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BBWC Home > Contents > Discussion > Latest long-term alerts
 
4.2 Latest long-term alerts
 
Where this section discusses conservation-listed species, it uses the now-current version of these lists, introduced in 2009 and abbreviated as BoCC3. The full paper (Eaton et al. 2009) details the criteria by which each listed species qualifies for its red or amber status. All of the red-listed species that breed in the UK satisfy criteria for UK decline, but amber-listed birds may be listed for other reasons (see Help on species accounts).
 
4.2.1 Long-term trends of PSoB red-listed species
The species considered in this section are red-listed wholly or partly because of severe UK population declines revealed by annual census data, amounting to more than 50% either over the 25-year period 1981–2006 or, in four cases (Skylark, Song Thrush, Marsh Tit and Linnet), over the 37-year period 1969–2006. The latest long-term population changes and alerts for these severely declining species are shown in Table 4.2.1, over the maximum period available (usually the 41 years 1967–2008) and over 25 years (1983–2008). The table thus provides updates to the figures that were used to produce the current BoCC3 red list.
 
The 19 species in Table 4.2.1 are listed in descending order of longest-term percentage change. Tree Sparrow heads the table once again, despite significant increases in numbers recorded by BBS over the shorter term. The figures for Lesser Spotted Woodpecker are likely to be a very large underestimate of the current population change, because the species had by 1999 become too rare for further annual monitoring.
 
For Linnet, Marsh Tit and Skylark, the latest 25-year change is less than 50%, indicating that, while these species meet red-list criteria for long-term change, their recent rate of decline has been lower overall than for most other red-listed birds. On the data we present here, Song Thrush fails to meet any red-list criteria, but by only a narrow margin: its 25-year trend is effectively stable. The 25-year trend for Lapwing is a significant decline of 50% but, as for Lesser Spotted Woodpecker, data quality does not allow us to be 90% confident that a decline occurred over the longer period.
 
See PSoB pages for information on red and amber criteria
 
4.2.2
Long-term trends of declining amber-listed species
There are 40 amber-listed species that are included in this report, of which about half (19 species) are listed because of UK population declines over the periods 1981–2006 or 1969–2006. Long-term trends are available from annual census data for 13 of these species, which are listed in Table 4.2.2 in descending order of longest-term percentage change (normally over the 41 years 1967–2008). Where available the 25-year change (1983–2008) is also shown.
 
See PSoB pages for information on red and amber criteria
 
Three species raise high alerts, having shown significant declines of greater than 50%. Whitethroat shows a massive decline over the 41-year period, since this includes the extraordinary population crash that occurred between 1968 and 1969, but the 25-year period has seen a partial reversal of this decrease. English Willow Warblers meet the red-list criterion for population decline, but it is likely that the overall UK decline has been less severe: Scottish and Welsh trends are less clear, but show shallow declines over the ten-year period to 2008. Redshank has declined steeply in lowland Britain, according to waterways surveys, raising high alerts; a major decline is also documented for its breeding sites on saltmarsh, and BBS data show that decline has occurred recently across a wide range of habitats. Our best estimate of long-term change in the English House Martin population also shows a decline of more than 50%, but statistically it is not significantly different from no change and therefore no alerts are raised for this species. This species is best regarded as data deficient, but may possibly be a future candidate for red listing. BBS data indicate that its numbers have been changed little since 1994, however.
 
Bullfinch was moved from the red to the amber list at the 2009 review. Its 41-year trend is only marginally below the red-list threshold, but the 25-year trend, although significant, is not large enough to raise any alert. Common Sandpiper, Meadow Pipit and Mistle Thrush continue to meet amber-list decline criteria in both periods. Data for Little Grebe and Curlew suggest a similar overall rate of decline but should be treated with caution, as the confidence intervals are very wide. For Little Grebe there is poor agreement since 1994 between WBS/WBBS data and BBS, which may cover a more representative set of habitat types for this species: BBS results show a non-significant increase.
 
Populations of Dunnock, Grey Wagtail and Reed Bunting are recovering and show stable or increasing trends over the shorter, 25-year period. Reed Bunting now shows only a shallow decline over the 41-year period and has ceased to raise any alerts for population decline.
 
4.2.3
Long-term declines of species that are not currently red or amber listed (for declines)
This section of the report draws attention to declines which apparently surpass red or amber criteria but which are not recognised in the current listings. Even though a review of the red and amber lists took place in 2009, there are a few species that remain in this category (Table 4.2.3).
See PSoB pages for information on red and amber criteria
 
The WBS/WBBS trend for Snipe is based now on a very small sample of plots, the species having deserted so many of its former riverside haunts, and was not presented in our previous report. It is currently amber-listed solely because it is a Species of European Conservation Concern (SPEC category 3) through its moderate decline on the European scale (BiE04). There is ample evidence, however, that its breeding range has contracted sharply, especially in lowland England.
 
