Oceanus Volume 26, Number 1, Spring 1983 ?• Seabirds and Shorebirds Oceanus The Magazine of Marine Science and Policy Volume 26, Number 1 , Spring 1983 Paul R. Ryan,£d/tor Ben McKelway, Assistant Editor Elizabeth Miller, Editorial Assistant Polly Shaw, Advertising William H. MacLeish, Consultant Editorial Advisory Board Henry Charnock, Professor of Physical Oceanography, University of Southampton, England Edward D. Goldberg, Professor of Chemistry, Scripps Institution of Oceanography Gotthilf Hempel, Director of the Alfred Wegener Institute for Polar Research, West Germany Charles D. Hollister, Dean of Graduate Studies, Woods Hole Oceanographic Institution John Imbrie, Henry L. Doherty Professor of Oceanography, Brown University John A. Knauss, Provost for Marine Affairs, University of Rhode Island Arthur E. Maxwell, Director of the Institute for Geophysics, University of Texas Robert V. Ormes, Associate Publisher, Science Timothy R. Parsons, Processor, Institute of Oceanography, University of British Columbia, Canada Allan R. Robinson, Gordon McKay Professor of Geophysical Fluid Dynamics, Harvard University David A. Ross, Senior Scientist, Department of Geology and Geophysics; Sea Grant Coordinator; and Director of the Marine Policy and Ocean Management Program, Woods Hole Oceanographic Institution Published by Woods Hole Oceanographic Institution Charles F. Adams, Chairman, Board of Trustees Paul M. Eye, President of the Corporation James S. Coles, President of the Associates John H. Steele, Director of the Institution The views expressed in Oceanus are those of the authors and do not necessarily reflect those of the Woods Hole Oceanographic Institution. Editorial correspondence: Oceanus magazine, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543. Telephone (617) 548-1400, ext. 2386. Subscription correspondence: All subscriptions, single copy orders, and change-ot-address information should be addressed to Oceanus Subscription Department, 1440 Main Street, Waltham, MA 02254. Telephone (617) 893-3800, ext. 258. Please make checks payable to Woods Hole Oceanographic Institution. Subscription rate: $20 for one year. Subscribers outside the U.S. add $3 per year handling charge; checks accompanying foreign orders must be payable in U.S. currency and drawn on a U.S. bank. Current copy price, $4.75; forty percent discount on current copy orders of five or more. When sending change of address, please include mailing label. Claims for missing numbers will not be honored later than 3 months after publication; foreign claims, 5 months. For information on back issues, see inside back cover. Postmaster: Please send Form 3579 to Oceanus, Woods Hole, Massachusetts 02543. irds and the Sea wn of many marine birds they can adapt to the ways ir environments. Adapt to Ocean Processes birds with the marine w avenues of research to d oceanographers. uins and Albatrosses A. Prince s are at the opposite ends of in terms of their ecology and ng Habits s all seabirds in their is reproduction. rdwatchers: nd Research, Too ceding orebirds end on marine habitats to tites. f the Red Knot ravels far south every year, land, South Africa, orTierra lival ul Spitzer victims of exposure to DDT, >p predators in estuarine 55 Conservation of Colonial Waterbirds by P. A. Buckley and Francine C. Buckley Marshes, bays, and inlets support a large, varied population of waterbirds that faces increasingly intense pressures from urban expansion. 62 Brown Pelicans — Can They Survive? by James O. Keith Unless the needs of this lovable bird are more carefully considered, this ancient species could disappear in a relatively short period of time. so John W. Farrington: Marine Geochemist by William H. MacLeish He is constantly being sought out by politicians, bureaucrats, businessmen, environmentalists, and others caught up in the emotional issue of what happens to oil released into the marine environment. Oil and Gas Group 72 Attacks Marine Sanctuary Program by Paul R. Ryan Suit by association in California questions validity of nationwide system. Ocean Dumping 76 Nations Vote Radwaste Suspension by Clifton E. Curtis Two-year moratorium set on disposal of low-level wastes. 78 The Cover: Herring gulls, photographer unknown. Back Cover: Collage by E. Kevin King of Arctic tern, photographed by Bruce Sorrie. Copyright ©1983 by Woods Hole Oceanographic Institution. Oceanus (ISSN 0029-8182) is published quarterly by Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543. Second-class postage paid at Falmouth, Massachusetts, and additional mailing points. Oceanus The Magazine of Marine Science and Policy Volume 26, Number 1 , Spring 1983 Paul R. Ryan, Editor Ben Me Ke I way, Assistant Edi tor Elizabeth Miller, Editorial Assistant Polly Shaw, Advertising William H. MacLeish, Consultant Editorial Advisory Board Henry Charnock, Professor of Physical Oceanography, University of Southan Edward D. Goldberg, Professor of Chemistry, Scripps Institution ofOceanog Gotthilf Hempel, Director of the Alfred Wegener Institute for Polar Research, Charles D. Hollister, Dean of Graduate Studies, Woods Hole Oceanographic John Imbrie, Henry L Doherty Professor of Oceanography, Brown University John A. Knauss, Provost for Marine Affairs, University of Rhode Island Arthur E. Maxwell, Direc tor oft he Institute for Geophysics, University of Tex. Robert V. Ormes, Associate Publisher, Science Timothy R. Parsons, Professor, Institute of Oceanography, University of Britis Allan R. Robinson, Gordon McKay Professor of Geophysical Fluid Dynamics, David A. Ross, Senior Scientist, Department of Geology and Geophysics; Sec Director of the Marine Policy and Ocean Management Program, Woods Hole Institution Published by Woods Hole Oceanographic Institution Charles F. Adams, Chairman, Board of Trustees Paul M. Fye, President of the Corporation James S. Coles, President of the Associates John H. Steele, Director of the Institution o i Q A The views expressed in Oceanus are those of the authors and do not necessarily reflect those of the Woods Hole Oceanographic Institution. HAVE THE SUBSCRIPTION COUPONS BEEN DETACHED? If someone else has made use of the coupons attached to this card, you can still subscribe. Just send a check- -$20 for one year (four issues), $35 for two, $50 for three* -to this address: Woods Hole Oceanographic Institution Woods Hole, Mass. 02543 Please make check payable to Woods Hole Oceanographic Institution 1930 *Outside U.S. rates are $23 for one year, $41 for two, $59 for three. Checks for foreign orders must be payable in U.S. dollars and drawn on a U.S. bank. Editorial correspondence: Oceanus magazine, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543. Telephone (617) 548-1400, ext. 2386. Subscription correspondence: All subscriptions, single copy orders, and change-of-address information should be addressed to Oceanus Subscription Department, 1440 Main Street, Waltham, MA 02254. Telephone (617) 893-3800, ext. 258. Please make checks payable to Woods Hole Oceanographic Institution. Subscription rate: $20 for one year. Subscribers outside the U.S. add $3per year handling charge; checks accompanying foreign orders must be payable in U.S. currency and drawn on a U.S. bank. Current copy price, $4.75; forty percent discount on current copy orders of five or more. When sending change of address, please include mailing label. Claims for missing numbers will not be honored later than 3 months after publication; foreign claims, 5 months. For information on back issues, see inside back cover. Postmaster: Please send Form 3579 to Oceanus, Woods Hole, Massachusetts 02543. 2 Introduction: Birds and the Sea by Richard C. B. Brown The immediate future of many marine birds depends on how well they can adapt to the ways man has changed their environments. 1 1 How Seabirds Adapt to Ocean Processes by Kevin D. Powers The interaction of seabirds with the marine environment otters new avenues of research to both ornithologists and oceanographers. 1 8 Antarctic Penguins and Albatrosses byj. P. Croxall and P. A. Prince These spectacular birds are at the opposite ends of the seabird spectrum in terms of their ecology and adaptations. 28 Seabird Breeding Habits by Warren B. King The activity that unites all seabirds in their dependence on land is reproduction. Woods Hole Birdwatchers: Ships and Dip and Research, Too oo The Food and Feeding of Migratory Shorebirds by David Schneider These small birds depend on marine habitats to satisfy their huge appetites. 44 The Migration of the Red Knot by Brian Harrington This Arctic shorebird travels far south every year, often visiting New Zealand, South Africa, or Tierra del Fuego in Argentina. 49 An Osprey Revival by Alan Poole and Paul Spitzer Coastal ospreys, once victims of exposure to DDT, are thriving again as top predators in estuarine ecosystems. 55 Conservation of Colonial Waterbirds by P. A. Buckley and Francine G. Buckley Marshes, bays, and inlets support a large, varied population of waterbirds that faces increasingly intense pressures from urban expansion. 