IM

A. C. Bent ® records that at this season in the lakes of Manitoba the
birds eat crawfishes, water dogs or salamanders, and aquatic insects.

HORNED GREBE.

(Colymbus auritus.)

‘The horned grebe (fig. 3), a species of wide distribution in the
Northern Hemisphere, ranges throughout the whole of the United
States and much of Canada. It breeds south as far as the northern
portion of the United States and migrates in fall and winter to
Florida, Louisiana, and southern California. Winter records from
the interior are mainly from the Great Lakes region, as at this season
these birds range more commonly along the coasts.

3 Life histories of North American diving birds, Bull. 107, U. S. Nat. Mus., p. 14, 1919.

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NORTH AMERICAN GREBES. ‘El

In breeding plumage the horned grebe has broad, flaring black
cheek feathers and lateral crests of yellow. The throat is black,
and the lower neck, breast, and sides are rufous. In fall and winter
adults and young alike lack the flaring head feathers, being plain
dusky above and white below.

Horned grebes are not shy when nesting, but from the nature of
their haunts are known at this season to comparatively few. During
fall and winter they are more frequently seen, as they are found on
open water. Favorable food conditions at times cause them to col-
lect in small flocks, and on our southern coasts it is common to find
bands of a dozen or more. Unlike other species, the horned grebes
when approached in boats often rise and splatter off across the sur-
face of the water for a hundred yards or more until out of harm’s
way. If approached a second time they usually disappear beneath
the surface. When the water is even moderately rough the birds
are unable to gain sufficient momentum to rise on the wing and must
perforce take refuge in diving.

FOOD.

For a study of the food of the horned grebe 122 stomachs were
available, taken in all months of the year except July. Most of this
material, as would be expected, comes from Alaska, Canada, the
Great Basin, and the eastern half of the United States, for the spe-
cies is at its maximum abundance in this region. On the Pacific
coast, Alaska, British Columbia, Washington, and Oregon are rep-
resented, but there is no material available from California. In this
collection 8 stomachs contained feathers alone, and so gave no idea
of the food habits of this grebe. In the remaining 114, animal food
formed 99 per cent and vegetable matter 1 per cent. In these,
feathers from the birds themselves formed 55.5 per cent of the
stomach contents, but were not considered as food.

Vegetable food occurred in only six individuals and may be re-
garded as accidental. It consisted of bits of wood or other rubbish
in four instances and occasional seeds of ragweed and stick-tight
(Bidens) in two others. Sand was found in two stomachs.

Of the animal food, fish remains found in 49 of the 114 stomachs
formed 34.6 per cent. In other words, fish occurred in 43 per cent
of the total number of stomachs and amounted to one-third of the
entire food. With few exceptions the species of fishes identified are

_ of little or no value. The carp (Cyprinus carpio), a species used as

food but one of tremendous damage to the propagation of fishes
much more valuable, occurred once, and other fishes of the same
family (Cyprinidae) once. Tessellated darters (Boleosoma olm-
stedi) were eaten by two grebes, and a small eel (Anguwilla) by an-
cther. Fragments of silvery anchovies (Stolephorus) and silversides
(Menidia), both small salt-water species and from their glistening
sides known usually as “ shiners,” were found in two instances.

The Alaska stickleback (Gasterosteus cataphractus), a salt-water
form ranging from San Francisco Bay northward, was taken by two
birds. This fish, known also as the “ salmon killer,” is locally abun-
dant along the north Pacific coast. In addition to these, the family
of sculpins (Cottidae), all of them worthless from the human stand-
point, furnished a large part of the fish eaten by the horned grebe.

12 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

This was noticeable in particular in specimens secured on the Pacific
coast and in those from Okanogan Lake, British Columbia. Among
these, fresh-water sculpins (Cottus) occurred six times. A peculiar
marine sculpin (Chitonotus pugetensis) was eaten once, while another
member of this family, eaten by one grebe, could not be defi-
nitely identified. Fragments of vertebrae or scales of bony fishes that
could not be named were found in 30 stomachs, and eggs of fishes
were identified in 3. One bird had eaten a fish belonging to the
group of perches. This and the eel and carp mentioned above
formed the only fishes of any particular commercial value encoun-
tered in studying the food of the horned grebe. On the whole, val-
uable fishes form a small, almost insignificant item in the food.

Crustaceans, found in 29 stomachs, are another important source
from which the horned grebe draws a supply of food. Crawrfishes,
encountered in 8 instances, amount to 10.4 per cent of the. total. In
2 cases these belonged to the eastern group of crawfishes (Cam-
barus), which in many places are injurious to various crops. Craw-
fishes were taken during the months from January to May, inclusive,
and in September and October. They are doubtless eaten rather
extensively during the summer months also, but the material -avail-
able is too scanty to show this.

Other crustaceans, eaten by 21 birds, form 7.5 per cent of the total
food. The common shrimp, or prawn (Palaemonetes vulgaris), a
species valuable chiefly as food for various predatory animals, was
identified 5 times. The Brazilian prawn (Penaeus brasiliensis),
a species which in contradiction of its name ranges on our eastern
coast north to Cape Cod, was found once, and the sand shrimp
(Crago septemspinosus) once. <A bird from the Pacific coast had
eaten another form of shrimp, Crago franciscorum, a species common
from San Francisco Bay northward, and still another had taken a
shrimp of the same genus, but not specifically identified. Shrimps
of the last forms are captured in nets and sold in the markets for
human consumption.

Following these, isopods, small flattened crustaceans that could
not be determined, were found twice, and a sowbug (Mancasellus)
belonging to the same group, once. <A curious form (JMichtheimysis
stenolepis) belonging to the opossum shrimps was eaten once.
Though found at times on the surface of the water, these shrimps
are more abundant below and may have been secured by diving.

