As the International Year of Biodiversity draws to a close, the publication of the BTO/JNCC Breeding Birds in the Wider Countryside Report highlights the latest increases and declines in UK bird populations.
The need to monitor and maintain global biodiversity has been at the fore of the conservation agenda in 2010, culminating in the recent conference in Nagoya. The latest Breeding Birds in the Wider Countryside Report, published this week, uses data collected by volunteer surveyors to determine the contrasting fortunes of 117 British bird species over the last 40 years.
Dr David Noble, a Principal Ecologist at BTO, explained: "The latest figures show that numbers of one in five of these species have fallen by more than 50% since the 1960s." The BTO produce the report in partnership with the Government's Joint Nature Conservation Committee (JNCC). Recent steep declines identified by the BTO/JNCC/RSPB Breeding Bird Survey suggest that Nightingale, Whinchat and Pied Flycatcher may be next in line to join this group.
Data collected by bird ringers and nest recorders help to shed light on factors responsible for these trends. "A number of declining species have also experienced a reduction in breeding success, including Spotted Flycatcher, Willow Warbler and Linnet," added Dr Dave Leech, a Senior Population Ecologist at BTO. "The fact that 39 species are continuing to advance their laying dates also shows that climate change is influencing their breeding behaviour with potentially severe consequences, particularly for woodland insectivores such as Pied Flycatcher."
It's not all bad news though, as 18 species have doubled in number over the same time period. A reduction in persecution coupled with increasing rabbit numbers may have allowed Buzzard populations to increase and expand. Great Spotted Woodpecker and Woodpigeon are increasingly utilising food provided in gardens and, along with species such as Green Woodpecker and Nuthatch, may also be benefiting from milder winters.
"This report provides another example of how a changing climate has already had substantial impacts on our native wildlife," said Dr Ian Mitchell, JNCC's Senior Monitoring Ecologist. "These annual updates provide us with vital evidence to help guide the ways we use the land to meet the demands of an expanding human population in a changing climate, without risking the long-term future of our native birds."
The current report highlights several key findings:
- The best long-term trends show population declines of greater than 50% for 24 species: Grey Partridge, Lapwing, Snipe, Woodcock, Redshank, Turtle Dove, Cuckoo, Little Owl, Lesser Spotted Woodpecker, Skylark, Tree Pipit, Yellow Wagtail, Whitethroat, Willow Warbler, Spotted Flycatcher, Willow Tit, Marsh Tit, Starling, House Sparrow, Tree Sparrow, Linnet, Lesser Redpoll, Yellowhammer and Corn Bunting;
- A further nine species show long-term declines of 25-50% over periods of 25 to 41 years: Common Sandpiper, Meadow Pipit, Grey Wagtail, Dipper, Dunnock, Song Thrush, Mistle Thrush, Goldcrest and Bullfinch;
- Populations of 18 species have more than doubled over the long term: Mute Swan, Canada Goose, Shelduck, Mallard, Tufted Duck, Sparrowhawk, Buzzard, Stock Dove, Woodpigeon, Collared Dove, Green Woodpecker, Great Spotted Woodpecker, Reed Warbler, Blackcap, Great Tit, Nuthatch, Jackdaw and Carrion Crow;
- Six formerly declining species have shown significant positive trends over the last 10 years: Grey Wagtail, Dunnock, Song Thrush, Whitethroat, Tree Sparrow and Reed Bunting;
- The new summary figure of Fledglings Per Breeding Attempt (FPBA) represents the mean number of young leaving each nest in a given year. Ten species show declines in FPBA over the past 20 years or more, indicating that reproductive output has decreased over time: the red-listed Nightjar, Spotted Flycatcher, Linnet and Yellowhammer, amber-listed Dunnock, Willow Warbler, Bullfinch and Reed Bunting, and green-listed Great Tit and Chaffinch;
- Increasing breeding performance may be helping to drive population expansion of a number of increasing species: Sparrowhawk, Buzzard, Stock Dove, Jackdaw, Magpie, Carrion Crow, Pied Wagtail, Grey Wagtail, Robin, Long-tailed Tit, Nuthatch, Redstart and Reed Warbler;
- Six further species show significant increases in productivity as populations decline, which may be due to density dependence: Kestrel, Skylark, Dipper, Starling, House Sparrow and Tree Sparrow;
- Data from the Nest Record Scheme provide strong evidence of shifts towards earlier laying in a range of species, linked to climate change, with 39 species, on average, laying 5-30 days earlier than in the mid 1960s. Species involved represent a wide range of ecological groups, including raptors (Kestrel — 8 days), waterbirds (Moorhen — 5 days), waders (Oystercatcher — 6 days), migrant insectivores (Pied Flycatcher — 11 days), resident insectivores (Robin — 8 days), corvids (Magpie — 30 days) and resident seed-eaters (Greenfinch — 15 days).
The full report is available online at www.bto.org/birdtrends2010.