A Curlew replacement clutch

20120802 Coombe Hill Curlew juvenile

Because of the difficulty of finding Curlew nests and eggs in the large hay meadows where they nest in the Severn and Avon Vales, it is hard to follow the nesting cycle of this species.  They don’t lay their eggs very early in the season because, being the largest wader, they would be an obvious target for foxes, crows and other predators (though Lapwings seem to take this risk, with some success).  So an incubation period of 28-30 days and a fledging period of 32-38 days (BTO guide to monitoring nests) means that a relatively early laying date of 15 April would give fledging on 23 June, and a laying date of 30 April would give fledging on 8 July.  On the rare occasions when we have found young birds, this has often been of unfledged chicks well into July, so some Curlews obviously don’t start incubating until early May.  All this means that that there is never going to be time for a second clutch, quite apart from the effects of predators or of damage by hay-making machinery.

This year, the Curlew breeding season has been disrupted by flooding, in particular the flood from the last days of April until mid-May; then there was another flood in late July.  As a result, it seems to me that in all the breeding areas along the Severn and Avon, clutches were washed out.  The birds have generally hung around at the favoured sites after the floods, but have not behaved as they do when they have young, flying round and round with agitated alarm calls.  I therefore suspect very strongly that the majority of Curlews have failed this year (though I still need a better final look at Upham Meadow, Twyning).

However, at Coombe Hill, south of the canal, not on the GWT reserve but on nearby fields belonging to Mr John Arkell (a regular breeding site for Curlew where “bubbling” displaying birds had been present since late March), one pair of Curlew (and a couple of Lapwings) successfully raised a replacement clutch.  There were birds nesting here before the April flood, but they must have been washed out in late April or early May, when water was nearly a metre deep in places.  When the floods dropped, I found a fresh clutch of Lapwing eggs on 26 May, clearly a replacement clutch as the site had been under water ten days previously.  I paid regular visits to the area to follow the success of the Lapwing clutch.  In doing so, I noted signs of Curlew nesting in long grass, and in early July, there was an agitated adult Curlew in the area (presumably the female), flying round and giving increasingly agitated alarm calls (the sharp “waup” call and the five-note alarm, both generally used when there are chicks about).   The last time I observed this behaviour over these fields by a single adult was on 24 July.  On 28 July three Curlew were flying about the scrapes on the GWT reserve, 100 yards away over the canal, at least one of which appeared to be a juvenile with a short bill (though this was not absolutely confirmed).  However on 31 July, an adult and two short-billed but fully-fledged chicks were well seen round the scrapes, and one of the juveniles was photographed by Dave Pearce on 2 August (photo attached).   These birds must thus have fledged between 24 and 28 July, a relatively late date compared with other local findings of Curlew chicks; on the basis of a 60-68 day cycle, and assuming fledging to be 25 July, this means the eggs must have been laid somewhere between 18 and 25 May, i.e. after the May flood.  Ergo, a replacement clutch!

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