Environmental conditions and life history constraints determine foraging range in breeding Adélie penguins

Abstract

Foraging movements of Adélie penguins are constrained both by environmental conditions (e.g. sea ice cover) and life history factors (e.g. regular offspring provisioning). We describe within season changes in foraging range, trip duration and body condition of Adélie penguins nesting at Béchervaise Island, East Antarctica, in the context of these constraints. Penguins were satellite tracked over multiple seasons during the incubation, guard, crèche and pre-moult phases of their annual cycle. They ranged farthest during incubation when sea ice was extensive and shortest during the guard stage when chicks were small and sea ice limited in extent. Prior to their annual moult the birds foraged hundreds of kilometres to the west and east of their breeding sites. A recurrent polynya facilitated access to the sea early in the season when ice cover was extensive. Kernel analyses showed that penguins foraged most intensively close to the colony, along submarine canyons and at the continental shelf break. Increases in foraging range, as the chick rearing period progressed, were consistent with changing energy requirements of adults and chicks and likely intraspecific competition. Whilst provisioning their offspring, penguins adopted a variable combination of time minimising and food maximising foraging behaviour in which choice of foraging rule was determined largely by adult body condition.

Foraging strategies of Adélie penguins: adjusting body condition to cope with environmental variability

“…Our results confirm those of Chastel et al (1995a, b), Weimerskirch et al (1997Weimerskirch et al ( , 2000Weimerskirch et al ( , 2001, Vleck & Vleck (2002), Takahashi et al (2003), and Clarke et al (2006), that relative body condition affects decision making in avian parents, following the predictions of life history theory: penguins in poorer condition made longer foraging trips, carried less food to young, and gained more mass per foraging trip than those in better condition. While previous researchers have hypothesized that longer foraging trips result in smaller food loads for Adélie penguin chicks (Drent & Daan 1980, Clarke et al 2002, ours is the first study to quantify this effect and the effect of adult body condition on this relationship.…”

“…With the narrow shelf near Bèchervaise Island, extensive coastal fast ice limits penguin access to the richest (neritic) waters (Clarke et al 2006, Emmerson & Southwell 2008. Another study compared the small colony at Hukuro Cove (< 2000 pairs), which had extensive fast ice (sea ice attached to land, with access to prey only available via sparse cracks), to colonies with more normal, loosely distributed pack ice at the (also small) Biomar colony and the larger Magnetic Island colony (17 200 pairs).…”

“…As a major habitat variable affecting penguin foraging and reproductive effort, sea ice coverage and prox-imity is important (Ainley 2002, Clarke et al 2006, Cockrem et al 2006, Emmerson & Southwell 2008, Beaulieu et al 2010. Given the choice, Adélie penguins feed in close proximity to sea ice, presumably because their preferred prey is found there, but potentially also because it offers a resting platform and easy source of drinking water (Ainley 2002).…”

“…A contrasting conclusion for Adélie penguins, consistent with flexible investment, has been postulated based on examination of diving behavior and foraging models (Ropert-Coudert et al 2004). Furthermore, 3 empirical studies have found that Adélie penguins alternate long, relatively low-activity, self-maintenance trips with short, high-activity, chick-provisioning trips (Clarke 2001, Clarke et al 2006, Angelier et al 2008). Finally, Vleck & Vleck (2002) showed that Adélie penguins with lower body mass at the onset of breeding were in poorer physiological condition and tended to have lower reproductive success than heavier individuals, and individuals with lower mass have elevated levels of corticosterone, suggesting they are more likely to abandon breeding efforts (Cockrem et al 2006).…”

Analytical approaches to investigating seabird–environment interactions: a review

“…Seabird distribution data have been reported in the literature as simple locations or density grids, as well as using more quantitative indices such as computing kernel densities (van Franeker et al 2002, Awkerman et al 2005, Clarke et al 2006. The simple display of distribution data has been much more commonly used than quantitative indices, with proportions ranging from 80 to 100% of the number of papers for any given 5 yr period.…”