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

Populations of long-distance migrant birds are declining but it is unknown what role land cover change in non-breeding areas may be playing in this process. Using compositional analysis, we assessed habitat selection by one such migrant, the Wood Warbler Phylloscopus sibilatrix, at a wintering site in the forest-savannah transition zone in Eastern Region, Ghana. There was a preference for forest, a habitat that is in marked decline at this site. Annual habitat mapping revealed that the area of forest declined by 26% between 2011/12 and 2013/14, mainly through clearance for conversion to arable land. Numbers of birds changed throughout the season, but despite the reduction in the preferred forest habitat, there was no change in the total number of birds recorded at the site over the study period. The number of birds recorded at a point was positively related to the proportion of cleared land, plantation and, to a lesser extent, dense forest within 100m. Investigation of the fine-scale habitat preferences of radiotagged Wood Warblers suggested that there was an optimum number of trees, around 66-143 per hectare, at which estimated probability of occupancy was 0.5, falling to a probability of 0.2 at 25 trees per hectare. We suggest that Wood Warblers may be buffered against the loss of forest habitat by their ability to utilize degraded habitats, such as well-wooded farmland, that still retain a substantial number of trees. However, the continued loss of trees, from both forest and farmland is ultimately likely to have a negative impact on wintering Wood Warblers in the long-term.