June 30, 2009

UK Survey Shows Steep Declines In Woodland Bird Populations

A 30-year survey of British woodland birds has found that the nightingale has effectively vanished from woodlands across the UK after its population had fallen by more than 95 percent, BBC News Reported.

The area has also seen a significant decline in seventeen other bird species as well, many of which overwinter in tropical west Africa where their habitat is suffering.

Starling, linnet, bullfinch and willow warbler populations all dropped, while 12 species, including the blackcap, magpie and collared dove, increased.

The British Trust for Ornithology's (BTO) Common Bird Census, which gathered data on 49 species between 1967 and 1999, said the results of the survey have not been reported before.

The data provides the longest and most up-to-date trends anywhere in the UK or Europe for how the composition of woodland bird species has changed over recent years.

Since 1967, the populations of 17 species significantly decreased, while the populations of 12 have significantly increased. But the nightingale population fell by an alarming 95 percent over the study period.

Numbers of starling fell by 91 percent, linnet by 89 percent, lesser redpoll by 85 percent, and spotted flycatcher by 83 percent.

The populations of collared doves in the woodlands increased by 1052 percent, and the stock dove and wood pigeon by 359 percent and 344 percent, respectively.

Chris Hewson of the BTO and colleague David Noble have published the latest trends in the journal Ibis. They say using these longer-term datasets can provide really important additional insights over the more recent ones.

"For instance, much ado was recently made over the Red Listing of the Cuckoo. But an equally iconic species that missed out by the skin of its teeth was the nightingale, which actually declined in woodlands by 95 percent over the period examined, more than any other species studied and greatly in excess of the 63 percent decline shown by the cuckoo."

If these longer-term trends had been taken into account, the nightingale would have been Red Listed too, Hewson said.

He noted that some scarce resident species such as the lesser spotted woodpecker, redpoll, willow tit and hawfinch have declined and they were still not absolutely sure why.

"But in some cases at least, less sympathetic woodland management looks a likely cause, along with possibly the impacts of browsing by an exploding deer population in some parts of the country," he added.

Habitat changes outside of the UK are also having a major impact, particularly on migrant woodland species that spend part of the year in Africa.

Hewson said the survey's results illustrate that whole suites of migrants are declining, but the species of migrant in decline changed over the 32-year period.

During the late 1960s and early 1970s, it was species such as the whitethroat and redstart that spend the winter in the arid Sahel just south of the Sahara that were suffering due to drought conditions in the area.

But Hewson said that rainfall levels have now recovered and these species are doing ok.

The British Bird Survey, which replaced the Common Bird Census in 2000, shows that all the woodland species that migrate from west Africa continue to decline.

He said this suggests they are suffering from changes occurring in west Africa, possibly due to the intensification of agriculture and other land use changes leading to habitat degradation.

A major research program started by the BTO and backed by an appeal called Out of Africa will begin to study these migrant birds by starting a field project in Ghana and Burkina Faso this October with the Royal Society for the Protection of Birds.


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