December 2, 2015

part twelve:

First field pictures of
Baikal Bush Warbler from Mongolia

text by Abu

( links to previous posts: part 1, 2, 3, 4, 5, 6, 78, 9, 10, 11 )

Baikal Bush Warbler, original version of the photo!
north of Sumber, Jun 2014, © A. Buchheim

There are two species of bush warbler on the Mongolian Bird list: Chinese or Tacsanowski’s Bush Warbler Locustella tacsanowskia and Baikal Bush Warbler L. davidi. Both subspecies of the latter could occur (even as breeders) in the country, but to our knowledge there are almost no sightings, and until now there was no photograph of a bird in field available. In fact, the only record of Baikal Bush Warbler known to us is of one bird captured in south-central Mongolia during migration. 

Note 1 The Asian bush warblers formerly subsumed within the genus Bradypterus have recently been ascribed to the genus Locustella.

Note 2 Baikal Bush Warbler was formerly considered conspecific with Spotted Bush Warbler L. thoracica (sometimes still called Bradypterus thoracicus).

Note 3 Gombobaatar & Monks (2011) list only B. t. przewalskii for Mongolia in the Mongolian Red List of Birds. This taxon, now considered a subspecies of Spotted Bush Warbler sensu stricto does not occur in Mongolia.

Bush warblers are notorious skulkers and very small, making any observation difficult, and it is hard to acquire decent photos. So, the first obstacle to overcome is always to find a bush warbler. After that, one has to find a way of taking a picture. The bird featured here was found by me by almost stepping on it while it was moving through ankle high grass just a few km north of Sumberexactly at the site, where we had recorded two new species for Mongolia in 2011 (Eastern Crowned Warbler and Band-bellied Crake). It flew to a low branch and gave a short juicy “chuck” call before it retreated into the thick undergrowth. I immediately sat down but it took almost 10 minutes until I got good enough views to identify it. Then I alarmed my fellow birdwatchers via radio. Unfortunately, they arrived too late and the bird did not show again then. A few hours later, Matze, Sönke and I (the others were bird watching elsewhere) tried the site again and indeed, the bird popped out from the very dark dense cover. We fired some shots but those I achieved were pitch black on the display of the camera (see above). With the help of some friends and a lot of digital processing it was possible to make the bird visible, see below. Amazing technology that is at hand nowadays!

Baikal Bush Warbler
The improved version of the picture from above
north of Sumber, Jun 2014, © A. Buchheim

Baikal Bush Warbler
An improved version of another picture
north of Sumber, Jun 2014, © A. Buchheim

Baikal Bush Warbler
north of Sumber, Jun 2014, © M. Putze

Baikal Bush Warbler
north of Sumber, Jun 2014, © M. Putze

All pictures are of the same individual, the only one we came across during our trip. It showed characters of the western subspecies L. d. suschkini (breeding from the foothills of the northern Russian Altai in a narrow belt to the southern part of the Baikal region), notably:

  • reddish brown confined to forecrown

  • greyish nape-sides

  • dark spots on breast coalescing to form a dark grey patch

This is a bit strange, since the bird appeared within or close to the potential breeding area of the eastern subspecies, the nominate form (breeding in Russia in SE Transbaikalia E to W Amurland, and NE China). However, it is quite likely that the bird was still on migration to its more westerly breeding grounds.

More to come soon…


Peter W. Fong said...

Beautiful work Abu! Thanks for giving us a glimpse of it . . .

egor_13 said...

Nice find!
As for subspecies... "?"
Igor F