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Climate, habitat and demography predict dispersal by an endangered bird in a fragmented landscape

Teunissen, Niki1; Kingma, Sjouke1; Peters, Anne2

Published Feb 24, 2025 on Dryad. https://doi.org/10.5061/dryad.6t1g1jx95

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Feb 24, 2025 version files 233.61 KB

Abstract

Worldwide, biodiversity is threatened by human-induced habitat degradation and fragmentation. Dispersal, particularly long-distance dispersal between isolated habitat fragments, is key for population connectivity and species persistence in the face of environmental change. However, we lack understanding of how habitat fragmentation and degradation itself affect the dispersal process. To identify conditions that promote or constrain connectivity, we need to reveal how habitat, demographic, and climatic conditions drive dispersal success and distance. This is challenging, however, because detecting dispersal events in wild animals, especially over long distances, is notoriously difficult.

Here we address this in the Endangered purple-crowned fairy-wren, Malurus coronatus, a small cooperatively breeding songbird in which individuals can opt to delay natal dispersal, and we are able to consistently detect dispersal by colour-marked individuals, including over long distances. Thus, an assessment of drivers of dispersal success and distance is achievable. Using data from a 17-year study, we analyse dispersal probability for 796 individuals, and distance of 206 dispersal events (up to 68 km).

We show that poorer quality and isolated habitat is associated with more frequent dispersal, and over greater distances.

Additionally, low population density promotes dispersal, while higher rainfall (which increases food availability for several months), especially during the wet season, increases dispersal distance, particularly at high population density. This indicates that, when the population is saturated, favourable conditions may allow birds to successfully disperse over the long distances required to connect fragments.

Policy implications: Our findings suggest that while habitat fragmentation and degradation may promote dispersal, such dispersal, especially over greater distances, may require benign climatic conditions, presumably to limit its cost. Our results highlight the need to integrate the impacts of climate change when assessing how habitat degradation and fragmentation affect population connectivity. Additionally, we recommend conservation management actions targeted at increasing source population density as an important first step in promoting connectivity between habitat fragments via long-distance dispersal.