Friday, November 12, 2010

Eastern Yellow Wagtails: 6th November 2010

When Trevor Ford and I visited Kampung Permatang Nibong on 5 November, there were around 500 Eastern Yellow Wagtails swarming over a couple of fields, so we went back the following day for a closer look.

Unfortunately for us, there were only about 100 left, but that was enough to be getting on with!

The taxonomy of Yellow Wagtails is a quagmire! The current 'state of play' is as follows:

1. Eastern Yellow Wagtail (Motacilla tschutschensis): includes nominate 'tschutschensis' (formerly 'simillima' and 'angarensis'), 'taivana' and 'macronyx'.

2. Western Yellow Wagtail (Motacilla flava): includes 'thunbergi' (sometimes called 'plexa')!

In Peninsular Malaysia, it is thought that the 'tschutschensis' race of Eastern is the commonest form, followed by 'macronyx' and then 'taivana'. The status of 'thunbergi' Western Yellow Wagtail is uncertain because of the difficulty of differentiating it from M.t.macronyx, but both forms have been identified from museum skins as occurring in the area (Wells 2007).

According to Wells, first winters can be told from adults by having a yellow-based lower mandible.

Added to the mix is a potential addition to the Malaysian list - Citrine Wagtail - which looks quite similar to Eastern and Western Yellow, particularly females and first winters (see here). Perhaps the key feature to look for in a Citrine is a complete pale surround to the ear coverts.

A nice easy one to start with - a male 'macronyx'. The only yellow males we saw were of this race.

Can't say too much about this one. Is it a non-breeding female? Perhaps 'tchutschensis' due to the supercilium?

A very different looking all I'm going to say about this one!

This should be a first winter (pale bill base) but gender? race? Who knows?!

Some birds contravene the Trade Descriptions act altogether - not a trace of yellow on this "Yellow Wagtail"! Interesting pale blue-grey rump. This must be a first winter.

A couple more 'female types'. The lower bird shows distinctly white vent/undertail coverts, which, according to Robson, is a diagnostic field character of non-breeding male Citrine. Hmmm!

What I learned about Yellow Wagtails today is that I have much more to learn about Yellow Wagtails!


Madibirder said...

Hi Dave,
Same here! I've a lot to learn about this species.

jytou said...

The "taivana" is sometimes split into another species, the Green-headed Wagtail. According to Wells (2007), this is the rarest of all forms in the Yellow Wagtail complex.

Your possible Citrine is very interesting, I never thought that they may look very similar to Yellow Wagtails in certain sex and age. From the illustration, breeding plumage is very distinct and the non-breeding not so distinct but should look different than the wintering Yellows. Maybe really need to keep an eye on these. Thanks.

jytou said...

viewing citrines on OBI, they all have a consistent pale ear patch/mask that as you described is completely bordered by a pale region starting from the supercilium and circled the ear patch. This feature is not seen in your suspected Citrine where it has a dark grey mask (not pale) and lacks the circling pale border.

The Yellow Wagtail complex (all forms) seemed to be probably highly variable in winter, with pure white underparts in 1st winters that has a confusing greyish back (that confuses me during my first encounter with this form), and a variation of differences in yellow in the underparts for wintering birds of other ages, some with yellow throat but probably whiter belly and some yellowish belly but seemingly a whitish throat, so I could not confidentally tell than the pure white vent is a very good feature to distinctly differentiate the Citrine from the Yellows.

digdeep said...

Hi Tou

I think you may have misunderstood my post. I didn't see any suspected Citrine; I only wish I had! I was simply alerting you and others to look out for them.



digdeep said...

Re-reading my post - the 'Hmmm' under the last pic didn't mean I think it might be a Citrine! It means I don't think that a white vent is a very good 'diagnostic feature'!

jytou said...

hi dave,

thanks for clearing the doubts.... haha, but true, keeping looking, we never know, they wont just show up in Singapore from no where, they must had been passing us under our nose, just that we didnt realize it....

John Holmes said...

Yellow Wagtails... we have (well, I have) much to learn indeed.

So many subspecies,soooo little time !