Monday, 13 February 2012

13th February 2012 Tone River & Choshi Harbour

Great Crested Grebe 4
Black-necked Grebe 3
Cormorant c.100
Japanese Cormorant c.2,000
Pelagic Cormorant 3
Grey Heron 5
Great White Egret 9
Bewick's Swan 6
Black Brant 1
Teal 2
Mallard 30
Scaup 50
Osprey 2
Black-eared Kite 8
Hen Harrier 1 ringtail
Eastern Marsh Harrier 4
Sparrowhawk 1
Buzzard 4
Kestrel 2
Coot 5
Black-headed Gull c.250
Black-tailed Gull c.1,000
Russian Common Gull 1 adult winter
Kamchatka Gull c.50
Vega Gull c.250
Slaty-backed Gull c.250
Glaucous-winged Gull 1 adult
THAYER'S GULL 4 ex. (2 1w, 2w & 3w)
Glaucous Gull 2
Kittiwake 1
Feral Dove c.50
Oriental Turtle Dove 4
Bull-headed Shrike 1
Large-billed Crow c.15
Skylark 1
Brown-eared Bulbul c.10
Fan-tailed Warbler 1
White-cheeked Starling c.20
Dusky Thrush 2
Blue Rock Thrush 1 female
Tree Sparrow c.30
White Wagtail 1
Meadow Bunting 6 ex.
Chestnut-eared Bunting 1 ex.
Rustic Bunting 3 ex.
Reed Bunting c.12

Reedbeds bordering the Tone River
Whilst we were in the fortunate position of having seen Japanese Reed Bunting and Japanese Marsh Warbler during a previous visit it soon became clear that the mature easily accessible reedbeds were supporting a good array of wintering passerines, especially Buntings. Unfortunately we did not have time to do the area justice as we did not want to miss the ebbing tide at Choshi when Thayer's Gulls tend to congregate at the small black sand beach at the southern end of the harbour on the south side of the river.

Female Eastern Marsh Harrier
Whilst male Eastern Marsh Harriers are quite distinctive from their western counterparts so are the females. Note its pale ashy head and upperbreast, contrast dark flight feathers and small white rump-band.

Non-breeding male Meadow Bunting along the Tone River

Whilst sexing Meadow Buntings in non-breeding plumage can be very tricky, this individual's whitish supercilium, blackish lores, pale central crown stripe and rufous scapulars all point to it being a male (Byers et al.).

Pale first-winter Slaty-backed Gull at Choshi
First-winter Slaty-backed Gulls are notoriously variable. It is not unusual for birds such as this individual to have bleached coverts from midwinter with their tertials and primaries beleached to brown recalling Glaucous-winged Gull but note its far more heavily marked mantle and scapulars than that species.

First-winter Slaty-backed Gull at Choshi
A slightly more abraded and yet darker individual than the bird above and note the difference in the primary pattern.

First-winter Slaty-backed Gull at Choshi

Primaries, tertials and secondaries darker still on this whiter-headed but less abraded and bleached individual.

Advanced second-winter Slaty-backed Gull at Choshi
Based on this individual's patterned tertials and its primary tips lacking true white spots I'll go for this being an advanced second-winter rather than a retarded third-winter but I could be wrong - I frequently am!

Fourth-winter Slaty-backed Gull at Choshi
This bird's insipid bill colour with an almost L. a. argentatus-like pinkish bloom basally made it stand out from the crowd and presumably points towards it being a fourth-winter. Note its broad white tertial and secondary tips and dark-pink legs. 
Adult winter Russian Common Gull L.c. henei at Choshi

Brazil (1991) and Olsen (2003) do not include this subspecies for Japan but it is included as occuring in Brazil (2009). Whatever, I can see nothing to suggest this isn't a henei whereas its 'familiar' head-pattern (from a European perspective) with streaking above eye and blotching on hindneck, greenish-tinged bill complete with darkish ring around its tip, dark looking eyes and green legs all seemed at odds with the accompanying Kamchatka Gulls L.c. kamtschatschensis. Very dark-mantled compared to L.c. canus, but this should be no surprise, as L.c. henei are at their darkest at the easternmost of their range being the likely origin of most occuring in Japan.

