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BBWC Home > Key Findings

Key findings

• Declining species

• New alerts

• Positive changes

• Reduced breeding success

• Increased breeding success

• Early nesting



Declining species

 

Best trend estimates over the longest available time period (usually 36 years) provide alerts to rapid declines of 50% or greater for 23 species. These are Grey Partridge, Little Grebe, Woodcock, Turtle Dove, Cuckoo, Lesser Spotted Woodpecker, Skylark, Tree Pipit, Yellow Wagtail, Song Thrush, Whitethroat, Willow Warbler, Spotted Flycatcher, Marsh Tit, Willow Tit, Starling, House Sparrow, Tree Sparrow, Linnet, Lesser Redpoll, Bullfinch, Yellowhammer and Corn Bunting.

Most of these rapidly declining species are already red or amber listed on the Population Status of Birds (PSOB) list (Gregory et al. 2002).

Tree Sparrow © Darren Frost

The Tree Sparrow has declined by a massive 97% over the last 36 years


The Whitethroat decline results from the severe crash between 1968 and 1969 linked to conditions on the wintering grounds. The Little Grebe decline should be treated with caution as we have long-term data only from waterways. Lesser Redpoll, Tree Pipit and Woodcock also have limited data. For several of the species listed here long-term trend data are only available for England, where BTO has more volunteers to record information. Different long-term trends could be operating in other parts of the UK.

A further ten species trigger alerts as a result of long-term declines of between 25% and 50% over periods of 25 to 36 years. These are Red-legged Partridge, Kestrel, Lapwing, Redshank, Common Sandpiper, Meadow Pipit, Dunnock, Mistle Thrush, Lesser Whitethroat and Reed Bunting. Most of these species are already on the PSOB list on account of their population declines.


Recent alerts

 
Cuckoo © Roger Tidman

The Cuckoo declined by 57% in England between 1967 and 2003, and may be a candidate for future red listing


In the 2005 report, we draw special attention to the alerts for three species that have recently crossed the 50% decline threshold. These are Yellow Wagtail (-67%), Willow Warbler (-60%) and Cuckoo (-57%). These may be candidates for future addition to the red section of the PSOB list.

We also identify two species that may become candidates to join the amber list due to declines of between 25% and 50%. These are Common Sandpiper (-28% over 28 years) and Lesser Whitethroat (-29% over 25 years). Red-legged Partridge also falls within this decline category
(-46% over 25 years) but would not be a candidate for amber listing because it is an introduced species.

Positive changes

 

Few of those species that have declined previously show evidence of improvements in status. Song Thrush numbers have increased by 23% over the last ten years but even after this recovery they show a 51% decline over the last 36 years. The 25-year decline measures for Marsh Tit and Reed Bunting are now below 50% as a result of their declines having levelled out in recent years. However, all of these species will need to show further improvements in status if they are to become candidates to leave the red list. For similar reasons Kestrel and Goldcrest could become candidates for removal from the amber list. Overall, most species that have declined show little sign of recovery in the last ten years (only six of the 37 species with long-term declines may now be recovering). Additionally BBS data indicate recent increases for Snipe and Grasshopper Warbler but we lack good annual monitoring data on longer-term changes in these species.

Grey Wagtail © Tommy Holden

The Grey Wagtail has now shown a consistent pattern of recovery over several years

 


Sixteen species have more than doubled over the longest time period for which data are available (usually 36 years). These are Mute Swan, Canada Goose, Shelduck, Mallard, Oystercatcher, Sparrowhawk, Buzzard, Stock Dove, Collared Dove, Woodpigeon, Green Woodpecker, Great Spotted Woodpecker, Nuthatch, Blackcap, Magpie, Carrion Crow.


Reduced breeding success

 
Linnet © Jill Pakenham

Linnets have declined as a result of
reduced breeding success

There are a number of species for which declines in breeding performance are likely to be driving the population declines (Linnet and Lapwing) or helping to inhibit recovery (possibly Reed Bunting). The importance of decreases in individual aspects of breeding performance for declining Yellow Wagtail, Dunnock, Mistle Thrush, Willow Warbler, Spotted Flycatcher and House Sparrow remain to be determined, as do the implications of the large reductions in CES productivity measures recorded for Song Thrush, Willow Warbler and Lesser Redpoll. Many declining species show improving productivity, probably as a consequence of density-dependent processes (there are more resources available to feed the young when population numbers are low).


Increased breeding success

Increasing breeding performance may be helping to drive population expansion of a number of rapidly increasing species: the predatory Grey Heron, Sparrowhawk and Buzzard; the corvids Jackdaw, Magpie and Carrion Crow; the seed-eaters Collared Dove and Stock Dove; and the insectivores Great Spotted Woodpecker, Pied Wagtail, Robin, Wren, Nuthatch, Blue Tit and Great Tit.


Early nesting

 

Data from the Nest Record Scheme provide strong evidence of shifts towards earlier laying in a range of species, linked to climate change (Crick et al. 1997, Crick & Sparks 1999). We have now identified 33 species that, on average, are laying up to 29 days earlier than they did 35 years ago. The species involved represent a wide range of taxonomic and ecological groups. Examples include Long-tailed Tit (16 days earlier), Greenfinch (13 days earlier), Blackcap (12 days earlier) and Oystercatcher (8 days earlier). The consequences of these changes for bird populations need further investigation.

 

Long-tailed Tit at nest © Derek Belsey

On average, Long-tailed Tits are now laying 16 days earlier than in 1968

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This report should be cited as:
Baillie, S.R., Marchant, J.H., Crick, H.Q.P., Noble, D.G., Balmer, D.E., Coombes, R.H.,
Downie, I.S., Freeman, S.N., Joys, A.C., Leech, D.I., Raven, M.J., Robinson, R.A. and Thewlis, R.M. (2006)
Breeding Birds in the Wider Countryside: their conservation status 2005.
BTO Research Report No. 435. BTO, Thetford. (http://www.bto.org/birdtrends)

Pages maintained by Susan Waghorn and Iain Downie: Last updated 11 November, 2008