559 Seabird Conservation P. Dee Boersma, J. Alan Clark, and Nigella Hillgarth CONTENTS 17.1 Introduction 559 17.2 Effects of Habitat Modification on Seabirds 560 17.3 Introduced Species in Seabird Colonies 561 17.3.1 Predators 561 17.3.2 Grazers 562 17.3.3 Plants 562 17.4 Human Harvest of Seabirds 563 17.4.1 Hunting 563 17.4.2 Egging 563 17.5 Human Intrusions in Seabird Colonies 564 17.5.1 Tourism 564 17.5.2 Scientific Research 565 17.5.3 Other Disturbances 566 17.6 Other Threats to Seabirds 566 17.6.1 Climate Change, Pollution, and Commercial Fishing 566 17.6.2 Interspecific Competition and Threat Interactions 566 17.7 Legal Protection 567 17.7.1 Federal Protections 567 17.7.2 State Protections 569 17.7.3 International Protections 569 17.8 Progress in Seabird Conservation 571 17.8.1 Policy Approaches 571 17.8.2 Research 572 17.8.3 Management and Restoration 572 17.8.4 Education 573 Literature Cited 574 17.1 INTRODUCTION The growth of human population and human resource consumption are probably the major factors affecting seabirds today. Between one third and one half of the Earth’s terrestrial surface has been modified by humans (Vitousek et al. 1997), and about one fourth of bird species have been driven to extinction by humans in the last 2000 years (Steadman 1995). The world’s population currently exceeds 6.1 billion people, and more than 1 billion people are added to the planet every 13 years (PRB 2000). The exponentially increasing human population is correlated strongly with species declines (Soulé 1991). Seabirds are no exception, and humans have had significant impacts on many seabird populations. 17 © 2002 by CRC Press LLC 560 Biology of Marine Birds Many of the same traits that make seabirds well adapted to their environment also make them particularly susceptible to population declines and extinction. They frequently aggregate in colonies to which they return each breeding season, even if the habitat is degraded or destroyed. During the breeding season, seabirds nest in coastal areas or on islands, both habitats that humans have developed extensively, destroying many seabird nesting sites. Two hundred and seventeen taxa (species or races) of birds have become extinct in the last 400 years, and over 200 of these taxa nested on islands (Rodda et al. 1998). Two thirds of all currently threatened birds are threatened on islands (Collar and Andrew 1992). Seabirds face intense threats to their survival both on islands and in coastal areas (see Nettleship et al. 1994 for a more in-depth treatment of seabirds on islands). Any effort to conserve seabirds needs to start with a determination and understanding of the major threats these species face. The primary reasons species become endangered are habitat loss, over-harvest, invasive species, pollution, and disease (Wilcove et al. 1998). These same factors are primarily responsible for the decline of seabirds. In this chapter, we give a brief overview of some of these major threats to seabirds. These threat categories are somewhat artificial and ignore the potential interactive and synergistic effects of multiple impacts. Nonetheless, understanding threats provides a foundation for informed discussion of seabird conservation. In addition to threats, we also discuss the role of legal systems in seabird protection as well as recent progress in seabird conservation efforts. 17.2 EFFECTS OF HABITAT MODIFICATION ON SEABIRDS In much of the world, habitat modification is the single most prevalent cause of species becoming endangered (studies summarized in Czech et al. 2000, Meffee and Carroll 1997). Seabird habitat includes three primary components: (1) nesting habitat, (2) foraging habitat during the breeding season, and (3) at-sea habitat during the nonbreeding season (Boersma and Parrish 1998). Foraging and at-sea habitat are most affected by commercial fishing and pollution, and may become highly affected by climate change. Because these impacts are addressed in detail elsewhere in this book, we will not focus on them here. Although some human activity, such as guano extraction (Duffy 1994a), destroyed seabird nesting habitat as long as 200 years ago (Figure 17.1), wide-scale destruction and modification FIGURE 17.1 Historically guano was removed from many seabird colonies. Unfortunately, guano (in this case from cormorants) was once removed when birds were breeding, causing colony-wide reproductive failure for that year. Guano mining is now more controlled and usually occurs after the breeding season. Nonetheless, guano mining remains a problem for some seabirds. (Photo by P. D. Boersma.) © 2002 by CRC Press LLC