An earlier post on Yellow-rumped Flycatchers HERE https://besgroup.org/2022/03/14/yellow-rumped-flycatchers-yellow-rumps/ led to a series of discussions with Dr David Wells that are reported here by Dato’ Dr Amar-Singh HSS.
Amar: Thank you very much for responding on my observations on flycatchers with yellow-rumps that I have been seeing. It is a bit longish and I have added the images here to help with the dialogue.
Some guides suggest that the female Narcissus Flycatcher (Ficedula narcissina)/Green-backed Flycatcher (Ficedula narcissina elisae) have yellow rumps. Wells 2007 and Handbook of the Birds of the World Alive 2018 both do not and indicate that the rump of these females is greenish or yellowish-olive (but not bright yellow). Hence any yellow-rumped bird cannot be a female Narcissus Flycatcher/Green-backed Flycatcher.
David: Correct; any first-winterer (either sex) or older female with yellow rump can only be a Yellow-rumped Flycatcher.
Amar: However, males of the Yellow-rumped Flycatcher (Ficedula zanthopygia), Narcissus Flycatcher (Ficedula narcissina)/Green-backed Flycatcher (Ficedula narcissina elisae) all have yellow rumps and when in first winter plumage can mimic the female Yellow-rumped Flycatcher (Ficedula zanthopygia).
David: Incorrect. Males of the narcissina complex do not acquire a yellow rump until after spring departure north (apparently at the complete moult of their second autumn). Females never do.
Amar: My third issue is how much yellow is the female Yellow-rumped Flycatcher (Ficedula zanthopygia) allowed? Many would label a pale-breasted flycatcher with a yellow-rump as a female Yellow-rumped Flycatcher (as many guides illustrate); but some can be quite yellow.
Wells 2007 on female Yellow-rumped Flycatchers states “Below, chin to belly and flanks variable off-white to pale sulphur yellow.” This makes the differentiation between adult female Yellow-rumped Flycatchers from the first winter males of the Yellow-rumped or Narcissus/Green-backed Flycatchers more difficult.
David: Uncertain; colour tone could be the difference between adult female and first-winterers and/or between first-winter sexes. Needs a bit more work as age-classes can be told apart on other characters (e.g. upper tail-covert colour).
Amar: In addition, the differentiation between adult female Yellow-rumped Flycatcher from first year/first winter Yellow-rumped Flycatchers (male or female) is not that easy.
One useful feature to identify first year birds is the size and limited development of the white wing bar (less prominent in first winter birds than adult females).
David: Apparently, yes; true.
Amar: Now to the bird ID’s.
Amar: The first flycatcher I saw with a bright yellow-rump (Post 1) was a pale bird, with hardly any yellow on the breast, a weak pale supercilium, a white eye ring and poorly developed white bars on the wing. I think this is a first winter Yellow-rumped Flycatcher and possibly a female.
David: Post 1. Female/first-winter Yellow-rumped.
Amar: One person said that as the bill is completely black it is an adult female. I still think this is a first winter Yellow-rumped Flycatcher and possibly a female.
Amar: The second flycatcher I saw with a bright yellow-rump had yellow on the breast, some faint barring or spotting on upper breast & neck, a yellowish eye ring and a clear large/broad white stripe on the wing (see also Post 3 of same bird).
Is this an adult female Yellow-rumped Flycatcher? But the white wing bar is too big and reminiscent of the males (Yellow-rumped or Narcissus/Green-backed Flycatchers).
However the supercilium is poorly developed at the present stage to offer help. I am inclined to think this is a first winter male Ficedula narcissina elisae (Narcissus/Green-backed Flycatcher) but open to opinions.
David: Post 2. Some key characters not in view but my guess would be immature male (second spring?) Narcissus (elisae). Post 3. First-winter>second spring male Yellow-rumped. Are you claiming your posts 2 and 3 were the same bird? Surely not as their wings look quite different. Also, post 2 has yellowish eye-ring, which is a Narcissus, not a Yellow-rumped character. Post 3 (presumably taken in Malaysia) can only be a Yellow-rumped male.
Amar: Yes, David, both images are of the same bird taken in Ipoh, Malaysia on 17th Sept 2018. The images were taken a few seconds apart as I was tracking/following this one bird with my camera and long lens. So no mistake there. Here is another image of the same bird at the same time. I have cropped harder to focus on the face (Post 4).
I wonder if it is a pale eye ring that lighting can affect easily? Light was strong at this time. To add to the discussion, Post 4 is another Flycatcher with a yellow-rump that I saw one week later (26th September 2018) at the same location.
I went back to look for the 2 birds but saw this one – 4 images.
A bright yellow-rump with yellow mainly on the lower breast (unlike the earlier bird), some faint barring or spotting on upper breast and neck, a pale white eye ring and a clear large/broad white stripe on the wing. Adult female Yellow-rumped Flycatcher?
Hope these adds to the conversation.
Dato’ Dr Amar-Singh HSS – Ipoh, Perak, Malaysia