The great group known as the amphipods form a valuable source
of food for the horned grebe, as they do also for fishes and other
predatory aquatic animals. One species taken (Chironestmus multi-
articulatus) belongs to a family whose forms are abundantly repre-
sented in Arctic waters, where they play the part of scavenger.
Any dead animal floating i in the water is rapidly eaten up by swarms
of these crustaceans.

Other families—Mefopidae, Pontogeniidae, and Calliopiidae—
usually found floating on the surface of the ocean, were also repre-
sented in these grebe stomachs. Sand-fleas (Gammarus) and
another related species (family Gammaridae) were each taken once.
Amphipod remains that were not identified occurred once, and mis-
cellaneous fragments of indeterminate crustaceans six times. Crus-
taceans other than crawfishes were eaten most commonly in winter,

NORTH AMERICAN GREBES. 13

when the horned grebe frequents salt water. In 18 stomachs secured
during the month of December crustaceans form nearly half the
food (47.5 per cent). |
The insect food of the horned grebe is greatly varied. Beetles alone
form 24.4 per cent and other insects 21.6 per cent, so that the two
combined: equal 46 per cent, or nearly half the fare of this bird.
Forms of water-dwelling insects are important food sources and well
represented. Water .boatmen (Corixidae) were relished apparently,

as they occurred 9 times. Back-swimmers (Votonecta) were eaten

3 times, a water strider (Gerridae) once, a true water bug (Belo-
stomidae) once, and another small species (Zaitha) belonging in the

‘last family, once. Caddisfly larvae were taken 4 times, and the larvae

of gnats (Chironomidae) twice. These two often occur in tremen-
dous numbers in western waters. Nymphs of Odonata, in three
instances those of damselflies, were eaten 5 times. Mayfly larvae
(Ephemeridae) were found once, and other aquatic larvae in 2 cases.

_ ;Aquatic beetles were well represented in the great mass of insect

material. Adult predacious water beetles (Dytiscidae) were taken
by 12 birds, and-larvae of this same group were eaten by 2. Water
scavenger-beetles (Hydrophilidae) were eaten by 15 individuals,
and crawling water-beetles (Haliplidae) by 5. These last are of
small.size, but are frequently eaten in Jarge numbers, as was shown in
the case of one bird that had swallowed 190 belonging to 5 distinct
species. An aquatic leaf-beetle (Donacia) was encountered once.

The insect forms mentioned are of aquatic habits and so are readily
available to these grebes. It is highly probable that when more
study material is available for the summer months they will be found
in much greater numbers, as many of these forms are present in
enormous abundance in the inland lakes and ponds on which the
horned grebe breeds.

In addition to the insects enumerated thus far, there is another
group still to be considered that is secured under somewhat different
circumstances. During the warmer months, as the adults of many
species of insects emerge for their seasonable activities, they swarm
in the air, where they fly abroad or are blown about by the wind.
Where chance carries these over water, some, deceived perhaps by
the apparent solidity of the surface, attempt to alight, only to remain
struggling about and eventually to drown. Frequently bodies. of
such hapless creatures are strewn thickly about on large water sur-
faces. This rich food supply is eagerly sought by the grebes, and
thus insects of varied groups, which under ordinary circumstances
would not be found by a water-haunting bird, come to form an article
of its diet. Stink bugs and many ants and miscellaneous Hymenop-
tera occur among these and with them are found many beetles, in-
cluding such diverse forms as sap-feeding beetles (Nitidulidae),
weevils, and metallic wood-boring beetles (Buprestidae).

Many species of ground beetles (Carabidae) are represented, as
are flies, moths, and caterpillars. All of this material represents
waste in animal life. Its utilization may be regarded as an adapta-
tion on the part of the grebe that has no particulr economic sig-
nificance as regards the maintenance or control of the specific forms
involved. The grebe simply seizes opportunity as it comes without
making special effort to secure the living animals as food, so that it

'
oh bre 1
vA

,

14 —s BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

can not be considered as of value as a control agent, or harmful
in destroying insects that may be accounted useful.

Other miscellaneous animal food, amounting to about one-half of
1 per cent, consists of fragments of marine worms (Nereis) in two
instances, another marine invertebrate in one, and bits of snails in
another. Spiders were taken three times.

SUMMARY.

From the above it appears that nearly one-third of the food of
the horned grebe is made up of fishes, one-sixth of crustaceans, and
approximately one-half of insects. 'Though fishes form an important,
item in the diet, especially in the case of birds taken during fall and
winter, most of the species eaten are of no particular value for human
food. Crawfishes form an important source of food, and in destroy-
ing them the horned grebe does a certain amount of good. Some of
the shrimps taken are palatable to man, but are not present in great
numbers in the grebe stomachs studied. The insects eaten represent
varied groups, part of them aquatic in habit and part individuals
that by chance have fallen into the water. When these facts are
carefully considered, the horned grebe can not be called injurious in
any way. As a harmless species it merits protection for the small
amount of good it may do in destroying crawfishes. f

TABLE 1.—IJtems of animal food identified in stomachs of the horned grebe,
with the number of times that each occurred.