Seabird Conservation 561 have taken place only in the last 50 to 70 years. Coastal and island real estate are highly valued and are being increasingly developed for human use, particularly in highly populous regions (Figure 17.2). Approximately 50% of mangrove ecosystems have been modified or destroyed by human activity (WRI 1996). Bryant (1995) calculated that half of the remaining coastal ecosystems in the world are at a moderate to high risk to development-related threats. In Europe, 86% of the remaining undeveloped coastline is at moderate to high risk (Bryant 1995). Other causes of habitat loss and modification include the interrelated threats of logging, farming, and grazing. The current trend of habitat loss for seabirds is a major threat to their survival. 17.3 INTRODUCED SPECIES IN SEABIRD COLONIES Another of the most prevalent causes of species endangerment is the introduction of nonnative species (Czech et al. 2000). The scientific literature is replete with examples of extinctions, extirpations, and drastic reductions in seabird populations caused by the introduction of nonnative species into seabird nesting habitat (see summaries in Jones and Byrd 1979, Moors and Atkinson 1984, Burger and Gochfeld 1994). Introduced species can be divided into three main categories: (1) escaped pets, such as cats and dogs; (2) accidental introduction, such as mice, rats, and snakes; and (3) intentional releases for food, sport, fur, and greenery, and as biological control agents (Boersma and Parrish 1998). Not all introduced species have had a detrimental impact on seabirds, but several introduced mammalian predators, grazers, and plants have had significant negative impacts. 17.3.1 PREDATORS Many seabird colonies are naturally free from mammalian predators and as a consequence, seabirds evolved without appropriate behavioral, ecological, and reproductive defenses against them (Loope and Mueller-Dombois 1989). The impact of introduced predators on seabirds is well documented (see compilation in Burger and Gochfeld 1994). Introduced predators with well-documented neg- ative impacts include cats (e.g., Ashmole et al. 1994), dogs (e.g., Everett 1988), rats (e.g., Hobson et al. 1999), mice (e.g., Drost and Lewis 1995), stoats (e.g., Taylor and Tilly 1984), ferrets (e.g., Moors and Atkinson 1984), hedgehogs (e.g., Monteiro et al. 1996), raccoons (e.g., Hartman and Eastman 1999), monkeys (e.g., Gochfeld et al. 1994), and fox (e.g., Bailey 1993). Recognition of the detrimental impacts of introduced predators led to eradication programs in many seabird FIGURE 17.2 A small sandbar in St. Petersburg, Florida provides the only remaining local habitat where these birds (pelicans, cormorants, gulls, terns, skimmers, and shorebirds) can roost to rest and preen their feathers. (Photo by E. A. Schreiber.) © 2002 by CRC Press LLC 562 Biology of Marine Birds breeding sites and the subsequent recovery of the seabirds (e.g., see discussions in Moors and Atkinson 1984, Drost and Lewis 1995, Taylor et al. 2000). However, eradication programs should be carefully planned and implemented, or they may have inadvertent negative impacts on the species of concern (Howald et al. 1999). 17.3.2 GRAZERS Unregulated introductions of grazing animals cause habitat destruction through trampling of nests, overgrazing, and erosion resulting from overgrazing (Jones and Byrd 1979, Schreiber and Lee 2000). In addition, some smaller grazers, such as rabbits, may also compete for nest space (Ainley and Lewis 1974). Feral mammals, including grazers, are a widespread problem at many seabird colonies. Introduced grazers significantly alter vegetation structure (Kirk and Racey 1991) and destroy habitat for use by seabirds (Figure 17.3). In the Seychelles, grazing hares appear to prevent the regeneration of Cauarina equisetifolia, a tree important for breeding seabirds (Kirk and Racey 1991). The impact of introduced grazers on seabirds, although less obvious than that for introduced predators, has been documented for many species, including rabbits (e.g., Monteiro et al. 1996), hares (e.g., Kirk and Racey 1991), goats (e.g., Keegan et al. 1994), and sheep (e.g., Schwartz 1994). In addition, Jones and Byrd (1979) found impacts on seabirds from introduced cattle, caribou, deer, elk, and musk oxen. Removing introduced grazers from colonies allows seabird populations to regenerate (e.g., McChesney and Tershy 1998). 