62 Brown Pelicans — Can They Survive? by James O. Keith Unless the needs of this lovable bird are more carefully considered, this ancient species could disappear in a relatively short period of time. r o John W. Farrington: Marine Geochemist by William H. Mac Lei sh He is constantly being sought out by politicians, bureaucrats, businessmen, environmentalists, and others caught up in the emotional issue of what happens to oil released into the marine environment. Oil and Gas Group 72 Attacks Marine Sanctuary Program by Paul R. Ryan Suit by association in California questions validity of nationwide system. Ocean Dumping 76 Nations Vote Radwaste Suspension by Clifton E. Curtis Two-year moratorium set on disposal of low-level wastes. 78 The Cover: Herring gulls, photographer unknown. Back Cover: Collage by E. Kevin King of Arctic tern, photographed by Bruce Sorrie. Copyright ©1983 by Woods Hole Oceanographic Institution. Oceanus (ISSN 0029-8182) is published quarterly by Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543. Second-class postage paid at Falmouth, Massachusetts, and additional mailing points. f\" 7 ^T ^ •r - ./** m * tf* Introduction: Birds and the Sea by Richard G. B. Brown tvolutionarily speaking, we vertebrates are a paradoxically inconsistent group of animals. Our amphibian ancestors first crawled out of the primeval waters more than 300 million years ago, and ever since then we have been trying to get back in again. We have tried it as reptiles of various kinds, from the extinct ichthyosaurs and plesiosaurs to modern turtles and sea snakes. We have tried it as mammals: whales, seals, otters, manatees, and polar bears. And we have tried it as seabirds. Families from all of these classes have become, to some degree, readapted to life in the sea. All of them differ from the ancestral fishes in the traces they show of their previous adaptations to life on land — lungs, for example, circulatory systems, and skeletal changes. In terms of number of species, the most successful of these groups today is the seabirds. There are at least 284 living species (the actual figure depends on how you define "seabird" and "species"), whereas there are about 115 living species of marine mammals, five sea turtles, one marine iguana, and about 50 sea snakes. "Seabird" is actually a catch-all term that covers birds from several families, each of which has adapted to marine life independently. The process began very early on. Birds as a class diverged from the reptiles 100 to 150 Red knots in flight. (Photo by David Twichell) million years ago, and fossil remains from the early Eocene Epoch (about 60 million years ago) show that the four principal groups of what we call "seabirds" were already in the process of evolution. These evolutionary lines are: V Pelecaniformes: boobies, gannets, cormorants, tropicbirds, and frigatebirds, as well as pelicans. 2) Lari-Limicolae: the ancestral shorebird stock that evolved into the auks (murres, murrelets, dovekies, and puffins — also known as alcids), jaegers, skuas, gulls, terns, and skimmers. 3) Tubinares (named for their tube-shaped nostrils): albatrosses, fulmars, shearwaters, prions, and petrels. 4) Sphenisciformes: the penguins, an offshoot of Tubinares. Roughly speaking, the gull/shorebird stock seems to have evolved in the Northern Hemisphere and the albatrosses and penguins in the South, although their distribution today is wider than that. Outside these four main groups, "seabirds" also includes members of other families: loons; grebes; ducks, geese, and swans; herons; and even a hawk, the osprey. Variations The extent of marine adaptations in this heterogeneous assembly varies considerably. Many of the birds, literally and figuratively, have done little more than dip their toes into the water again and cannot even swim. Examples include the herons, the osprey, and almost all shorebirds. Others, such as ducks, cormorants, loons, grebes, and most of the gulls and terns, keep to the shallow inshore zone and seldom or never go out of sight of land; the majority of these species divide their time between fresh water and salt. But the most highly adapted seabirds, such as the auks, albatrosses, petrels, penguins, and gannets, have no representatives on land or fresh water. They are true oceanographers' seabirds, and they spend much of their lives far out at sea. Once a young albatross has fledged, for example, it may be another 5 years or more before it sets foot on land again. Seabird species have evolved a variety of techniques for living in their newly reacquired marine environment. Some of them plunge from the air into the water to catch their prey, head-first like the gannets and terns or feet-first like the osprey. Some, like the eiders and other ducks, dive deeply and feed at the bottom on benthic organisms. Others, like the auks, penguins, cormorants, and some of the shearwaters, actively pursue their prey underwater, using their wings and feet for propulsion. Frigates, skuas, and jaegers feed partly by pirating food from other seabirds. Skimmers and prions feed in flight, skimming their bills along the surface of the sea. Many species dip in flight to catch food at the surface, or sit on the water and feed on living or dead prey there. Small phalaropes, the only swimming shorebirds, pick at the zooplankton trapped in tide rips and along convergences. Giant albatrosses, at the other end of the scale, feed at the surface on squid. Many of these surface feeders - especially the gulls and fulmars — have learned to Cormorant pursuing fish underwater. (Photo by Doc White, Nicklin & Associates) scavenge on the debris left behind by fishing and whaling vessels. In many cases, the same feeding technique has evolved independently in different stocks of seabirds. The dovekie of the Arctic and the diving-petrel of the Sub-Antarctic both hunt by diving for zooplankton, and the two have become almost identical in foraging behavior, size, bill-shape, and even plumage; everything except the minor anatomical details that prove they are basically quite unrelated — a classic case of convergent evolution. The anatomy of seabirds has evolved along with these foraging techniques. Birds that plunge down from the air nave thin, streamlined bodies and pointed beaks and, in the case of the gannets, skeletal features that absorb the shock when they strike the water. The forms of the legs, feet, and bills of the various shorebirds allow them to specialize on preys of different sizes, at different depths in the sand or underwater. The phalaropes, for example, have a flat fringe of skin on the outside of each toe that acts as a simple web for swimming. Unlike other hawks, the osprey's foot has two toes pointing forward and two behind, and these, along with the roughened "sole" of the foot, give it a good grip on a fish. The most specialized divers, the auks and penguins, have compact, streamlined bodies with the legs and feet set well back for steering and propulsion; their short wings act as paddles, and, in the penguins and the extinct great auk, the birds have gone further and altogether lost the power of flight. By contrast, the albatrosses and frigates have long wings adapted for gliding, allowing them to cover long distances with a minimum expenditure of energy. More fundamentally, since seabirds ingest a large quantity of salt when they eat or drink, they have developed a gland that extracts the salt from the bloodstream and excretes it through the nostrils. For this reason most seabirds have perpetually runny noses. The Halcyon Factor In other words, seabirds are marine animals, and the more specialized groups like the penguins are as well adapted as most of the higher marine vertebrates for their lives at sea. There is, however, one important difference. Seabirds can feed at sea, but they cannot breed there. Like seals, sea turtles, and some sea snakes, they thus are always to some extent tied to the land. The ancient Creeks had a pleasant fantasy about a seabird called the halcyon, which never came to land at all; it laid its eggs on the sea in a nest of foam during the "halcyon days," the calmest season of the year. In sober fact, the nearest any specialized seabirds have come to this, the last logical adaptation to a marine life, are certain murrelets in the North Pacific. These auks incubate their eggs for six weeks and then take their chicks away to sea only two days after they have hatched. Young murres leave their colonies three weeks after they hatch, and often travel several hundred kilometers before they can fly. But this is an exceptionally short time for a seabird chick to stay in its nest, and the feeding strategies of most species require the parents to bring the food to their young, and not the other way around. The young of the larger penguins and albatrosses, for example, may remain at their nesting sites on land for a year or more. The reasons for this link are plain to see. Seabirds are warm-blooded animals whose eggs require incubation at temperatures of around 40 degrees Celsius, and the newly hatched chicks require brooding and feeding as well. Clearly the birds cannot cast their eggs into the sea and leave Skua attacking an adelie