Recent changes in bird populations in British broadleaved woodland

Abstract

This paper presents estimated national and regional changes in numbers of breeding woodland birds in predominantly broadleaved woodland in Britain between the mid 1980s and 2003-04, derived from the Repeat Woodland Bird Survey (RWBS). A total of 405 sites across Britain for which historical data on bird populations were available were re-surveyed by BTO and RSPB fieldworkers during the RWBS. Changes were estimated separately for sites surveyed by the RSPB ( n = 252) and BTO ( n = 153) because of differences between the two groups in the field methods used in the original surveys. Changes between the 1960s and 1970s and 2003-04 were also estimated with the BTO data set only. The BTO and RSPB sites provide geographically complementary coverage of Britain and together provide much more widespread coverage than did the Common Bird Census (CBC), the former national monitoring scheme. Nationally, between the 1980s and 2003-04, six species declined significantly and three increased significantly based on the RSPB data, whereas eight declined and 13 increased according to the BTO data, with good correspondence between the changes recorded by the two data sets (only seven of 34 species showing trends differing in direction). Eight species showed large national declines ( > 25%) according to both data sets: The declines detected by the RWBS for Garden Warbler, Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus were not evident from the national monitoring schemes. Most of the increases detected by the monitoring schemes were confirmed by the RWBS. However, the large increases detected by the RWBS for Coal Tit, Goldcrest, Great Tit and Eurasian Treecreeper were unexpected. All long-distance migrants have declined whilst medium-distance migrants (Blackcap and Common Chiffchaff ) have increased. Also, rare and specialist woodland species have fared less well than common and generalist species.

Declines in British-breeding populations of Afro-Palaearctic migrant birds are linked to bioclimatic wintering zone in Africa, possibly via constraints on arrival time advancement

“…There is growing evidence that many Afro-Palaearctic migrant bird populations in Europe have undergone dramatic population declines over recent decades (Böhning-Gaese & Bauer 1996, Sanderson et al 2006, Hewson et al 2007, Heldbjerg & Fox 2008. However, the complexity of migrants' life-cycles can make it difficult to determine the causes of population change, as limiting factors may operate on breeding, wintering or staging grounds (Robbins 1989, Sherry & Holmes 1996, Holmes 2007.…”

“…Farmland birds such as Yellow Wagtails Motacilla flava and European Turtle Doves Streptopelia turtur showed steep declines in the 1980s, which have been linked to agricultural intensification (Siriwardena et al 1998, Chamberlain et al 2000. More recently, woodland bird species such as Tree Pipits Anthus trivialis and Wood Warblers Phylloscopus sibilatrix have declined, with possible causes including changes in forest structure, predation and deer browsing (Fuller et al 2005, Hewson et al 2007, Hewson & Noble 2009, Newson et al 2011.…”

Assessing breeding success in common woodland birds using a novel method

“…fledging, as opposed to other reproductive parameters such as clutch or hatch size) are unavailable for many species (Gilbert et al 1998). As a consequence, there have been few studies of predation of natural nests of, for example, woodland songbirds in Britain or elsewhere in Europe (Hewson & Fuller 2003, Nicoll & Norris 2010, even though around ten bird species which use British woodlands have undergone declines in recent years (Baillie et al 2010, Fuller et al 2005, Hewson et al 2007, resulting in several being red-or amber-listed (Eaton et al 2009). The populations of other woodland species have not increased, even though woodland cover in the UK has increased by at least 20% since 1980 (Forestry Commission 2003, Vanhinsbergh et al 2002).…”

Comparison of habitat‐specific trends in the abundance of breeding birds in the UK

“…More recently, general declines in woodland species have been reported (Fuller et al . 2005, Hewson et al . 2007.…”