17.3.3 PLANTS For some seabirds, specific vegetative communities or individual plant species are important, or even critical, elements of nesting habitat (Feare et al. 1997). Introduced plants often dramatically change terrestrial landscapes and make them unsuitable for use by seabirds. Plants may colonize areas that previously contained few to no plants, interfering with nesting by species that require open ground. Introduced plants may also crowd out native species used by seabirds for nesting. For example, in the Seychelles, the spread of epi bleu (Stachytarpheta jamaicensis), an introduced plant, has reduced suitable nesting habitat for Sooty Terns (Sterna fuscata, Feare et al. 1997). An introduced cane grass (Arundo donax) in the Azores archipelago is blamed for major losses of suitable burrowing ground for the Cory’s Shearwater (Calonectris diomedea; Hamer, cited in Monteiro et al. 1996). FIGURE 17.3 Sheep grazing in a Magellanic Penguin colony reduces habitat quality through trampling, overgrazing, and erosion. (Photo by P. D. Boersma.) © 2002 by CRC Press LLC Seabird Conservation 563 Humans can spread detrimental species to seabird breeding areas (Van Driesche and Van Driesche 2000). Increased travel to, and settlement in, remote areas is also increasing the threat of unwanted introductions of such species as mice and rats. Furthermore, seabird populations may also be threatened by diseases carried by introduced species (de Lisle et al. 1990). Efforts to prevent the further introduction of nonnative species into seabird colonies and efforts to control and eliminate species from colonies where they have been introduced are valuable conservation measures. 17.4 HUMAN HARVEST OF SEABIRDS Seabirds have been exploited directly and indirectly throughout human history, and avian extinctions have followed in the wake of human exploration and settlement for at least a millennium (Steadman 1995, 1997). The demise of the Great Auk (Pinguinis impennis) is an early example. This flightless seabird flourished in massive numbers in the North Atlantic from the Arctic Circle to Massachusetts. Because they were flightless, Great Auks and their eggs were easy to harvest (Wilcove 1999). Early explorers and sailors began harvesting Great Auks in the late 1400s, and the last two great auks were killed in 1844 (Allen 1876). Although human consumption has driven few other seabirds into extinction in the last 200 years, human exploitation continues to be a significant factor in the decline of many seabird populations (Steadman 1997, Schreiber and Lee 2000). Humans have harvested seabirds for food (commercial, subsistence, and recreational), ornamentation (e.g., feathers), cloth- ing (e.g., gloves), and oil. 17.4.1 H UNTING At the turn of the century, many seabirds were still heavily harvested by humans, and it is surprising that more species were not lost due to hunting for food, feathers, and oil. During the late 19th and early 20th centuries, ornamental feathers on women’s hats were highly fashionable in both Europe and North America, and many birds, including seabirds, were killed to supply the millinery trade. Between 1897 and 1914, over 3.5 million seabirds were killed for their feathers in the central Pacific Ocean alone (Spennemann 1998). Some seabird species are rich in fat deposits, making them valuable for their oil. During the 19th and early 20th centuries, production of penguin oil resulted in the killing of millions of adults. A single company in the Falkland Islands rendered 405,000 birds for their oil in 1867 alone (Sparks and Soper 1987). Although there is a more responsible and sustainable attitude to harvesting seabirds today, there are regions where hunting continues to threaten seabird populations. In Newfoundland, 300,000 to 725,000 murres are shot annually, which may be more than the murre population can sustain (Elliot et al. 1991). In West Greenland, hunters kill 283,000 to 386,000 murres annually (Falk and Durinck 1992), and murre populations may have declined by 80 to 90% (Kampp et al. 1994). 17.4.2 EGGING The collection of eggs as a food source has probably occurred everywhere humans have come into contact with seabird colonies (Cott 1953, Boersma and Parrish 1998). Eggs were consumed by sailors on long voyages, and local settlers used eggs as an important protein source (Spennemann 1998). In 1897, over 700,000 eggs were taken from penguin colonies along the coast of South Africa, and during a 30-year period, over 13,000,000 eggs were collected from the Cape Islands of South Africa (Frost et al. 1976, Shelton et al. 1984). Egging can have community-level effects. For example, harvest of Jackass Penguin (Spheniscus demersus) eggs has been identified as the primary factor that initiated the replacement of this species by the Cape Gannet (Morus capensis; Crawford 1987). While egging is no longer common nor commercial for most seabirds (Yorio et © 2002 by CRC Press LLC 564 Biology of Marine Birds al. 1999), egging continues to have a significant impact on others (e.g., Canada, Blanchard 1994; the Caribbean, Schreiber and Lee 2000; Greenland, P. D. Boersma unpublished). 