Plumage in Honey-buzzard


Literature on Plumage


Ferguson-Lees and Christie (2001) describe the Western Honey-buzzard (Pernis apivorus) as very variable:

p.337-338 Partly through sex and age differences in colours of head and flight-feathers, tone of upperparts, markings of tail and sharpness of patterns, but more particularly through exceptional range of colour morphs affecting mainly underside of body and wing-linings, Honey-buzzard more variable than any other raptor.

p.63 The reason for the great variability of the Western Honey-buzzard appears to be that it mimics more powerful raptors and so achieves protection from enemies (Edelstam & King, in press).

p.341 Western Honey-buzzard is then monotypic but, in parallel with its eastern counterpart, polymorphic to extent of being arguably more diversified in colour and pattern (chiefly head, underbody and wing-linings) than almost any other wild bird species.

p.690 Though typical barred-morph adult Honey-buzzard very distinctive, great variations in plumage of both buteos and Honey-buzzard make it best first to concentrate on flight actions and shapes, then seek additional confirmation from particular patterns.

Forsman (1999) attaches more significance to plumage.

p.33 Quotes the typical pattern of the remiges and rectrices. Adults show dark finger-tips and the remiges are sparsely barred, with a broad black subterminal bar and a few additional bars proximally. The same pattern is repeated in the tail. Underwing coverts are boldly barred in most birds (rather uniform in dark individuals) …

p. 34 Variation. Although the pattern of the flight-feathers is rather constant, the body plumage varies individually. All dark underbody and underwing coverts are rather rare in adults but predominate in juveniles.

However later Forsman (2004) in an article on Rough-legged Buzzard Buteo lagopus identification (p.34) says that Rough-legged Buzzard is a straightforward raptor to identify if seen well. It lacks the seemingly endless plumage variation of Honey-buzzard Pernis apivorus and Common Buzzard [Buteo buteo] but it does nevertheless show some degree of aberration.

The Collins Bird Guide (1995), like Forsman (1999), also stresses plumage details with the comment:

p.34 … than Buzzard from which (and from other same-sized raptors) best told by three dark bands on pale tail, two at base and one at tip, as well as three dark bars across pale underwing.

The Collins Bird Guide (2001) places much less stress on plumage details with the first seven identification points all concerning structure and jizz (p.90).


Own Experience


Adult males and females are fairly readily distinguishable in the field on their head colours: male's heads appear pale grey or even white in strong light and female's appear brown or very dark. When the underwing is turned towards the light, the darker underwing of females is normally apparent with a broad dark envelope on the wingtip and leading and trailing edges. In males the envelope is narrower on the wingtip with the black limited to the fingers. So assigning a gender for adults is not too difficult with practice.

The pattern on the underwing is not easy to see in breeding areas as the light is absorbed by the rich green vegetation in the woods or pastures. As so little light is reflected back onto the underwing the observer may just see a fairly uniform dark underwing with a pale band down the middle. If the observer is close to a bird and using a facility such as an HD camcorder, then there is much more opportunity to view and capture the underside of the wing and in particular the barring across the remiges. With females, which are more likely to be seen closely through their defence of the nest, this barring typically comprises three broad bars in addition to the broad dark trailing edge and is most conspicuous across the secondaries. A Common Buzzard would show 5-6 much finer bars. A disturbance permit is usually needed for such close views. Such permits are issued for scientific use, not for taking coffee-table type pictures, for which you need a photography permit which will not be lightly issued. Photography is permitted with a disturbance permit for opportunistic supporting evidence.

The upperwing can be seen very well if the bird is in the valley below the observer or even at the same height with some movement in the wings. With the light onto the top of the wing, detail is seen clearly. The upperwing is often a ruddy-brown for adult females and grey-brown for adult males. The upperwing appears to be more constant from bird to bird than the underwing, showing relatively dark secondaries, trailing edge, primary tips, primary coverts, scapulars and lesser coverts and relatively pale tail, bases to primaries and median and greater coverts. The dark outer secondaries and primary coverts combine to give a band across the wing. The upperwing is more contrasting than in Common Buzzard adults which have a relatively uniform upperwing and in Common Buzzard juveniles which have pale coverts but more uniform bases to primaries.

The tail bars also show better from above with the broad subterminal and narrow middle ones being reasonably clear at close range. The third narrow bar can be buried in the undertail coverts. From below the combination of close views and a facility such as a HD camcorder does not help nearly so much with tail bars as with the barring on the remiges. The birds often have closed tails when seen at close range in woods, which is not the ideal pose for seeing the bars.

Sometimes a missing feather can help the observer. A missing feather will let light through from the upperside, revealing extra plumage features such as barring on feathers adjacent to the missing one.

Juveniles pose many more problems. Not only are they very variable with a number of distinct morphs but the barring on the remiges is finer and less sparse than in adult females with typically four bars, hence closer to the 5-6 of Common Buzzard. However, their flight is weaker and they can come close of their own accord to an observer thus enabling the detail to be seen. The tail pattern seems to be very variable as to the number of bars that are visible.


Discussion


It is only recently that plumage has been elevated by some commentators to high importance in identifying Honey-buzzard. At migration sites plumage details can be seen relatively easily because the bird may be flying over sand, rock, stones and sea with much light reflected onto the underside of the wing. On passage through Israel, Gibraltar or Falsterbo, therefore plumage details can be readily captured. However, as indicated above underlighting is much poorer over woods and pastures inland, the typical breeding habitat of Honey-buzzard. Steve Roberts (2003), from his experience of Honey-buzzard in breeding habitat in Wales, said at Penrith on 22nd November 2003:

"To try and identify them from plumage I think is a loser to begin with. If you’re still going to go down that road you’re going to be very, very limited. You need to be able to identify Honey-buzzard from their structure. Every book you pick up will tell you that a Honey-buzzard has got three bars on the tail and I can imagine loads and loads of birders going out looking for three bars on the tail. [shows a picture of Honey-buzzard from underside]. That’s a good Honey-buzzard and it’s close. You were lucky seeing that one flying by so close. You don’t see three bars on the tail, it’s just lighting. Look at that one also. That’s a good Honey-buzzard but you cannot see the tail bars. If you start thinking that you’ve got to see plumage details to identify Honey-buzzard, you’re missing the point. You’ve got to identify Honey-buzzard from their shape and structure”.

This accorded well with my experience until I acquired a disturbance permit and an HD camcorder: the former enabled me to get closer to the bird and the latter to record such detail as was visible. I would now use plumage features to support identification in such circumstances. However, for longer distances identification using plumage is only going to enable a few percent of Honey-buzzard to be identified, thus leading to precise but highly inaccurate results. Oddie and Doherty (video, undated) sum up well the situation for Honey-buzzard noting that “Plumage is exceptionally variable which means that shape and the way they fly becomes particularly important”.


Conclusion:

Plumage-wise the Honey-buzzard is one of the most variable raptors in the world. The three tail bars and three broad bars on the remiges in females are rated by some authorities as the most consistent features and are useful when clearly seen as at migration points where underlighting is good. However, these plumage features are inconspicuous on the underwing in the breeding habitat of woodland and pastures inland where the underlighting is poor, unless close views are obtained, ideally confirmed by a facility such as an HD camcorder. In addition there are gender/age differences to take into account with two bars on remiges in males and four in juveniles and variable numbers of bars on tails in juveniles. Views of the upperside of the bird do show more detail, which is useful for identification. However, overall, shape, structure, jizz and calls are the best field features.


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