Fine‐scale habitat use during the non‐breeding season suggests that winter habitat does not limit breeding populations of a declining long‐distance Palearctic migrant

Abstract

For migrant birds, which habitats are suitable during the non‐breeding season influences habitat availability, population resilience to habitat loss, and ultimately survival. Consequently, habitat preferences during winter and whether habitat segregation according to age and sex occurs directly influences migration ecology, survival and breeding success. We tested the fine‐scale habitat preferences of a declining Palearctic migrant, the whinchat Saxicola rubetra, on its wintering grounds in west Africa. We explored the influence of habitat at the territory‐scale and whether dominance‐based habitat occupancy occurs by describing the variation in habitat characteristics across wintering territories, the degree of habitat change within territories held throughout winter, and whether habitat characteristics influenced territory size and space‐use within territories or differed with age and sex. Habitat characteristics varied substantially across territories and birds maintained the same territories even though habitat changed significantly throughout winter. We found no evidence of dominance‐based habitat occupancy; instead, territories were smaller if they contained more perching shrubs or maize crops, and areas with more perching shrubs were used more often within territories, likely because perches are important for foraging and territory defence. Our findings suggest that whinchats have non‐specialised habitat requirements within their wintering habitat of open savannah and farmland, and respond to habitat variation by adjusting territory size and space‐use within their territories instead of competing with conspecifics. Whinchats show a tolerance for human‐modified habitats and results support previous findings that some crop types may provide high‐quality wintering habitat by increasing perch density and foraging opportunities. By having non‐specialised requirements within broad winter habitat types, migrants are likely to be flexible to changing wintering conditions in Africa, both within and across winters, so possibly engendering some resilience to the rapid anthropogenic habitat degradation occurring throughout their wintering range.

Patterns in departure phenology and mass gain on African non‐breeding territories prior to theSahara crossing in a long‐distance migrant

“…This may not be the case in the Old World, however, where suitable wintering habitat may be more abundant (Newton ) and differences in quality between habitats not so well defined (Cresswell ). Indeed, there is no evidence of sex‐ or age‐based habitat occupancy for wintering Whinchats over the study area based on fine‐scale habitat characteristics (Blackburn & Cresswell ,b), although it is possible these habitat characteristics do not necessarily reflect prey abundance. A lack of segregation would be expected in an area with low competition (Whinchats are not at carrying capacity in this area; Hulme & Cresswell ) and where energy costs are low (Whinchats spend only 11% of the day foraging; Barshep et al .…”

“…Individuals hold small, discrete territories during the winter (Barshep et al . , Blackburn & Cresswell ), and their preference for open habitat and tendency to perch on low shrubs make them highly detectable (Hulme & Cresswell ).…”

Apparent resilience of a declining Afro‐Palaearctic migrant to forest loss on the wintering grounds

“…It has been suggested that, unlike open‐country migrant species (Cresswell et al . , Hulme & Cresswell , Blackburn & Cresswell , 2016), those species that are more dependent on shrubby and wooded habitats may suffer the consequences of the loss of native vegetation (Cresswell et al . , Mallord et al .…”

“…This is particularly true for Afro‐Palaearctic migrants (Vickery et al . ), although this is improving (Blackburn & Cresswell , , Mallord et al . , Willemoes et al .…”

“…Whereas open‐country species may be able to take advantage of habitats newly created by degradation of wooded habitats (Cresswell et al . , Blackburn & Cresswell ), these changes are likely to be more harmful to woodland species. The aims of this study were three‐fold.…”