Funding: North Pacific Marine Research Program, University of Alaska, Fairbanks

Dr. Alexander Kitaysky, Research Associate, Zoology Department, University of Washington, Box 315800, Seattle, WA 98020, kitaysky@u.washington.edu, 206-543-7623

Prof. John C. Wingfield, Chair, Zoology Department, University of Washington, Box 315800, Seattle, WA 98020, jwingfie@u.washington.edu, 206-546-7622

Dr. John F. Piatt, Research Biologist, USGS, Alaska Biological Science Center, 1011 E. Tudor Rd., Anchorage, AK 99503, john_piatt@usgs.gov, 907-786-3549

Some populations of seabirds at colonies in the Bering Sea have fluctuated markedly during the past few decades. One hypothesis to explain these changes is that seabird populations are responding to long-term changes in food supply that are part of a natural ecosystem response to changes in ocean climate regime. Traditional field methods for assessing effects of varying food supply on the reproductive performance of seabirds sometimes give equivocal results. In this project we apply an additional tool: The measure of stress hormones in free-ranging seabirds. Food stress can be quantified by measuring base levels of stress hormones such as corticosterone in the blood of seabirds, and the rise in blood levels of corticosterone in response to a standardized stressor: capture, handling and restraint. This well-known response (found throughout vertebrates from fish to mammals) provides a strong assessment of whether or not a free-living population is chronically stressed. We are applying these "field endocrinology" techniques to seabirds breeding in the southeastern Bering Sea and to captive birds under controlled experimental conditions. We will focus on a comparison of Red- and Black-legged Kittiwakes breeding at Bogoslof Island (increasing population trends, Fig. 1) with those nesting at the Pribilof Islands (declining population trends, Fig. 2). This study provides a unique opportunity for a concurrent field and captive study of the behavioral and physiological consequences of food stress in seabirds. Moreover, it will have broader applications for seabird monitoring programs in the Bering Sea. This research is a component project of a multi-disciplinary, process-oriented research program "Regime Forcing and Ecosystem Responses in the Bering Sea". The research is also coordinated with ongoing Exxon Valdez Oil Spill Trustee Council studies of food stress among seabirds in Lower Cook Inlet.

During the past few decades, reduced productivity, increased mortality and subsequent population declines occurred among some seabirds and marine mammal species in the southeastern Bering Sea and Gulf of Alaska. It has been suggested that declines in food availability and in abundance of high-quality forage fish resulted in food-related stress (Merrick et al. 1987, Hunt et al. 1996, Piatt & Anderson 1996, Anderson & Piatt 1999). Anthropogenic factors such as pollution and commercial fishing may have exacerbated these effects. In this context, nutritional stress can be defined as changes in the physiological condition of individuals that experience a long-term shortage of food or rely on low quality and/or contaminated food resources that impair their ability to reproduce successfully. Alternatively, less severe food shortages may allow reproduction to proceed, but additional stress from anthropogenic sources may precipitate reproductive failure. It is frequently difficult, or impossible, to detect these types of perturbations by using traditional field methods (Piatt & Anderson 1996, Kitaysky et al. in press a).

An approach using well-characterized hormone responses to stress provides a sensitive indicator of chronic stress in the environment, or the potential impact of future stressors (Wingfield et al. 1997). Food-related stress is associated with elevated levels of corticosteroids (also known as "stress hormones") in the peripheral system of affected animals (Axelrod & Reisine 1984; Wingfield, 1994). In seabirds, corticosterone levels were elevated in free-living Magellanic penguins exposed to oil pollution (Fowler et al. 1995), in Black-legged Kittiwakes and Common Murres breeding under poor foraging conditions (Kitaysky et al., in press a and in prep.). Also, chronically elevated corticosterone levels were documented in seabird chicks reared on low quality food (Kitaysky et al. in press b). Chronically elevated corticosteroid levels are known to result in regression of the reproductive system, suppression of memory and immune systems, lead to muscle wasting and cause neuronal cell death (e.g. Sapolsky 1987, Wingfield 1994). Exposure to pollution, poor quality of food and/or decreased food availability can have similar debilitative effects on foraging and reproductive behaviors in seabirds. The effects of the stress can be detected and monitored through measurements of baseline plasma levels of corticosterone in the peripheral system of affected seabirds. The pattern and extent of a corticosterone increase following application of a standardized acute stressor such as capture, handling and restraint can also indicate potential for future stress effects. Furthermore, experimental manipulations with corticosterone levels in captive seabirds provide a way to examine the mechanisms by which increased mortality and decreased reproduction are expressed.

