Yellow Wagtail – making sense

posted in: bird, Species | 0

Yellow Wagtails (Motacilla flava) have such diversity, are fascinating and have been split by some authorities into Western Yellow Wagtail and Eastern Yellow Wagtail with numerous subspecies (with mitochondrial and DNA evidence). Seeing them when not in breeding plumage adds to the challenge of making a more precise field identification. Leaving aside the split into Western and Eastern Yellow Wagtails, four subspecies are said to migrate to the Malay Peninsula (see Wells 2007, based on work by Alstrom & Mild). Key features in breeding adults summarised include:

  1. 1. M. f. tschutschensis – the predominant species (90%) with a clear, full-length white supercilium, grey to black ear coverts, grey cap.
  2. M. f. taivana – least common, dark cap with a yellow supercilium.
  3. M. f. thunbergi – not common, with a dark cap (darkening further on forehead), a short or absent white supercilium behind the eye, a possible necklace of darkish flecks across the upper breast.
  4. M. f. macronyx – not common, like M. f. thunbergi but no darkening on forehead and no dark necklace across the upper breast (macronyx and thunbergi are not generally safely separable in the field).

Some Yellow Wagtails allow a closer approach and offer good views/images. I am going to offer two such birds and ask for opinions; failing which we’ll just call them ‘Yellow Wagtails’. I have framed some questions for myself for thinking. I am also using good work/descriptions by Bot et al 2014: Sander Bot, Dick Groenendijk & H Herman van Oosten. Eastern yellow wagtails in Europe: identification and vocalisations. Dutch Birding 36: 295-311, 2014 (available online).

Is this a Western Yellow Wagtail & Eastern Yellow Wagtail? (I see no reason why the Western Yellow Wagtail species could not occasionally migrate to our region). In this first bird (top) there is a relatively long hind claw; see below. Bot et al 2014 states “In both eastern yellow wagtail and Citrine Wagtail the hind claw is on average longer than in western taxa but there is considerable overlap (table 2). Thus, when a yellow wagtail in Europe shows a long hind claw (plate 403) this is an indication, but not proof, of eastern origin.” I know I am not in Europe but this is an additional useful feature in the field to help distinguish Eastern from the possible occasional Western Yellow Wagtail.

Is it a first winter bird?

Initially I considered this to be a first winter – there was some suggestion of a gape. I am not good with moulting or unmoulted juvenile-type feather in wing coverts; so cannot comment there. But the bird has a more brown-and-yellow plumage rather than the grey-and-white plumage that can be seen in some first winter birds (Bot et al 2014 states that in “M. f. tschutschensis, one-third to almost half of all first-winter are grey-and-white”. Aymí 1995 & Alström et al 2003 state that “Grey-and-white birds are often females”). Also the nice patch of yellow on the throat with dabs of yellow on belly and sides of breast so early in migration suggest an adult. But there is no yellow in undertail-coverts. Appreciate opinions.

Which sub-species is this? 

A daunting identification when seen outside their breeding areas and in non-breeding plumage. However the prominent supercilium supports either M. f. tschutschensis or M. f. taivana. No calls were heard to offer support.

 

Amar-Singh HSS (Dato’ Dr)

Ipoh, Perak, Malaysia

 

Location: Malim Nawar, Perak, Malaysia

Habitat: Ex-mining pools, fish farming, wetlands

Date: 2nd November 2018

Equipment: Nikon D500 SLR with Tamron SP 150-600mm f/5-6.3 Di VC USD, handheld

 

 

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