The non-breeding ecology of Common Whitethroats Curruca communis in central Nigeria

Abstract

Identifying what drives or prevents long-distance migrants from responding to environmental changes requires a complete understanding of the ecology and behaviour of individuals throughout their annual cycle. The non-breeding period represents a significant part of an Afro-Palearctic migratory bird’s life; what occurs during this period influences an individual’s survival and future reproductive success. I studied factors that influence the population dynamics of Common Whitethroats Curruca communis during three non-breeding periods in Nigeria (2017–2020). First, I collected and analysed data from six geolocators deployed in 2019 to understand how non-breeding and breeding sites are connected. Second, I used data collected from >300 colour-ringed individuals and daily resightings to understand site persistence, within- and between-years site fidelity, fine-scale spatial movements, and habitat preference and availability. Lastly, I used daily resighting and long-term ringing data to calculate annual and overwinter survival rates. Results indicate that Whitethroats bred across eastern Europe, suggesting a somewhat high migratory spread defined by a north-eastern flight pattern, and a predominantly intermittent migratory strategy. All birds undertook a loop migration and stopped at a first non-breeding site in the Sahel. At core wintering grounds Whitethroats showed a great degree of individual variation regarding temporal and spatial behaviour: individuals exhibited different residency periods (from 1–165 days), a high degree of within- and between-years site fidelity, and many individuals established small home ranges with little significant variation through time, age, sex, and residency, despite habitat changing through the winter. Shrubs were identified as the preferred main vegetation type. High overwinter survival rates and a potential generalist strategy during the wintering period all strongly indicate that this period is likely a low-mortality period for Whitethroats. This study highlights the importance of conserving suitable habitats for Whitethroats over a very large area in both the breeding and non-breeding grounds, particularly the Sahel region, an important refuelling and stationary site.