The factors regulating seabird populations are poorly understood. Variations in mortality of adult birds and reproductive success due to natural fluctuations in the availability of food and anthropogenic impacts are probably among the most important factors (Cairns 1992). Life-history theory predicts that in long-lived animals, an increase in parental investment in current reproduction may impair post-breeding survival of parents and the probability of their successful reproduction in the future (Williams 1966, Charnov & Krebs 1974, Stearns 1992). Being long-lived animals, with an estimated life span of about 25-30 years (e.g., Ydenberg 1989), seabirds might buffer the cyclic variability of food resources by pursuing long-term reproductive strategies (Ricklefs 1990). For example, some seabirds can maintain their investment in reproduction at a constant level despite a large variation in foraging conditions (Pugesek 1981, Bolton 1995, Kitaysky 1996). This parental strategy can result in large fluctuations in reproductive success but relatively small variations in the post-breeding survival of parent seabirds. Other seabirds are known to adjust their effort in current reproduction in relation to foraging conditions during a particular breeding season (Burger & Piatt 1990, Shea & Ricklefs 1985, Shea & Ricklefs 1996, Kitaysky 1996, Kitaysky et al. submitted c). For example, if feeding conditions are poor, adults should increase foraging effort to raise young. This parental strategy results in relatively low variation in bird reproductive success, but large variation in post-breeding survival of parent seabirds. In both scenarios, a trade-off between reproduction and survival must be balanced to maintain populations.

Natural fluctuations in food availability and anthropogenic impacts such as pollution or commercial fisheries may shift the balance between reproduction and survival in seabird populations (Golet et al. 1998) We hypothesize that a shift in the balance between reproduction and survival is responsible for the marked decline of some seabird populations in the Bering Sea. In this study, we will use baseline levels of circulating corticosterone in seabirds to indicate current stress state and relate this to current patterns of reproduction and diet composition (both being examined by other investigators, see below). Patterns of hormone secretion in response to capture and handling will also indicate vulnerability of populations to future stress. Based on observations of stress in birds at Bogslof and the Pribilof islands, and more extensive research in lower Cook Inlet, we should be able to determine whether food stress is responsible for limiting reproductive success of kittiwakes and murres in the Bering Sea. Low reproductive rates can also result from the decreased post-fledging survival of juvenile seabirds that have experienced long-term food shortages or were fed poor quality food during their development. It will not be possible to follow the fate of fledglings from Bogoslof and the Pribilofs, but we will be testing this hypothesis in the laboratory by examining the ability of chicks raised on differing food regimes to learn foraging skills after ‘fledging’. Finally, the question of how current stress affects future adult survival requires a multi-year study of survival in relation to current stress (Golet et al. 1998). This work is presently under way in Cook Inlet, and these results should allow us to determine whether seabirds at Bogoslof and the Pribilofs are facing increased risk of mortality under current feeding regimes.

In this study we are examining the consequences of food-related stress by measuring circulating levels of plasma corticosterone in free-ranging seabirds. NPMR funds from the University of Alaska were obtained late in summer 1999, allowing us to initiate some pilot work to compare stress hormone levels in populations of Red-legged Kittiwakes, Black-legged Kittiwakes, Common Murres, and Thick-billed Murres breeding at colonies on Bogoslof Island (about 60 nm west of Dutch Harbor in the eastern Aleutians), and at the Pribilof Islands (St. Paul and St. George islands).

