DOI: 10.5061/dryad.3tx95x6k2
title: Huntable UK waterbird data

description: Life history characteristics, harvest data, population trends and
 conservation statuses of huntable waterbirds in the UK. Wintering bird
 populations for the UK were obtained from the latest published estimates
 (Frost et al. 2019). The estimate for mallard was increased by 2.6 million
 birds to account for the annual release of captive-raised birds for
 shooting purposes (Madden 2021). We estimated a standard deviation for the
 population estimates by averaging the Wetland Bird Survey (WeBS; Frost et
 al. 2021) index for each species for the winters 2012/13 – 2016/17, which
 corresponded to the period used to estimate duck populations. We treated
 this mean index as equal to the estimate from Frost et al. (2019) and then
 calculated population estimates for each year based on their WeBS indices
 and calculated the standard deviation of these estimates. Population
 estimates for greylag goose, pink-footed goose, golden plover, snipe and
 woodcock were based on single years, but the same time frame was applied
 to standard deviation estimates in order to account for any interannual
 differences. The latest (2016) harvest estimates and 95% confidence
 intervals were taken from Aebischer (2019). Species specific body mass was
 taken from Robinson (2005). Where sex-specific body mass was reported we
 averaged male and female masses.
description: We modelled the resident and migratory populations of greylag
 geese and woodcock separately. The resident woodcock population was
 estimated as three times the number of breeding males. This was subtracted
 from the total estimated overwintering woodcock population to provide an
 estimate of the migratory woodcock population. Resident woodcock harvest
 was estimated as equal to the proportion of breeding birds in the
 overwinter population (13%) The remaining 87% of total harvest was
 assigned to migratory woodcock. We recognise that further mortality of UK
 breeding woodcock will occur outside the UK in southern Europe, but we
 have no estimate of this mortality and can only consider the contribution
 of UK hunters to the harvest of birds that winter in the UK in this
 initial assessment. Population estimates for Icelandic and British greylag
 geese overwintering in the UK are reported separately and no adjustment is
 needed. An estimated harvest of migratory Icelandic greylag geese in the
 UK (Frederiksen 2002) was deducted from the total UK greylag goose harvest
 to provide an estimate of the harvest of British greylag geese. However,
 it should be noted that the estimate was from 1996-2000 and no new
 estimates have been made.  Short-term (2008-2018) and
 long-term (1970-2018) wintering population trends were taken from Burns et
 al. (2020), except for common snipe and Eurasian woodcock. Common snipe
 trends were taken from Woodward et al. (2020), with caution advised due to
 the small sample size. Resident woodcock long-term and short-term
 population trends were estimated at -29% for both on the basis of reported
 declines in breeding woodcock (Balmer et al. 2013; Heward et al. 2015).
 Migratory woodcock short-term and long-term trends were estimated at -11%
 and -22% on the basis of a 4-18% decline from 2008-2018 and an 11-33%
 decline from 1980-2018 (BirdLife International 2021). Bird population
 status in the UK (Red/Amber/Green) was taken from Birds of Conservation
 Concern 5 (BoCC5; Stanbury et al. 2021). Estimates of
 adult survival were taken from Robinson (2005) with reported standard
 errors multiplied by 1.96 to give an approximate 95% confidence interval.
 The average standard error for all reported waterbirds (0.03) was used for
 species when no standard error was reported (e.g. wigeon, shoveler,
 greylag goose, woodcock and golden plover). We used the same survival
 estimates for both resident and migratory populations of woodcock and
 greylag geese. These adult survival estimates include mortality from
 hunting and so are likely to underestimate the maximum achievable survival
 rates under optimal conditions and so survival was also estimated using
 species mass. Age at first reproduction (alpha) was also taken from
 Robinson (2005).