Solitary Nesting: A Unique Breeding Strategy in Penguins

Jenn Hoskins
29th April, 2024

Image Source: Natural Science News, 2024

Key Findings

In Antarctica, Adélie penguins sometimes nest alone, away from the safety of large groups
Solitary-nesting penguins' chicks face a mortality rate six times higher than those in groups
Despite risks, solitary nests are reused, suggesting they may help penguins pioneer new colonies

Understanding the breeding behaviors of seabirds, particularly those that form large colonies, is essential for conservation efforts and ecological studies. One species that has been the focus of such research is the Adélie penguin, which breeds in the harsh conditions of Antarctica. Researchers from Point Blue Conservation Science have conducted a study^[1] focusing on the less common practice of solitary nesting within this species, providing insights into the risks and potential benefits of this behavior. Adélie penguins typically breed in dense groups known as subcolonies. This behavior has been thought to provide several advantages, including protection from predators like the south polar skuas. The 'selfish herd' hypothesis suggests that by forming compact groups, individual penguins can reduce their risk of predation. However, the benefits of colonial breeding may not be the same for all individuals, particularly those on the subcolony's edge, who might face higher predation rates. The recent study tracked 50 solitary-nesting Adélie penguins at Cape Crozier, Ross Island, during the 2021 nesting season. These solitary nesters choose to establish their nests far from others, seemingly at odds with the 'selfish herd' hypothesis. The researchers compared the breeding success of these solitary nesters with their counterparts in the more traditional subcolony setting. They found that while both solitary and subcolony nests could raise chicks to the size necessary to join crèches—groups of young penguins that gather together—chicks from solitary nests had a mortality rate more than six times higher during the transition from being brooded or guarded by adults to joining these crèches. Despite the higher mortality rate, solitary nesting was not completely unsuccessful. In the following 2022 nesting season, previously used solitary nests were often re-occupied. This persistence suggests that solitary nesting may be a strategy for pioneering new breeding locations, potentially leading to the establishment of new colonies. This finding ties into earlier research^[2] that has shown the benefits of chick aggregations, such as crèches, in gentoo penguins. These aggregations can reduce energy expenditure in cold, wet conditions and provide protection from predators and adult aggression. The success of solitary-nesting Adélie penguins in raising chicks to the crèche stage, despite the higher risks, indicates that the drive to form aggregations is strong, even if the initial breeding strategy deviates from the norm. The study also complements previous work on group foraging behaviors, as observed in the Socotra cormorant^[3]. Group foraging, which may seem counterintuitive due to increased competition for food, actually provides benefits such as improved prey detection and capture. Similarly, the Adélie penguins' crèche stage may offer collective benefits that outweigh the initial risks of solitary nesting. Furthermore, the research adds to our understanding of sexually size-dimorphic species, like the Adélie penguin, where growth rates and diets can differ between sexes^[4]. Such differences can affect the survival of chicks depending on their sex, which may influence the breeding success of solitary nests versus those in subcolonies. The persistence of solitary nesting among Adélie penguins, despite its apparent disadvantages, highlights the complex balance of risk and reward in breeding strategies. It also underscores the importance of considering individual variability within a species when assessing the impact of environmental changes and conservation measures. The work of Point Blue Conservation Science in this area not only sheds light on the adaptive strategies of a key Antarctic species but also on the potential for these strategies to change in response to environmental pressures, ultimately influencing the dynamics of seabird populations.

Wildlife Ecology Marine Biology

References

Main Study

1) I need some space: solitary nesting Adélie penguins demonstrate an alternative breeding strategy at Cape Crozier

Published 28th April, 2024

https://doi.org/10.1007/s00300-024-03246-9

Related Studies

2) Why Huddle? Ecological Drivers of Chick Aggregations in Gentoo Penguins, Pygoscelis papua, across Latitudes.

https://doi.org/10.1371/journal.pone.0145676

3) Group foraging in Socotra cormorants: A biologging approach to the study of a complex behavior.

https://doi.org/10.1002/ece3.2750

4) Sex-Based Differences in Adélie Penguin (Pygoscelis adeliae) Chick Growth Rates and Diet.

https://doi.org/10.1371/journal.pone.0149090

Key Findings

References

Main Study

Related Studies

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