There have been quite many Eastern Yellow Wagtails (Motacilla tschutschensis) passing through my local patch since late August. Most of them were either in non-breeding or juvenile plumage. It’s always fun to see the variation of both plumage. In this post, I’d like to share some photos of the juveniles that I’ve photographed and some identification notes for the different subspecies.
To our current knowledge, at least 6 subspecies of Eastern Yellow Wagtail are recorded in Thailand, including tschutschensis, plexa, similima, angarensis, macronyx, and taivana. However, it’s not always possible to identify to the subspecies level. Not to mention that some subspecies of Western Yellow Wagtail (M. flava) actually look nearly identical to Eastern Yellow Wagtail and possibly can’t be identified without sufficient photographic evidence and good sound recordings. Anyway, let’s not start the discussion on that topic yet. I’d like to focus on the identification of the 3 main subspecies groups (tschutschensis, macronyx & taivana) for now.
Although there are as many as 4 subspecies (tschutschensis, plexa, similima & angarensis) within the nominate tschutschensis subspecies group, I have no idea about how to identify them in the juvenile plumage. It seems that only the males in breeding plumage can be identified to the subspecies level, which I’ll leave it to the future post. So for this post, I’ll only call them tschutschensis-type.
In juvenile plumage, the long bold white supercilium is still the most diagnostic feature for tschutschensis-type, just like in the adult plumage. Unlike the adult, the juvenile has no (or very little) hint of yellow on the underparts. The throat and underparts are normally whitish with some slight buffish wash on the breast. The juvenile also has dark brownish marking on the neck side and upper breast forming what seems like a gorget around the throat. Another diagnostic feature of a juvenile, which is consistent among all subspecies, is the bold white tips to the greater coverts which forms a bold white wing bar. The adult would have duller and more yellowish fringes to all wing coverts and tertials.
Next is the subspecies M. t. macronyx (Mongolian Yellow Wagtail), of which I don’t have many photos of the juvenile plumage. Most juveniles of this subspecies that I’ve seen had faint and very narrow supercilium, but they can completely lack the supercilium (like this individual) as well. The underparts often appear cleaner than in juvenile tschutschensis-type with less clearly marked gorget around the throat and upper breast. Another characteristic which I often see in juvenile macronyx, and not so pronounced in other subspecies, is the peachy wash on upper breast. It can be very obvious in some postures, particularly while walking and when seen in profile.
The last subspecies is the M. t. taivana (Green-headed Wagtail) which is the least common subspecies in Thailand among the previously mentioned subspecies/subspecies group. The juvenile of this subspecies usually appear similar to the adult but with overall duller plumage. The supercilium and underparts usually appear more yellowish than in other subspecies although variable. The crown and mantle are also quite distinctly more olive than in other subspecies as well.
Last spring, I could also get many photos of Eastern Yellow Wagtails in full breeding plumage while they were passing through Mae Faek paddies. I’ll compile the photos and do a write-up about the various subspecies and variation of the breeding plumage in the next post.