In the UK there is little evidence that declines are strongly linked to factors affecting them on their breeding grounds. Availability and quality of western oakwoods is largely unchanged (Amar et al. 2010), although it is possible that timing of breeding has become increasingly mismatched with prey availability as warmer and advanced springs result in earlier availability of invertebrate food (see my previous BOU blogs here and here). Such a phenological mismatch has been linked to European Pied Flycatcher declines (Both et al. 2006) although UK data suggests some adaptation, with advances in egg laying date at the same time as relatively unchanged productivity (Baillie et al. 2014). Although these factors may play some role, it seem likely that other important pinch points exist outside of the breeding season.
 
We know so little about the non-breeding and migratory ecology of Pied Flycatchers partly because we have been unable to follow individuals. Without any precise information about where they go between breeding seasons we have little to go on. In the UK, 645,000 Pied Flycatchers have been ringed since 1909, and yet just five UK breeding (and no UK hatched) have subsequently been found in African wintering grounds. This is one recovery per 129,000 birds; ringing alone is not going to help us. But continued miniaturisation of the lightest available tracking devises, geolocators, now means we are able to track Pied Flycatchers.

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In 2012 Chris Hewson (BTO) fitted geolocators to 20 adult male Pied Flycatchers at my long term monitored population at East Dartmoor National Nature Reserve in Devon, UK (Burgess 2014). This transpired to be an unlucky choice of year. The following spring was the coldest since 1962 with winter-like conditions continuing into April resulting in the latest Pied Flycatcher first arrival date at the study site for 23 years (despite a long term trend for earlier arrival). It was an extra nervous wait for tagged birds to return. But once they did arrive we quickly identified two birds, caught them and removed their loggers. The late and cold spring meant return rates were low for both tagged and untagged males and so we retrieved fewer loggers than we hoped. But the two tags we did retrieve revealed tracks and timings to Africa and back, and the two winter locations derived from 20 loggers is equivalent to 35 years of national effort ringing hundreds of thousands of individuals.

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Just one track from a species can be newsworthy and provide totally new information, such as recent work on Red-necked Phalarope Phalaropus lobatus and Ring ouzel Turdus torquatus (Sim et al. in press). Our two UK breeding Pied Flycatchers went to the same region as the UK ring recoveries – Liberia or southeast Guinea. This is important information, suggesting UK birds are concentrated in a relatively small portion of the species’ winter distribution in sub-Saharan western Africa.