The decline ofAfro‐Palaearctic migrants and an assessment of potential causes

Abstract

There is compelling evidence that Afro-Palaearctic (A-P) migrant bird populations have declined in Europe in recent decades, often to a greater degree than resident or shortdistance migrants. There appear to have been two phases of decline. The first in the 1960s-1970s, and in some cases into the early 1980s, largely affected species wintering predominantly in the arid Sahelian zone, and the second since the 1980s has mostly affected species wintering in the humid tropics and Guinea forest zone. Potential drivers of these declines are diverse and are spread across and interact within the migratory cycle. Our knowledge of declining species is generally better for the breeding than the non-breeding parts of their life cycles, but there are significant gaps in both for many species. On the breeding grounds, degradation of breeding habitats is the factor affecting the demography of the largest number of species, particularly within agricultural systems and woodland and forests. In the non-breeding areas, the interacting factors of anthropogenic habitat degradation and climatic conditions, particularly drought in the Sahel zone, appear to be the most important factors. Based on our synthesis of existing information, we suggest four priorities for further research: (1) use of new and emerging tracking technologies to identify migratory pathways and strategies, understand migratory connectivity and enable field research to be targeted more effectively; (2) undertake detailed field studies in sub-Saharan Africa and at staging sites, where we understand little about distribution patterns, habitat use and foraging ecology; (3) make better use of the wealth of data from the European breeding grounds to explore spatial and temporal patterns in demographic parameters and relate these to migratory pathways and large-scale patterns of habitat change and climatic factors; and (4) make better use of remote sensing to improve our understanding of how and where land cover is changing across these extensive areas and how this impacts A-P migrants. This research needs to inform and underpin a flyway approach to conservation, evaluating a suite of drivers across the migratory cycle and combining this with an understanding of land management practices that integrate the needs of birds and people in these areas.

Analysis of Ring Recoveries of European Turtle DovesStreptopelia turtur— Flyways, Migration Timing and Origin Areas of Hunted Birds

“…Bächler et al, 2010;Catry et al, 2011;Akesson et al, 2012;Bairlein et al, 2012;Kristensen et al, 2013) and satellite tracking [Geo Location Sensor (GLS), Eraud et al, 2013;López-López, 2016;Lormee et al, 2016)], are now used for tracking Afro-Palearctic migratory birds, including Turtledoves (Eraud et al, 2013;Lormee et al, 2016). Application of these emerging tracking technologies to North African Turtle-doves would help identify their migratory pathways and strategies (Vickery et al, 2014).…”

“…Birds have been the focus of intensive research because declines in Palearctic-African migrants have been recorded throughout the Palearctic (Sanderson et al, 2006;European Bird Census Council, 2012;Vickery et al, 2014). The effective conservation of this group poses a particular challenge since migratory birds exploit geographically distinct habitats throughout the annual cycle, including different refuelling sites along migratory corridors.…”

Conditions at autumn stopover sites affect survival of a migratory passerine

“…For example, studies of two populations of Reed Warblers from central Europe (Schaefer et al 2006;Halupka et al 2008) revealed that increased temperatures observed in recent years during the breeding season were correlated with a higher number of nestlings produced by breeding pairs. However, as various recent estimations of population trends for the Reed Warbler have produced equivocal results (Ockendon et al 2012(Ockendon et al , 2014Vickery et al 2014, Inger et al 2015, further detailed studies are needed.…”

“…Recent analyses suggest that Reed Warbler numbers are declining in Europe (Vickery et al 2014, but see Ockendon et al 2014;Inger et al 2015). demonstrated that Reed Warbler populations breeding in neighbouring areas of Europe tend to undertake similar migration routes and have wintering grounds in the same parts of Africa.…”

Insights into the migration of the European Roller from ring recoveries

“…Describing the spatio-temporal distribution of migrant bird populations at all ages and throughout their annual cycle is particularly pertinent given their widespread decline (Sanderson et al 2006;Vickery et al 2013). In particular, understanding the processes by which naïve first-year migrants navigate to and from their first winter site [to which they will usually return with high fidelity in subsequent years (e.g. ]…”