ANNULATA (Worms). HETEROPTERA (Bugs).
N2VCISS Dee a BS eee F ee 1 Huchistusesp 22 ee eee 2
Unidentified Pentatomidae___________ 10
AMPHIPODA (Shrimplets). MYOROChG SErVipes= = sss eee 1
Ht €GuUUtOlUS Sp == ee eee i
Chironesimus multiarticulatus_______~- t-)}Gerridae = 22 be re 2 es eee il
Calliopiidae:-2—> = = ie ee ee 1 »|, Notonecta sp_--— 2 = 4s<~_ 26 see 1
IPONntOren Nae. 2 2 es ee Lo 40tthe (SD. see ee ee 1
MetOpidaey <6! 2m ree eee 1 | Unidentified Belostomidae__--_-_-_~_ it:
Gammaridae (unidentified) __________ 1--|\ Conrixi daie@=> .. <3 29s vk - 2 tres ee 9
Ganuilarnus spe oe {Se ee eee ee 1 ! Unidentified Heteroptera. -__-~---—_ 7
Unidentified amphipods____-____-_~-- 2
LEPIDOPTERA (Moths and Butterflies).
IsopopA (Sowbugs).
Unidentified moths. 22 — 2 1
Mancaseculus Sp" =. Ee Pee eee 1°] Unidentified’ caterpillars] 92322. 2 2

Unidentified: jsopods=2= =. 2] ==
: s COLEOPTERA (Beetles).

ScHIzZOPODA (Opossum Shrimps).

AMOQTG.. Sp: 238-4 te ee eee 1

Michtheimysis stenolepis_______----- 1° |) COhlaenius sp-- ao) == 2. oa ee i
A gonoderuspalupes= 1

Decapopa (Crabs, Shrimps, etc.). ANISOUECLYLULS. SP 1

; Unidentified) Carabidae “ul

Palaemonetes vulgaris=_-— = = 5. |: Habolus raiicots SSS 1
Crago. {ranciscorum 2-2 eee 1 | Haliplus connezus_—~_--_--_--__--__ af
Crago-septemspinosus=——-—=_- = Se i> |SHalinlis Specs > St ase ee ee 3
OfGGO Sees a ae SAS ee ial -eeleodytes= Callosus ss. — = ee 1
Penocusy trasiliensisn_ = 22a 2s see li Peltodytes: 12-punctatus es Se 2h
COmUaiis Spe 2 Ss ee 8 eae 2 | -Peltodytéessedentulus--— =) ee Se 1
Unidentified crawfishes________-~-__- 6 | Coclambusysp2_ 22 Se eee af
Unidentified crustaceans==—=-—----==~ 6 ny droporus Spe 2 ee eee af!
‘AgdbDUS Spe = ee ee eee at

ANISOPTERA (Dragonflies). Colymbetes’ “sculptiitis=. SS 1
Colymbetes Sp=232 2-2 SS eee aul

Infor Aa al) 6) OVS oR le A ee ee 5 | Dytiscid larvae = 2222) ee 2
Unidentified Dytiscidae______-_-______-_ 7

AGNATHA (Mayflies). Unidentified Gyrinidae--_______-_-~_ 1
TTODISteTmuUssSp eee 3,

Mayfly. larvae. 6} Sessa s Se = 1 | Hydrocharis obtusatus_______--_--- al
IBCrGSUs Spee ee eee 2

ORTHOPTERA (Grasshoppers, etc.). Hydrovius clobosa== = = alt
Hydrovius- uscipess == nl

Unidentified srasshopper2==>-=—2- 1 | Unidentified Hydrophilidae_______-~- 5

SS ee ee 6 ee a - h

NORTH AMERICAN GREBES. 15

_ TABLE 1.—Items of animal food identified in stomachs of the horned grebe,

with the number of times that each occurred—Continued.

CoLEOPTERA-—Continued. HYMENOPTHRA— Continued.
BetRnyinIgd: lanTvae= =. ofa 1/-) "Unidentilied ants 4 4
- Unidentified Staphylinidae__________ f |. Pinhia snortata iS "se ee 1
CS Se ee ee i Onloralictas Spoa == eee 1
Unidentified Nitidulidae____________ i} Ceratina dupla_== 22 = es 1
PCL OCrI AE SDe = ee ee 1 | Unidentified hymenopterans__________ 4
Bee incs aieteridas Lees ieee s
niden e CUP R ES) BUCY ee ee ARACHNID i : aye
Be oains BRL TLEVEINC US = = te ee) . eee
oan). J JS SSS Unidentified spiders. 5- 4-2 = 5 eee 3
Unidentified Cerambycidae______--__ i giarets
Bessey Cixycomaidae 4 MouLusca (Snails, Mussels, etc.).
Tomicua sp. --------------. 4 | Unidentified snail ____—_-___________
Unidentified Rhynchophora___-_--_-_ + 4
PISCES (Fishes).
DIPTERA (Flies). ; ;
Cypriaes: curpi0=— == _=2s 5 ae
MHITONOMIt: IAT VAG ==- = = oe 27 Unidentified; Cyprinidae —-_- = 2s
ery TaUGNIES oST= oe el ATLORLALLGL IS 281 SO eS eee ee
Unidentified Muscidae______________ 1 || SS COLEDIOTUSESD — 2-5 So) ee eee

Gasterosteus cataphractus___________

MaMENOPTORA (Wasps, Bees, and Ants). |. Menidia sp --~ ~~__+=--_.__---+-_---
. Umnidentitied (Percoidea,—= 2s == J

Boteosema olmstead + = Se eee
Chitonotis: pugetlensis= == 2S
ATOLLS ACY) pee ee ed ee ee ee Se
Dnidentitied; Cottidae a2 = a2 = yaaa

OU RT oe te
BCORPRER Sie tant 2 ae
Camponotus herculeanus ____________
UOTE SS SP 82S

HORNED Hee Re

ba fa feed

EARED GREBE.

(Colymbus nigricollis californicus.)

The American form, or subspecies, of the eared grebe is confined
to the western part of North America, where it breeds from central
and southern Canada south to California, Arizona, New Mexico, and
northern Iowa. In winter it passes south to Lower California and

Guatemala. In breeding plumage the eared grebe has a distinct

crest that distinguishes it at once from the horned grebe, but during

- fall and winter the two are very similar in color. At this season

the eared grebe may be told by its distinctly smaller size and by the
form of the bill, which is flattened so that it is broader at the base
than it is high. In the horned grebe the bill is laterally compressed,
so that the width is less than the height.

