Britain's House Sparrow Passer domesticus population has declined by 68 percent since 1977. Though still relatively plentiful in small towns in the countryside and by the sea, the bird has disappeared in many major conurbations, including central London, where the species has virtually vanished. House Sparrows are also disappearing from Bristol, Edinburgh, and Dublin, as well as Hamburg, Prague, and Moscow. Now, according to a scientific paper to be published in a forthcoming issue of the journal Animal Conservation, there's a compelling theory for why: insect decline.
Based on research conducted in Leicester, scientists from the Royal Society for the Protection of Birds, De Montfort University in Leicester, and Natural England have shown that sparrow chicks are starving in their nests because their parents can't find enough insects to feed them. So many chicks are dying that the birds' population level as a whole is declining.
"Where there were few insects, young House Sparrows were likely to die," the lead author told the Independent newspaper. "Young House Sparrows need insects rather than seeds, peanuts or bread to survive."
Population declines among invertebrates in general and insects in particular were the subject of a very sobering article in the newspaper earlier this week. "There are more extinctions among invertebrates than in any other groups, and a greater proportion of the species are in decline, and the decline is steeper, than in plants, birds, and mammals wherever there is data," says Matt Shardlow, director of Buglife, the Invertebrate Conservation Trust.
Examples from the Independent:
Two-thirds of Britain's moth species have declined in the past 40 years, some by enormous amounts.
Seven in 10 of Britain's 58 butterfly species have declined in the past 30 years.
Of the 25 species of bumblebee traditionally native to Britain, three have gone extinct, and four more are designated "UK Biodiversity Action Plan species" in recognition of their precarious situation.
Among insects, mayflies appear to have dropped in abundance by about two-thirds in the past 50 years.
At least 250 of Britain's 4,000+ species of beetle have not been seen since 1970.
"A very severe problem is that many invertebrates are highly specialised in what they require," Shardlow says. "They can't just live anywhere, they need a specific habitat feature, and often these habitat features are now highly fragmented and isolated, such as fenlands, or ancient woodland."
Source: Birder's Magazine, 20 November 2008
http://bwfov.typepad.com/birders_world_field_of_vi/2008/11/insect-crash…
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