Our woodcock research aims at better conservation of the species. At a European scale we need to understand the status of different breeding populations, their migratory routes, breeding success and winter survival. The main emphasis of our current work is woodcock migration. New technology makes gathering this information much more feasible.
We have analysed stable isotopes on almost 1,000 wing feathers to find out the hatching and moulting locations of woodcock wintering in Britain and Ireland. The technique relies upon the fact that isotopes in a bird’s food are locked into the keratin of its feathers until the next moult – typically a year later for the flight feathers. We aim to determine the proportions of British- and foreign-bred woodcock in mid- winter and to find out where the foreign migrants come from. Hydrogen isotope values in woodcock feathers show good correspondence with known geographical isotope patterns in rainwater across Europe.
Our preliminary results suggest that approximately 17% of woodcock shot in Britain and Ireland are British breeders, 51% are from Russia and the Baltic states and 32% are from Scandinavia and Finland. Variation in the isotope values at each winter site suggests mixed populations from many different breeding areas. However, the proportions of woodcock from these three broad breeding areas differed across five wintering regions of Britain and Ireland. Woodcock from Russia and Belarus must travel to Britain across a broad front, because each of the five wintering regions in the UK had a similar proportion of birds with isotope values typical of this region. However, Scandinavian birds appear more restricted to the north and west, with higher proportions occurring in south-east Scotland, Wales and the west of Ireland than in Norfolk and Cornwall. This is in agreement with ring recoveries, which show birds from Norway and Sweden passing through Scotland on route to Ireland.
In 2010 we will focus on collecting more samples from known breeding areas and investigate the potential of trace elements as additional markers, refining the interpretation of the isotope values, all of which should lead to greater accuracy in determining woodcock origins.
We also plan to use miniature geolocators on woodcock wintering in Britain and France, in collaboration with French scientists. These will give us information on the timing and routes of individual birds travelling to and from their breeding grounds. We remain unsure about the status of breeding woodcock in Britain. Despite the fact that our 2003 breeding woodcock survey recorded far higher numbers than previously estimated (see Review of 2007), it gives us no information on whether breeding numbers have declined. Since 2003 we have counted roding woodcock annually at about 40 sites and the trend in numbers in these woods has been stable. However, these sites are not a random sample and many have higher than average woodcock densities. Hence, we plan to repeat the national survey in 2013.
We are grateful to the Countryside Alliance Foundation, Shooting Times Woodcock Club, Natural Environment Research Council and contributors to the Woodcock Migration Appeal for funding.
We would also like to thank everyone who has contributed feathers for stable-isotope analysis and those counting woodcock each spring.