Eared grebes are seen commonly on open water even during the

_ breeding season and, on the whole, are less timid than other grebes.

They nest in large colonies on shallow lakes where there is suitable
cover of rushes growing in the water. During the mating season
the birds are found in pairs and have many courtship antics of

interest. At this season they call constantly with pleasing whistled

notes which at night blend with the voices of other marsh birds to
form a wild chorus.

In winter eared grebes are found on salt water along the Pacific
coast. They are common also during migration in the strongly saline
waters of Great Salt Lake, where they are attracted by the multi-
tudinous brine shrimps (Artemia) that swarm in many bays. Be-
cause of the density of the water the birds seem to rest lightly on
the surface and after diving bob up like corks. On a few occasions
eared grebes, attracted by innumerable larvae of alkali flies, have

lingered on Owens Lake, Calif., another saline lake, until thousands,

poisoned by the concentrated alkalis in the water, have become weak-

ened and died. Their bodies drift ashore and are cast up in wind-

16 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

rows, together with the puparia.of the almost incredibly numerous
alkali fhes (Zphydra). Formerly the eared grebe was killed by
thousands by the plume hunters for the thick, satiny breast feathers.
Fortunately for the continuance of the species, this is now pro-

hibited.

FOOD.

For a survey of the food of the eared grebe 27 stomachs were
available from many localities in the Western States. In this series
three months—January, February, and August—were not repre-
sented. Vegetable matter had been taken by two birds, but was pres-
ent in such small quantity that it did not figure in the percentages.
Animal food may therefore be considered as making up 100 per
cent, disregarding, as in the other species of grebes treated, the pres-
ence of feathers. In one case the vegetable matter consisted of a
seed of a Polygonum, and in the other of matter that may be classed
only as vegetable rubbish. Feathers were present in less quantity
than in the stomachs of the other species of grebes examined, as this
item amounted to only 27 per cent.

In only 5 of the 27 stomachs examined were remains of fishes en-
countered, or in less than one-fifth of the total. One bird killed
near Portland, Oreg., had eaten a small sculpin (family Cottidae),
while in four others the fish remains were identified merely as those
of small bony fishes. These amount to only 9.8 per cent of the total
food.

The insect food of the eared grebe was abundant and varied.
Heteroptera alone amounted to 40 per cent, and had been eaten by
13 of the birds examined. Except for one bug of the family Redu-
viidae, these were all aquatic species. Water boatmen (Corixidae)
were most abundant and had been taken by 11 birds, in one of which —
they totaled more than 1,300 individuals. Among other forms water
bugs (Lelostoma) and back-swimmers (Votonecta) were taken.

Dragonflies and damselflies were eaten by 8 birds and amounted
to 19.5 per cent. They consisted mainly of nymphs. Beetles, mainly
water-dwelling forms, were eaten by 12 birds and amounted to 14.3
per cent of the total. The crawling water beetles (Haliplidae),
though of small size were well represented, as 3 species were defi-
nitely identified. Following these come many predacious diving-
beetles (Dytiscidae) and water scavenger-beetles (Hydrophilidae).
Rove beetles (in one case Philonthus fusiformis) and click beetles
(Elateridae) also were taken. Leaf beetles (among them Myochrous
squamosus, M. longulus, and a Diabrotica) were found 4 times
and weevils 4 times. Larval forms of beetles as well as adults were —
encountered frequently. Larvae of ground beetles (Carabidae) were
taken once, the immature forms of predacious diving beetles 4 times,
and larvae of water scavenger beetles once. Miscellaneous insects of
other groups amounted to 10.9 per cent. Caddisfly larvae were -
found in two stomachs and a grasshopper in one. Caterpillars of a
moth (Pyralidae) were eaten twice, and remains of other Lepidop-
tera were found twice, as also were remains of Diptera and Hymen-
optera. Miscellaneous animal matter, taken by 9 birds and amount-
ing to 5.5 per cent, completes the tale of food in the material
examined. In this material were found a centipede, 2 spiders, an

NORTH AMERICAN GREBES. Ly

aquatic mite, and a snail (Planorbis); remains of a marine worm
(Nereis) and of a frog; and, representing the group of crustaceans,
an amphipod (Gammarus), an opossum shrimp (Veomysis), and
2 unidentified forms. |

In the field the writer has observed eared grebes swimming about
in pursuit of alkali flies (Kphydridae) that rested lightly on the
surface film of the water. As they came within reach they were
seized with an almost unerring thrust of the bill. On Lake Burford,
northern New Mexico, at dusk the birds gather in flocks on a broad
open expanse to secure the ants and beetles, which, flying out from
the sage-grown hills surrounding the lake, are entrapped and drowned
in the water. Gnats (Chironomidae) and Mayflies that emerge in
myriads from the water also furnish an eagerly sought supply of
food. Insects drifting in the water form a favorite source of sub-
sistence with these birds and are often intermingled with living prey.
The tireless activity of these grebes in feeding is shown by the
stomach contents of one bird secured in Montana at the end of May.
This one individual had eaten 315 weevils (//yperodes), 650 water
scavenger-beetles of one genus (Berosus) and 52 belonging to three
or more other genera, 42 leaf beetles (A/yochrous squamosus), 2
billbugs (Sphenophorus), 3 rove beetles, 6 ground beetles with two
larvae belonging to the same family, 61 caterpillars, 1 bug, 2 centi-
pedes, and 3 or more spiders, a total of at least 1,139 individuals.

SUMMARY.

