The species considered here were red-listed due to long-term declines of more than 50% over the 25-year period 1974–99. The latest long-term population changes and alerts over the maximum period available (usually 39 years) and over 25 years are shown in Table 4.2.1. The species are listed in descending order of long-term percentage change.

The results confirm the declining status of all of the 16 species concerned (although the 25-year change for Reed Bunting is now a non-significant increase). All these updated changes fire alerts, except for the 25-year change for Song Thrush, both changes for Reed Bunting and the 31-year change for Lesser Spotted Woodpecker (which, although apparently large, has very wide confidence limits and is thus not statistically significant). Linnet, Marsh Tit, Skylark and Song Thrush now show declines of less than 50% over the most recent 25-year period, partly reflecting the fact that their long-term declines started more than 25 years ago. Bullfinch and Reed Bunting now have both long-term and 25-year declines of below 50%. Populations of both species increased between the late 1960s and the mid 1970s, before the rapid declines that gave rise to their current conservation listing.

Most of the species considered here were amber-listed due to long-term declines of more than 25%, but less than 50%, over the 25-year period 1974–99. In addition, three species where the best trend estimate was a decline of more than 50% were listed amber, rather than red, on the grounds that the census data were sparse or maybe unrepresentative. The latest long-term population changes and alerts over the maximum period available (usually 39 years) and over 25 years are shown in Table 4.2.2. The species are listed in descending order of long-term percentage change. These results confirm the declining status of most of the 15 species concerned.

Our best estimate of long-term change in the English House Martin population now also shows a decline of more than 50%, but statistically it is not significantly different from no change. Thus no alerts are raised for this species. House Martin is probably best regarded as data deficient rather than as a candidate for red listing. BBS data indicate that its numbers have been stable or increasing since 1994.

Dunnock ceased its decline in the early 1990s, and has subsequently shown significant increase: consequently, its 25-year trend shows no significant change. Grey Wagtails have also been increasing recently, especially since the late 1990s, and as a result their 25-year change is now +28%, while the decline over the longest period for which we can measure changes in their populations (31 years) is just 23%. If the positive trend continues they might be removed from the amber list at a future revision. Kestrel and Lapwing show an opposite pattern to Grey Wagtail, with smaller declines over 39 years than 25 years, reflecting modest increases prior to the declines that are now a cause of concern. For Kestrel, the 39-year trend shows little overall change. For Lapwing, the 25-year decline now exceeds 50%, which could make it a candidate for future red-listing, and it has already been promoted to a priority species on the UK Biodiversity Action Plan. Goldcrest is a difficult species for status assessments because its populations show such wide fluctuations. Numbers increased by 42% over the 39-year period and decreased by only 18% over 25 years, neither change being statistically significant. More recently, BBS data show that numbers have increased by 25% over the last 11 years, and it is questionable that the status of this species should be of particular concern.

We have identified eight species that are currently showing long-term declines of greater than 25% but are not currently included on either the red or amber lists (Table 4.2.3). Should their downward trends continue, these species may be possible candidates for red or amber listing at the next review.

The position of Whitethroat at the head of this list is somewhat misleading. Much of the recorded 62% decline is the result of the well-documented crash between 1968 and 1969 (Winstanley et al. 1974). The 25-year change for this species is a 65% increase, representing a partial recovery to former levels. The Little Grebe data should be treated with caution as they are based on a small sample from linear waterways. WBS shows an ongoing decline in this habitat over the last ten years while BBS, which is likely to cover a more representative set of habitat types for this species, shows an increase over the same period.

Evidence for a Little Owl decline is statistically significant for both the 39-year and 25-year periods. Tawny Owls have shown a very slow decline since the early 1970s, which became more rapid around 1999, and now show a decline of 25% which just reaches statistical significance. These figures must be treated with some caution, however, because CBC and BBS census techniques are not designed with nocturnal and crepuscular species in mind.

Reed Warbler shows a decline of 31% over 21 years in its core habitat of large reedbeds, based on CES data. In clear contrast, however, CBC/BBS and WBS indices, both show strong and ongoing significant increase in this species, and are supported by atlas data showing range expansion. Further investigation is required of how the population changes of this species may differ with respect to region and habitat. For Sedge Warbler, a strong decline is indicated by CBC/BBS, WBS and CES schemes but is statistically significant only for CES.

Two wader species, Common Sandpiper and Curlew, also appear in the table. Declines for Curlew have wide confidence intervals and are not matched by WBS data, which show increase. Common Sandpipers were recorded by WBS as increasing up to the mid 1980s, and a smaller decline (22%) is therefore estimated for the 31-year period.

The Waterways Bird Survey supplements the results from more broadly based schemes, such as CBC and BBS, by measuring trends in the bird populations alongside linear waterways. For a few waterways habitat specialists, such as Grey Wagtail and Common Sandpiper, WBS provides our best information on population trends but for 20 or so others it provides supplementary information from this sensitive habitat. Long-term declines of greater than 25% recorded from WBS plots are listed in Table 4.2.4.

The trends for Yellow Wagtail and Reed Bunting are consistent in direction with those reported from CBC/BBS, but in each case are more severe. The trend for Little Grebe is discussed in section 4.2.3. The Pied Wagtail decline of 53% is intriguing because it contrasts markedly with recent increases as measured by CBC/BBS. Over the 25-year period 1981–2006, Pied Wagtails declined by 39% on linear waterways, compared with no change in the UK as shown by the CBC/BBS trend. The cause of its decline along waterways is currently unknown. For Redshank, WBS has provided valuable data to support the amber listing of this species.

A full set of alerts raised by WBS, and long-term increases detected by that scheme, are tabulated in section 7.2.

The Constant Effort Sites Scheme provides trends from standardised ringing in scrub and wetland habitats. It is our best scheme for monitoring certain 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 22 years (Table 4.2.5).

Most of the species that are declining on CES sites also show similar trends from CBC/BBS data. Linnet, Yellowhammer, Willow Tit, Reed Bunting and Song Thrush are already red listed while Lesser Redpoll and Willow Warbler are amber listed. The decline of Whitethroat has also been discussed above (section 4.2.3). Both Whitethroat and Lesser Whitethroat are doing less well on CES sites than in the UK as a whole. Over the ten-year period 1996–2006, Whitethroats increased by 14% in the UK but decreased by 37% at CES sites. Similarly Lesser Whitethroats increased by 8% in the UK as a whole but decreased by 49% on CES sites. Longer-term comparisons show a similar picture. Numbers of juveniles captured at CES sites show very similar patterns of decline to adult captures for both species. It is unclear why these two species are doing so poorly on CES sites as many of these are located in the good-quality scrub habitats that are preferred by these species.

Reed Warbler and Sedge Warbler present further similar cases. CES has both as declining enough to raise an alert, whereas over similar time periods CBC/BBS records little change for Sedge Warbler and substantial increase for Reed Warbler. Increase for the latter species, also noted by WBS, accords better with the considerable range extensions recorded by atlas projects.

A full set of alerts raised by CES, and long-term increases detected by that scheme, are tabulated in section 7.3.