Identification of Honey-buzzard
Field Experience
Some 19 years in Northumberland from the start of the re-colonisation in 1993 to 2011. Also many hundreds seen abroad in visits to Morocco, Spain, France, Germany, Belgium, Finland, Sweden, Ethiopia, Kenya and South Africa. The Northumberland study area now holds a nationally significant number of birds, more indeed than other study areas such as the New Forest and the Welsh one, though the density is comparable with that in other study areas.
Literature
Much of the literature on Honey-buzzard identification is either focused on features that are difficult to see or on identification at high-volume migration points where light conditions are near optimal. The effects on identification of increases in body weight during the breeding season and of variations in the size of the crop in the digestive system also perhaps need some investigation.
The best field guide is that by Collins (2001) which places less stress on plumage details with the first seven suggested identification points all concerning structure and jizz (p.90):
more long-winged than Common Buzzard
neck slim
head held forward in flight in Cuckoo fashion
tail rather long, about as long as width of wing
sides of tail slightly convex and corners rounded
smoothly down-curved wings in glide
active flight with slower, more elastic wingbeats
Plumage points covered include the small amount of black on primary tips, the tail bands and the bands across the remiges.
The voice is described as a plaintive or whistling 'peee-lu' or 'glu-i-yu', at times recalling Grey Plover Pluvialis squatarola in general structure. Mechanical ticking calls near the nest are also described.
Also useful is Clark's Field Guide to the Raptors (1999) which gives succinct details of the plumage of adult males and females and of juveniles and which describes flying birds as distinctive, appearing somewhat pigeon-headed with small head and long neck and long tail with rounded corners.
The much larger handbook by Ferguson-Lees & Christie (2001) provides the most comprehensive, up to date description of the Honey-buzzard. This book deals in more detail with the extreme variability of the Honey-buzzard (plumage wise), the use of plumage features by the Honey-buzzard to mimic larger, more powerful raptors and the behaviour, habitats and calls of the Honey-buzzard.
Discussion on Honey-buzzard breeding in Northumberland can be found on BirdForum (2003-7). I am grateful in particular to Andrew Rowlands, Wayne Percy and Greg McIvor for their comments. Useful discussions have also been held with David Jardine.
Phenology
Honey-buzzard are one of the latest birds to breed in Britain. In Northumberland they breed about 4 weeks later than Common Buzzard. Pairs of buzzards in full display in late May or early June or with very recently fledged young in late August or early September are worth close inspection. In Holland and presumably Germany, the breeding season runs considerably earlier. See Dutch Phenology for details. More recently Honey-buzzard have been returning earlier to Northumberland with an increase in April records; however it is not clear that the nesting is starting earlier.
Calls
Honey-buzzard have distinctive calls. They are thinner than those of Common Buzzard and their use appears to be restricted to the vicinity of their nesting sites. In this study, the following forms have been identified for adults: flight, anger, alarm, owl, single short pipe, wailing and ticking. Flight and begging calls for juveniles have also been studied.
From the present study, see Calls for recordings (wave format) and analysis (spectrograms in jpeg format). Some comparisons are available with Common Buzzard and Peacock calls and with Honey-buzzard calls from other studies. A Summary is made of each call in terms of its pitch, harmonics, elements, duration and volume. Some calls have also been derived using Sony PMB software from videos: these are available at Videos with derived stills and calls in wma or wave format with spectrograms in jpeg.
Visually in Flight
Videos
Videos capture the jizz, that is the field experience, of Honey-buzzard. From the present study, see Videos with derived stills and calls for recordings (wmv format), stills taken from the videos at appropriate moments and some analysis for adults and juveniles.
Stills
Stills are derived now usually via the Sony PMB software from the HD videos rather than taken with a conventional camera. So from the present study since 2004 see Videos with derived stills and calls for recordings in jpeg format. In earlier work up to 2004 stills were taken with a conventional camera and can be viewed at Earlier work in jpeg format.
Tail/wing Ratios
These are assessed objectively by comparing observed ratios with those expected from the literature. See Analysis of Tail/Wing Ratios in Photographs of Honey-buzzard
Moult Considerations
The state of primary moult is very useful in filtering birds because of the different strategies of Honey-buzzard and Common Buzzard. The Honey-buzzard's short stay in Britain and the pressures of migration mean that only a limited moult is possible here. The Common Buzzard's sedentary habits mean that a complete moult is performed from spring to autumn. See Moult in Honey-buzzard and Common Buzzards for details.
Jizz
Knowledge of how Honey-buzzard behave is crucial for their identification. The differences between their behaviour and that of Common Buzzards in their British breeding areas is, however, often rather subtle. A discussion of the differences may be found at Honey-buzzard Jizz
Plumage in Honey-buzzard
This aspect is deliberately left to near the end. Plumage is probably the least useful feature for identifying Honey-buzzard in their breeding areas unless very close views are obtained, which is only practicable if the observer is in possession of a disturbance permit. Not only is the plumage very variable but poor under-lighting makes it very difficult to detect features on the underside. On passage through Israel, Gibraltar or Falsterbo, bright under-lighting as a strong reflection of sunlight from sand, rock, stones and sea does highlight better the plumage on the underside of the bird. If the upperside can be seen, for instance by the bird being below in a valley or alongside with wing movement, then the plumage is definitely more useful in identification as is also the case with close-up underside views, preferably recorded with an HD camcorder, where the barring on the remiges can be captured. See Plumage in Honey-buzzard for details.
Bare Parts in Honey-buzzard
On juveniles seen closely in flight, the nearly all-yellow bill and yellow cere are useful support for identification as a Honey-buzzard. See Bare Parts in Honey-buzzard for details.
Wing Formula in Honey-buzzard
The primary feather lengths for Honey-buzzard and Common Buzzard are very similar for P1-P8. However, P10 is on average 10% longer in Honey-buzzard than in Common Buzzard and P9 7% longer. The tendency is therefore for the Honey-buzzard to have a fuller, more rounded tip than a Common Buzzard, which can appear to have a rather swept back appearance on the tips of its outermost primaries. See Wing Formula for Honey-buzzard and Common Buzzards for details.
References
See the Literature compiled for Honey-buzzard.
© Copyright Nick Rossiter 2003-2011