17.5 HUMAN INTRUSIONS IN SEABIRD COLONIES While not as obvious as the impacts of hunting or direct habitat destruction, the negative impact of human visitors to seabird colonies, particularly tourists, is extensively documented (e.g., Manu- wal 1978, Anderson and Keith 1980, van Halewyn and Norton 1984, Rodway et al. 1996). These impacts commonly include nest desertion, temporary nest abandonment, increased risk of predation, and, ultimately, reduced breeding success (see Burger and Gochfeld 1983, 1993). 17.5.1 TOURISM Humans are traveling in ever-increasing numbers to previously remote areas throughout the globe. The World Tourism Organization estimates that nature tourism generates 7% of all international travel expenditure (noted in Lindberg et al. 1997). Nature-based tourism is also one of the fastest growing segments of the tourist industry, growing at an annual rate between 10 and 30% (Lindberg et al. 1997). A positive aspect of this trend is that people who have close encounters with nature are more likely to support conservation measures. Tourism in the Antarctic increased from under 300 people/year in the 1950s, to over 5,500 people/year in the early 1990s (Enzenbacher 1993, Kenchington 1989). In the Galapagos Islands, tourist numbers grew from negligible levels in 1970 to over 60,000 in 1998 (Damsgard 1999). At Punta Tombo, Argentina, the number of tourists at a penguin colony grew from a few hundred per season (September through April) in the early 1970s to over 55,000 in the late 1990s (Boersma unpublished). The presence of tourists in or near colonies can decrease bird numbers and must be carefully managed. Tourists trampled approximately 28% of all burrows at a penguin colony in the Punihuil Islands, Chile (Simeone and Schlatter 1998). Tourists may also cause adult seabirds to abandon nests, making eggs and chicks susceptible to predation (DesGranges and Reed 1981) or to temperature extremes and other inclement weather (Hunt 1972). However, tourist impacts can be reduced through thoughtful management (Tershey et al. 1997) and tourism is often compatible with seabird colonies when proper management practices are in place (Figure 17.4). FIGURE 17.4 Well-controlled ecotourism can often coexist with successful nesting by seabirds and is an important part of promoting conservation. Here a tourist (M. Gochfeld) to Antarctica learns about King Penguins (Aptenodytes patagonicus). (Photo by J. Burger.) © 2002 by CRC Press LLC Seabird Conservation 565 17.5.2 SCIENTIFIC RESEARCH Scientific research programs may have short- or long-term impacts on seabird populations if they are not implemented carefully (see summaries in Rodway et al. 1996, Carney and Sydeman 1999, Nisbet 2000, Carney and Sydeman 2000). Seabirds have varying responses to researcher distur- bance, and while some are unaffected by it, others are susceptible to being disturbed. Some populations of Atlantic Puffins (Fratercula arctica) readily desert their eggs when disturbed by researchers (Rodway et al. 1996), and Adélie Penguin (Pygoscelis papua) populations decreased in one colony as a result of disturbance associated with scientific studies (Woehler et al. 1991). Studies on Red-tailed Tropicbirds (Phaethon rubricauda) and Brown (Sula leucogaster) and Red- footed Boobies (S. sula) indicate that these species are not particularly susceptible to human disturbance (Schreiber 1994, 1999). With appropriate precautions, researchers can often reduce their impact and conduct research without decreasing nesting success (see discussions in Burger and Gochfeld 1993, Nisbet 2000). Appropriate and constructive management decisions cannot be made without quality data on the species involved (Figure 17.5). We are dependent on researchers to provide these data (Schreiber 2000). It is impossible to effectively manage seabird populations without knowing such basic biological information as clutch size, incubation period, fledging period, energetic constraints, and the threats seabirds face during each of their reproductive phases. Furthermore, without understand- ing the ways in which different threats, such as predators, pollutants, or humans, affect seabirds, it is impossible to design effective management plans. In most cases, the risks to individual birds from research activity can be drastically reduced by