penguin. Aggressive birds, skuas rob penguins of eggs and baby chicks. (Photo by William R. Curtsinger, courtesy of the National Science Foundation) them to develop there, like the eggs of most fishes. Marine mammals are viviparous. Many of the reptiles which have become adapted to life at sea, like the extinct ichthyosaurs and most of the modern sea snakes, have solved this problem by becoming ovoviviparous, retaining the eggs in the mother's body until they hatch. But seabirds' eggs are quite large, about 10 percent of the mother's body weight in the murre, for example, and one may doubt whether a flying bird could carry such a weight for the tour or more weeks needed for incubation. Conversely, the smaller the egg the more helpless the chick when it hatches and so, presumably, the less its chances would be of surviving birth at sea. On the face of it, seabirds have no alternative but to retain the pattern of their terrestrial ancestors and lay and incubate their eggs on land. The fact that no seabird has become a halcyon has placed important restrictions on the evolution of the group as marine animals. The most obvious restriction is on their movements. The great advantage that flight gives seabirds over other marine animals is that it allows Black skimmer. (Photo by Phyllis Green berg, Photo Researchers) FRIGATE Dipping JAEGER vs. AUK Aerial pursuit SKUA vs.GULL Aerial GULL Dipping PETREL PRION filtering GIANT FULMAR Scavenging Skimming Pattering Hydroplaning PELICAN TERN GANNET ALBATROSS Pursuit plunging . • Surface seizing SHEARWATER Surface plunging DIVING- PETREL Deep plunging Pursuit diving: wings VX ~MURRE PENGUIN CORMORANT Pursuit diving : feet EIDER Bottom feeding Seabird feeding methods (after Ashmole, 1971). them to travel widely in search of food and suitable climatic conditions. Terns and red knots from the Canadian Arctic spend the winter off South Africa and in Patagonia, respectively, and the immature terns move on to Antarctica. Conversely, greater shearwaters from the South Atlantic and Wilson's storm-petrels from Antarctica "winter" in our summer in the North Atlantic, from Georges Bank northward. The shearwaters are able to exchange the cool-temperate oceanic zone off Tristan da Cunha for the corresponding one off eastern North America, 10,000 kilometers away. Once they are off our shores, they can follow the course of capelin spawning along the Newfoundland coast, move on to catch the later capelin season off southern Greenland, and then come back to the euphausiid swarms off Nova Scotia on their way back south again. But only nonbreeders can exercise such options. The peak demand for food is during the breeding season, when the adult seabirds must find food tor both themselves and their chicks. At this season, they are restricted to whatever they can find within economical cruising range of their colonies. As an additional complication, the seas may be rich in food but, as in the waters around Antarctica, there may be no land nearby where the birds can nest. The halcyon factor, in other words, is a restriction on the birds' distributions and, as a corollary, on their population sizes as well. The need to breed on land has had an even wider effect on the adaptive radiation of seabirds as marine animals. A diving bird that must travel long distances from its colony to find food must retain the power of flight. It therefore cannot reduce its wings to the penguin-like paddle shape that is the most efficient form of propulsion underwater. This in turn sets limits on the depths it can reach and the efficiency with which it can chase its prey. The speed of swimming vertebrates is also related to their size; there is a limit to how much a bird can weigh and still be able to fly, and so a lighter bird is limited underwater in both its speed of pursuit and the size of prey available to it. Penguins, of course, are not restricted in this way. They are the seabirds most highly adapted to the marine environment. Emperor penguins, the biggest species, can reach depths of 265 meters and speeds of 9.6 kilometers per hour and can remain submerged for 18 minutes — a performance fully comparable with that of seals. On the other hand, the flightlessness of penguins undoubtedly restricts their foraging range. For example, there have been recent declines in the populations of many seabirds breeding in South Africa, related to overtishing. The species affected worst is the jackass penguin, the one with the narrowest foraging range. It appears that these penguins now no longer have an abundant, predictable source of food within range of their colonies, whereas the flying seabird species are able to respond more flexibly to this new situation. Vulnerability Lastly, and most immediately, seabirds on land are exceptionally vulnerable animals. Their anatomical specializations for life at sea have in many cases made it difficult for them to walk about, to take off, and to avoid or defend themselves against land predators. The radiation of penguins in the Southern Hemisphere has undoubtedly been assisted by the absence there of such northern predators as polar bears, foxes, rats, and raccoons, all of which would have been devastating to flightless seabirds. Even flying seabirds tend to nest in trees, on cliffs, or on offshore islands free of ground predators, or a combination of the three, to minimize risks. We know all too well what happens when this strategy breaks down. Cats, rats, foxes, mongooses, pigs, and goats, deliberately or accidentally introduced by man, have for one reason or another all ruined seabird colonies. But the greatest devastation usually comes about when man himself is the predator. The fate of the great auk, the flightless "penguin" of the North Atlantic, is a case in point. This seabird's last sanctuary in the New World, on Funk Island, 30 miles off the Newfoundland coast, was free of every ground predator until the colony was first discovered by European man in 1534. From that point on, men came to slaughter the great auk for three separate reasons during the last 300 years of its existence. First came the fishermen from the Grand Banks, hunting for fresh meat like any other ground predator. They pillaged the Funks so regularly that it is surprising to learn that they were still able to kill a "boatload" of birds there as late as 1785. But that was before the New England merchants took to putting crews ashore to kill the birds and boil them down for their feathers and oil. In the face of this industrial fishery, the colony collapsed. The only great auks then left anywhere were on a small rock off the southern coast of Iceland, and museum ornithologists finished them off; the rarer a species was, the more necessary it became to collect it. The birds' inaccessible rock sank in an earthquake - another of the perils of land for a breeding seabird - Some seabird migration routes. (Adapted from the National Geographic Society) OCEAN MIGRANTS 1. Parasitic jaeger 2. Short-tailed shearwater 3 Greater shearwater 4 Sa bine's gull 5. Fork-tailed storm-petrel 6 Wilsons storm-petrel 7 Wandering albatross 8. Manx shearwater 9. Arctic tern 10 South polar skua 11 Sooty shearwater 7 and the alternative site was far less secure. The last great auks were killed on June 3, 1844, and that was the end of a very promising evolutionary experiment in the specialized adaptation of a marine bird to its marine environment. New Predators, New Dangers The moral of this tragic history is that in the last 400 years, and especially in the last 40, there has been a radical change in the factors that control the survival of seabird populations. Evolutionary strategies depend on long-range probabilities: that the breeding colony will not be invaded by ground predators; that the food supply will remain predictably close and abundant; that mortality from such "random" events as winter storms and cold breeding seasons is on average low. No species is immortal, and these probabilities are bound to break down in the very long run, of course. But recent events suggest that the tempo of such events has increased drastically, and that seabirds are faced with novel sources of mortality which are quite outside their 60 million years of evolutionary experience. For example, it is unlikely that ground predators have ever reached predator-free seabird colonies at quite the rate that man and his commensals did during the age of European exploration. The seabird populations of Peru have always fluctuated irregularly, following population . ~ ' Spilled or dumped oil creates a problem for birdlife. This oil-soaked gannet on a North Carolina beach could not fly and soon died. (Photo by Jack Dermid, U.S. Fish and Wildlife Service) "crashes" of their main food, the anchoveta, after intrusions of warm water along that coast (known as the El Nino phenomenon — see Oceanus, Vol. 23, No. 2, pp. 9 -17). But excessive fishing has added another dimension, and it is feared that this, combined with the El Nino of 1976, has left the populations of both anchovetas and seabirds at a permanently low level. The modern emphasis on harvesting the