Bogoslof Island was visited in late July for 3 days during the course of seabird and marine mammal population surveys being conducted by the Alaska Maritime National Wildlife Refuge (AMNWR) in cooperation with the National Park Service (Bogoslof is a NPS National Monument). Access to this small, remote island is limited largely by sea conditions, and we were fortunate to have a window of good weather and logistic support from the M/V Tiglax. Blood samples were collected by Sasha Kitaysky (U. Washington) and John Piatt (USGS), while Vern Byrd and Jeff Williams of AMNWR and Bruce Robson (NMFS) assessed populations and breeding status of seabirds and marine mammals. Capable assistance was provided by Catherine Berg, Karen Boylan, and Rosa Meehan (USFWS, Anchorage), Bob Adamcik (USFWS, Washington, D.C.), and Joel Gay (Homer News, Homer). At St. George Island, personnel from the AMNWR (Art Sowls, Dean Kildaw) were already conducting biological studies of seabirds and collected blood samples for us in early August. At St. Paul Island, USGS biologists April Nielsen and Jeb Benson collected blood samples from seabirds in early August, with support from AMNWR personnel on St. Paul. At all sites, blood samples for baseline and acute stress series were obtained from at least 3 of the 4 main study species (birds on some islands had failed reproductively and were not accessible for capture).

Methods used to capture and sample blood are illustrated in the following series of pictures. First, birds attending nest sites are captured using a long pole with a small noose at the end (Fig. 6). The noose is slipped over the head, and the bird is quickly pulled to the ground (this takes only a few seconds, and causes no harm to the bird). In order to measure baseline stress hormone concentrations, birds must be sampled within 3 minutes of initial capture (usually only takes 1-2 min). A small (microliter amount) sample of blood is taken by pricking a vein in the wing and collecting blood with a hematocrit tube (Fig. 7). After this time, the natural endocrine response to stress of capture results in a rapid increase in circulating corticosteroid hormone concentrations. Hormone levels increase for about 30 minutes, and typically level off after that time in healthy birds. To study this ‘acute response’, we retain birds in a holding bag for 50 minutes after capture, and take micro-samples of blood at 10, 30 and 50 minutes after capture. Following this, birds are measured (Fig. 8) and weighed (Fig. 9) to obtain data with which to assess the body condition of birds (e.g., starving birds will have low mass for their measured size). Birds are then released (Fig. 10), and most return to breeding sites on the cliffs within a short time. Blood samples are later processed (Fig. 11) and plasma is separated using a centrifuge. Samples are frozen and returned to the laboratory at the University of Washington where plasma concentrations of corticosteroids are measured using radio-immunoassay techniques.

Our work is being conducted in conjunction with two other NPMR funded projects-- all falling under the collaborative project entitled "Regime Forcing and Ecosystem Response" (ReFER). In the first project, Vern Byrd and colleagues at the Alaska Maritime National Wildlife Refuge are testing the hypothesis that divergent trends in populations of kittiwakes (Rissa spp.) at Bogoslof and the Pribilofs are related to differences in community structure and food web production. Specifically, they will evaluate whether parameters of reproduction, such as productivity and chick growth rates, are higher at Bogoslof (increasing populations) than in the Pribilofs (decreasing populations). This work entails direct observations of kittiwakes on their breeding cliffs throughout summer (Fig. 12). They will also evaluate historic patterns of population change, timing of nesting events, and various reproduction parameters (e.g., clutch size, laying success, hatching, success, fledging success, chick growth) to assess whether these parameters are correlated with environmental factors. Although the research is focused on kittiwakes because of their contrasting population dynamics, similar data will be gathered on Thick-billed and Common Murres at all colonies (populations declining everywhere). This work compliments and will benefit from an ongoing seabird monitoring program in the Pribilof Islands funded by the U.S. Fish and Wildlife Service.

