Honey Buzzard Jizz
Wing Loading
So what does the Honey Buzzard flight look like in its breeding areas? Physically the Honey Buzzard has a 15% lower wing loading than the Common Buzzard because of, on average, its slightly longer wings and slightly lower body weight. Ferguson-Lees & Christie (2001, p.341, p.693) give wing measurements as 370-441mm for male Honey Buzzard and 372-447mm for female Honey Buzzard, compared to 350-418mm and 374-432mm for male and female Common Buzzard respectively. On average, male Honey Buzzards appear to have a 5-7% longer wingspan than male Common Buzzards and female Honey Buzzards a 0-3% longer wingspan than female Common Buzzards.
Weights vary enormously. The same source gives weights for male Honey Buzzard as 440-943g and female Honey Buzzard as 450-1,050g and weights for male Common Buzzard as 427-1,180g and female Common Buzzard as 486-1,360g. The largest Common Buzzards appear to be significantly heavier (25-30%) than the largest Honey Buzzards while there is little difference for the smallest (or leanest) of each species.
This lower wing loading enables the Honey Buzzard to fly earlier in the morning than other broad-winged raptors on migration. It also enables it to soar in less favourable thermal conditions than Common Buzzards so they can be active earlier in the morning, often an hour or two before Common Buzzards soar.
There is one complication in this simple analysis. During the breeding season Honey Buzzards increase in weight with Cramp (1980, p. 22) giving weights for males as average 632g (range 440-770) in June increasing to 836g (790-943) in August and for females as average 620g (450-885) in June rising to 962 (790-1050) in August. Ferguson-Lees & Christie (2001, p.341) note that adults are 20-80% heavier in August than in June. The very low weights of 440-450g at the bottom of the ranges in the post-spring migration period are striking. Honey Buzzards feed very little on migration, particularly across the Sahara Desert. A Honey Buzzard in May, crossing the Mediterranean, may have an empty crop and look rather emaciated. Honey Buzzards in their breeding areas, once they have recovered from the spring migration, are therefore likely to look solider than those on migration. With fuller crops they will also look significantly thicker around the base of the neck although the head and upper neck will remain clearly thin. The extent to which the increase in weight actually affects identification perhaps needs further investigation. Panuccio et al (2006) show a Honey Buzzard in Italy with a full crop which has a much thicker neck than Honey Buzzards depicted in field guides. The same authors point out that most Honey Buzzards are thought to fast on migration to improve soaring efficiency through having a lower weight. But some birds seen closely did have fuller crops and must have fed recently. This work by Panuccio et al (2006) is important as it shows the variation in crop size that occurs and the effect this will have on the appearance of the front of the bird.
Looking at identification criteria used in France where the Honey Buzzard Bondrée apivore is a familiar breeding species, it is clear that the thin neck is downplayed. For instance on oiseaux-libre net the first photograph shows a Honey Buzzard with a very heavy body, a long neck thick at the base but rapidly narrowing to accommodate a small protruding head. At oiseaux net some photographs taken of birds in flight show very thin necks and are presumably of migratory birds. Photographs of perched birds show thick necks and these are presumably of breeding birds. The text says “Diffère des buses au vol par les ailes plus étroites à la base, la queue plus longue et une tête plus petite sur un cou plus long”, that is: differs from buzzards in flight by the wings that are narrower at the base, the longer tail and a smaller head on a longer neck. A sketch in Ou Voir les Oiseaux en France on p.189 (coordinator Philippe J Dubois, publ: Nathan, Paris, 1989) shows a long tail, small head and a neck that is long but quite thick.
Besides the invalidation of the rule, heavy build = Common Buzzard, light build = Honey Buzzard, it is likely that the heavier birds will have a slightly different jizz. In particular it is likely that, as observed in this study, the heavier Honey Buzzards will raise their wings to some extent at low altitude to increase their lift. Either the front of the wing will be raised slightly (to increase the angle of attack) or the tip will be raised slightly (to reduce turbulence). The raising of the wings at very low altitude may also be a deterrent against Goshawk Accipiter gentilis by the mimicking of a Common Buzzard at a vulnerable time in the flight.
Even more intriguing is the evidence that Common Buzzards lose weight in the breeding season with Ferguson-Lees & Christie (2001, p.687) reporting that all individuals are about 20% lighter in weight at the end of the breeding season than in winter. Cramp (1980, p. 190) gives weights for nominate buteo as: April-May male average 732g (range 552-846), female 881 (486-1197); June-July male 692 (600-813), female 865 (727-946); August-September male 706 (427-850), female 911 (800-988); October-November male 828 (620-985), female 1052 (710-1327). The heaviest weights are in October-November, the lowest in June-July.