Adult winter Kamchatka Gull L.c. kamtschatschensis at Choshi

Olsen (2003) describes this as a distinct (the largest) taxon, probably requiring fully specific status. Note its virtually clean yellow bill, pale eyes, yellowish legs and densely dark-marked hindneck and neck-sides.

Adult winter Kamchatka Gull at Choshi

An even more striking individual courtesy of its even brighter and more richly yellow coloured bare parts.

Adult winter Vega Gull at Choshi

Adult winter Vega Gull at Choshi

Compare the hindneck streaking on this individual to the hindneck blotching on the previous individual above.

Adult winter Vega Gull at Choshi

This bird's extensively dark streaking to its head and breast would appear to be at the extreme end of the variation for adult winter Vega Gull and somewhat reminded us of adult winter American Herring Gull but note its dark-eyed appearance.

Third-winter Thayer's, juvenile Kamchatka and adult Black-tailed Gulls at Choshi

Third-winter Thayer's Gull at Choshi

A small-looking individual with a small head and nice rounded crown. Its bill complete with a greenish tinge also appeared small and rather weak so presumably a female. At any distance it appeared dark-eyed even though its iris was grey. In flight it showed the remnants of a dark tailband.

 Second-winter Thayer's Gull at Choshi
After several 'close misses' over the years a classic individual at last! A nice advanced (for a 2w) grey mantle forming a smooth grey saddle, dark tail, in flight the dark upperwing-coverts and dark secondaries forming a neatly demarcated 'dark perfect rectangle' contrasting with its paler primary coverts and (especially inner) primaries, venetian blind accross its outer primaries by virtue of its dark outer webs and silvery inner webs (tipped dark), head and body plumage a rather smooth brown, dark-based tertials and at rest its narrow pale edges forming pale crescents to the tips of its primaries. Nice bubblegum pink legs too.

With Thayer's Gulls, controversy all too often tends to quickly follow... the 'classic' second-winter was soon joined by a second Gull that appeared near-identical in size, structure and jizz and adopted the same feeding strategy. Whilst its all-dark bill and dark eye suggested it was a first-winter, its 'advanced' rather plain mantle was completely at odds with the hoped-for oft-quoted retained heavily-barred juvenile mantle of a 'classic' juvenile Thayer's Gull...

First-winter Thayer's Gull at Choshi

... but despite my sense of unease at the appearance of this bird's mantle, it does appear to be a close match to some of the first-winter Thayer's Gulls photographed at Choshi included on this website: and the above image of it with its wings raised reminds me of the Birding World front cover illustration of a first-winter Thayer's Gull by David Quinn Vol. 11 No. 3.

First-winter Thayer's Gull with second-winter Vega Gull in the background

This image reveals the small size and delicate proportions of the Thayer's Gulls at Choshi.

Juvenile / first-winter Thayer's Gull at Chosi

An overall much paler individual although with a more retarded mantle and scapulars. The bill appears slightly open in the lower image making it appear heavier than in life.

First-winter Glaucous Gull L.h. pallidissimus at Choshi

Olsen (2003) describes first-winter eastern form L.h. pallidissimus as generally paler and less marked than nominate, many appearing whitish with only weak brown markings with legs and sometimes bill more strongly rosy-tinged all of which apply nicely to this individual.

Adult winter Glaucous Gull L.h. pallidissimus at Choshi
Olsen (2003) describes adult L.h. pallidissimus as on average paler than nominate with less sharply defined primary tips (merging into pale grey primary bases) and as having weaker head-streaking. The dark mark on the bill is intriguing - does it suggest it is a fourth-winter?