In the second collaborative project, Alan Springer (Institute of Marine Science, UAF) and Sarah Iverson (Dalhousie Univ., Canada) will be studying the diets of seabirds at Bogoslof and the Pribilof islands. This project will adapt a technique for assessing diets of marine mammals using fatty acid signatures. The method has numerous advantages over other more common approaches that use ratios of stable isotopes or stomach content analyses to assess diet composition. It will permit them to test hypotheses that diets of populations of conspecific seabirds differ between oceanic and shelf habitats and that differences in diet account for opposite trends in abundance at the Pribilof Islands (shelf habitat) compared to Bogoslof Island (oceanic habitat). As part of the study, they will develop an inventory of fatty acid profiles of key forage species in the region that will be useful for diet studies of not only seabirds, but of trophically related marine mammals including sea lions, fur seals, and harbor seals. For this study, small numbers of kittiwakes (spp.) and murres (spp.) will be collected at all colonies during the breeding season. Stomachs from these specimens will be analyzed for diet composition in the traditional way, while fat from these specimens will be analyzed for fatty acid signatures. Samples of fish and invertebrates that comprise important prey for these seabirds will be obtained from stomachs, chick meal deliveries, and from trawls, and these prey will be examined for their fatty acid composition.

During the coming year, the project will consist of field and laboratory components. Blood samples collected in 1999 are being analyzed in the laboratory, and results will be summarized this winter. During the 2000 field season, we will focus on the comparison of the endocrinological characteristics of Black-legged and Red-legged Kittiwakes, and Common and Thick-billed Murres breeding at Bogoslof Island with those nesting at the Pribilof Islands. Laboratory analyses, and captive-rearing, learning, and foraging efficiency trials will be conducted at the University of Washington.

Field component: Correlations among corticosterone levels, reproductive stage and varying foraging conditions. To assess whether seabirds from the different populations are chronically stressed or not, we will determine baseline levels of corticosterone in relation to the reproductive stages (pre-incubation, incubation, and early and late chick-rearing). Adult birds will be captured at the breeding colonies (working out of camps established by AMNWR) and blood collected as described above in the summary of 1999 field work. To determine the potential for stress in different populations we will measure circulating levels of corticosterone in response to a standardized stressor (capture, handling and restraint; as described above). Blood samples will also be collected from chicks using similar methods as for adult birds. About 10-15 adult birds and chicks will be sampled at each colony at every stage of the reproductive period (total 50-75 birds of each species per colony/year). After sampling, adult birds will be released at the colony and chicks returned to their nests. Previous field and captive studies indicate that taking blood does not affect the long-term physiological condition or behavior of birds (J. Wingfield, personal observations). Similarly, bleeding captive seabird chicks does not appear to affect their behavior or development (A. Kitaysky and M. Romano, personal observations).

Laboratory component: Captive study of the effects of food-related stress. To test whether the food/pollution-related stress affects behavior, morphological development and physiological condition of young seabirds, we will raise Red-legged Kittiwake and Common Murre chicks on different nutritional regimes in captivity according to already established protocols. For the experimental treatments (10 chicks per each treatment) we will use the methods described by Romano and co-authors (Romano et al., unpublished; Kitaysky et al. in press d) where either quantity or quality of the chick diets will be altered. In particular, one group of young will be raised on reduced quantities of the high quality food (sandlance Ammodytes hexapterus, capelin Mallotus villosus, herring Clupea harengus, or Myctophids). Chicks from the second experimental treatment will be raised on sufficient amounts of food of poor quality (juvenile pollock, Theragra chalcograma). Control chicks will be raised on the food of high and poor quality given ad libitum. Behavioral trials testing foraging efficiency and learning abilities of experimental birds will be carried out according to a standardized protocol (see Clayton 1995 for details).

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Murres and Tufted Puffin survey fur seals on the beach at Bogoslof Island

April Nielsen measuring Red-legged Kittiwake on St. Paul Island

Murre cliffs on Bogoslof Island

Fur seal family on Bogoslof Island

Grubbing for Puffins on Bogoslof Island

Fur seal beach on Bogoslof Island

Just a little bit higher please! Capturing kittiwakes on Bogoslof Island.

Fishing for murres on St. Paul Island

This is summer? Taking blood sample from a Thick-billed Murre on St. Paul Island in August.

You want stress? I’ll give you stress! Two Tufted Puffins duke it out on Bogoslof Island.