Distribution and migration
The great majority of Woodcocks living in Europe are migratory by nature. Migration takes place over a relatively long period (approximately 1,5 months) and on a wide front, without precise migration corridors except for mountain passes.
Autumn migration begins at the end of September - beginning of October for the birds residing more to the North and East of Europe (Finland, Russia). The general migratory movement takes place in October and November.
Spring migration begins between the end of February and the beginning of March. The furthest breeding territories are reached at the end of March in Finland and at the beginning of May in Russia. The majority of woodcock come back to nest in the region where they were born.
Migration strategy differs according to the woodcock's origin. The most northerly and easterly birds (long migration) spend the winter in the southernmost and westernmost parts of the wintering zone. The extreme opposite is the case of birds born in France or Great Britain, for example, which are almost non-migratory. The extremities of the wintering area are as far apart as the bird's penchant for a long migration. The woodcocks of Finland, for example, are wintering in the British Isles or Greece and in North Africa.
Biology of reproduction
Within the distribution area, the breeding period of the woodcock lasts from February to August. The peak laying time successively goes from March to May from the south-west towards the north-east : the middle of March in France, the end of March in Great Britain and Ireland, the beginning of April in Germany, mid-April in Denmark, the end of April in Sweden and the beginning of May in Finland and north-west Russia.
The woodcock nests on the ground. Its defence is guaranteed by a plumage which integrates into the surrounding ground it inhabits. Finding a woodcock nest is still a "luck of the draw". The mean clutch size is 4 eggs. If the first clutch is destroyed, the woodcock may lay a replacement clutch. Initiation of a second laying nest in the same season after a successful first hatching has never been observed. At least part of the population would be concerned here.
Only the female sits on the eggs. The incubation period is between 21-22 days. All this time, the woodcock is very sensitive to disturbance and will not hesitate to abandon the nesting site. The young are able to fly around at the age of about 20 days. Losses during the reproduction phase are estimated at 30%.
From February to August, the male flies at dusk and at dawn. These flights, accompanied by song, make up a display, termed roding. The main purpose of roding is to find females. At this time of day observation is easy and does not cause disturbance. It is estimated that a male rodes over some 300 hectares during the season. Several males are roding the same area.
A male can mate with several females. The male and female only stay together for 3 or 4 days. Then the male restarts his roding flights.
The females can breed in their first year of life. Some one-year-old males engage in roding routines with no evidence that they have mated with a female.
At the present time, the only monitoring of breeding woodcock populations has been carried out in France and the Vaud canton in Switzerland.
This monitoring is based on an original method devised to observe males at the time of their ritual displays. Forest listening points are chosen at random and visited once in May-June. The number of males seen and/or heard (contacts) is noted. The results are expressed in terms of frequency of occurrence and interpreted in terms of spatial occupation. In France, around 1,000 listening points have been visited each year since 1991. The same procedure is applied in Switzerland on a basis of around fifty listening points.
Even though this method only applies to the numbers of males in the population, it is probably also valid for detecting demographic trends in the female population. In fact, analysis of bag tables has shown that the sex-ratio of shot birds has remained relatively constant. If the demographic trend differed between the two sexes, in sex-ratio variations would have been noted.
It must be pointed out that the Woodcock belongs to the group of species falling within programmes of the Atlas, Common Bird Census or Breeding Bird Survey type, in Austria, Denmark, Finland, Great Britain, Luxembourg and the Netherlands.
The number of breeding woodcocks is considered to be stable in all European countries with the exception of Great Britain and Switzerland, where the numbers would be going down, and Denmark where the numbers would be going up.
At the present time, no information are available about the demographic trend of breeding woodcocks in Russia although a very important part of the European woodcock population is breeding in this country. Monitoring of these breeding woodcock population has started from spring 1999 and should inform in the future of the demographic trend of the Russian woodcock population.
Analyses of hunting bags, whether or not they are linked to wing collection, are carried out in Denmark, Great Britain, Greece, Italy, and in France. The methods of collection data vary from one country to another.
With the exception of France, no country of the wintering range is carrying out large scale ringing programmes on the species at the present time. The method of night capture of this species as used in France since 1984 has allowed to ring over 17,000 wintering woodcocks (between 2,000 and 3,000 birds per year since 1995). This ringing programme resulted in 3,700 recoveries.
The recovery rate of roughly 20% seems to be important. Interpretation of the ringing results in terms of survival rates is going on. The first analyses show that the survival rate has not significantly changed since the mid 80's.
Marking in the breeding range (Fennoscandia, Denmark, the Baltic countries and Russia) has been organised each year since 1987 by the French Office National de la Chasse et de la Faune Sauvage (National Wild Fauna and Hunting Bureau). Since that date, more than 3,000 woodcocks have been ringed in these countries.
These operations allow, in particular, to obtain an estimation of the proportion of young birds to adults at the start of the autumn migration and of the dispersion of birds in the wintering area.
Yves Ferrand and Francois Gossmann
Office National de la Chasse et de la Faune Sauvage