 |
| Adult male Goshawk: distinctly protruding head, full body, rounded tail tip, wings proportionally longer than Sparrowhawk, clearly narrowed hand. |
Some sources minimise the purported difficulties and stress how clearly different the two are in respect of several key features; some suggest, perhaps partly 'tongue-in-cheek', that if there's any question over identity, then the bird is probably a Sparrowhawk because the Goshawk stands out by its presence and flight behaviour. But it has taken me a long time, and many views of Goshawks in flight (occasionally at quite close range rather than a distant dark speck in the sky), to start seeing the differences with any confidence.
Almost all my sightings have been of adult male or juvenile Goshawks; the former typically while leaving the nest site after prey delivery, and the latter as they become increasingly active in flight in late summer. I have never yet had prolonged views of an adult female (and have never yet been able to watch birds in display because the hills seem invariably covered in snow or cloud or rain when I've visited in late winter/early spring!).
A small selection of sources on Goshawk recognition that I've found particularly useful, beyond the usual field guides, is listed at the end of this post. Orton (1989) has a few words on goshawk field identification: "...the goshawk wing looks proportionally longer than the spar's and is often beaten with a more leisurely stroke...the head of the gos protrudes relatively further...the tail, relatively shorter, spreads to end with a more pronounced curvature..." (slightly abbreviated from paragraph on pp218-219). Pertinent, concise, and perhaps the most useful short summary available?
In my limited experience, I think the differences in (1) wing and (2) head shape tend to be the most easily seen features in flying individuals, the former usually more obvious than the latter, and aspects of (3) tail shape can provide a secondary source of information. These structural features are discussed and illustrated below; some non-structural features (plumage patterns, flight style) may be noted in later posts.
 |
| Composite image to show some key features for identification. In Goshawk (right, adult male, June 2015) note in particular: proportionally longer wings, protruding head and wider neck section, width across breast and belly, tail with strongly convex end and here parallel-sided when closed (often tapering). The head protrudes very little in the Sparrowhawk shown (left, September 2011), the body is slimmer, the tail in this individual is somewhat angular at the corners. The fact that the Gos shown is a larger bird than the Sparrowhawk can be gauged from the apparent narrowness of the head; the head would in fact be as wide or wider than the Sparrowhawk but appears narrow mainly because the Gos was much further from the camera. |
Both the 'arm' (from the trunk out to the 'wrist' = carpus) and the 'hand' seem to contribute to this appearance, ie. both wing sectors look fractionally more elongated in Gos compared with Sparrowhawk.
Also, the Goshawk hand is typically slightly narrowed in relation to the secondaries (front to back), ie. the trailing edge of the wing tends to show a distinct S-curve, convex along the secondaries then narrower from the first primary outward (see the last post on the thread HERE, last accessed 23.i.16, which presents ratios derived from approximate measurements of images of both species). This slight narrowing probably contributes to the overall appearance of wing length. By contrast, the trailing edge of the Sparrowhawk wing tends to show a simpler curve; the section of hand made up by inner primaries is usually less distinctly narrowed in relation to the secondaries, and the primaries overall often look rather like a spread fan radiating from the end of the wing with scarcely any distinct 'palm' to the hand.
Of course the shape of the wing varies according to flight mode, eg. the degree of extension or flexion at the wrist, and age and the stage of moult (so if one or two inner primaries are missing, the Sparrowhawk wing can show a similar S-curve often seen in soaring Goshawk). Looking at a live bird in flight, rather than an image, it can be difficult to register the narrowing of the hand in relation to the secondaries but it probably contributes to the long-winged impression.
 |
| Composite image to show some key features for identification. In Goshawk (right, adult male, June 2015) note in particular: protruding head and wider neck section, width across breast and belly, tail with slightly convex sides and rounded corners. The fact that the Gos shown is a far larger bird than the Sparrowhawk (left, June 2015) can be gauged from the apparent narrowness of the head; the head would in fact be as wide or wider than the Sparrowhawk but appears small mainly because the Gos was more distant. The stronger S-curve of the Goshawk trailing edge and narrowed hand can be seen. The head protrudes very little in the Sparrowhawk shown, the body is slimmer, but the tail end in this individual is quite convex and similar to the Goshawk. Note also the narrow tail base of the Sparrowhawk even when the tail is closed, in contrast to the Goshawk shown, where the tail is closed but appears parallel-sided because of the greater width across the tail base; often in Gos the closed tail tapers distally because of the wide 'hips'. |
This greater prominence is in part because the neck is often somewhat extended in flight, seemingly reflecting the effort put into active flight or prospecting for prey, and in part because the bill is proportionally larger, both longer and deeper. The head usually looks less prominent in Sparrowhawk; the neck is not routinely extended and the bill is often scarcely visible. Hence the distinct flight silhouettes, often described as 'T-shaped' in Sparrowhawk and 'cross-shaped' in Goshawk. But this typical difference is not fixed: the Goshawk may fly without the neck fully extended, and the Sparrowhawk head can appear prominent if the bird is actively looking around in flight.
 |
On the Sparrowhawk shown (left) the head is somewhat protruding and Gos-like, but does not show the distinct extended neck often seen in Goshawk; the Goshawk (right, juvenile) has the head withdrawn and tilted down a little and so looks small-headed and very like a typical Sparrowhawk in this image. The Sparrowhawk shows the typical proportionally shorter wing with a slight step between arm and hand, and the hand appears short and not distinctly narrowed; in the young Goshawk the trailing edge shows the characteristic S-curve, with hand distinctly narrower than secondaries. The Sparrowhawk tail, partially spread, arises from a proportionally narrower base, with a relatively straight end and is angular at the corners. The hips of the young Gos are not as wide as in adults but the half-spread tail shows a well-rounded end with rounded corners.
|
The tail in Goshawk typically shows a distinctly rounded end when closed, and at various degrees of spreading the outer tail feathers still show rounded tips. In contrast, the Sparrowhawk tail can look quite straight-ended and usually has squared-off corners whether closed or spread. The state of moult affects the appearance to some extent. I find it difficult to perceive a consistent difference in relative tail length; some sources (like Orton, cited above) state the tail is proportionally a little shorter in Goshawk (others suggest the opposite).
For brief notes on Goshawk identification, with several very impressive and informative images, see:
http://andybutlerdiaries.blogspot.co.uk/2015/09/goshawk-flight-identification-and.html
Darlaston, M. 2008. That tricky accipiter. Devon Birds 61 (1) (April): 18-23.
Jowett, A. 2004 (?). 3 page discussion of Goshawk identification, available in pdf at www.bradfordbirding.org/ARTICLES/Goshawk.pdf
(note added 30.04.2017: this article apparently no longer available on bradford site)
Orton, D A. 1989. The Hawkwatcher. London: Unwin Hyman.
No comments:
Post a Comment