Yellow-rumped Flycatcher Ficedula zanthopygia is a rare winter visitor to Borneo, only recorded 3 times on the mainland of Borneo thus far. Once each in Brunei (1984), Kalimantan Tengah (1993) and Tawau, Sabah (1998).
Records from Hong Kong show that most sighting there are female birds, indicating that male is less seen in migration, despite adult male's prominent identification field marks which make it easier to spot in the field.
This bird was photographed in Tawau (fourth record for mainland Borneo and second for Tawau), it was foraging around a location for over two weeks in late December 2011.
It was first thought to be a female Narcissus Flycatcher Ficddula narcissina, which is considered relatively common and seen here during winter quite regularly.
You can see from the following two images that they actually look very similar. However, Yellow-rumped normally has a white wing patch made up of white on its greater coverts and edges of tertials, but this feature is conspicuously absent on this bird, making it look more like a Narcissus with its plain looking wings.
Narcissus Flycatcher ♀
The conspicuous lemon yellow rump is partially visible here, positively confirming its identification.
The following images is more interesting, it shows the rump and some black upper-tail coverts which is a feature of first winter male, it also shows the unmistakable yellowish wash on its flanks, which together with the overall more yellowish underparts shown in earlier images indicate that this is a young male starting to moult into adult plumage.
Young male of Narcissus Flycatcher is ruled out because its yellow back is much higher up on its back, not low on the rump as shown in this bird.
In view of the similarity with female Narcissus Flycatcher, there might be cases of female Yellow-rumped being discounted as female Narcissus on first glace in the field, so if you see one, it is worth to take a second look.
Photodocument of Wild Birds of Borneo.
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