07 July 2010

Incestuous pairing amongst Wood Warblers

Jerry Lewis writes:
I have been monitoring Wood Warbler nests in Larch plantations (Wentwood Forest, Gwent) for about 10 years, and densities are quite good at about 10 pairs per sq km. I ring most of the chicks so when I catch an adult I can usually see how the chicks have dispersed from the natal nest to the breeding site (males move further than females on average). Last month I caught a pair at one site which turned out to be siblings from a nest about 1400m away in 2009. I suppose that although this may not be particularly unusual, it is not often recorded. It was also interesting that 4 of the 6 eggs did not hatch (I seldom record unhatched eggs in nests), perhaps indicative of the "poor" pairing, and unfortunately the chicks were subsequently taken by a predator when about 10 days old.

Lee Barber adds:
Our ringers have ringed about 20,000 Wood Warblers so far and only 47 had been recovered by the end of 2008. The majority of the reports we receive about this species are from ringers doing this kind of valuable work but we have also received a few reports of birds found abroad. All of these were of dead birds and were from Italy (8), Morocco (1) and Algeria (1). We have had no foreign ringed birds being found or caught in this country yet.

Posted on behalf of Jerry Lewis and photo by Jez Blackburn

1 comment:

  1. Interesting - in most passerines it is females that disperse further than males.

    I've also had a pairing of siblings in my tit population, although there is always the chance that extra-pair copulations by the mother means that they are only half-siblings.