Michael Walters latest report:
Last month I mentioned the unwelcome find of a clump of Spanish bluebells in the wood; I am therefore grateful to a reader who drew my attention to a post on the BBC website which suggested that the Spanish bluebell may itself be a hybrid, and is less fertile than our native bluebell, so unlikely to hybridise it out of existence.
A surprising sight on 27th May was of a flock of about 80 jackdaws wheeling over the treetops. We tend to associate them more with nesting in town chimneypots, but they are very much at home in Blean Woods, using old woodpecker holes and similar cavities in which to lay their eggs. The number of pairs breeding here varies from eight to thirty, so 80 birds could represent our entire population plus their young. Why they should have congregated just then is a mystery; the birds started drifting away after a few minutes and I haven’t seen a repeat performance. In the 1960s professor Wynne-Edwards proposed that animals controlled their populations through a process known as group selection, and he might have cited my jackdaw gathering as a means by which the birds could assess the total numbers in the wood, and then regulate their numbers to match the available food resources by laying larger or smaller clutches, or perhaps not breeding at all if the wood was drastically overpopulated. His theory has since fallen out of favour, and in any case probably couldn’t be applied here as the gathering took place immediately after the breeding season, when it would be harder to adjust numbers, so the reason for this convocation remains unknown, perhaps mired in the subconscious depths of the jackdaws’ minds.
Early morning monitoring of birds has now drawn to a close, and I have made a start on producing territory maps for the 19 species that I concentrate on. First off the drawing board was the map for willow warblers, and what a disappointment that has proved. The graph shows a steady decline since the first part of the reserve was acquired in 1981, with numbers plummeting from 94 territories in 1982 to just six this year, the lowest figure ever. This is a reflection of the national picture where, although this species, with its sweet, wistful song, is increasing in Scotland, it is disappearing at an alarming rate from southern England, and there is a distinct possibility that it will become extinct here within a few years.
Blean Woods Butterfly Walk – 1.30pm Sat 29th June
The walk starts from the car park at the RSPB Reserve in Rough Common. It must be booked by phoning 01227 464898 or emailing email@example.com. The cost is £3 for members and students, £5 for non-members, and children under 16 are free.
Willow warbler is in severe decline at Blean Woods. Photo courtesy of Dave Smith
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