Aspects of the ecology of the European woodcock Scolopax rustlcola L

Abstract

The trends in the numbers of British breeding woodcock Scolopax rusticola and the Continental woodcock that visit Britain in winter were examined using ringing recoveries and bag records. The proportion of foreign: British woodcock present in S England and Wales is appreciably higher than in N England and Scotland. Average annual survival rates for adult British and foreign- ringed woodcock were estimated as 58% and 54% respectively. Calculations of the annual production of young woodcock, based on British Trust for Ornithology nest record cards from Britain and on data collected in NE Derbyshire, suggested that too few young woodcock are produced to compensate for the current rate of adult mortality among British woodcock. Woodcock chick mortality was the key factor in an analysis of 15 years of data from Derbyshire. Overwinter loss was density-dependent and the main regulatory, or k, factor. This is important because it means that the arrival of Continental woodcock in Britain in winter probably increases mortality among the resident British birds. A simulation model based on the Derbyshire data was used to estimate the maximum sustainable shooting yield and the effectiveness of shooting bans in cold weather. When feeding at night in winter, woodcock select grass fields in preference to arable fields and use areas dominated by grass. They probably select between the older fields on the basis of the relative availability of earthworms and other soil invertebrates, particularly leather]ackets, Tipulidae larvae. British woodcock are faithful to the natal or breeding site in winter and Continental woodcock exhibit lower wintering site fidelity. Woodcock experience higher mortality in cold winters, when freezing conditions prevent the birds feeding, and the recovery of the population following severe winters took three-year. Most cold weather movements within Britain are probably only made by Continental migrants. In the breeding season, woodcock selected areas of shrubby cover, typical of the edges of stands, within lowland mixed deciduous woodland. In an upland area of birchwood and heather moorland, feeding woodcock preferred dense young birch thickets although the birds nested in more open areas typically dominated by bracken Pteridium aguilinum and heather Calluna vulgaris. In both situations, the habitats used most intensively supported higher available densities of earthworms than habitats that were avoided. Clearly, conversion of grassland to arable fields will reduce the area of suitable habitat for woodcock in winter. The loss of managed coppice in Britain in the last 50 years has probably contributed to the decline in the British breeding population, because coppice provides ideal habitat for breeding woodcock. The fact that woodcock do not breed in SW Britain maybe due to increased overwinter mortality, because a high density of Continental woodcock occur there in winter.