The surprising conclusion, nowhere mentioned in identification guides, is that Honey Buzzards are on average actually heavier than Common Buzzards for part of the breeding season, In June male and female Common Buzzards are 9% and 40%, respectively, heavier than male and female Honey Buzzards. In August it is the other way round: male and female Honey Buzzards are on average 18% and 6%, respectively, heavier than male and female Common Buzzards. As mentioned above though, there will of course be enormous individual variation, depending in part perhaps on the richness of the habitat. In rich feeding areas Honey Buzzards appear to put on weight earlier, during late May and June.
Juvenile Common Buzzards have the following weights in August-September: male 680g (495-796), female 823 (569-1008). In the study at Inverness at least one of the juvenile Honey Buzzards tracked, the one that made the epic journey in 2002 (1010g), was over 1000g when 'fitted-up'.
Soaring
When a Honey Buzzard launches itself into the air from trees, it is always an impressive sight at such low altitude. The large size and broad inner wing can, to the inexperienced raptor watcher, cause confusion with larger raptors at this stage such as Osprey Pandion haliaetus. Flapping is kept to a very strict minimum as the bird floats searching for a thermal with wings level or with the tips slightly raised. The tail can be flexed to some extent as the bird steadies itself. Forsman (1999) notes the slight raising of the tips at times. It is only slight and the wings are always smoothly curved, never kinked at the elbow as in Common Buzzard. Honey Buzzards gain height amazingly quickly even when thermals are not strong. They also do this in a very majestic way with every sinew strained to give maximum wing area. Roberts (2003) noted the steadiness of Honey Buzzards in ascent compared to the unstable Common Buzzard:
“If you look at Common Buzzard all day, as we do with hundreds in the area and the population through the roof, you try and pick out a Honey Buzzard from a bunch straight-away as being rock stable while the Common Buzzard is rocking about. Little things like this are important”.
In the soar the wings quickly become level and they are often pushed forward. This latter feature is noted by Forsman (1999) but not by Ferguson-Lees & Christie (2001). The long tail (as long as the wing width or slightly longer) is a prominent feature and it is usually slightly fanned during the soar. The neck is often retracted during soaring so the well-known small head and extended neck are not that obvious. It is relevant that Roberts (2003) does not emphasise this as an identification feature while the tail is rated as of high importance. He said:
"Obviously length of tail is important. [shows photo of Common Buzzard, then one of Honey Buzzard] You cannot see much markings on them, the difference is obvious immediately without showing any markings. The difference in structure is obvious, forget plumage. If someone starts describing plumage to you, stop listening. Someone should be telling you about the shape of the bird. Obviously the tail is important. The one characteristic that does stick out is the tail. This [photo] is a typical Honey Buzzard with long full tail. Tail is always bulging a bit with a notch at the end. You can see the long tail on a Honey Buzzard a long way off".
The tail shape probably varies more than Roberts indicates. As the Honey Buzzard is a ground-feeder, the tail shape can be affected by wear and tear (Ferguson-Lees & Christie, 2001, p.338).
Some experts have queried whether Honey Buzzards ever retract their necks. Examples of many Honey Buzzards in soaring mode with retracted necks are found on Plate 23 in Forsman (1999) and in a photograph on p.32 of Birdwatch, no 156 (2005). A group from Forsman is shown here. In nearly every other mode of flight the extended neck and small head is an excellent identification feature for Honey Buzzard.
Active Flight in Soar
A very good field identification point is the mode of active flight. Unfortunately Honey Buzzards generally avoid this as much as possible in their breeding areas. They can float without any active flaps for five to ten minutes. In active flight the Honey Buzzard shows much more movement in the wings than Common Buzzard, which tend to give a series of stiff shallow wingbeats (unless they are carrying prey). The Honey Buzzard has slower and deeper wing beats than the Common Buzzard and there is a rippling action along the wing in each beat. The wingtip generally goes much lower than in Common Buzzard on the downstroke and the wings are distinctly arched at this point.
Top of Soar/Stalled Mode
Honey Buzzards often soar to a great height and then level off and either float slowly around in reconnaissance or drift off towards a distant feeding area. At this point when peering around they can show the classical extended neck and small head. They can also show a characteristic 'vulture' pose with wings pushed very well forward, tail fully fanned (and therefore looking shorter) and extended neck and protruding small head. They do not quite hover but, in slow circling, repeatedly come to a brief almost complete standstill (or stall).
Descent
Descent is normally done in a dive. Sometimes just one dive is done but more typically a series of dives are performed, each one taking the bird lower until a final swift drop back into the trees with legs well out-stretched.
Active Flight at Low Altitude
When flying out of woods at low altitude over fields or through the tops of the trees, Honey Buzzards can look like large Carrion Crows Corvus corone. Compared to Common Buzzards they show longer necks, smaller heads (often held raised above the body level), longer tails and a more steady, regular, swinging wing action. The barring on the underside of the wing is relatively conspicuous in such flights on the downstroke perhaps because they are being viewed from the side. The tail bands though remain invisible.
