Relationships between oceanography and the demography & foraging of auklets (charadriiformes, alcidae - Aethia; merrem 1788) in the Aleutian Islands, Alaska

Bond, Alexander Lyons (2011) Relationships between oceanography and the demography & foraging of auklets (charadriiformes, alcidae - Aethia; merrem 1788) in the Aleutian Islands, Alaska. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

I investigated bottom-up climate-mediated control of population of auklets (Aethia Cristatella, A. pusilla, and A. pygmaea) in the Bering Sea over two decades of environmental variability, broadly, this thesis comprises two parts: 1) examining the relationships between chick diet and survival in the context of large-scale climate and oceanographic patterns; and 2) using stable-isotope analysis to infer foraging patterns throughout the annual cycle of different age classes of auklets, using information on chick diet and local oceanography to interpret the results. -- I found that large-scale oceanographic patterns during the winter and spring in the North Pacific were related to auklet productivity the following breeding season. I hypothesized bottom-up control of auklet productivity through food limitation, but found that chick meal composition throughout the Aleutian Islands did not differ among years or sites. Auklets’ main prey, Neocalanus spp. Copepods were most prevalent in chick diets when local sea-surface temperature (SST) during the breeding season was around 4.5 ± 1.0°C, but that outside this range, the proportion of biomass represented by Neocalanus copepods declined rapidly. There was significant overlap among Least, Crested, and Whiskered Auklets in the composition of chick meals, suggesting little trophic segregation. -- Using information on moulting patterns, I found that stable-isotope ratios in the innermost primary feather (grown during incubation) indicated a shift by adult auklets to a more productive foraging location (e.g., oceanic fronts), presumably as a mechanism for reducing their own maintenance costs during chick rearing. I then found that, among three auklet colonies in the Aleutian Islands, there were no differences among sites of years in the foraging patterns of Least Auklets during pre-breeding (breast feathers), incubation (primary 1), or post-breeding (primary 10). There appeared to be some level of ecological segregation between adult Least and Crested Auklets at Gareloi Island. -- Together, these results also indicate that local factors, such as introduced Norway rats (Rattus norvegicus) at Kiska Island, are important factors in populations’ demography, and that demographic responses are not solely driven by bottom-up processes. Future studies should focus on the winter ecology and movements of auklets.

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