Heavier Arctic Geese Synchronize Breeding in Colder New Habitats

Global warming is altering Arctic environments, causing spring onset to advance, especially in the Arctic, and challenging migratory species. Animals like the Pink-footed Goose (Anser brachyrhynchus) may respond by advancing their phenology or colonising colder areas. Recently, Pink-footed Geese from Svalbard showed extreme range expansion by establishing new breeding grounds in the colder Novaya Zemlya, involving a new migration route. Researchers investigated the potential costs and benefits associated with breeding in this new area.

Using GPS-tracking, long-term monitoring, and remote sensing, the study compared these two flyways. They found that while spring had advanced in Svalbard, goose arrival dates had not kept up, leading to challenges for migration timing. In contrast, Novaya Zemlya presented a later spring, but geese arriving there were larger and relatively heavier, possibly carrying larger capital body stores to cover harsher pre-laying periods. Although egg-laying in Novaya Zemlya occurred later than in Svalbard, it was earlier relative to local spring onset (e.g., snowmelt and green-up), suggesting a smaller mismatch with environmental conditions.

These findings suggest that colonizing new breeding areas can enable populations to regain phenological match with their environment, particularly when advancement of migration timing was limited. However, this adaptation comes with a trade-off. Breeding in a colder region may require more parental investment, such as the body stores observed in Novaya Zemlya geese. As lead author Schreven notes in the paper, "Thus, a benefit for offspring comes at a cost for parents." This mechanism illustrates how climate change can both drive and facilitate colonization, especially for individuals capable of making large investments, leading to heterogeneous effects within a population at the 'cold' edge of range shifts.