anchovetas, capelin, and krill that are the seabirds' own food, instead of the large predatory fish that are the birds' competitors, is also likely to work to the birds' disadvantage — as it already has tor the jackass penguins of South Africa. There are many direct sources of mortality as well, and they occur more regularly. The effects of oil pollution are well known; our mythical halcyon and its floating nest would be hard-put to survive in the polluted Mediterranean of today. Pesticide residues, working their way up the food-chain and accumulating in theoodies of seabirds, have affected the fertility of the eggs of ospreys, pelicans, gannets, gulls, and even the cahow petrel of Bermuda, already on the brink of extinction because of introduced ground predators. Monofilament gill-nets, almost invisible and virtually indestructible, have drowned large numbers of auks off Greenland and Newfoundland and in the North Pacific. Less specialized marine birds, such as shorebirds and waterfowl, are perhaps more endangered on migration and in the winter than they are during the breeding season. The market-hunting that brought meat to the markets of Boston and New York during the 19th century put an end to the Labrador duck, which became extinct around 1875, and has virtually wiped out the eskimo curlew as well. But the main risk is the loss of their feeding habitat. It is a paradox that although marine birds can and do travel long distances outside the breeding season, along the coasts and out at sea, the number of places in which they can find the right kinds of food in the right quantities is actually very limited. Migrating red knots move down to Patagonia and back along a track marked by a few well-defined pit-stops — beaches and mudflats where they can rest and build up their fat reserves for the next leg of their trip. At the end of the breeding season most of the semipalmated sandpipers and northern phalaropes in the eastern Canadian Arctic leave the tundra and migrate, probably nonstop, down to the Bay of Fundy. The sandpipers go to half a dozen very restricted mudflats at the head of the bay, while the phalaropes feed in the tide-rips off the Maine and New Brunswick coasts. Greater snow geese breed only in the region of northern Baffin Island, and they have only two feeding sites farther south: in winter in Chesapeake Bay, and in spring and fall at Cap Tourmente, a salt marsh just outside Quebec City. These birds are clearly as vulnerable in their way as was the great auk on its isolated breeding rocks. Cap Tourmente has already been menaced at least once by an oil spill. There are plans to use the Fundy tides to generate electrical power, and if carried out, this project would eliminate at least one of the semipalmated sandpipers' stopovers. If these or any of the other marine birds lose their preferred feeding habitats, it 8 is an open question whether they can find alternatives. What of the Future? What, then, can we say about the future of seabirds? If we think only in evolutionary terms and leave man completely out of the picture, how much further can birds go in their adaptations as marine animals? Their next step depends on whether they can solve the riddle of the halcyon, and evolve a means of breeding out at sea. Could a seabird nest on one of the enormous Antarctic icebergs and drift along with it through the dense swarms of krill? Nonbreeding seabirds already use these as bases for their foraging, and ivory gulls have been known to breed on ice islands up in the Arctic. Could a murrelet lay its eggs on a mass of sargassum weed and hunt for lumpfish and sargassum fish among the fronds below? What would happen if a penguin became ovoviviparous? Dougal Dixon has "preconstructed" a world 50 million years in the future in which the Southern Ocean is populated by ovoviviparous "pelagornids" - penguin descendants that have taken over the ecological roles of the whales, from dolphin-like fish-eaters to giant birds that feed on krill, as baleen whales do today. It is a fantasy, but on the evolutionary scale of time, who can tell? Of course the biggest fantasy of all is to leave man out of the picture. We have changed the situation far too much to do this, and the immediate future of marine birds undoubtedly depends on how well they can adapt to our changes. It is not too difficult to make predictions from what we already know about their reproductive strategies. There are two basic patterns, named for the mathematical constants that define them, "/(-selected" species lay only one egg in a season and have a long period of adolescence before they start to breed and a very low annual mortality as adults. This is the strategy that has been evolved by the seabirds most highly adapted to marine life: auks, penguins, and albatrosses and their relatives. It has proved effective in the past because the sea was normally a safe and predictable place to live, and the birds' life on land was confined to a largely predator-free environment. By contrast, "r-selected" species lay several eggs in a season and usually have short adolescent periods and relatively high annual rates of adult mortality. The species least adapted to marine life, such as ducks, geese, shorebirds, and, up to a point, gulls and cormorants, tend to show this pattern. Clearly an "r-selected" species, with its higher annual rate of reproduction and population turnover, will be better placed than a "/(-selected" species to absorb and recover from man-induced mortalities, such as net-drownings or oil spills. For example, the short-tailed albatross of the Bonin Islands off Japan was persecuted almost to extinction by feather hunters until the early 1930s; its population is only just showing signs of revival. Herring gulls, similarly persecuted in New England, received protection in the early 1900s, and by 1930 the population had expanded so rapidly that the birds were becoming a menace to terns and other birds. •60° Post-breeding migrations of some birds in the northwest North Atlantic. SG: greater snow geese to Chesapeake Bay, via Cap Tourmente, Quebec. F: Bay of Fundy; a migratory stopover for most of the semipalmated sandpipers and northern phalaropes breeding in the eastern North American Arctic. M: migrations of thick-billed murres - (Ml) from the eastern Canadian high Arctic to western Greenland; most of these birds later move on to Newfoundland waters; (M2, M3) from western Greenland and Hudson Strait to Newfoundland; (M4) from Spitsbergen and Novaya Zemlya to western Greenland. P, K: Atlantic puffins (P) from Iceland, and black-legged kittiwakes (K) from northwestern Russia to Newfoundland. G: greater shearwaters from the South Atlantic Ocean, initially to Georges Bank and the Grand Banks. However, reproductive strategies are not the only key to a seabird's chances of survival. The adaptability of its feeding and nesting habits is also important. The herring gull expansion was, literally, fueled by the availability of edible garbage during the winter, which increased the chances of survival of the first-winter birds, the age-class with the highest natural mortality. Herring gulls also have shown an astonishing versatility in their choice of nest sites: cliffs, sand dunes, moors, salt marshes, and now, in Britain, the roots of city buildings. The kittiwake, a more specialized and oceanic gull, is exploiting fish offal and other human wastes at sea, and in England is even nesting on waterfront warehouses instead of its more usual island cliffs. And who would have believed that as specialized a bird as the osprey could learn to nest on man-made structures, such as power pylons, and is on its way to becoming a bird of the suburbs? Odds and Omens The odds are therefore quite good for many species of marine birds, especially species with "r-selected" reproductive strategies that can not only absorb the increased mortalities caused by man but can go even further to take advantage of the new opportunities we have created for feeding and nesting. It is encouraging that populations of ospreys and pelicans are recovering from the damage done to them by chemical pollutants. Much of what happens next depends on man, of course. We must be careful to monitor the chemicals we spill into the sea and quick to put a stop to them if their effects are dangerous. We also must preserve the pieces of shoreline habitat that are crucial feeding areas for many of the birds. But the omens are not nearly as good for the more specialized seabirds. I hope our species has gone beyond the direct, deliberate slaughtering of a species into extinction. But the effects of our commensal animals continue, and we are still living with the effects of direct exploitation and other man-made mortalities in the not-so-distant past. Hunting, egg-collecting, and net-drownings have caused recent, drastic declines in murre colonies in the Canadian Arctic, western Greenland, northern Norway, and Novaya Zemlya. Murres and other auks were once hunted in Britain, and suffered losses from oil pollution, too. It is encouraging that their numbers there are slowly starting to increase again, though it is