If the status of species that have shown long-term declines were now improving, we would expect to find trends to be more positive in recent years than in the earlier part of the time series. To examine this, we list in Table B1 the best change estimates over the most recent ten-year period for which we have data (2008–18 in all but three cases), for all of the declining species listed in Tables A1–A3 (previous section). For Lesser Spotted Woodpecker, Woodcock and Shelduck, the ten-year period for which data are tabulated is 1989–99.
Table B1 also includes four further species that are listed red or amber in BoCC4 because of recent breeding decline, and for which we can report ten-year trends, but which lacked annual monitoring data before 1994. These are Whinchat, Grasshopper Warbler and Wood Warbler (all red listed), and Swift (amber listed).
|Table B1 Ten-year trends for species that have shown long-term declines|
|Turtle Dove||10||CBC/BBS UK||-82||-87||-75||>50|
|Tufted Duck||10||WBS/WBBS waterways||-56||-68||-35||>50|
|Lesser Spotted Woodpecker||10||CBC to 1999||-51||-75||-22||>50||Small sample|
|Little Owl||10||CBC/BBS UK||-46||-53||-36||>25|
|Woodcock||10||CBC to 1999||-40||-62||-11||>25||Small sample|
|Grey Partridge||10||CBC/BBS UK||-34||-44||-24||>25|
|Willow Tit||10||CBC/BBS UK||-34||-49||-16||>25|
|House Martin||10||CBC/BBS England||-28||-33||-22||>25|
|Tree Pipit||10||CBC/BBS England||-27||-45||-1||>25|
|Grasshopper Warbler||10||BBS UK||-27||-43||-11||>25|
|Sedge Warbler||10||CBC/BBS UK||-24||-33||-13|
|Marsh Tit||10||CBC/BBS UK||-24||-36||-14|
|Grey Wagtail||10||WBS/WBBS waterways||-22||-32||-9|
|Wood Warbler||10||BBS UK||-22||-47||2|
|Little Grebe||10||WBS/WBBS waterways||-20||-38||13||Small sample|
|Common Sandpiper||10||WBS/WBBS waterways||-19||-29||-7|
|Willow Warbler||10||CBC/BBS England||-18||-23||-11|
|Mistle Thrush||10||CBC/BBS UK||-15||-20||-11|
|Garden Warbler||10||CBC/BBS UK||-12||-21||-2|
|Spotted Flycatcher||10||CBC/BBS UK||-11||-20||2|
|Tawny Owl||10||CBC/BBS UK||-8||-21||9|
|Meadow Pipit||10||CBC/BBS England||-2||-9||6|
|Song Thrush||10||CBC/BBS UK||2||-1||4|
|Shelduck||10||CBC to 1999||3||-21||40|
|Reed Bunting||10||CBC/BBS UK||5||-2||12|
|House Sparrow||10||CBC/BBS England||6||2||11|
|Lesser Redpoll||10||CBC/BBS England||7||-17||42|
|Corn Bunting||10||CBC/BBS UK||7||-11||26|
|Tree Sparrow||10||CBC/BBS England||14||-4||38|
|Yellow Wagtail||10||CBC/BBS UK||25||8||47|
Species are listed in ascending order of population change. Thus the species with the steepest recent decline appear first. Towards the foot of the table are species that remain in long-term decline but have shown partial recovery of those losses during the recent ten-year period.
As indicated by their position at the top of Table B1, there is high confidence that the populations of Turtle Dove, Greenfinch and Tufted Duck have halved within just the last ten years, or even a shorter period. These are the only species in long-term decline that suffered a 50% fall during 2008–18 (but Lesser Spotted Woodpecker also met these criteria during the most recent ten-year period for which data are available). Note that whilst the 25-year WBS/WBBS decline for Tufted Duck in Table A3 does not raise a formal alert due to wide confidence intervals, the 10-year decline is statistically significant so does raise a high alert: unless this recent steep decline is reversed it is likely that formal alerts will be raised against the longer-term trends in the future. A further 12 species also raise alerts, having declined significantly by more than 25% (but less than 50%) in their most recent ten-year period. All these declines compound earlier losses for these species.
The ongoing declines of so many of the species listed in Table B1 raises serious conservation concern. A special case is Turtle Dove, for which the 10-year decline has remained at 80% or greater in each of the last ten BirdTrend report and shows no sign of slowing.
The 25% threshold, which is used to define decreases over the 25-year period that are worthy of amber listing, is equivalent to a change of 10.9% over ten years, assuming a constant rate of change. Thus a decrease of 11% or greater listed in Table B1 indicates that these species (32 in all, including non-significant declines for Little Grebe, Redshank, Wood Warbler, Spotted Flycatcher, Nightingale and Whinchat) are on course for new or renewed red or amber listing for breeding population decline.
A smaller decrease, or an increase, indicates that the population decline may be easing off. Species that have declined in the longer term but with losses smaller than 11%, or with no significant population change, over the ten-year period are Shelduck, Curlew, Tawny Owl, Skylark, Whitethroat, Song Thrush, Dipper, Tree Sparrow, Dunnock, Meadow Pipit, Lesser Redpoll, Corn Bunting, Yellowhammer and Reed Bunting.
Five species at the foot of the table show significant gains in population over the last ten years. The increases in Snipe, House Sparrow, Yellow Wagtail, Bullfinch and Linnet numbers is very welcome but the upturns are coming from such a low level that numbers remain far below those of the mid 1970s, with the population trend graphs still showing little sign of clear recovery.
This report should be cited as: Woodward, I.D., Massimino, D., Hammond, M.J., Barber, L., Barimore, C., Harris, S.J., Leech, D.I., Noble, D.G., Walker, R.H., Baillie, S.R. & Robinson, R.A. (2020) BirdTrends 2020: trends in numbers, breeding success and survival for UK breeding birds. BTO Research Report 732. BTO, Thetford. www.bto.org/birdtrends