careful research design and implementation. This may involve limiting time in the colony, FIGURE 17.5 Research is a vital part of conservation because it provides the basis for sound management. Here R. W. Schreiber replaces a worn band on a Laysan Albatross on Midway Island in order to continue following birds banded 30 years before. (Photo by E. A. Schreiber.) © 2002 by CRC Press LLC 566 Biology of Marine Birds visiting colonies only during specific periods during the day or reproductive season, or altering investigator behavior. For example, some birds are less disturbed by slow movement through a colony (as opposed to running), by indirect approaches, and by not making eye contact (Burger and Gochfeld 1994). In some cases, noninvasive methods can be used, such as collecting feathers for heavy metal analysis or collecting nonviable eggs, and taking some nest and colony site measurements after the birds are no longer present. In other cases, the conservation problem may be best addressed by collecting individuals to assess physiological parameters, determining con- taminant effects, and providing voucher specimens for historical archives (Remsen 1995, Schreiber 2000). Furthermore, many techniques, such as banding and physiological studies, are critical to obtain data on reproductive success, long-term survival, and population dynamics, which in turn aid in managing populations. 17.5.3 OTHER DISTURBANCES Impacts to seabirds from disturbance can be subtle. For example, some seabirds are negatively affected by the presence of artificial lights (Reed et al. 1985). Negative impacts on seabirds have also been attributed to noise and disturbance from helicopters (McKnight and Knoder 1979), motorboats (Burger 1998), and personal watercraft (Burger and Leonard 2000). Recreational activ- ities can reduce reproductive success if unmanaged (Burger 1995). However, recreation does not necessarily present a direct conflict with seabird conservation if such activities are carefully man- aged (Burger et al. 1995, Knight and Gutzwiller 1995). Human recreational activity at nesting colonies has the potential to cause mortality, reduce reproductive success, or degrade nesting areas. Some seabirds are adversely affected by any visitation or disturbance (Burger and Gochfeld 1993, Yorio and Quintana 1996), but others habituate to the presence of humans (Yorio and Boersma 1992, Burger and Gochfeld 1999). If well managed, human presence appears to have little impact on the reproductive success of many habituated birds (Burger and Gochfeld 1983, Yorio and Boersma 1992). 17.6 OTHER THREATS TO SEABIRDS 17.6.1 C LIMATE CHANGE, POLLUTION, AND COMMERCIAL FISHING Several other major threats face seabird populations. Three of these are so significant that they are treated in separate chapters: climate change (Chapter 7), pollution (Chapter 15), and commercial fishing (Chapter 16). For many seabird populations, these threats, individually or in combination, present the greatest danger to their persistence (Figure 17.6). 17.6.2 INTERSPECIFIC COMPETITION AND THREAT INTERACTIONS Interspecific competition is a major factor in the decline of some seabird populations. For example, at some seabird colonies, competition from increasing numbers of gulls is the primary cause of population declines (Anderson and Devlin 1999). But many gull species are increasing because of human activity, such as the presence of garbage dumps (Hunt 1972) and offal from fishing operations. Often, more than one threat faces a seabird population and these can act synergistically. For example, Williams (1995) concluded that the Yellow-eyed Penguin (Megadyptes antipodes) suffered steep population declines because of a combination of human disturbance, habitat modification, introduced predators and grazers, and fisheries impacts. Multiple physiological stresses from several sources can produce severe problems (Livingstone et al. 1992). It is not difficult to imagine a population already affected by pollution, predators, and/or disease might be more heavily impacted by climate change or fishing impacts than would an otherwise healthy population. © 2002 by CRC Press LLC Seabird Conservation 567 17.7 LEGAL PROTECTION Laws protecting seabirds differ dramatically from country to country and from state to state. However, the principles of legal protection are similar in most jurisdictions, and we focus primarily on U.S. law for illustrative purposes. In the U.S., legal protection for seabirds occurs almost entirely at the state, federal, and international levels. No major state or federal law focuses exclusively on seabirds. Rather, legal protection of seabirds is found within laws protecting wildlife generally or in laws regulating fishing. State and federal law is a combination of statutes passed by elected officials, regulations promulgated by implementing agencies, agency policies, and decisions by courts. International law, however, consists primarily of treaties between countries (Figure 17.7). 