too soon to say how tar this trend will go, or if or when it will extend to the northern populations. We still seem quite prepared to countenance the extermination of seabird populations, and even species, by indirect means. Abbott's booby breeds only in the treetops of the virgin forest on Christmas Island, in the Indian Ocean, but the whole island is rapidly being excavated for its phosphate deposits. Competition with the fishing industry would be slower, but just as drastic in the long run. The puffins in the biggest colony in Norway have had only a single successful breeding season since 1969. There is a scarcity of their principal food, immature herring, attributable to over-fishing of the Norwegian herring stock in the previous two decades. The developing new industrial fisheries therefore will have to be monitored very carefully. The latest of these is for krill, the euphausiid shrimps that are central to the food webs of seabirds and all the higher marine predators in Antarctic waters. We must limit our catches so that the stock of krill is not damaged and enough is left for our competing marine predators. This will not be easy because man, as a fisherman, is under enormous pressure to find enough protein for fellow members of our own rapidly increasing, and increasingly hungry, species. In the last analysis, we ourselves, through our technological achievements, have joined the ranks of higher vertebrates that have tried to go back to the sea again. Our trouble is that we have done this so recently that we are still trying — unsuccessfully, so far -- to find our place in a balanced marine ecosystem. Richard C. B. Brown is a research scientist with the Canadian Wildlife Service's Seabird Research Unit at the Bedford Institute of Oceanography in Dartmouth, Nova Scotia. Suggested Readings: Ashmole, N. P. 1971. Seabird ecology and the marine environment. \r\Avian Biology, vol. 1, D. S. Farner and ). R. King, eds. New York: Academic Press. Bourne, W. R. P. 1976. Seabirds and pollution. In Marine Pollution, R. Johnston, ed. London: Academic Press. Brown, R. C. B. 1980. Seabirds as marine animals. In Behavior of Marine Animals, Vol. 4, J. Burger, B. I. Olla, and H. E. Winn, eds. New York: Plenum Press. Dixon,D. 1981. After Man: A Zoology of the Future. London: Nelson. Fisher, |. and R. M. Lockley. 1954. Sea-Birds. Boston: Houghton-Mifflin. Caston, A. J. and D. N. Nettleship. 1981. The Thick-Billed Murres of Prince Leopold Island. Ottawa: Canadian Wildlife Service. Mills, S. 1 981. Graveyard ot :the puff in. New Scientist 91 (1260): 10-13. Nelson, B. 1980. Seab/rds. New York: Hamlyn. Abbott's booby, with chick. (Photo by). B. Nelson) 10 The editors would like to thank Ian Nisbet, Vice-President and Principal Science Advisor for Clement Associates, Inc., in Arlington, Virginia, for reviewing several of the manuscripts in this issue. How Seabirds Adapt to Ocean Processes - by Kevin D. Powers ' r/W '&'//A Albatrosses, fulmars, shearwaters, and petrels all have external tubular nostrils through which excess salt is expelled, giving these birds the nickname "tubenoses. " This is Leach's storm-petrel. (Photo by Joseph Van Os, Nature Tours, Vashon, Washington) 11 > Naturalists recognize, moreover, that the ranges of fishes and of innumerable marine invertebrates can be readily correlated with temperature and chemical content of sea water. But oceanic birds seem, in the main, to have been regarded somewhat naively as aerial rather than aquatic animals, notwithstanding that their relationships to sea and land, as concerned with feeding and breeding, respectively, are precisely the same as those of the seals among mammals or the sea turtles among reptiles. Members of none of these groups have escaped the necessity of using the land as a cradle, but their true medium, and the source of their being, is, nevertheless, the sea. Robert Cushman Murphy, 1936, Oceanic Birds of South America jeabirds have adapted to their marine environments in a variety of ways, both physiologically and behaviorally. The species we usually call seabirds come from a wide variety of families: penguins; tubenoses (including albatrosses, shearwaters, and petrels); pelecanitorms (including gannets, boobies, and cormorants); gulls and their relatives (including jaegers, skuas, terns, and skimmers); and alcids (including puffins, murres, and dovekies). All of these birds, in different ways, have had to solve the paradox which Murphy describes: how to make their living at sea while needing to breed on land. Yet another paradox exists concerning the study of these avian mariners. Their adaptation to the terrestrial part of their lives has been the subject of many important studies during the last 70 years; however, they spend 50 to 90 percent of their lives at sea. It is this portion that is still poorly understood. The study of seabirds at sea is one of trie last frontiers in ornithology, and the integration of this science with oceanography has, in recent decades, greatly enhanced our knowledge. The survival of seabirds and their young in breeding colonies is influenced by such factors as the availability of food and nest sites and the presence or absence of land predators. But seabirds at sea have few predators. Their survival depends mainly on their ability to find food in sufficient quantities, when their prey is often irregularly and patchily distributed over a wide and seemingly featureless ocean. Adaptations The great variety of feeding abilities in seabirds has allowed them to exploit most sources of food available near the surface in the world's oceans. Fish, crustaceans, and squid are types of prey most commonly taken by seabirds, but carrion and offal are important and often underestimated sources of food. It has been through competitive interaction between seabirds and their marine environment that important adaptations have evolved to partition these available food resources. The most obvious of these adaptations for efficient foraging are the differences in bill form and wing structure. Variation in bill form is a structural adaptation that corresponds to differentiation in feeding abilities. Plankton-feeders, like dovekies and auklets, have short but relatively wide bills with flattened palatal surfaces and fleshy tongues. This form is most efficient in capturing small, soft-bodied organisms. Fish-eaters, like murres, have longer, narrower bills with palatal grooves and less-fleshy tongues. Similarly, gannets and boobies have long, strong, deeply serrated mandibles, which are well-suited for holding larger fish. Finally, the powerful and sharply nooked bills of skuas are most useful in tearing apart carrion or other seabirds which they often snatch from nests. This diversity in bill form has probably evolved from an overall evolutionary pressure to divide up the food resources among members of seabird communities. Wing structure and flying ability are also related to feeding and hunting strategies. The complete dependence on flight by albatrosses and the complete flightlessness of penguins are the two extremes. Seabirds in tropical waters must forage over large areas because their prey is sparse, and scarce near the surface in daylight hours. They are able to do so economically because they have long wings relative to their body sizes. Such wings are structural adaptations toward energy-efficient gliding, as opposed to energy-expensive flapping flight. Thus, seabirds inhabiting tropical or equatorial waters feed at the surface by dipping over schools of predatory fish such as tuna, snatching the smaller prey that are being chased to the surface and into the range of the birds. Other tropical seabirds feed on larger and more dispersed prey by plunging from the air, using momentum gained during descent to carry them down below the surface. However, the wing structure that allows energy economy in flight is not conducive to the underwater pursuit of prey. Underwater swimming broadens the selection of available prey, but only at the expense of flight mobility; short and narrow wings require a flapping rather than gliding flight. Many seabirds in areas of upwelling and in the higher latitudes of both hemispheres are pursuit-divers. A greater abundance of potential prey in these areas permitted the evolution of this strategy; pursuit-diving birds need not range as far as tropical seabirds. Ecology Seabirds are found throughout the world's oceans, but they are more abundant in some areas than others. This is related to the fertility of the oceans; most animal life in the sea ultimately depends on primary production of plant matter — phytoplankton - through the process of photosynthesis. The nutrients that fertilize the growth of phytoplankton come from inorganic and organic sources, such as silt and the bodies of decaying marine organisms. In stable, permanently stratified, tropical waters these nutrients sink to depths far below the euphotic zone (the layer that receives enough sunlight for photosynthesis). The primary production of plants in such waters is usually very low, except at local areas of upwelling where vertical circulation in