From this detailed enumeration of the food of the eared grebe
it appears that the species is harmless to human interests. The
fishes taken are few in number and apparently of little or no eco-
nomic value. Insects form a greater proportion of the food than
in the three preceding species, but have little economic significance.
A considerable number of dragonfly nymphs are eaten, but these
are destructive of small fishes, though adult dragonflies are valuabie
as enemies of mosquitoes. Like the horned grebe, the present species
picks up many dead insects that are drifting about on the surface
of the water. Like its larger cousin, the western grebe, this grebe
was formerly killed in large numbers for its plumage, but fortunately
laws and fashions changed in time to prevent its extermination.
There is no longer danger of a recurrence of this slaughter, as the
killing of the eared grebe is now prohibited by law, a protection that
2 ee merited on account of the bird’s harmlessness in its choice
of food.

TABLE 2-—Items of animal food identified in stomachs of the eared grebe,
with the number of times that each occurred. .

ANNULATA (Worms). ZYGOPTERA (Damselflies).

_ EDU pg 2 ae eee eae 1 | Unidentified damselflies _____._._______ 1
AMPHIPODA (Shrimplets). ANISOPTERA (Dragonflies).
ERLE TAG) | ee ee eee oe ees 1 | Libellulid nymph___ ee a a

Unidentified nymph_________ eS 1

ScHIzZOPODA (Opossum Shrimps).
ORTHOPTERA (Grasshoppers, etc.).
BTS A) 2 aS eens eae
Unidentified crustaceans____-_-______ 2 | Unidentified grasshopper________~ a 1

18 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

TABLE 2.—Items of animal food identified in stomachs of the eared grebe,
with the nuniber of times that each occurred—Continued.

HETEROPTERA (Bugs). CoOLEOPTERA—Continued.
Unidentified Reduviidae_____________ as, Monocrepidius vespertinus___________ 1
IBeClLOStOMA. Spots: DAA eilhs 1} Monoerepidigs spo.id = - 0.) eet a ae 1
SOLON CCIG, SDL wen = eo NE ee 1: Myochrous tonguius. = ee 1
Unidentified: “Corixinde:: hs Babee 11 Myochrous squamosus_______-__ | 2

¢ ‘ Diabroticassp =~. ae Oe eee il
PHRYGANOIDEA (Caddisilies). Hyperodese ps. = Sens ie eee ee 2

. i Unidentified Curculionidae___________
Unidentified caddisfly larvae_________ 2 | Sphenophorus Woneer yee ee A i

LEPIDOPTERA (Moths and Butterflies). DIPTERA (Flies).

Pyralid poner pillardes #2043 iso for 2 | Unidentified stratiomyid larva_______ 1
Unidentified caterpillar... __+- 1 | Unidentified dipterous larva________ J
Mmidentitied ‘ipupal so. 0S. i er 1) Unidentified, Diptera.2. 2 re ee ae 1

COLEOPTERA (Beetles). HYMENOPTERA (Wasps, Bees, and Ants).
PCHOUAGIAETIY® SM ses SE 2 Ichneumonidace= 222. te ee eee ee 1
HU STM) US ae CM ORE Spe es Be ee bees ke 2 nige ies clee Los BAe eee 1
Unidentified CarAapid. larvast 8" - 2 af
Unidentified Carabidae________ eee a 4 CHILOPODA (Centipedes).
Haliplus cribrarius___-_______---____ 1
Haliplus longulus_____________--___ Ls} Unidentified centipede-—* _-_)- es i
JSR OU TASES SC See Date Saas i Ns re) 2
TPECULOAYTES) ACOLLOSUS 3 Ns al ARANEIDA (Spiders).
Unidentified Haliplidae______________ 1 hes kis
Coelambus inaequalis_______________ it Unidentified ‘spiders2-232 3) eee 2
Coelambus patruelis__.....___-____ 1
Deronectes griseostriatus____________ 1 ACARIDA (Mites).

Rhantus binotatus_ 4 1

RUM CECR Sirete' 4 2 Sk eh he 28) 1 | Unidentified aquatic mite_____.___ aged i
LENE IITIS LS) CSE See ON SEY Ot iia SMe ay One ne Pe 1

Unidentified dytiscid larvae__________ 4 MOLLuScA (Snails, Mussels, etc.)
Unidentified Dytiscidae _.___________ 2

eh AS) SE a a a i> '|*Planorbis. Spin = eee 2 2 eee i I
Helaprorus. sp. (22. 3 er eee EY Ye |

direnesternits Jspies!s 3 Gs ok er hits PIScES (Fishes).

Berosus striatus__-______,. Be ge SO 2

HR OAS ee eee WS Pe oe FX iy Bi 2) ie Unidentified j\Cottidae-292- 226243 1
Philhydrus hamiltoni___-_--________ | Onidentified tishes => 2 = see ae 4
PRAY OrUs Spee e sot ES il

Unidentified hydrophilid larva _______ a ee AMPHIBIA (Frogs, Toads, and Sala-
Unidentified Hydrophilidae__________ nk manders).

Philonthus fusiformis________-______ al

Unidentified Staphylinidae_______ ropa 4. Se Ue es Se 1

MEXICAN GREBE.

(Colymbus dominicus brachypterus.)

The Mexican grebe, the smallest representative of its family found
in North America, is fairly common in favorable localities in southern
Texas, but is not known to occur elsewhere in the United States.
In the lower Rio Grande Valley, near Brownsville, it is reported to
nest in fair numbers and may be resident throughout the year.

In general habits this bird is said to resemble other grebes. It
is found in small ponds and lakes where there is proper concealment
furnished by growths of cat-tails, rushes, and sedges.