17.7.1 FEDERAL PROTECTIONS Federal law provides the primary protective regime for most wildlife, including seabirds (for discussions of U.S. wildlife law, see Bean and Rowland 1997, Musgrave et al. 1998). The first statute passed by Congress to protect wildlife was the Lacey Act of 1900 (current version at 16 U.S.C. §§ 701 and 3371–3378 and 18 U.S.C. § 42), which was passed because of growing national concern over the demise of the Passenger Pigeon (Ectopistes migratorius) and the decimation of heron and egret populations for the millinery trade. Although the Lacey Act did not provide explicit protection for seabirds, it provided for federal enforcement of state laws protecting wildlife by prohibiting interstate transfer of wildlife killed in violation of state laws. The first major U.S. wildlife statute that included protection of seabirds was the Migratory Bird Act of 1913 (Ch. 145, 37 Stat. 828, 847 [repealed 1918]). Passed because of continuing concern over reductions in bird populations, this ground-breaking law prohibited the hunting of migratory FIGURE 17.6 Oil pollution kills a large number of seabirds. Here, an oiled adult Laysan Albatross transfers oil to its chick. (Photo by E. A. Schreiber.) © 2002 by CRC Press LLC 568 Biology of Marine Birds game birds, insectivorous birds, and other migratory nongame birds (which included seabirds) except in compliance with federal regulations. This Act was quickly challenged as unconstitutional (U.S. v. Shauer, 214 F. 154, E.D. Ark. 1914). Recognizing the weakness of its legal arguments, the federal government abandoned its legislative approach. Instead, the federal government entered into an international treaty in 1916 with Great Britain (on behalf of Canada) to provide these same protections (Convention for the Protection of Migratory Birds). The U.S. eventually entered into treaties protecting migratory birds with Mexico (1936), Japan (1972), and the former Soviet Union (1976) as well. The 1916 treaty was implemented by Congress’ passage of the Migratory Bird Treaty Act of 1917 (MBTA: current version at 16 U.S.C. §§ 703–711). Ruling on a legal challenge to the constitutionality of the MBTA, the U.S. Supreme Court held that Congress’ treaty gave it power to protect migratory birds (Missouri v. Holland, 252 U.S. 416, 1920). Another well-known U.S. statute protecting several seabirds is the Endangered Species Act of 1973 (ESA; 16 U.S.C. §§ 1531–1543). Under the ESA, listed species are protected and conserved, habitat critical to the species is to be preserved, and federal actions are not to jeopardize the species (see Clark 1994 and Bean and Rowland 1997 for discussions of the ESA’s basic provisions). The ESA also implements the Convention on International Trade in Species of Wild Fauna and Flora, an international treaty (discussed in more detail below). The list of endangered species protected under the ESA includes several seabirds threatened both nationally and internationally (see Table 17.1). However, the ESA’s protections apply only to the boundaries of the U.S., U.S. territorial waters, and persons under U.S. jurisdiction. Despite these limitations, the ESA has provided significant benefits for some seabirds. For example, U.S. courts have affirmed regulations promul- gated under the ESA that protect Marbled Murrelet nesting habitat (Marbled Murrelet v. Babbitt, 83 F.3d 1060, 9th Cir. 1996). Indirect protection of seabirds is found in federal regulation of various fishing methods (e.g., gill nets, long lines, driftnets, etc.), such as the Magnuson-Stevens Fishery Conservation and Management Act of 1976 (16 U.S.C. §§ 1801–1882), Fish and Wildlife Conservation Act of 1980 (16 U.S.C. §§ 2901–2911), Driftnet Amendments of 1990 (16 U.S.C. §§ 1826, 1857–1859), and High Seas Driftnet Fisheries Enforcement Act of 1992 (16 U.S.C. §§ 1826a–1826c). Because seabirds are often killed during fishing efforts, regulation of fishing methods provides significant protection to seabirds. FIGURE 17.7 King Penguins nest by the thousands on Maquerie Island around the massive drums (digestive tanks) used to boil penguins in the late 1800’s to make oil. (Photo by J. Burger.) © 2002 by CRC Press LLC [...]... component of the major threats to seabirds, few of which are listed under CITES (see Table 17. 