I have been grappling with the field identification of Papuan Harrier
(Circus spilothorax) for some years, with well-marked male Swamp
Harriers a major i.d. problem, and immatures very difficult to
separate indeed. I agree that the very clear photo of recent postings
is clearly Swamp Harrier, adult male Papuan would be much darker on
the head, probably have better defined black breast streaks and a well
defined black trailing edge.
Here is a draft of part of the account from my field guide:
Male very distinctive, head, mantle and breast heavily streaked black,
black above with black tipped silvery-grey secondaries, upper tail
coverts white, grey tail, whitish beneath with variable dark streaks
on body, dark of breast always ragged, not cleanly demarcated from
underparts. It is reported that a form with a sharply demarcated black
head and breast (similar to male Pied Harrier) exists in central
highlands. A rare dark morph is mostly black with a dark grey tail; F.
dark brown with pale uppertail coverts, conspicuous dark tail bands,
paler underparts with dark breast streaks. Some birds show white
around head. In flight adult male is a very striking species
resembling male Pied Harrier, with blackish wingtips, blackish
upperwing coverts, silvery grey secondaries and inner primaries;
underwing whitish with black primary tips and dark trailing edge. F.
plumage largely very dark brown with silvery underside to primaries
and darker underwing coverts, tail with dark bands. May show white or
pale rump but this often absent. Iris yellow, cere greenish-yellow,
legs and feet yellow, orange-yellow on male. Imm. birds are dark brown
with pale cream buff on nape or on nape, crown and face, may often
lack white upper tail coverts. Shows whitish buff streaking on mantle
and silvery undersides to primaries and tail. Sub-adult male has
blackish streaked throat and breast.
Swamp Harrier is a major pitfall, status of this species not well-
known in NG due to identification difficulties. Two useful separation
features may be dark bands on the tail of female and young Papuan
Harrier, and pale patches on the head and/or nape of that species when
immature. Swamp Harrier imm. shows rusty underparts. Vagrant Pied
Harrier has also been claimed but no doubt confused with ad. male
Papuan, which is larger, has less white on leading edge of wing,
usually has well-streaked chest with no clear division between breast
and underparts.
As ever, if you can get a photo of any putative Papuan Harrier that
greatly aids the chances of correct identification; I suspect female
or immature birds are much more numerous than adult males and hence
the most likely to be vagrants.
Phil Gregory
Email:
Website 2: Http://www.cassowary-house.com.au
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