Philip Gosse* records that the stomachs of birds killed by him
were filled with a finely ground substance which, from his descrip-
tion, appears to have been feather remains, so that it would seem
that the Mexican grebe shares the feather-eating habit of its relatives.
No other references to the food of the Mexican grebe have been
found in literature, and as there are no stomachs of this species at —
hand for examination, no further data are available in regard to —
its economic status. It is probable that the bird lives largely upon ~

* Birds of Jamaica, p. 448, 1847.

NORTH AMERICAN GREBES., 19

aquatic insects, but this statement must not be accepted as fact, as
it is based entirely upon knowledge of the feeding habits of other
species.

PIED-BILLED GREBE.

(Podilymbus podiceps.)

The pied-billed grebe, the most widely distributed species of its
family occurring in the United States, ranges over most of North
and South America where suitable conditions are found. In North
America it breeds as far north as Canada, though in the southern
part of the United States it is often local in distribution. While

Eke Guetta.

——— = =>

Blss3M.

Fig. 4.—Pied-billed grebe.

not so hardy as some of the species of more typically Boreal habitat,
hi during the winter months it occurs to some extent in the United
tates.

The pied-billed grebe is known familiarly to every country boy,
as it appears regularly on ponds and slow-running streams and is
not restricted to the larger lakes and watercourses, as is usual with
other grebes. The marvelous facility that grebes exhibit in diving
is well shown in the present species, and this habit has become legend,
associated with the name “ hell-diver.”

At all times pied-billed grebes are birds of fresh-water habit,
and though they may occur in river mouths and lagoons where the
influence of the tide is felt, it is exceptional to see them on salt
water. In summer they haunt ponds and streams bordered with cat-
tails and tules, and in the seclusion of these growths conceal their
nest, a mass of vegetation piled up in shallow water as a platform
that barely projects above the surface. The strange cadenced calls
of the males come regularly from the rushes, but the birds remain

.

20 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

hidden, so that few persons are familiar with the true source of
these notes. Even during the breeding season these birds are more
solitary in habit than other grebes. The males are savage fighters,
so that even coots, recognized bullies of the marsh, treat them with
marked respect.

The short, strong bill, higher than wide, and with a dark bar,
serves to distinguish the pied-billed grebe from our other species.
(See fig. 4.) The plumage in general is dark dull brown, blacker
above, somewhat brighter on the breast, and nearly white on the
abdomen. In breeding plumage both sexes have a jet black throat
patch which is lacking during the winter season. After the nesting
season and the molt of feathers that follows it, these grebes leave
their secluded haunts and appear more often in the open.

FOOD.

As the pied-billed grebe is common and widely distributed, it has
been possible to secure abundant material for the study of its food,
in spite of its reputed immunity to the weapons employed by the
hunter. In the present studies 180 stomachs of these birds have been
available for examination. The feather content of these (an almost
invariable constituent in stomachs of grebes) reached 52.5 per cent,
or slightly more than one-half. As in the preceding forms, this was
disregarded in estimating the total food, and the remaining items
were apportioned on the basis of 100 per cent.

Six stomachs contained feathers alone, leaving 174 available for a
résumé of the food. The sustenance of the pied-billed grebe is taken
almost entirely from the animal kingdom. In the present series
only 3 birds had secured small quantities of vegetable matter, so that
the presence of such substances may be considered as accidental.
These were made up of rubbish in two instances and of a single seed
(Nymphaea) in the third.

Of the total food, 24.2 per cent was made up of fishes of a variety
of species. Among these, catfishes occurred 3 times, in one case the
remains being those of a channel cat (/ctalurus punctatus) and in
two others those of bullheads (Ameiurus). It was interesting to
note that the thorny pectoral and dorsal spines of the channel cat had
been broken, apparently before the fish had been swallowed. A
small sucker (Catostomus commersoni) had been eaten by one bird
and a chub (Leuciscus) by another. The bream (Abramis chryso-
leucus) was taken twice, and remains of carp (Cyprinus carpio)
were found 5 times. Where carp are abundant, numbers may be
eaten at one meal. Thus, of 2 birds taken on the lower course of
Bear River, Utah, one had secured 8 and the other 17 small carp.
Unidentified fishes belonging to the carp family (Cyprinidae) were
taken in two cases. An eel (Anguilla chrysypa) was found once,
and killifishes (Poeciliidae) 7 times—in 6 cases identified as top
minnows (Fundulus). A silverfish (Hirtlandia), one of the small
forms commonly known as “shiner,” was eaten by one bird. Sun-
fishes seemed relished also, as the common sunfish (Hupomotis gib-
bosus) was taken once, sunfishes of another genus (Lepomis) 6
times, and unidentified forms belonging to the sunfish family (Cen-
trarchidae) 6 times. Members of the family of perches (Percidae)
were taken twice. One bird had eaten a miller’s-thumb (Cottus

—

— a. — Sl | | Ee

%

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NORTH AMERICAN GREBES. yaa

_ ictalops) and another fresh-water sculpin belonging to the same
genus. Other bony fishes that could not be identified were found
in 36 stomachs.

In all, fish remains were encountered in 69 of the 174 stomachs.
_ The catfishes, eel, perches, and part of the sunfishes taken may be
- considered valuable; the others have little importance. A part of
the latter, as the sucker and carp, are used by man, but are not con-
sidered first-class food fishes. The majority of the unidentified
bony fishes were undoubtedly minnows of no value except as food
for other animals of larger size. Fishes were eaten only in small
quantities from May to August, inclusive, when the birds were on
their nesting grounds, but formed a considerable part of the food at
other seasons. |

The crawfishes eaten by these birds amount to 27 per cent of the
total food. They occurred less commonly in birds taken in Novem-
ber than at other seasons. Common eastern forms (Cambarus)
were taken in 44 instances, and western ones (Potamobius) in 6.
Crawfishes 34 inches long often were found and from their appear-
ance and position in the stomach had been swallowed tail foremost.
In the larger individuals the claws had been sheared off near the
body before the animals were swallowed. The larger eastern craw-
fishes sometimes do serious damage in cultivated fields, where they
destroy young plants or in some cases cause trouble by throwing
out mud “chimneys.” At times they also cause breaks in the dams
of artificial ponds by boring holes through them.

