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Case Summary for:
Submission No 263: Eastern Marsh (Papuan) Harrier Circus spilonotus spilothorax; Lennox Head, NSW, August 1997 - November 1998 (Unpublished). Verdict: Not Accepted This case relates to a series of sightings supported by photographs from the Lennox Head region of NSW between August 1997 and November 1998. All incidents were considered to involve one individual but there is a remote possibility that two birds may have been involved. The evidence presented is certainly sufficient to indicate an adult male harrier of one of the following three taxa: (1) Eastern Marsh (Papuan) Harrier C. spilonotus spilothorax of New Guinea; (2) Eastern Marsh Harrier Circus spilonotus spilonotus of E. Asia; or (3) the Swamp Harrier Circus approximans of Australia. As described and depicted in the photographs the bird was a rather pale adult male harrier with pale grey dorsal tones and a contrasting upperwing pattern that included blackish innerwing-coverts and prominent black wing-tips; a markedly pale underbody with a contrasting blackish ‘hood’; and a whitish underwing with black wing-tips. The key features mentioned in the description as identifying the bird as a Papuan Harrier are its generally pale appearance coupled with a contrasting blackish hood and black wing-tips (on both wing surfaces). Fortunately, most committee members are fully aware of how important it is to understand that adult males of all three forms are broadly similar in plumage pattern and the way in which they vary with age. In particular, adult males of all three forms become noticeably paler with age. Thus typical adult males of spilonotus and spilothorax and older (ie. paler) males of approximans can and often do show the general plumage characters evident in photos of the Lennox Head bird: (1) contrasting tricoloured upperwing pattern: pale grey with predominantly dark (blackish or dark brown) innerwing-coverts bordered by a narrow pale leading edge of varying prominence; a prominent and contrasting black wing-tip (formed by the outer five or so primaries); and a narrow dark trailing edge to the secondaries and inner primaries; (2) dark brown or blackish head, mantle, back and scapulars; (3) a prominent white rump-patch contrasting strongly against the dark saddle and grey tail; (4) pale grey uppertail with little or no dark barring; (5) dark brown or blackish face, chin, throat, foreneck and upper breast forming a dark ‘hood’ set off against a mainly white underbody marked only with sparse dark brown or blackish streaking running off the hood (streaking may be absent in some spilothorax); (6) a predominantly white underwing save for obvious narrow dark trailing edge to secondaries and a contrasting dark underwing-tip (formed by fingered outer primaries, which are variously barred or uniformly black according to species); and (7) a whitish undertail with faint or no dark barring. After careful analysis the majority of the committee agreed that the photos show unequivocally that the bird observed was in fact a fairly pale adult male Swamp Harrier C. approximans! Primarily the difficulty with the identity of this individual lies with perceptions of the inner upperwing-coverts and the wing-tips. The former are described as black or blackish brown while the wing-tips are described as black, with no mention of barring. Taken in combination with the dark-hooded appearance (giving bold contrast against the white underbody), the bird does indeed broadly conform to published descriptions and illustrations of Papuan Harrier e.g. those in Simpson & Day (1993) and Mackay (1991). However, in at least some of the colour prints of the bird it can be seen that the inner upperwing-coverts have a slight brownish cast and in all photos showing the upperparts they appear very similar in colour to the dark saddle (mantle, back & scapulars), and both the saddle and the coverts appear distinctly less black than the wing-tips, matching the general field impression of a male Swamp Harrier seen at distance (when precise colour tones are difficult to discern). The blackish brown colour of these coverts conforms with some male Papuan Harriers but is equally typical of an older adult male Swamp Harrier (HANZAB Vol 2). The absence of any obvious pale tips to the innerwing-coverts also agrees with a Swamp Harrier whereas many immature and adult male Papuan Harriers show prominent whitish tips to these coverts, giving a spotted or mottled appearance to the posterior portion of the dark innerwing-covert panel, as shown in illustrations of perched adult male spilonotus and spilothorax in Handbook of the Birds of the World, Vol. 2. The pattern of the underside of the primaries provides the clearest evidence of incorrect identification. In all of the smaller image photos the underwing-tip does indeed appear quite uniformly blackish, giving strong contrast. But in the one close-up shot of the bird in flight, the fingered portions of the primaries show an alternating pale and dark barring through them (narrow blackish bars on a light grey ground) – a pattern entirely consistent with adult male Swamp Harrier and quite wrong for Papuan Harrier. The latter invariably has the fingered portions plus a little more of the basal area of the primaries a solid black, and these show in flight views as the characteristic large and clear-cut black wing-tips of that form (see descriptions and illustrations in Beehler et al 1986, Coates 1985). When viewed at distance and especially when shadowed, the fingered portions of the under-primaries of an adult male Swamp Harrier frequently give the impression of a wholly dark wing-tip sharply demarcated from the rest of the underwing; only in fairly close views and when directly lit does the dark barring on a paler grey ground become apparent. Similarly, the dark or blackish brown head, foreneck and upper breast of paler older adult male Swamp Harriers can give the appearance of a well-defined hood contrasting against the predominantly white underbody; and any narrow dark streaking running off the hind border of the hood or elsewhere over the lower breast, belly and flanks also ‘disappears’ at distance, especially when the bird is strongly lit. Taken together, the dark hood contrasting against a seemingly unstreaked white underbody, and the seemingly solid-black underwing-tip of a pale adult male Swamp Harrier can form a strong resemblence to an adult male Papuan Harrier. This aspect is poorly illustrated in the mainstream field guides. A ‘pied’ morph adult male Eastern Marsh (Papuan) Harrier Circus spilothorax spilothorax, a species recorded no closer to Australia than Borneo (Coates 1991), is also eliminated by the dark though clearly barred (not solid black) underwing-tips similar in pattern to a male Swamp Harrier though giving a darker wing-tip impression. Also, the inner upperwing-coverts of that species invariably have bold pale spotting while typically the saddle has some contrasting pale scalloping, at least in fresh plumage.
References and Bibliography
Tony Palliser |