The ageing and sexing of Golden Orioles is something that not too many ringers in Britain are lucky enough to have experience of. So this evening I've had time to sieve through the photographs of our recent bird and try to come up with an answer. Both adult and first-year Golden Orioles undergo a virtually full moult in their African wintering grounds. But the young birds are very unusual in that they moult into a plumage which is virtually identical to that which they left the nest with. Adult females can sometimes look similar to these spring birds but there are several features which can be used to identify a second calender-year bird. In the younger birds the greyish white underparts are distinctly streaked, grey on the breast, blacker on the belly (as can be seen on the photographs below); an adult female would typically have only faint streaking on the belly. The yellow along the outermost tail feather would also extend further than shown above if the bird were adult and the central tail feathers would be more rounded. The retained secondaries, although distinctive, are not an ageing criteria as both adults and second calender-years show this feature (although the retention is more frequent in younger birds). The percentages of retained secondaries noted by Jenni and Winkler are S6 25%, S5&6 35%, S4-6 15%, S3-6 15% and S3-7 10%, so our bird falls nicely into the typical pattern. The extensive, stepped, whitish tips to the primary coverts are much more typical of a male bird, but this sexing method is not thought to be 100% accurate. (c) Richard Brown
Sunday, May 8, 2011
Heavy rain and an absent moon in the early hours led to a very dark spell at about 2am. Little in the way of small stuff seemed to be moving with only a Sedge Warbler, a Whitethroat and a Blackbird attracted. But 34 Manx Shearwater circled the tower and I managed to catch and roost 23 of them. The morning census yielded little in the way of new arrivals but the second Turtle Dove of the year toured the island and a few Swifts passed through. A Golden Oriole we found visiting the gardens this afternoon was presumably the bird from two days ago but without views of its right leg there was no way of being certain. Other scarcer visitors included a Pied Flycatcher, four Spotted Flycatcher and a couple of Tree Pipits and Garden Warblers. Two Cuckoos remain, one a singing male and one a probable female antagonising the Meadow Pipits.
Posted by Rich and Giselle at 12:10 PM