Other crustaceans amount to 4.1 per cent of the food for the year.
They were taken in December, January, and February and consist
of shrimps (Crago), prawns (Palaemonetes), and fiddler crabs
(Uca), Unidentified crustaceans were found 9 times and may in
part be fragments of crawfishes too far digested to be recognized.

The insect portion of the food made up 46.3 per cent of the whole.
Heteroptera (bugs), Coleoptera (beetles), and the groups contain-
ing the dragonflies and damselflies were best represented. Heter-
optera alone made up 16.2 per cent of the food and were rather
evenly distributed throughout the year. The true water bugs, pred-
atory species, were especially well represented, and members of this
family (the Belostomidae) were found in 32 stomachs, in 25 of which
there were remains of the large species belonging to the genus Belos-
toma, Which contains the familiar giant water-bug, or “ electric-light
ee These are predacious and are highly destructive to young fry
of fishes as well as to other aquatic life, so that in the evident predi-
lection of this grebe for them the bird is rendering good service.
Back-swimmers (Votonecta) were taken 13 times, and water boatmen
(Corixidae) 26 times. Four common eastern water-creepers (Pelo-
coris femoratus), a species that feeds on other insects, were encoun-
tered, and one water scorpion (/anatra), a curious long-bodied form
that is also predatory. Heteroptera as a whole were noted in 68 of
the stomachs examined.

Coleoptera were found about as often as Heteroptera in the food
of the pied-billed grebe, as they formed 16.1 per cent of the total
and were found in 93 stomachs. The majority of these were aquatic
species of fair size, evidently secured by direct chase. The pied-
billed grebe apparently is more active in pursuit of prey than the

22 BULLETIN 1196, U. S. DEPARTMENT OF AGRICULTURE.

horned or eared grebes, and only occasionally is there evidence that
it resorts to dead insects floating on the water as a source of food.
The crawling water-beetles seem too small to attract much attention
from this bird, as they were encountered only 5 times. Adult pre-
dacious diving beetles were favored in this group, especially those
species of moderate or large size. The larvae of these beetles were
encountered in only one instance, but adults of various forms were
identified no fewer than 76 times:

The active whirligig beetles (Gyrinidae) also figure to a some-
what surprising degree in the food, being identified 16 times. These
are probably secured by diving, as they seem less erratic in their
movements when submerged than when on the surface. Water
scavenger-beetles (Hydrophilidae) were less favored, occurring only
13 times. The enumeration above is in striking contrast with that
in the case of the horned and eared grebes, where Hydrophilidae
and miscellaneous beetles, secured when dead, figured so prominently.
In the case of the present species beetles other than aquatic were
taken rarely, as is shown in Table 3, following this section.

Remains of dragonflies and damselflies amount to 8 per cent and
were eaten during the warmer months from May to October, in-
clusive. In July and August these insects form a considerable part
of the food, as in 19 stomachs representing these two months their
remains amount to 34 per cent. The greater part were nymphs of
dragonflies, as damselflies figured in the food of only one bird.

Miscellaneous insects of other groups amounted to 2.3 per cent.
They were made up of remains of grasshoppers and caterpillars in one
instance, the puparia and larvae of flies in three, and some miscella-
neous fragments of Hymenoptera. The dipterous remains are those
of aquatic species easily obtained by a diving bird. The others
may well have been floating about on the water, where they were
picked up at random.

Other miscellaneous animals of a variety of forms, but not eaten
frequently, amounted to 2.1 per cent. Spiders were taken 3 times,
marsh snails (Physa and Limnaea) once, other aquatic snails not
certainly identified 3 times, and small frogs 5 times.

SUMMARY.

Though nearly one-fourth of the food of the pied-billed grebe is
made up of fishes, the majority of those taken belong to species of
slight economic importance. Those of value are compensated for by
the large number of crawfishes destroyed, as in bulk these amount to
more than the fishes taken. Aquatic Heteroptera and Coleoptera also
are favored and together comprise one-third of the diet. Predacious
species in both groups are well represented, some of them being of
sufficient size to prey upon fish fry. In eating these, therefore, the
grebe more than compensates for the fishes consumed.

Complaint is made of pied-billed grebes around fish hatcheries.
There they may do considerable harm, though the evidence at hand
shows that even in such localities they seem to take many water
bugs and crawfishes, all of injurious habits. Grebes, however, will
not confine their attention to this kind of food, and when they appear
on the ponds and it is not possible to drive them away they should

PHYLLOPODA (Brine Shrimps, etc.).

DeEcApPopA (Crabs, Shrimps, etc.).

LOD SD. Ul bias =e ee ee eee
0 Dy i UPI ee a
CLOTS > Ti eae

: nme (ES ST Le Ee es eee ee

ZYGOPTERA (Damselflies).
‘Unidentified nymph_________________

rr

ANISOPTERA (Dragonflies).

Unidentified libellulid nymph________
Unidentified aeschnid nymph-________
Unidentified dragonfiy nymphs___-_-~-~-
ae dragonfiy

ORTHOPTERA (Grasshoppers, etc.).

wOrRH

f,

Swrmdentined Acrididae--~. .--__-___
Unidentified Locustidae_____~_______
imidentines Orthoptera_-_.-_

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HETEROPTERA (Bugs).