Similarly, Woodcock is currently amber-listed solely because it is a Species of European Conservation Concern (SPEC category 3) through its moderate decline on the European scale (BiE04). The only UK census data indicating a trend are from CBC, which recorded steep declines. Samples were small, however, and the CBC's mapping method was not well suited to monitoring this species: for these reasons, the CBC trend is no longer used to support the species' conservation listing.
 
Little Owl meets amber-list criteria for population decline but, as an introduced species, is not eligible for any conservation listing. Although the trends are statistically significant, it should be borne in mind that neither CBC nor BBS field techniques cater well for nocturnal and crepuscular species.
 
Fluctuations in the UK Dipper population since 1974 appear to be underlain by decrease. The current estimate of long-term change clearly raises an alert but decrease over the 25-year period has been moderate and not statistically significant. The UK Goldcrest population has historically shown very wide fluctuations but is currently at a relatively low level, marginally raising an alert in England for the 25-year period.
 
4.2.4
Declines along linear waterways
The Waterways Bird Survey and Waterways Breeding Bird Survey supplement the results from CBC and BBS, which are more broadly-based surveys, by measuring trends in bird populations alongside rivers and canals. Joint WBS/WBBS trend are now available, allowing trend assessment to be continuous since 1974 for up to 25 species that were covered by WBS. WBBS, ongoing since 1998, includes all bird species but WBBS trends for species are presented here only for waterway-specialist species, for which joint WBS/WBBS trends are available. A full set of up-to-date WBS/WBBS trends can be obtained from the Table generator section of this report.
 
For several species, such as Canada Goose, Goosander and Kingfisher, that are abundant in waterway habitats, the WBS/WBBS trend provides our headline information on population trends. For Redshank, Little Grebe, Common Sandpiper, Grey Wagtail, Snipe and Dipper, which are also in this category and are in decline, details appear in Tables 4.2.2 or 4.2.3, as appropriate. Where WBS/WBBS is not the headline trend for a species, however, the waterways data nevertheless provide valuable supplementary information from this sensitive habitat.
 
Table 4.2.4 lists all statistically significant declines of greater than 25% recorded from the full period of waterway monitoring (nominally 1975–2008). It does not include Little Grebe, for which the decline is not statistically significant (Table 4.2.2). Four species are included for which WBS/WBBS is not the headline trend and so are not listed in Tables 4.2.2 or 4.2.3.
 
The trends for Yellow Wagtail and Reed Bunting are consistent in direction with the 41-year trends reported from CBC/BBS, but in each case the declines on waterways have been more severe. For Reed Bunting, recovery along waterways has also been weaker than in the countryside as a whole. The Pied Wagtail declines along waterways, which are significant in all the periods assessed, are intriguing because they contrast markedly with the fluctuating but generally upward trend as measured by CBC/BBS. The cause of the decline along waterways is currently unknown.
 
For Sedge Warbler, the headline trend is a non-significant 41-year decrease of 21% from CBC/BBS. Large fluctuations make trends difficult to determine in this species, but the WBS/WBBS data add firmer evidence for a long-term moderate decrease.
 
A full set of alerts raised by WBS/WBBS, and long-term increases detected by that index, are tabulated in Appendix 7.2.
 
4.2.5
Declines on CES plots

The Constant Effort Sites Scheme provides trends from standardised ringing in scrub and wetland habitats. It is possibly our best scheme for monitoring some bird populations inhabiting reed beds but its main objective is to collect integrated data on relative abundance, productivity and survival for a suite of species. The longest trends currently available from the CES cover a period of 24 years (Table 4.2.5).

 
 
Most of the species that are declining on CES sites show broadly similar trends to those from CBC/BBS or WBS/WBBS data. Linnet and Willow Tit are red listed on the strength of their CBC/BBS declines (Table 4.2.1). Similarly, Willow Warbler, Reed Bunting, and Whitethroat are amber listed.
 
For reasons unknown, CES trends for Lesser Whitethroat, Sedge Warbler and Reed Warbler are considerably more negative than those from census data. Both CBC/BBS and WBS/WBBS show strong increases for Reed Warbler, in clear contrast to the CES data.
 
A full set of alerts raised by CES, and long-term increases detected by that scheme, are tabulated in Appendix 7.3.
 
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This report should be cited as: Baillie, S.R., Marchant, J.H., Leech, D.I., Renwick, A.R., Joys, A.C., Noble, D.G., Barimore, C., Conway, G.J., Downie, I.S., Risely, K. & Robinson, R.A. (2010). Breeding Birds in the Wider Countryside: their conservation status 2010. BTO Research Report No. 565. BTO, Thetford. (http://www.bto.org/birdtrends)

Pages maintained by Iain Downie, Mandy T Andrews and Laura Smith: Last updated 21.10.2010