Foraging effort does not influence body condition and stress level in little auks

• Published in: Marine ecology. Progress series (Halstenbek) 2011-06, Vol.432, p.277-290
• Main Authors: Jakubas, Dariusz, Głuchowska, Marta, Wojczulanis-Jakubas, Katarzyna, Karnovsky, Nina J., Keslinka, Liliana, Kidawa, Dorota, Walkusz, Wojciech, Boehnke, Rafał, Cisek, Małgorzata, Kwaśniewski, Sławomir, Stempniewicz, Lech
• Format: Article
• Language: English
• Subjects: Bird nesting; Body condition; Breeding; Diet; Food; Food availability; Foraging; Sea birds; Seas; Zooplankton
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps09082

In conditions of deteriorating food availability, seabirds may maximize their breeding success by increasing reproductive effort, which compromises body condition, stress level, survival, and future reproductive success. We studied a small planktivorous alcid, the little aukAlle alle, in 2 breeding colonies in west Spitsbergen, Norway (Hornsund and Magdalenefjorden) with contrasting oceanographic conditions (Arctic and Atlantic environments, respectively). We hypothesized that the chick diet composition and parental foraging effort differs between these colonies, which results in intercolony variation in body mass and stress level of both adults and chicks. We found differences in sea temperature and salinity (both lower in Hornsund) and the abundance of Atlantic copepodCalanus finmarchicus(3.6 times less abundant in Hornsund) between foraging areas. Birds from both colonies foraged selectively onCalanus glacialisCV. Composition, total biomass and energy content of food loads were similar in both colonies, though food delivered to nestlings in Magdalenefjorden was more diverse. The frequency of feeds was also similar in both colonies. Parent little auks in Magdalenefjorden, however, performed longer foraging trips than in Hornsund (medians 183 vs. 124 min). Longer foraging trips suggest that these birds traveled longer distances to find abundant prey at the marginal sea ice zone and/or spent more time foraging close to the colony but in poorer foraging areas. Despite increased parental efforts in Magdalenefjorden, body mass and stress levels of adults and chicks were similar in both colonies. This suggests that little auks from northwest Spitsbergen did not reach a threshold requiring prioritization of self-maintenance over chick provisioning.