BTO/Game Conservancy Trust
Breeding Woodcock Survey 2003

How many Woodcock breed in our woods?

Introduction

The Woodcock is an intriguing species, often missed in BTO surveys due to its crepuscular habits. We are really interested in what is happening to the numbers of this bird, which was ‘amber listed’ in the recent revision of Birds of Conservation Concern. In 2003, therefore, the BTO and The Game Conservancy Trust ran a national survey of breeding Woodcock with the aim of establishing a baseline population index against which future survey results can be compared. The data collected on distribution and abundance of breeding Woodcock are being correlated with variables describing woodland structure, species composition and the land uses adjoining each wood or forest. This will provide a far more extensive insight into the habitat requirements of the species. A preliminary report on the survey was published in the July-August 2004 issue of BTO News (No. 253).

Listen to a Woodcock Call with thanks to Jeff Blincow

The two BTO breeding bird atlases indicated that a 29% contraction in range occurred in Britain between the late 1960s and early 1990s. The Common Birds Census data also suggests that a large decline has occurred over the last three to four decades, although the CBC sample is probably not representative of the full geographical and habitat range of the species. This new survey will enable us to establish a far more accurate picture of the status of the Woodcock than has been possible previously.

Woodcock Ecology

Woodcock breed in both deciduous and coniferous woodland, often choosing areas with glades or rides, patches of damp soil and at least some undergrowth. The distinctive roding flight of the Woodcock is usually carried out in the twilight shortly before dawn and at dusk. Roding birds fly in circuits 3-30 m above the woodland canopy whilst issuing repeated calls consisting of low pitched ‘grunt’ notes and loud shrill disyllabic whistles. The sounds can carry up to 300 m and probably attract the attention
of a female, which in turn entices the male to the ground.

Background to Survey Methodology

The survey was based on counts of roding males made during May and June at fixed, pre-selected points within woodland. Counts of roding males provide the only feasible way of monitoring breeding Woodcock populations on a national scale, but raw count data are difficult to interpret because Woodcock have a polygynous mating system. This means that a few older, dominant males rode for the longest each day and obtain most of the matings with females, whereas first-year males only rode for short periods. However, previous work has shown that individual male Woodcock have distinctive, recognisable calls. The Game Conservancy Trust has quantified the relationship between the number of observations of roding Woodcock and the number of individual males, by recording the calls of all the displaying birds (figure 1). This work shows that counts of roding birds gives an index of the numbers of males.

A pilot survey in 2002 involving data collection at over 50 sites, with good coverage across the whole of the country, helped us to refine the method for the main survey. In the main survey, volunteers visited randomly selected woods of varying size across the country. In addition, some volunteers surveyed woods known to hold breeding Woodcock as well as the random site. This will enable us to develop a better picture of the type of woods that Woodcock frequent. The response to the survey was excellent with nearly 1000 completed forms received. A small number of repeat counts took place from 2004-2008 and a few more are planned over the next few years.