Denne hanlignende rødstjert er faktisk en hun. Den er blevet set i par med en han fodre unger i en redekasse, og i øvrigt også ruge på æg, hvad kun hunnen gør hos rødstjerter.
This very male-looking Redstart, apeared to be the female part of a breeding pair. It has has been seen incubating eggs and feeding chicks in a nestbox, along with a male.
Thank you for your comment, and I understand your scepticism, but in my opinion there's no doubt at all, that the bird is a female.
We didn't take a blood sample to confirm it, but I find the scenario of a female laying eggs, whereafter a feminin male chooses to incubate the eggs and feed the chicks along with a normal looking male rather unrealistic. It is well known that some females can develop male-like caracters with age, but I've never heard that they should be sterile, and I guess that would be variable. The bird did have brood patch, and a cloacal opening similar to other females caught and smaller than the males. It was also very much different from any other males (I did choose a picture that showed the black throat and white forehead, but the angle might over exaggerate the male likeness a bit).
The bird was also seen in a pair with a normal male last year, according to the local ringer.
The fact that females with damaged or undeveloped sexual organs can become very male-like in plumage is well documented, but hardly the case here.
A true broodpatch, smaller than average male measurements, chape of cloacal opening and the fact that the bird was paired to a male last year as well, all point to the conlusion that Common redstart female can indeed look very much as a normal (late winter/early spring) male - the tips of the feathers on head and throat seem less abraded than on a normal male from June.
Certainly a most unusual bird. Lars Svensson writes about females with male-characters that "it is extremely rare that they have all chin- and throat-F based blackish."
On this bird, however, the black is NOT restricted to the bases, so you may have found something much more rare than an overshooting Melodious Warbler -to mention but a few:)
Best regards
Peter
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English version
Peter Sunesen skriver tirsdag 8. juni 2010 kl. 16.13 