the water column returns the nutrients to the euphotic zone. In seasonally colder climates, on the other hand, winter gales ensure that the water column is well mixed each year. 12 Southern skuas. (Photo by M. F. Soper, National Audubon Society/PR) Least auklet. (Photo by Karl W. Kenyon, U.S. Fish and Wildlife Service) Thick-billed murre. (Photo by D. H. S. Wehle) Dovekie. (Photo by Allan D. Cruickshank, National Audubon Society /PR) 13 The seas over shallow continental shelves, such as on Georges Bank off the New England coast and the Grand Banks off Newfoundland, are exceptionally rich in nutrients, though primary production in these regions is limited somewhat by reduced amounts of sunlight during the winter months. Growth in stocks of phytoplankton stimulates production in the higher trophic levels. Thus, there is a greater abundance of zooplankton, fish, and higher predators, such as seabirds and marine mammals, over boreal continental shelves than in most tropical seas. The relationship of bird life to a marine environment can be observed off the northeastern United States (Figure 1). To the south of the Gulf of Maine is Georges Bank, a submerged plateau 40 to 100 meters beneath the water's surface. Water depth on the northern edge of the Bank drops rapidly from 40 to more than 300 meters into the Gulf of Maine. The southern flank of Georges is the edge of the continental shelf, where the depth quickly drops to 2,000 meters. Two distinct water masses meet there. Water within the 200-meter isobath at the outer edge of the continental shelf is known as shelf water. The deeper, warmer, saltier water just off the shelf is called slope water. In winter months (December to March), shelf waters are well mixed vertically because of cold air temperatures and frequent strong winds from storms. In contrast, during summer months (June through August) shelf waters generally are well stratified; the layers of water cannot mix because of a seasonal thermocline from increased solar radiation. The exception to this pattern is Georges Bank, where tidal currents prevent the formation of a thermocline and allow water from off the Bank to mix with surface layers throughout the year. Seasonal differences in the hydrography of the marine environment are reflected in the distribution and abundance of seabirds, in that the structure of the bird communities (species composition, density, biomass) is related to stratification of surface waters. During winter, the total abundance and species composition of birds is similar among the various regions of the shelf (Gulf of Maine, Georges Bank, and Middle Atlantic Bight). Average density ranges from 13 birds per square kilometer in the Middle Atlantic Bight (the waters over the continental shelf extending from Nantucket Shoals, southeast of Nantucket Island, Massachusetts, to Cape Hatteras, North Carolina) to 21 birds per square kilometer on Georges Bank Figure 7. This satellite photo taken in March of 7979 shows the shelf/slope front off the northeastern coast of the United States. The cooler temperature of the shelf water shows up as pale grey along the coast and includes Georges Bank. Paler grey and white areas to the south and east are clouds. The dark circle directly south of Cape Cod is a warm core eddy. (Courtesy of NOAA, Satellite Data Services Division) 14 Gannet. (Photo by William Curtsinger, PR) (Figure 2). This is in marked contrast to slope water, which averages only two birds per square kilometer at this time. Fourteen species occur regularly in shelf water during winter, including surface-feeding fulmars, gulls and kittiwakes, plunge-diving gannets, and pursuit-diving razorbills, murres, and puffins. Only four species are found in slope water, all of which are surface-feeders. In summer, total bird abundance and species composition on Georges Bank contrast with those of surrounding waters. Total bird density on the Bank increases to its yearly maximum, 50 birds per square kilometer. Similar summer peaks in bird abundance do not occur in the Gulf of Maine, in the Middle Atlantic Bight, or in slope water. High rates of primary productivity are found in summer months in all shelf waters off the northeastern United States, but the large numbers of greater and sooty shearwaters and Wilson's storm-petrels in this region, all winter migrants from the Southern Hemisphere, concentrate only on Georges Bank and its perimeter. These species are surface and subsurface feeders that perhaps exploit the zooplankton, fishes, and squids that migrate up into surface waters at night. Productive Mixing One might expect a direct correlation between productivity and bird density; that is, large concentrations of phytoplankton should go with high densities of birds. The summertime discrepancy between bird densities on and off Georges Bank might best be explained by mixing regimes and how the energy of primary productivity is transferred to the rest of the food chain. As summer progresses in stratified waters, surface concentrations of phytoplankton die out because of nutrient depletion. Stratified shelf waters are quite productive in summer, but the layer of maximum primary productivity is 30 to 40 meters below the surface, where the water is richer in nutrients. Therefore, herbivorous zooplankton graze at these greater depths, and their energy is potentially available to benthic and pelagic food webs. This in turn means that carnivorous zooplankton, fishes, and squids stay too deep for birds to reach them. 30 n E JC 0) c re C re CO "c re *-» < >• 20' CO «^ 3 0 k. O 0) O 4) •o TJ 0) a o z 10- i CO LU O I — I 1 SUMMER (June-August) Figure 2. The seasonal abundance and distribution of seabirds are directly related to the degree of mixing in selected water masses off the northeastern coast of the United States. 15 However, water on Georges Bank is continually mixed vertically by mechanisms that include strong tidal currents running over shallow shoals. This mixing enhances the level of surface productivity, because deep nutrient-rich waters around the perimeter of Georges Bank are continuously injected into the surface layer. Bird abundance in slope water is low because productivity there is low. Limited availability of nutrients in the surface layers prevents the growth of any large stocks of phytoplankton. Further nutrient depletion during springand summerand the low rate of mixing in fall and winter set slope water apart from the shelf system. Bird density is permanently lower in equatorial waters, for the same reasons. The fact that the mixing regime of the water masses adjacent to Georges Bank is more typical of equatorial waters, and the Bank itself is more characteristic of the well-mixed regimes found over boreal shelf regions, is especially interesting since the summer seabird communities in the area reflect both types of regime. Cool-water species, such as the greater, sooty, and Manx shearwaters and Wilson's and Leach's storm-petrels, are most common on the northern and eastern flanks of Georges Bank and in the Gulf of Maine. Subtropical species, such as Cory's and Audubon's shearwaters, are more common on the southwest flank and on the adjacent Middle Atlantic Bight and slope water — the area most influenced by the subtropical waters of the Gulf Stream farther offshore. These differences in the seabird communities undoubtedly reflect the well-known differences in the communities of fishes and zooplankton at lower trophic levels, the prey on which the birds feed. Within this broad oceanographic picture, oceanic fronts play a particularly important role in causing bird aggregations at sea. Fronts are boundaries between different water masses. They are often easily detected because of sharp changes in temperature and salinity and, on the surface, by lines of floating debris. Frontal regions are generally areas of relatively high biological productivity, traditionally thought to be caused by a vertical flux of nutrients into the euphotic zone. However, dense concentrations of plankton observed in frontal regions could be merely the accumulation of biological material that is physically trapped at or near the surface where one water mass sinks below the other. Soofy shearwaters. (Photo by Bruce A. Sorrie) 16 Greater shearwater. (Photo by Kenneth C. Parkes, Cornell University Laboratory of Ornithology) One such frontal region is at the edge of the outer shelf in the Middle Atlantic Bight, at the boundary between the shelf and slope water masses. In spring (April-May), the shelf/slope front is nearly vertical, stretching from the surface to the bottom and separating well-mixed shelf water from weakly stratified slope water. At this time the maximum concentration of chlorophyll is on the shoreward edge of this front, and the peak abundance of small grazing-type zooplankton occurs in the outer region of the shelf. During late summer to early fall (August-September), the shelf and slope waters are fully stratified so that the surface thermal expression of the front is obscured by the strong seasonal thermocline. Likewise, there is no surface expression in chlorophyll; instead it peaks at