BPclocaris 7emoratus_— 4
SET TO 2 ee ee eee 6
Nymphs of Belostoma sp__—____-—-_~_
Unidentified Belostomidae___________
PTS TET A A ee 1
_Notonecta Ti SS eee eee

LEPIDOPTERA (Moths and Butterflies).
| Unidentified caterpillar_____________~

COLEOPTERA (Beetles).

=

Unidentified Garafiaas Le eee ae
TUT SS |
_Peltodytes callosus
_ Peltodytes muticus
= Onidentified Haliplidae__._______._.___
_ Colpius infiatus
LOE TSS i
muuhanius tostus =
0 EE Se ee ee
lt

_ Pterostichus sp

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OOH R RHE HER HN RHR Rp

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NORTH AMERICAN GREBES.,

be killed if Federal and State laws
ditions, however, pied-billed grebes should not be molested. They
are not game birds and are not used for food, so that as a matter
of fact they are seldom molested except by persons who, unacquainted
with them, kill one occasionally through curiosity.

| Donacia ape oo wre eee pa

23

permit.* Under ordinary con-

TaBLe 3.—/tems of animal food identified in stomachs of the pied-billed grebe,
with the number of times that each occurred.

COLEOPTERA—CoOntinued.

Unidentified Gyrinidae
Tropisternus sp
A yarop halts triangularis 21)

Balaninus sp
‘Unidentified Curculionidae__________
Sphenophorus costipennis____________
Sphenophorus sp__-==—_.=> >= ==

SEEDER Oh pow a

DIPTERA (Flies).

Unidentified chironomid larya________
Unidentified chironomid pupa_____ ~~~
Unidentified stratiomyid larva__.____

fad ped bed

HYMENOPTERA (Wasps, Bees, and Ants)

Unidentified Camponotidae__________
Unidentified (Pinpriidae = Ss
Unidentified Chalcidoidea____________

bok bt ed

ARANEIDA (Spiders).

jee)

Unidentified spiders==—* =2-_4=_ =
Mo.Liusca (Snails, Mussels, etc.).
LANNE SPs = FS oe eee 1

Phys sp 4 * 22 ee eee
Unidentified: snaris=* 8 2 > Se eee

w=

PISCES (Fishes).

Tetaluras punctatus- eee
AMCHINUS Spa + 22 Fa S a ee
BCLs Gus: Spl. 22h Awe es eee
Abramis chrysoleuycus______-________~—
Cyprinus Carpio= =o SS eee
Dnidentified Cyprinidae___________-_ -
Anguitlo. chrysypas. = ee
Hundiluecsp 2 2 Se ee
Bighiaggia: p22 22 ee
Leponis (spi= eee
Eupomotis gibbosus________. 2
Unidentified Centrarchidae_____.._.._ __
Usniidentified /Percidae-=2+- += 2 2
Cottus fetatops. =.=. sss eS
Cottus sp
Unidentified: fishes. _- - 3" 4-32 ss

AMPHIBIA (Frogs, Toads,
manders).

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SD A ADD Sp AOD EP eS OTL et

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and Salsa-

Rana s
bnidentified. anuran=. 2% 1 82.2 Yee.

ORGANIZATION OF THE
UNITED STATES DEPARTMENT OF AGRICULTURE.

November 19, 1923.

secretary ..of- Agriculture ~ 222) HENRY C. WALLACE.

SISLON TaD CCTELOTY. 2g eee et a4 ih 2 Howarp M. Gore.

Director of Scientific Work_____ he Sea BE: D: “BAL.

Director of Regulatory Work BLey ___. WALTER G. CAMPBELL.

Director of Extension. Work. ..-___._- = — C. W. WARBURTON.

1 BT Ne BSI Lat a Mee xe ae A PO CHARLES F. Marvin, Chief.

Bureau of Agricultural EHconomics_______- Henry C. Taytor, Chief.

Bureau of Animal Industry____-_-___-______ JOHN R. MouteEr, Chief.

Bureau of Plant Industry 2 2, OWA ASS PAN TOR, “Cites:

Porest -Service______. ON 4_\.75 W.B. .Grenvny, -Oniep

Bureau of Chemisiry_________-___- __._ C. A. Browne, Chief.

Pere ROIE Ty SOUS. te eee oe Mitton WHITNEY, Chief.

Bureau of Entomology__~——- Th. es Ga Os Bow aEp iC hier.

Bureau of Biological Survey___-___----__- E. W. NEtson, Chief. 4

Bureau. of Public Roads—____--___-____ THoMAS H. MacDonaxp, Chief. i

Bureau of Home Economics__________--_- Louise STantxry, Chief. 1

Fized-Nitrogen Research Laboratory_____-. F. G. CorTrret., Director.

Division of Accounts and Disbursements_. A. ZAPPONE, Chief.

CDi eS SR OSG Ne Nee Rc Ld CLARIBEL R. BARNETT, Librarian.

Federal Horticultural Board____--~~-~-_- C. L. MARLaTtT, Chairman. /

Insecticide and Fungicide Board____-_-__. J. K. Haywoop, Chairman. b |

Packers and Stockyards Administration___.| CHESTER MorRiLL, Assistant to the §

Grain Future Trading Act Administration_.{ | Secretary. .

fencer ny, the SONCiOY 2. Sn ee R. W. WitiiAMs, Solicitor. ;

4

This bulletin is a contribution from

Bureau of Biological Survey_-._---------- E. W. NEtson, Biologist and Chief.
Division of Food Habits Research__-_~-. W.I.McATEE, Assistant Biologist,
in Charge.
24

ADDITIONAL COPIES
OF THIS PUBLICATION MAY BE PROCURED FROM
THE SUPERINTENDENT OF DOCUMENTS
GOVERNMENT PRINTING OFFICE
WASHINGTON, D. C.
AT

5 CENTS PER COPY

‘ PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS
COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY 11, 1922

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