Tuesday, November 23, 2010

Changing trends in British birds.

With the International Year of Biodiversity drawing to a close the varying situation of species from across the planet has been much examined of late. The latest BTO Breeding Birds in the Wider Countryside Report adds to this debate at a national level and deals with many species with which we are familiar, some less frequently nowadays than previously!! The data is based on the efforts of volunteers and derived from the many surveys British Trust for Ornithology (BTO) has administered over the years, some of them being very long standing constituents! The report advises on the contrasting fortunes of 117 British bird species, the full text of which can be accessed at http://www.bto.org/birdtrends2010/

The figures show that numbers of 20% of these species have fallen by over half since the 1960's. Some of the declining species are also showing a reduction in breeding success, e.g. Spotted Flycatcher, Willow Warbler and Linnet and 39 species are shown to be laying their eggs earlier, which is thought to be the effect of climate change. Such a trend could have severe consequences for woodland insectivores like Pied Flycatcher, which,it is suggested, is likely to join the group above whose populations have reduced by more than half since the 1960's.

As has been pointed out many times previously some of these species are those we have taken for granted in past times, as their presence and abundance has given no cause for alarm. Now, even some of those which are household names are viewed with increasing concern.

However, not everything is disappointing news. 18 species have actually doubled their numbers! Great spotted Woodpecker and Woodpigeon are increasingly availing themselves of food provided in gardens and appear to be benefiting from warmer winters.

On Islay and Jura a number of species have declined noticeably through recent times, e.g. Tree Pipit and Whinchat, and possibly Wood Warbler. To these must be added Common Scoter whose regular presence may now be a thing of the past. On the credit side the recent appearance of several Tree Sparrows, very much a species eliciting concern in many other areas, and their subsequent successful breeding in two seasons, is a cause for celebration. And let's not forget the humble House Sparrow and Common Starling, species lost from some locations, but whose presence we still enjoy fairly generally.

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