Adverse foraging conditions may impact body mass and survival of a high Arctic seabird

Abstract

Tradeoffs between current reproduction and future survival are widely recognized, but may only occur when food is limited: when foraging conditions are favorable, parents may be able to reproduce without compromising their own survival. We investigated these tradeoffs in the little auk (Alle alle), a small seabird with a single-egg clutch. During 2005-2007, we examined the relationship between body mass and survival of birds breeding under contrasting foraging conditions at two Arctic colonies. We used corticosterone levels of breeding adults as a physiological indicator of the foraging conditions they encountered during each reproductive season. We found that when foraging conditions were relatively poor (as reflected in elevated levels of corticosterone), parents ended the reproductive season with low body mass and suffered increased post-breeding mortality. A positive relationship between body mass and post-breeding survival was found in one study year; light birds incurred higher survival costs than heavy birds. The results of this study suggest that reproducing under poor foraging conditions may affect the post-breeding survival of long-lived little auks. They also have important demographic implications because even a small change in adult survival may have a large effect on populations of long-lived species.

Population control of an overabundant species achieved through consecutive anthropogenic perturbations

“…We present evidence of how these two consecutively occurring perturbations have been extremely effective in reducing the population density of a generalist opportunistic bird, which has not recovered in the three years following these events. Under strong perturbation pulses (Martı´nez-Abraı´n et al 2012) or intense environmental variability (Harding et al 2011), the density-dependent responses of demographic parameters appear insufficient to buffer population changes. Although an isolated perturbation, such as poisoning, seemed to have an important short-term effect, it is reasonable to believe that it was the closure of the landfill site that led to a permanent decrease in the carrying capacity of the system and hence a long-lasting reduction in population numbers, as previously suggested by Oro and Martı´nez-Abraı´n (2007).…”

Little auks buffer the impact of current Arctic climate change

“…For all adults caught at the 3 colonies, we recorded body mass, headbill length and wing length, and these measurements were used to calculate an index of body condition (body mass corrected for structural size) as detailed in Harding et al (2011). Adult survival rates of birds from KH and KF were determined using a capture-mark-recapture analysis.…”

Parent-offspring interactions in a long-lived seabird, the Little Auk (Alle alle): begging and provisioning under simulated stress

“…Experimental manipulations appear to be the best way to predict birds' reactions during unfavourable environmental conditions. The recognised positive corticosterone response to adverse trophic and environmental conditions (Harding et al 2011;Kidawa et al 2014) allowed us to artificially enhance the corticosterone level in Little Auk chicks and adult birds, to study changes in their behaviour.…”

“…We also expected that chicks with one parent implanted with corticosterone fledge later and with a lower body mass than chicks of two untreated parents. Due to the evident linkage between body condition and survival (Harding et al 2011), adult birds should govern the degree of parental investment against the negative consequences on their own body condition. Exploring the mechanisms that regulate the parental investment might help to evaluate the trade-offs involved in the reproductive performance in Little Auks, which are particularly important in predicting their response to the worsening foraging conditions in the Arctic Kwasniewski et al 2012).…”