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The three plumages of the Northern Goshawk by Dick Forsman

January 29 2018

The three plumages of the Northern Goshawk by Dick Forsman

The Northern Goshawk, Swarovski Optik’s logo bird, is usually depicted in either of two distinct plumages, the longitudinally streaked juvenile or the transversely barred adult. However, there is a third plumage, which can be identified even in the field. This is the first adult plumage.

In the nest young Goshawks grow a plumage, which is streaked below. The ground colour of the underparts varies from whitish to a rather deep ochre or even tawny colour and the streaking can be either fine or broad, even close to spotted in some. The upperparts are brown, often with some lighter markings to the upperwing coverts.

 

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Fig 1 Juvenile Northern Goshawk showing typical streaked breast

 

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Fig 2 Juvenile Northern Goshawk of the whiter and more spotted type

 

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Fig 3 A buffish juvenile Northern Goshawk of the finely streaked type

 

Old adults are plain grey above, while the underparts are white and finely barred.  A broad whitish eyebrow separates the uniformly dark crown from the similarly dark ear-coverts, giving the adults a diagnostic look.

Between these two plumages is a third one, adult-looking by large, but still recognizable. This first-adult plumage, which is acquired during late summer at the age of approximately one year, could be overlooked as “just” an ordinary adult, if you don’t know what to look for.

First of all, the upperparts are different. The back is not pure grey or bluish grey as in full adults, but of a duller, browner colour. The head pattern can be similar to older birds, but the crown is often streaked, recalling a young bird, while the face appears more streaked and with less contrasting ear-coverts, which are brown rather than black. The underparts differ in showing a sparser and more irregular barring, the irregular pattern showing particularly on the upper breast, as each feather has fewer and more pointed cross-bands compared to older birds.

 

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Fig 4 Female Northern Goshawk in the first adult plumage. Note more completely barred flight-feathers, irregularly barred upper breast and less distinct head-pattern and compare with older adults in fig 7 and 8.

 

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Fig   5 Male Northern Goshawk in first-adult plumage. Compare head-pattern underwings and breast barring with definitive adults in fig 7 and 8

 

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Fig 6 Male Northern Goshawk in first-adult plumage. Note streaked crown and sparse and pointed bars of upper breast.

 

In flight definitive adults appear very light from below with finely barred breast, while the wings are clearly barred only at the tip, with the remaining flight feathers only softly and indistinctly barred. In first adults the flight-feathers are all more distinctly barred, with the pattern resembling more a juvenile’s than an older adult’s.

 

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Fig 7 Male Northern Goshawk in final definitive adult plumage. Note the distinct head markings, typical of males especially, and the softly barred flight-feathers

 

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Fig 8 Adult female Northern Goshawk in display flight  over the territory. Similarly whitish below like the male, clean-looking and finely barred, with only outer wing clearly barred.

 

In addition to the normal individual variation, which may create some tricky-to-age individuals, there is also an average difference between males and females. When comparing males and females in definitive adult plumage males tend to be bluer above than females, more distinctly marked in the face and more finely barred below.  However, in the first adult plumage this sexual difference is less marked, since also males are brownish grey above, the facial markings are less striking and the underparts are more coarsely barred, all features normally related to females. Although there is a considerable size difference between males and females, with females weighing up to twice as much as males, this difference is rarely of use in the field, unless both sexes can be compared directly. In the field male Goshawks give the impression of a big and chunky piece, and are surprisingly often wrongly sexed as females, as shown by numerous photographs even in expert literature. Besides, there are small and big individuals and sometimes the difference between a small female and a bigger male can be difficult to appreciate, as in fig 9, with male on the left and female right.

 

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Fig 9 Male Northern Goshawk on the left, female on the right

 

About the author

Dick Forsman is a Finnish ornithologist, author, artist and travel guide. Dick's deep interest in birds, raptors in particular, started during his early childhood and ever since he has built his life around this passion. www.dickforsman.com

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