Origins and non-breeding ecology of Eurasian woodcock
Keywords: stable isotopes
migrant
resident
non-breeding
winter
Woodcock

The Eurasian woodcock Scolopax rusticola (hereon woodcock) is a wader adapted to woodland and farmland habitats. It is an important quarry species, widely hunted across Europe, but owing to its cryptic plumage and elusive nature, there exists only poor information concerning its natural history. As such, the conservation status of the woodcock remains uncertain. One area that is particularly lacking is knowledge of its ecology outside the breeding season. Generally, avian ecological studies have focused on breeding season events due to the importance of reproductive success in determining fitness. However, it is now apparent that the non-breeding season represents an equally important period of the annual cycle. For example, recent studies have shown that declines in some migratory bird populations were due to events during the non-breeding season, either during migration, or on the wintering grounds.
In Britain, the non-breeding woodcock population comprises both British breeding and non-British breeding birds, yet the origins and relative distribution of these sub-populations is not fully understood. Nor is it known whether ecological differences exist between them. This thesis addresses these two aspects of woodcock biology, using stable isotope and radio-tracking methods. The former was used to assign birds to their likely origins and determine population-specific distributions across Britain. The latter was used, in conjunction with the former, to determine whether ecological differences exist between locally-breeding and non-locally breeding birds residing in Hampshire in winter.
A large degree of mixing between birds from different breeding populations was apparent for woodcock residing in Britain over winter. Russia and Fennoscandia comprised the most likely origins of migratory birds and regional differences in distributions were apparent. The highest proportions of birds from Russia were found in Norfolk and Wales, whilst the highest proportions of birds from Fennoscandia were found in Scotland. The presence of non-breeding residents in Cornwall and Ireland also provided strong evidence for the short-distance, south-westerly movements of resident birds, which probably originated from Scotland.
Locally, the movements and behaviour of birds were found to vary with age (adult vs. juvenile) and/or predicted migratory status (resident vs. migrant), with adult residents potentially representing the dominant group. Differences in habitat use, commuting flights, home range size and activity patterns were all apparent. As such, these findings might have important consequences for the relative survival rates and breeding success of resident and migrant woodcock.
This work has provided new insights into the non-breeding ecology of woodcock in Britain and contributes significantly to European efforts to better understand this bird species. Given the importance of seasonal interactions, an understanding of events throughout the annual cycle is necessary and this can only be achieved through concerted efforts. Indeed, an integrated approach is imperative to develop the conservation plans necessary to ensure the sustainability of the woodcock.