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

Abstract

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 100 m. 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.

Autumn migration and wintering site of a wood warbler Phylloscopus sibilatrix breeding in Denmark identified using geolocation

“…A recent study showed no change in wood warbler abundance despite habitat conversion, indicating resilience of this species to loss of primary forest at the wintering grounds at least on the short term [28]. The combined knowledge of migration patterns (this study), breeding [26,29] and non-breeding habitat requirements [28,30] as well as other potential impacts at breeding sites [31] will form the basis for effective conservation strategies for declining migratory songbird species such as the wood warbler. Because we could not track spring migration, it remains unknown whether the autumn route is traced back or a more direct route is chosen as indicated by more westerly recoveries in the Mediterranean in spring than autumn [32].…”

“…Their preferred habitats in both seasons are broadleaved forests with a relatively open forest structure [16,[25][26][27]. A recent study showed no change in wood warbler abundance despite habitat conversion, indicating resilience of this species to loss of primary forest at the wintering grounds at least on the short term [28]. The combined knowledge of migration patterns (this study), breeding [26,29] and non-breeding habitat requirements [28,30] as well as other potential impacts at breeding sites [31] will form the basis for effective conservation strategies for declining migratory songbird species such as the wood warbler.…”

Spatial behavior and habitat use in widely separated breeding and wintering distributions across three species of long‐distance migrant Phylloscopus warblers

“…Given the lower wintering range tree cover, moderate tree felling might not affect the area of suitable habitat negatively (Mallord et al, 2018). This indicates that an otherwise common assumption of niche-tracking might not apply on a fine scale.…”

“…Tree felling and destruction of natural habitat are widespread throughout Africa. Given the lower wintering range tree cover, moderate tree felling might not affect the area of suitable habitat negatively (Mallord et al, 2018).…”

Action before certainty for Africa's European migrant birds

“…With the miniaturization of tracking devices we can follow more species throughout their annual cycle, identifying migration routes, staging and wintering areas and even the location of mortality of individuals (Tøttrup et al, 2011; Hewson et al, 2016). Field studies in non-breeding areas have documented habitat preferences and/or tree selection by individual species, such as the wood warbler, or in particular habitats such as the Sahel (Zwarts et al, 2015; Mallord et al, 2018). However, the small sample sizes of fieldwork and tracking studies, particularly in Africa, make it impossible to draw general conclusions about multiple, complex and interacting factors operating over several years and across vast areas.…”