Planktivorous Auklets (Aethia pusilla and A. cristatella) nesting on St. Lawrence Island, Alaska as indicators of marine conditions in the northern Bering Sea (original) (raw)
Related papers
The Influence of Diet and Ocean Conditions on Productivity of Auklets on ST Lawrence Island, Alaska
Marine ornithology, 2009
1USGS–Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, 97331, USA (Sheffield.Lisa@gmail.com) 2Current address: 11539 Corliss Avenue N, Seattle, Washington, 98133, USA 3Current address: ABR, Inc., PO Box 80410, Fairbanks, Alaska, 99708, USA 4Migratory Bird Management, US Fish and Wildlife Service, 1011 East Tudor Road, Anchorage, Alaska, 99503, USA
Journal of Ornithology, 2012
Seabirds are effective samplers of the marine environment, and can be used to measure resource partitioning among species and sites via food loads destined for chicks. We examined the composition, overlap, and relationships to changing climate and oceanography of 3,216 food loads from Least, Crested, and Whiskered Auklets (Aethia pusilla, A. cristatella, A. pygmaea) breeding in Alaska during 1994-2006. Meals comprised calanoid copepods (Neocalanus spp.) and euphausiids (Thysanoessa spp.) that reflect secondary marine productivity, with no difference among Buldir, Kiska, and Kasatochi islands across 585 km of the Aleutian Islands. Meals were very similar among species (mean Least-Crested Auklet overlap C = 0.68; Least-Whiskered Auklet overlap C = 0.96) and among sites, indicating limited partitioning of prey resources for auklets feeding chicks. The biomass of copepods and euphausiids in Least and Crested Auklet food loads was related negatively to the summer (June-July-August) North Pacific Gyre Oscillation, while in Whiskered Auklet food loads, this was negatively related to the winter (December-January-February) Pacific Decadal Oscillation, both of which track basin-wide sea-surface temperature (SST) anomalies. We found a significant quadratic relationship between the biomass of calanoid copepods in Least Auklet food loads at all three study sites and summer (June-July) SST, with maximal copepod biomass between 3-6°C (r 2 = 0.71). Outside this temperature range, zooplankton becomes less available to auklets through delayed development. Overall, our results suggest that auklets are able to buffer climate-mediated bottom-up forcing of demographic parameters like productivity, as the composition of chick meals has remained constant over the course of our study. Keywords Aethia Á Aleutian Islands Á Auklet Á Climate Á Diet Á Overlap Zusammenfassung Seevögel ,,beproben'' ihre marine Umwelt und können so verwendet werden, um mittels des für die Küken bestimmten Futters die Ressourcenaufteilung zwischen Arten und Orten abzuschätzen. Wir haben die Zusammensetzung, Ü berlappung und Beziehung zu Veränderungen in Klima und Ozeanographie von 3,216 Futterportionen von in Alaska zwischen 1994 und 2006 brütenden Zwerg-, Schopf-und Bartalken (Aethia pusilla, A. cristatella, A. pygmaea) untersucht. Die Futterportionen enthielten calanoide Ruderfußkrebse (Neocalanus spp.) und Leuchtkrebse (Thysanoessa spp.), die marine Sekundärproduktion widerspiegeln, und es gab diesbezüglich keine Unterschiede zwischen den Inseln Buldir, Kiska und Kasatochi, die sich innerhalb der Aleuten über 585 km erstrecken. Die Futterportionen waren für die verschiedenen Arten (mittlere Zwergalk-Schopfalk-Ü berlappung C = 0.68; Zwergalk-Bartalk-Ü berlappung C = 0.96) und an den verschiedenen Orten sehr ähnlich, was auf eine begrenzte Aufteilung der Beuteressourcen Küken fütternder Alken Communicated by P. H. Becker.
Breeding Biology of Least Auklets on the Pribilof Islands, Alaska
The Condor, 1986
Aspects of Least Auklet (Aethia pusilla) breeding biology that pertain to the growth and development of chicks were studied on St. George Island, Bering Sea, Alaska, during the 198 1 and 1982 breeding seasons. Yolk was 41% of fresh egg contents, a greater value than in the eggs of other alcid species. Adult incubation shifts averaged 24 hr, and both parents frequently spent the night together in the nest during both the incubation and chick-rearing periods. Adults brooded nestlings continuously during the day until 6 days post-hatching; diurnal brooding then declined gradually until cessation by Day 18. Chicks grew rapidly and achieved peak mass by 20 days posthatching; most fledged at masses greater than average adult body mass. Nestlings were fed an average of 5.3 meals day-l; meals averaged 5.4 g and consisted mostly of Neocalanus copepods. Estimates of breeding success (72% and 66% in 198 1 and 1982, respectively) were about average for alcid species. The short nestling period of Least Auklet chicks is associated with frequent meal delivery and extended brooding made possible by the diurnal, nearshore foraging behavior of parents. Diurnal activity and nearshore foraging during the breeding season appear to be adaptations that minimize the duration of nesting and the associated risk of fox predation.
2008
A warming trend since the early 1990s is changing the Bering Sea ecosystem, causing increased sea surface temperatures and reduced sea ice cover. Models suggest that these changes may alter the availability of prey to a diverse array of upper trophic level consumers, including seabirds. To better understand how seabird productivity would be affected by potential changes in prey availability and ocean conditions in the Bering Sea, we studied the two most abundant species of planktivorous seabirds in the region, Least Auklets Aethia pusilla and Crested Auklets A. cristatella nesting on St Lawrence Island. We investigated the relationships between chick survival, taxonomic composition of chick diets, timing of sea ice retreat, winter sea ice cover, and flow through the Bering Strait during 2000–2004. Interannual variation in diet explained the largest percentage of variation in chick survival. Our results are consistent with the hypothesis that Least Auklet chick survival is negatively...