the base of the euphotic zone, approximately 30 meters deep. Under such conditions there is no mixing in the surface layers, and the offshore populations of zooplankton are far below their spring peak. The timing and routing of seabird migrations are apparently influenced by these seasonal variations. Red phalaropes feed at the surface on small zooplankton. They breed in the Arctic and spend the winter at sea. Fronts, with their locally high densities of surface zooplankton, are known to be important feeding areas for nonbreeding phalaropes. When these birds migrate north in April and May, their distribution in the Middle Atlantic Bight is clustered along the shoreward edge of the shelf/slope front, where local densities commonly exceed 100 birds per square kilometer (Figure 3). Both the distribution and the timing of migration suggest that the birds are exploiting the spring zooplankton peak there. By contrast, there is no comparable concentration of red phalaropes off the northeastern United States when the birds move south again in August and September; the mean density is less than 0.1 bird per square kilometer, and the maximum rarely exceeds 10 birds per square kilometer. This is not too surprising, given the scarcity of zooplankton in the shelf/slope frontal Figure 3. On their way north in April and May, red phalaropes (inset) cluster along the shoreward edge of the shelf /slope front to take advantage of the annual peak in zooplankton abundance there. (Photo by Karl W. Kenyon, PR) RED PHALAROPE (Phalaropus fulicarius) • = f lock of more than 100 birds APRIL- MAY, 1977-1981 ..".. f O^"" .'• "•.-. -GV> •&.&:..-, r::-" Shelf /Slope Front (mean position ) 66° region at this time of year. However, the migrating birds do visit well-defined surface fronts farther north, off eastern Canada. In other words, it appears that the phalaropes' migration patterns have evolved to take advantage of the local concentrations of food provided at different points along their route by the mechanisms associated with oceanic fronts. An increased awareness and a better understanding of how seabirds interact with their marine environment offer new avenues of research to both ornithologists and oceanographers. Seabirds are effective hunters in a seemingly faceless environment and are well suited to exploit a variety of food resources in surface and subsurface waters. It makes sense that the traditional areas used by such predators have something to tell us about the structure of seabird habitats; in this case, certain oceanic features indicate those areas and times when a food web is developed to higher levels. A comparison of the characteristics of these areas to areas adjacent but not used by seabirds offers interesting research potential to marine biologists. Kevin D. Powers is a research scientist at the Manomet Bird Observatory in Manomet, Massachusetts. Acknowledgment This research is supported by contract number DE-AC02-78EV04706 from the U.S. Department of Energy. Suggested Readings Ashmole, N. P. 1971. Seabird ecology and the marine environment. Chapter 6 in Avian Biology, vol. 1, D. S. Farner, Jr., R. King, and K. C. Parkes, eds. New York: Academic Press. Brown, R. C. B. 1980. Seabirds as marine animals. In Behavior of Marine Animals, vol. 4, J. Burger, B. I. Olla.and H. E. Winn, eds. New York: Plenum Press. Bumpus, D. F. 1973. A description of the circulation on the continental shelf of the East Coast of the United States. Progress in Oceanography 6: 111-156. Fisher, )., and R. M. Lockley. 1954. Sea-birds: An Introduction to the Natural History of the Sea-birds of the North Atlantic. Boston: Houghton Miftlin Co. Murphy, R. C. 1936. Oceanic Birds of South America. New York: American Museum of Natural History. Nelson, B. 1979. Seabirds: Their Biology and Ecology. New York: A& W Publishers, Inc. Walsh, J. )., T. E. Whitledge, R. W. Barvenik, C. D. Wirick, S. O. Howe, W. E. Esias, and ). T. Scott. 1978. Wind events and food chain dynamics within the New York Bight. Limnology and Oceanography 23: 659-683. Wright, W. R. 1976. The limits of shelf water south of Cape Cod, 1941 to 1972. Journal of Marine Research 34: 1-14. 17 m /46ove, parf of a colony of macaroni penguins on Bird Island, off South Georgia Island. (Photo by P. A. Prince) Left, a courtship display by wandering albatrosses. (Photo by P. A. Prince) Antarctic L and Albatrosses by J. P. Croxall and P. A. Prince /\lbatrosses and penguins are the most characteristic and spectacular birds of the Southern Ocean. Both groups have their greatest number of species and individuals between 45 and 60 degrees South latitude, with vast breeding concentrations at sub-Antarctic islands or south of the Antarctic Convergence.* They are the two most marine of all families of birds, yet, in terms of their adaptations and ecology, they are at opposite ends of the seabird spectrum (Table 1). Albatrosses have light bodies on vast wings, supremely adapted for apparently effortless gliding over storm-swept seas, while penguins are entirely flightless, with heavy, compact bodies superbly adapted for swimming and diving. Furthermore, albatrosses typically delay breeding until they are more than 10 years old, lay a single egg per breeding pair, and live for 30 years on average. Most penguins start breeding at age 3, lay two eggs per nest, and rarely survive long into their teens. The details of these very different life-styles provide insight into the relationships between seabirds and their environment. Penguins Six of the 16 penguin species are characteristically Antarctic. These belong to two main groups — the large emperor and king penguins and four smaller species. Emperor penguins breed on the ice of the Antarctic Continent, king penguins on beaches at sub-Antarctic islands. It takes a pair of these large birds a long time to raise their single offspring, which must fledge and become independent in the Antarctic summer, when food resources are most abundant. King and emperor penguins have solved this problem in very different ways. Emperor penguins lay in autumn and rear chicks throughout the Antarctic winter, under the most extreme conditions faced by any bird, with average temperatures of -20 degrees Celsius and *A frontal system around the Antarctic continent, between the latitudes of 50 and 60 degrees South, at which cold waters from the Antarctic and warmer waters from the middle latitudes converge and sink. An emperor penguin with chick. (Photo courtesy of Sea World) winds of 40 kilometers per hour (sometimes reaching 200 kilometers per hour). To survive this, heat-conserving adaptations are crucial. These include very small flippers and bills for birds of their size, excellent insulation from long, double-layered, high-density feathers, and highly efficient systems for minimizing heat loss. The nasal passages, for Table 1. Some characteristics of Antarctic penguins and albatrosses. Species Weight (kg) Breeding age First Mean Breeding success (% ) Annual survival (%) First yr. Adult World annual breeding population (pairs) PENGUINS: Emperor King Adelie Chinstrap Gentoo Macaroni 30 13 4 4 6 4 3 4 3 3 3 5 5 I 6 7-8 64 57 40-50 c. 50 40-60 c. 50 25 95 ? 82 50-60 70-80 ? c. 80 65 86 200,000 750,000 5-10 million 6-8 million 250,000 8-10 million ALBATROSSES: Wandering Grey-headed Black-browed Light-mantled sooty 9 4 4 3 7 9 8 9 11 13 11 13 60 50 40 40-45 45 40-50 40-50 95 95 92 95 20,000 80,000 600,000 1 5,000 20 example, recover 80 percent of the heat added to cold inhaled air. However, even all these adaptations cannot keep individuals alive through extended fasts: 110 days tor males during courtship and incubation (when they may lose 45 percent of body weight) and 40 days for brooding females. Therefore emperors huddle tightly together in large groups, reducing individualheat loss by a further 25 to 50 percent. Such social behavior is unique among penguins and is only possible because the male can move around with his egg balanced on his feet and covered with a pouch-like fold of abdominal skin. Despite the extremely cold climate, breeding success is high (60 percent), but emperor chicks become independent in summer at only 60 percent of adult weight. All other penguins rear their chicks to 90 to 100 percent of adult weight. Presumably, emperor behavior differs because adults need to molt (change all their feathers) and return to breeding condition before winter, and cannot devote any more time and effort to their offspring. Only 20 to 30 percent of the young survive the first year on their own. However, an early start at breeding (age 3 to 4) and good annual survival of breeders (95 percent — much higher than for other penguins) enable population levels to be maintained. King penguins lack the extreme physiological adaptations of emperors, and, although the two species may shuffle around incubating their eggs in a similar fashion, breeding king penguins maintain a constant distance between each other. Only the chicks huddle to keep warm in winter. King penguins lay from November until mid-April, with marked peaks in the number of eggs produced at the beginning and near the end