The pied flycatcher Ficedula hypoleuca is a summer visitor to the UK, migrating north from Africa to breed in the upland oak woods of Dartmoor. Pied flycatchers are distinctive black and white birds and there was a tangible sense of anticipation, as we waited for the first sighting of these birds to be recorded at the Reserve this year. On 5 April two male flycatchers were spotted in Yarner Wood.
Their population have been monitored at East Dartmoor National Nature Reserve for over 60 years and they are also one of the best studied passerines across Europe. But although much is now known about their breeding, we still know very little about where they go after breeding.
The UK population has declined by 53% since 1995, raising the importance of understanding their movements and ecology throughout the year. The quality and extent of the upland oak wood breeding habitat of pied flycatchers is largely unchanged in recent decades and as the birds seem able to adjust the timing of breeding to match food availability – it would seem that declines are linked to factors outside of their breeding range.
It is hoped that advances in technology may provide answers to many of these questions. Miniaturisation of the lightest available tracking devices, known as geolocators, now enables pied flycatchers to be tracked to their wintering grounds for the first time.
A miniature 0.36g geolocator and leg loop harness ready for use; 0.36g geolocator being fitted to a male pied flycatcher in 2015 Photos: David Price
In 2012, Malcolm Burgess (University of Exeter) and Chris Hewson (BTO) fitted geolocators to 20 adult male pied flycatchers at East Dartmoor National Nature Reserve. Unlike GPS transmitters, data from geolocators can only be obtained directly from the birds’ devices when they return the following year. The spring of 2013 was the coldest since 1962, which delayed the pied flycatchers’ arrival and made for an extra anxious wait for the scientists!
Eventually though, two birds were found and their geolocators retrieved. The late and cold spring impacted hugely on the whole population, giving very low return rates for all flycatchers that year. Luckily these two geolocators proved very fruitful; revealing that the plucky East Dartmoor NNR birds had travelled to Liberia and southeast Guinea, and back!
Just two geolocaters have generated a massive shift in our knowledge; strongly suggesting that UK birds are concentrated in a relatively small portion of their winter distribution in sub-Saharan western Africa. From a conservation perspective this study powerfully highlights the need for further study and conservation efforts in wintering areas. The work at East Dartmoor NNR contributes hugely to national and pan-European work on pied flycatchers and to the growing literature on migration ecology. In 2015, a further 20 adult pied flycatchers were fitted with geolocators, that are 39% lighter than those used in 2012. Suffice to say, the return of these birds is very eagerly awaited!
Look out for further updates of the pied flycatchers at East Dartmoor National Nature Reserve… part 2 to follow soon…
Blog by Simon Lee, Senior Reserves Manager for Natural England