Gone fishing: Adélie penguin site-specific foraging tactics and breeding performance

Abstract

The ecological drivers underlying breeding performance are expected to differ across the geographical range of seabird species, but few studies have compared trade-offs between colonies with different local conditions. During chick-rearing (2000–01), we compared the foraging trips, diet and breeding parameters of two Adélie penguin colonies in the Ross Sea, at Edmonson Point (EdPo; ~2000 breeding pairs) and Inexpressible Island (InIs; ~24 000 breeding pairs). Penguins from InIs travelled farther and performed longer feeding trips. The quantity of food brought to the nest was the same for the two colonies, but penguins from InIs brought more fish and less krill. Eggs hatched earlier at EdPo. Breeding success did not differ, but chick weight during hatching–fledging was greater at InIs. Despite worse weather conditions at InIs, the larger proportion of high-energy food brought by penguins from InIs (i.e. fish) may explain their offspring‘s better performance. In addition, the persistence of fast ice at EdPo may have led to greater energy expenditure of breeding individuals, possibly reducing chick growth. The greater intraspecific competition expected at InIs may have been reduced by longer foraging trips and/or counteracted by the more nutritious diet. Our findings reveal complex trade-offs between foraging effort and environmental constraints in determining the breeding performance of Adélie penguins.

Genetic diversity in clustered colonies of an Antarctic marine mesopredator: a role for habitat quality?

“…Skua predation is the major cause of egg and chick loss, accounting for up to 40% during the breeding season (S. Olmastroni, unpublished data 1996–2018). However, breeding success, diet, foraging range and adult survival rate for the Edmonson Point population are similar to those of other colonies (Ballerini et al 2009, Olmastroni et al 2020) and other parts of the Antarctic (Jenouvrier et al 2006). Immature pre-breeders are important to population demography (Bicknell et al 2014), although Ballerini et al (2009) reported a low recruitment of birds marked as chicks (25%) for this colony.…”

“…Killer whales ( Orcinus orca , ecotype B) have been observed travelling along the fast-ice edge and shoreline among the Wood Bay and TNB area (Lauriano et al 2011). A previous study showed that the penguins fed little inside the TNB polynya area, but rather used it to reach the pack ice that rings the polynya, rather than to walking (Olmastroni et al 2020).…”

“…At the beginning of the breeding season (early November), a total of 50 occupied nests were selected in each colony for carrying out different research activities in the framework of the PenguinERA project (PNRA2016 AZ1.11) and for the long-term monitoring of the Adélie penguins in the TNB area (cf. Olmastroni et al 2020). An Adélie penguin colony is composed of numerous separated subgroups of different sizes and shapes (Ainley 2002); therefore, we attempted to balance sampling spatially.…”

Spatial and temporal diet variability of Adélie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) Penguin: a multi tissue stable isotope analysis

“…The availability of krill and P. antarctica as prey for penguins is related to sea ice dynamics (Ainley et al 1998). In fact, increased availability of krill as prey for penguins seem to occur in seasons or areas characterized by a greater pack ice presence while there is an increase in fish availability in areas without sea ice (Ainley et al1998(Ainley et al , 2003Strickland et al, 2008;Olmastroni et al 2020).…”

Pitfalls and advances in morphometric sexing: insights from the Adélie penguin Pygoscelis adeliae

“…If sexual dimorphism in bill size was due to sexual selection, one could speculate that a lower sexual selection on bill size may have occurred because of the relatively low habitat quality at Edmoson Point. In this colony, persistent fast-ice and high density of terrestrial predators (South Polar Skua Stercorarius maccormicki) seem to increase energetic constraints of penguins (see Clarke et al 1998;Olmastroni et al 2004Olmastroni et al , 2020Pezzo et al 2007;Mori et al 2021, for environmental-related constraints at Edmonson Point), which might have reduced the potential investment in sexual selection. Nevertheless, this hypothesis remains to be tested across colonies differing in habitat quality/predator density.…”