of this period. Incubation duties are shared by the parents, typically in five-day shifts. Early breeders raise their chicks to 80 percent of adult weight by June and feed them sporadically until September, when regular feeding resumes. By this time, most chicks have sustained a weight loss of about 40 percent. The chicks depart in mid-summer. The adults then molt and usually lay again in February or March. When winter arrives, the new chicks are smaller than their older siblings were the year before, and many die. Those that survive finally fledge late in the Antarctic summer. Parents with this timetable cannot breed again until the following year. Pairs that fail to produce a chick in summer usually molt and breed again as soon as possible. The variety of breeding and molting schedules means that in any colony at most times there are adults, eggs, and chicks at many stages of molt, incubation, and growth. Large penguins dive to considerable depths in search offish and squid (Figure 1). Emperors, with dives lasting 18 minutes and reaching 265 meters, hold all the records for single dives, but in work with Drs. C. L. Kooyman and R. W. Davis of Scripps Institution of Oceanography, we found that on four-to-eight-day feeding trips, king penguins rearing chicks each made 500 to 1 ,200 dives. More than half the dives we observed exceeded 50 meters, and two reached 235 meters. We calculated that only about 10 percent of the dives resulted in prey King penguins near Schliper Bay, South Georgia Island. The cylindrical device is a dive recorder. (Photo by R. W. Davis) capture. Despite all this diving activity, the average daily energy cost of these trips was only about twice that of incubation — testimony to the superb hydrodynamic design of penguins. The other four typically Antarctic and sub-Antarctic penguins — adelie, chinstrap, gentoo, and macaroni — are all smaller and similar to each other in weight and stature. Three are basically circumpolar in distribution, adelies mainly around the continent and gentoos and macaronis at sub-Antarctic islands. Chinstraps are virtually confined to the Antarctic Peninsula and Scotia Sea, where all four species coexist, and have vast colonies in the South Sandwich Islands. The shrimp-like crustacean Euphausia superba (krill), the hub of the Southern Ocean food web, is the main food of all these penguins. Krill-eating penguins are not deep divers. Of 1 ,100 dives made by chinstrap penguins, 70 percent " i— i_ Krill, Euphausia superba. (Photo courtesy of British Antarctic Survey) 21 600- LLJ O ^ cc HI CD 5 P1 1217 dives 4 days P2 dives days P3 ago dives 8 days 300 430 157 ISO 35 136 131 SO 1 253 141 5O 13O ISO 34 O H9O 35 SO 13O 18O 24 O 29O 5 DEPTH (meters) 50 130 1BO 240 29O Figure!. Frequency analysis of the diving depths of three king penguins (PI, P2, P3). All three birds departed and returned to the colony within four to eight days. The minimum threshold of the depth recorder for P2 was higher than for the other two penguins. (From G. L. Kooyman, R. W. Davis, ]. P. Croxall, and D. P. Costa. 1982. Science277,p. 726. Copyright 7982 by the American Association for the Advancement of Science.) 56 - BO - South America 5 a 4 2 Falkland Islands Beauchene Island Bird Island /^"South ^Georgia 2 Soi Sand,w>ch nds South Orkney Islands Signy Island South Shetland Islands, / Antarctic Peninsula 1. Gentoo penguin 2. Macaroni penguin 3. King penguin 4. Black-browed albatross 5. Grey-headed albatross 6. Light-mantled sooty albatross 7. Wandering albatross Figure 2. The foraging ranges of seven species during chick-rearing. The dotted lines are shelf boundaries. were shallower than 20 meters and none exceeded 70 meters. Large krill are almost certainly caught individually. Penguins diving at night may be helped by the krills' bioluminescence and perhaps by a simple form of echolocation relating to the birds' swimming movement. Much feeding, however, is done during daylight. When raising young, penguins are greatly restricted in feeding range by the need to provision their chicks regularly (Figure 2). Our research leads us to believe they are effectively confined within 100 kilometers of the colony and probably stay over continental shelves and shelf/slope areas, places where krill concentrations are frequently located. Although similar in diet, these small penguins are by no means identical in their ecology and reproductive biology; gentoo and macaroni penguins represent the two extremes. Gentoos lay two similar eggs, exchange incubation duties daily, make foraging trips lasting less than 10 hours, take nearly 100 days to rear their chicks, and accumulate fat reserves for molt relatively slowly. Their foraging range rarely exceeds 30 kilometers, and they supplement their krill diet by taking fish from the 22 The Evolution of Penguins A chinstrap penguin. (Photo by C. Lishman) A gentoo penguin. (Photo by P. A. Prince) A macaroni penguin. (Photo by G. Lishman) lenguins are birds: creatures whose bodies are covered with feathers — special skin outgrowths no other animals possess. Penguins are especially adapted for "flying" underwater. Birds, as a class, are thought to have arisen sometime in the early Mesozoic Era — more than 150 million years ago — from reptilian ancestry. Among modern birds, penguins are relatively ancient; they were well established by the close of the Eocene Epoch, 40 million years ago. The structure of the penguin's flipper is the key to the bird's evolution. The flipper has all the elements of a flying bird's wing. Tnis means that, for its structure to make sense, the penguin had to evolve through an aerial stage. The penguin wing is now highly specialized for moving through water, a denser medium than air. Because they differ so from other modern birds, penguins are considered a separate order. Three functional factors differentiate penguins from the flying birds that are most like them structurally or ecologically. They are: the penguin method of swimming underwater; terrestrial locomotion in an upright position; and insulation — feathers (which are down-like and extremely numerous in penguins) and blubber. A look at the classification of a modern penguin provides a brief synopsis of its evolution. The Modern Penguin Kingdom: Animalia Phylum: Chordata (notochord) Subphylum: Vertebrata (a backbone of vertebrae) Class: Aves (the birds) Subclass: Ornithurae (modern birds with no teeth) Superorder: Carinatae (birds with a particular type of breastbone) Order: Sphenicitormes (penguins) Family: Spheniscidae Genus: Aptenodytes (king and emperor) Species: forsteri (emperor) 23 inshore kelp beds. In years of high krill availability, both chicks are reared; in seasons when krill do not appear close to shore, a gentoo colony may experience complete breeding failure, as in 1978 at South Georgia Island. Macaroni penguins also lay two eggs, but only the larger, second egg usually hatches. Incubation and brooding duties are completed in two long shifts (one by each sex), during which 30 percent of body weight may be lost. Foraging trips last 30 to 40 hours, allowing macaronis a much greater feeding range than gentoos. This increases the chances of finding krill, and breeding success is fairly constant from year to year. Chicks are reared in 55 days, after which parents depart immediately for two weeks of intensive feeding, nearly doubling their body weight in order to survive a three-week fast ashore during molt (Figure 3). Adelies and chinstraps are intermediate between these extremes. They are rather similar ecologically but probably different physiologically. Adelies are basically adapted to the regions of the Antarctic continent, and chinstraps to the southern sub-Antarctic. In some places where their territories overlap, on and near the Antarctic Peninsula, chinstrap populations are increasing nearly twice as fast as adelies. It may be that the chinstrap is the superior competitor in these areas, but is unable to colonize the continent effectively. Because we have been able to measure the energy costs of incubation, molting, and foraging for penguins and have detailed information on their breeding timetables, activities, and diet, we are in a good position to assess their consumption of krill. For example, at South Georgia, macaroni penguins eat about 4 million metric tons each year, about 70 percent of the krill consumed by all seabirds and significantly more than the amount taken by present-day seal and whale stocks in the area. Not enough is known about the biomass of krill (and its replacement rate) around South Georgia to assess the effect of this substantial predation, but the impact on the krill population may be magnified by the birds' peak demand coming in February, when female krill are in reproductive condition. Albatrosses Four species of albatross are characteristically sub-Antarctic. The wandering albatross, with a 10-foot wingspan, is the largest of all seabirds. It breeds in loose colonies on flat areas that are convenient for its spectacular pair and group November December January February March April 7OOO — 6500 — 1 6000 - 55OQ - £ 5000 to IMI O) 4500 X O