2) The Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) was enacted because of the fear of negative consequences from unregulated harvest of krill in Antarctica and the loss of Antarctica’s rich biological diversity Unique among international treaties is its TABLE 17. 2 Seabirds Listed... 19: 45–55 SCHREIBER, E A 1999 Breeding biology and ecology of the seabirds of Johnston Atoll, Central Pacific Ocean Report to the Dept of Defense, Aberdeen, MD SCHREIBER, E A 2000 The vital role of research and museum collections in the conservation of seabirds Pp 126–133 in Status and Conservation of West Indian Seabirds (E A Schreiber and D S Lee, Eds.) Society of Caribbean Ornithology, Special Publication... Studies of High Latitude Seabirds 2 Conservation Biology of Thick-Billed Murres in the Northwest Atlantic (W A Montevecchi and W A Gaston, Eds.) Canadian Wildlife Service, Ottawa, Ontario Enzenbacher, D J 1993 Antarctic tourism: 1991/1992 season activity Polar Record 29: 240–244 EVERETT, W T 1988 Biology of the Black-vented Shearwater Western Birds 19: 89–104 FALK, K., AND J DURINCK 1992 Thick-billed... population declines in seabirds Pp 108–118 in Transactions of the Fifty-Fifth North American Wildlife and Natural Resources Conference (R E McCabe, Ed.) BOERSMA, P D., AND M C SILVA 2001 Fork-tailed Storm-Petrel (Oceanodrom furcata) in The Birds of North America No 569 (A Poole and F Gill, Eds.) The Birds of North America, Inc., Philadelphia BOERSMA, P D., AND J K PARRISH 1998 Threats to seabirds: Research,... 1989, 1991) To attract birds, decoys of breeding birds are placed in an area where the birds bred historically or where habitat seems suitable (Kress 1983, Kotliar and Burger 1984) In addition to decoys, sometimes mirror boxes are used to increase the perceived density of attending birds, and sound systems may be installed to play the breeding calls of the birds, giving the impression of an established... Conservation of West Indian Seabirds Society of Caribbean Ornithology, Special Publication No 1, Ruston, LA SCHWARTZ, S J 1994 Ecological ramifications of historic occupation of San Nicolas Island Pp 171 –180 in The Fourth California Islands Symposium: Update on the Status of Resources (W L Halvorson and G J Maender, Eds.) Santa Barbara Museum of Natural History, Santa Barbara, CA © 2002 by CRC Press LLC 578 Biology. .. by CRC Press LLC 578 Biology of Marine Birds SHELTON, P A., R J M CRAWFORD, J COOPER, AND R K BROOKE 1984 Distribution, population size and conservation of the Jackass Penguin (Spheniscus demersus) South African Journal of Marine Science 2: 217 257 SIMEONE, A., AND R P SCHLATTER 1998 Threats to a mixed species colony of Spheniscus penguins in Southern Chile Colonial Waterbirds 21: 418–421 SOULÉ, M E... Conservation: Marine and Freshwater Ecosystems 10: 437–458 JONES, R D., AND G V BYRD 1979 Interrelations between seabirds and introduced animals Pp 221–216 in Conservation of Marine Birds of Northern North America (J C Bartonek and D N Nettleship, Eds.) Wildlife Research Report 11 U.S Fish and Wildlife Service, Washington, D.C KAMPP, K., D N NETTLESHIP, AND P G H EVANS 1994 Thick-billed murres of Greenland:... and protection of seabirds and their habitat Pp 117 129 in Seabirds of the Russian Far East (A Y Kondratyev, N M Litvinenko, and G W Kaiser, Eds.) Canadian Wildlife Service Special Publication, Ottawa KOTLIAR, N B., AND J BURGER 1984 The use of decoys to attract least terns (Sterna antillarum) to abandoned colony sites in New Jersey Colonial Waterbirds 7: 134–138 KRESS, S W 1983 The use of decoys, sound... CHARDINE 1996 Effects of investigator disturbance on breeding success of Atlantic Puffins Fratercula arctica Biological Conservation 76: 311–319 SCHREIBER, E A 1994 El Niño–Southern Oscillation effects on chick provisioning and growth in redtailed tropicbirds Colonial Waterbirds 17: 105–119 SCHREIBER, E A.1996 Experimental manipulation of feeding in Red-tailed Tropicbird chicks Colonial Waterbirds 19: 45–55 . Hillgarth CONTENTS 17. 1 Introduction 559 17. 2 Effects of Habitat Modification on Seabirds 560 17. 3 Introduced Species in Seabird Colonies 561 17. 3.1 Predators 561 17. 3.2 Grazers 562 17. 3.3 Plants 562 17. 4 Human. Harvest of Seabirds 563 17. 4.1 Hunting 563 17. 4.2 Egging 563 17. 5 Human Intrusions in Seabird Colonies 564 17. 5.1 Tourism 564 17. 5.2 Scientific Research 565 17. 5.3 Other Disturbances 566 17. 6 Other. Seabirds are no exception, and humans have had significant impacts on many seabird populations. 17 © 2002 by CRC Press LLC 560 Biology of Marine Birds Many of the same traits that make seabirds