| WETLAND - TRACKING WOODCOCK
Migration of woodcock wintering in the British Isles Individual woodcock did not always follow the same migration route each spring, despite returning to the same breeding site. © Serkan Mutan
KEY FINDINGS Satellite-tracking of woodcock has yielded important details concerning migrations, such as the timing of movements and countries that birds wintering in the British Isles pass through. This information is the first step towards better monitoring of woodcock, and dialogue between countries, at a flyway-scale. The main arrival period of migrant woodcock in the British Isles is during late October to late November. Peak spring departure is during the third week of March. North-west Russia is a key breeding area for woodcock wintering in the British Isles. Germany, Poland, Lithuania, Latvia, Estonia and Belarus constitute important stopover areas along the main flyway for migrant woodcock that winter in Britain and Ireland.
Andrew Hoodless Chris Heward
50 | GAME & WILDLIFE REVIEW 2019
Owing to the importance of the British Isles as a wintering destination for woodcock, the GWCT decided in the mid-2000s that we needed to know more about the origins and migrations of these birds. Having deduced the main breeding areas with a stable-isotope study (see Review of 2011, pp. 24-27), we proceeded to fit 64 woodcock with satellite tags during February-early March 2012-2018; 56 of these proved to be migrants and completed at least one spring migration. We tagged woodcock in seven geographically distinct regions, from northern Scotland to the west of Ireland, from Cornwall to Norfolk, to improve the likelihood of obtaining data representative of the range of migration routes used by individuals visiting Britain and Ireland. Peak spring departure of our satellite-tracked woodcock was during the third week of March, but departure times spanned a five-week window from 3 March to 13 April. Spring departure date varied between years, being appreciably later in the cold spring of 2013 (average 9 April), when the mean UK temperature in March was 3.3°C below the 1981-2010 average, than in other years (average 23 March). Analysis of our data showed that periods of movement during spring migration coincided with higher air temperature, favourable wind direction and lower relative humidity. Most of the tracked woodcock minimised the distance flown across the sea on spring migration. Except for birds breeding in Norway, which flew directly across the North Sea, woodcock typically passed through France, Belgium or the Netherlands, and then Germany, before heading up across Denmark and north of the Baltic Sea to reach Sweden or Finland, or heading south of the Baltic Sea to reach Finland, Belarus or north-west Russia (see Figure 1). Peak arrival at breeding sites was in mid-April, with tracked birds taking an average of 23 days to complete spring migration. However, the range of arrival dates spanned two months, from 21 March (Latvia) to 24 May (central Russia). The duration of spring migration was related to migration distance, such that woodcock arrived at breeding sites two days later for every 300 kilometres (km) extra travelled. Migration routes in autumn were largely similar to those taken in spring. Consequently, Germany, Poland, Lithuania, Latvia, Estonia and Belarus constitute important stopover areas along the main flyway in April and October-November for migrant woodcock that winter in Britain and Ireland (see Figure 2). Satellite data gave a mean departure date from the breeding grounds of 10 October, with 10 November the average arrival date in the British Isles (range 3-23 November). These individuals, however, were adults (at least a year old) and we know from intensive ringing in Hampshire and mid-Wales that first-year birds usually arrive before adults. Our ringing data show that adults comprise less than 20% of the birds caught in October, rising to about 35% in November and stabilising at about 40% in December. Consequently, we estimate the peak arrival of first-year woodcock to be in late October-early November. Individual woodcock did not always follow the same migration route each spring, despite returning to the same breeding site. A bird tagged in Wales, which took a route through Germany with a stop in central Poland to a breeding site near Vyazma, Russia (55º19’N, 33°32’E) in 2012 and 2013, then detoured further south in 2014, stopping in Slovakia and Belarus instead. In the cold spring of 2013 the migration took
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