Saturday, November 14, 2015

Khao Dinsor: Raptor Heaven/Accipiter ID hell!

One of the big challenges of my trip to Khao Dinsor in late October was getting to grips with Accipiter identification, one of my most confounding ID conundrums in Thailand because most of my encounters with Accipiters are when I flush them from cover on my local patch and they invariably disappear without me getting much of a view; secondly and more importantly there are at least five key species involved, which have at least 3 main plumages (adult male, adult female and juvenile, so that is 15 different plumages to learn); and thirdly there can be HUGE variation...especially within juvenile birds.

So, how do you do them?  Well, I feel like I am still learning a great deal, but the first step seems to be to count the number of "fingers" on the open wing as this helps to narrow down the field:
  • 4 fingers = Chinese Sparrowhawk
  • 5 fingers = Japanese Sparrowhawk, Shikra and Besra
  • 6 fingers  = Eurasian Sparrowhawk (and Northern Goshawk)
As a migration watch point, Khao Dinsor allows observers to get relatively prolonged, often close views of the majority of raptors passing, and this includes Accipiters. Taking photos is a good way of helping make sure you get the ID correct - counting "fingers" in the field can be a bit of a nightmare, especially given the large numbers of birds passing and the fact that you are dealing with extremely bright light and seriously hot weather, which can make observations challenging.

Here are a few images of the protagonists:

Adult Accipiters

Adult female Chinese Sparrowhawk
On this adult Chinese Sparrowhawk note the very black primaries that make 4 "fingers", the lightly marked underparts, and the richly coloured breast.  The yellow iris makes this a female (males have orange eyes).

Adult make Shikra

Adult female Shikra

Adult Shikras are typically pale grey, with lightly barred underparts.  They wing shows five fingers which are greyish. The sexes are told by iris colour (yellow in female, orange in male). Shikra also lacks an orbital ring (present on Besra and Japanese Sparrowhawk), though personally I find this hard to judge on many photos (and pretty much impossible to discern under most field conditions).

Adult male Japanese Sparrowhawk
Japanese Sparrowhawk shows five "fingers", with no dark tips. Male shows a rufous wash on the breast with rather diffuse barring; upperparts are darker than Shikra.

Adult female Japanese Sparrowhawk
Adult female Japanese Sparrowhawk
Japanese Sparrowhawk female looks very similar to Eurasian Sparrowhawk with brown upperparts and brown barring on underparts, but shows only five "fingers" and appears generally more compact and shorter-tailed.

female Eurasian Sparrowhawk
Eurasian Sparrowhawk is rare at Khao Dinsor, and indeed in much of Thailand.  This bird (note six fingers) was only ID'd from photos.

Juvenile Accipiters

1st calendar year Chinese Sparrowhawk

1st calendar year Chinese Sparrowhawk

On juv Chinese Sparrowhawk the combination of heavily marked belly, uniformly pale underwings and four blackish "fingers" is diagnostic.

1st calendar year Shikra

1st calendar year Shikra

1st calendar year Shikra
Juv Shikra is highly variable, as you can see from these images above and to my mind, as a result provides the biggest pitfall amongst the Accipiters encountered in Thailand. Things to look for are the five fingers, absence of an orbital ring, tear-drop shaped spots on the belly, quite lighlt marked underwing coverts and a rounded tail tip.

1st calendar year Japanese Sparrowhawk

1st calendar year Japanese Sparrowhawk

1st calendar year Japanese Sparrowhawk

1st calendar year Japanese Sparrowhawk

Juv Japanese has an orbital ring present, five fingers, v-shaped or heart-shaped spots on the belly, a more square-ended tail and heavily spotted underwings.

The teasers

So after a lot of editing my images, I was left with these three that really messed with my head. They all show 5 fingers, so are either Shikra, Besra or Japanese Sprawk...

Teaser 1

Teaser 2

Teaser 3

Teaser 1 - Shikra
This one I posted on a the "raptor mania" facebook page, which Thai birders use to share info on raptors.  The comments I got back included "It's a Shikra because of the lack of yellow orbital eye ring. That's the easiest way to tell Shikra apart from Japanese/Besra"...."Shikra - The underwing covert is quite clean, sparsely spotted. It looked heavy-chested"..."the spots on the breast /belly are of different shape [arrow-shaped] on juv Japanese".  

Teaser 2 - Japanese  Sparrowhawk
This one I initially got right, ID'ing it as a Japanese Sprawk, but a few days later I looked again and suspected that it looked rather broad-winged and heavily built, so started to suspect Shikra.  However when posted on Raptor mania my initial ID of Japanese was confirmed by others (note the arrow-shaped markings on the belly).

Teaser 3 -Besra
I posted this one on "raptor mania" too, thinking it was a Japanse though I had wrestled with the idea of Besra. I was informed  that it was a "Besra because of the longish tail compared to Japanese, also with cleaner underwing coverts (not always clean though)." Besra is a rare bird at Kaho Dinsor, and this was the only one I encountered during my two days there.


Lee Dingain said...

An excellent and informative post. Brilliant stuff matey.

Sacha Barbato said...

Great post. The Sparrowhawk is presumably nisosimilis (Eastern race) and does appear paler than the ones I see here in Europe.