Tuesday, 1 January 2013

Happy New Year and a Barley Bird in France

After a frustrating week without any broadband connection I would like to start this blog by wishing all readers of this blog my best wishes for 2013, and may your year be filled with many wildlife adventures.

I thought I would start this year with news of an interesting recovery of one of the nightingales that I had previously ringed at Botley Wood, Hampshire in April 2011. The bird was originally ringed on 21st April 2011, as a first year, therefore hatched in the summer of 2010. It was fitted with individually identifiable colour rings, but unfortunately it was not these that generated the recovery.

First Year Common Nightingale 21st April 2011

On the 27th June 2012 (433 days after its original ringing date), this bird was found freshly dead in the Vienne region of France 488 kilometres to the south of its original ringing site, having hit glass. This is the first foreign recovery of one of the Botley Wood ringed nightingales which is exciting in itself, but the date of the recovery is something that has got me thinking. 

Common nightingales typically arrive at Botley Wood from mid April and are usually paired up and nesting by mid May. Their chicks tend to hatch around early to mid June and by late June/early July they are fledging the nest. From mid to late July adults undergo a complete moult before migrating around early to mid August. Adult birds show a high degree of site fidelity, and will return to the same territory year after year, so seeing that this bird had been recovered in France in late June got me thinking what it was doing there.

My first thought was that the bird had failed to find a mate in the previous year and had decided to stay in France to breed during the 2012 breeding season. This strikes me as very unusual behaviour, given the level of site fidelity previously exhibited by the species at Botley Wood. Alternatively, it could be that this bird usually breeds in this region of France but had over shot the previous year and ended up at Botley Wood.

My second thought was that the bird had returned to Botley Wood but had not been a successful breeder during 2012 and therefore had began its autumn migration early. There are two reasons why this may have happened; the weather during 2012 was very bad and many species had poor breeding success, given that nightingales are only single brooded in the UK, a failure could instigate an early southward movement. This was certainly experienced with some species during 2012, whereas as other species stayed on their breeding grounds and had very late broods. The second reason may be due to a lack of habitat at the breeding site. During 2012 the National Grid replaced overhead power cables that pass over parts of the site, in doing this they removed all of the scrub where this bird was holding a territory in 2011. Therefore it may have returned and been unable to find a suitable nesting location and/or a mate and moved back south.

My third thought was that the bird had been held up on its northward migration due to bad weather over the Mediterranean in the spring, but a delay of two months from its normal arrival date is probably too much of a delay for this to be the case.

Unfortunately I will never know the answer but it is still a very interesting recovery that will keep me wondering for a while yet.

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