Saturday, 27 August 2016

Bird of the week - Cuckoo

This bird was driving me crazy.  I made five trips to see it in a week and after the first four I had only three photos to show for ten hours watching and waiting.  It was fifth time lucky as I struck gold.  I spent almost two hours alone with the bird who was quite unconcerned by my presence although by the end it was wondering which of us was cuckoo.

This is a juvenile cuckoo and it spends its time hopping along the paths in the dunes eating caterpillars and sitting thinking.  It has long wings and tail and is already a fast powerful flyer.

Everything about this bird is amazing.  It never saw its parents who headed off back to Africa in June.  It was brought up by foster parents, probably reed warblers or meadow pipits, and then set about feeding itself, choosing the poisonous caterpillars of the cinnabar moth.  (The caterpillar absorbs the poison from ragwort, its food plant, but the cuckoo is not affected by the poison.)  Within the next couple of weeks or so it will set off to fly to sub-Saharan Africa alone, probably having never seen another of its kind.

The cuckoo (Cuculus canorus) has been in decline in the UK for the last thirty years and is on the red list.

The BTO Bird Atlas abundance map shows that cuckoos avoid London and have a patchy distribution elsewhere.

The decline in numbers has been most evident in England, Wales and southern and central Scotland.

To help to investigate reasons for the cuckoo's decline the BTO has been satellite-tracking cuckoos since 2011.  You can read about the project here.  This image below shows the migration routes taken by three birds in 2013/14.  You won't be surprised to hear that the cuckoo providing the most reliable data was called Chris!  The BTO data showed that he spent almost half of the year in the Congo, over a third on migration and only 15% in the UK.

This is Thomas Bewick's painting of an adult cuckoo, an engraving of which appeared in A History of British Birds in 1797.

In Bewick's day the brood parasitism of the cuckoo had only recently been described, in a paper presented to the Royal Society in 1787 by Dr Edward Jenner FRS, perhaps more famous as the pioneer of smallpox vaccination.

You can listen to Sir David Attenborough's BBC Radio 4 Tweet of the Day on the cuckoo here.  And watch a video of a young cuckoo being fed by reed warblers after fledging at WWT Slimbridge here.

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