Display in Spring
There are two periods of activity: display and post-fledging. Display takes place in Northumberland in late May and early June. On first arrival in mid-May the birds are rather lazy perhaps feeding and resting after the long migration. The lazy flight with long periods of effortless floating, interspersed with the very occasional stall or spell of active flapping, occurs over their breeding areas at this time. Display is brief and in poor springs may not be too conspicuous, though it does occur even in drizzle if few decent days occur.
In better weather the display is obvious. The male can appear already up in the air and may call with a characteristic thin tri-syllabic (somewhat like a Grey Plover Pluvialis squatarola (see Calls)) whistle or a di-syllabic whistle (somewhat like juvenile Common Buzzard). The female then comes out of the trees in a normal soar. At height the birds engage in a lot of interaction, typically alternating floating and diving at each other. The display can get wilder with one bird engaging in a series of enormous stoops across the sky, only losing a bit of height overall because of the strong bounce from the stoops. The classical butterfly display is not seen that often but was more conspicuous in 2003, perhaps because of increased density of breeding pairs and fine weather at the right time. The description of Porter et al (1981) cannot really be bettered:
"After a long glide it rises steeply and, slightly hovering, 'shakes' wings above back in rapid succession, usually six or seven times. This performance [is] repeated several times during display flight".
Another display feature, particularly noted in 2006, is the follow-me pattern of flight by a pair. In slow action one bird follows the other, faithfully copying every turn and move. This occurs particularly at high altitude in fine weather but can also occur at low altitude if the birds come out of the trees together.
Fast Gliding
This is most noted in display flights, with birds moving at some pace across the sky. The pose is perhaps more like a harrier or a kite with obvious long thin tail, carpal well forward, long hand trailing behind, neck and head protruding well and tips of wings slightly depressed so that the shape of the bird head-on is smoothly arched. The body looks small. While the pose of Honey Buzzard in this mode of flight is supposed to be very distinctive compared to Common Buzzard, it is worth adding the cautionary note that Common Buzzards also appear to have long tails in this mode. Sometimes in this mode, Honey Buzzards accelerate with a flap-glide action rather like Goshawk Accipiter gentilis with a few quick shallow beats followed by relatively long pauses. This flight action may also be used occasionally in spring when patrolling their territory.
Summer Secrecy
After the spring display, Honey Buzzards then become very difficult to detect. As Steve Roberts (2003) says: "Anybody who has done any work with Honey Buzzards knows that once they start incubating they don’t fly out of the woods, they dig tunnels and walk out". In Northumberland the period between mid-June and early August is not a good time to search for Honey Buzzards unless you are very experienced with their appearance. Glimpses may be brief as the birds fly low over the trees or along glades into or out of their nest sites. However, non-breeding birds can be more obvious into July as they continue soaring in fine weather while nesting birds sit tight. In addition even breeding birds will soar occasionally, some using the tactic of commuting between feeding areas and nest sites by vertically soaring to a great height, planing at high speed and finally diving into their destination from some height.
Fledging in Autumn
Honey Buzzards become more active as fledging approaches with some anxious patrolling mid-August. After fledging (from mid-August-early September in Northumberland) the family parties engage in considerable soaring activity. These family parties typically comprise three birds in Northumberland (two adults, one juvenile). The first evidence that a flight is about to begin is sometimes provided by a series of thin calls -- from the female in the trees or the male in the air or even from the juvenile on the ground or in low trees somewhere. The female leaves the trees before the juvenile which in its first flights may be quite hesitant, reluctant to get much above the trees and floating in an unsteady manner. Some juveniles in late August show outer primaries that are still growing. Once in the air the female often escorts the juvenile which when it gains height may be ambushed by the male. The flight can become quite vigorous as the juvenile rapidly becomes more experienced with considerable diving at each other. Some of the autumn flights are made at great height as the adults prepare for departure.
Post-fledging
Once the adults leave, which at least for the male, is quite soon after fledging, the activity drops markedly, particularly for isolated sites. A single juvenile may engage in some practice flights but is generally well out of sight feeding. More recently the juveniles from adjacent nests have formed groups after the adults have left and these groups engage in strenuous practice flights on the edge of the moors. These groups leave together, typically around 15th-25th September.
Kite-like or Buzzard-like?
Experienced Honey Buzzard watchers appear to rely on detecting the kite-like (milvus) features in the otherwise general buzzard-feel (buteo) to the bird. Honey Buzzards thus have a long tail expertly twisted in flight (allowing for impressive manoeuverability) and wings long and more sharply pointed than in buzzard, held slightly arched downwards in flight and with deep and loose wing-beats in active flight (Couzens 2003, p. 60,70). However, some kite-like features are often missing in flight in Honey Buzzard such as projecting carpal joints in the soar and head and long tail held in slight droop. There are differences of opinion as to whether the wings of Honey Buzzard are broad (as in buteo) or narrow (as in milvus). In truth the apparent width of the wings is very variable, depending much on the flight action: in the soar the wings are broad, in the glide narrow. Indeed Honey Buzzards look more buzzard-like when soaring and more kite-like when gliding and in active flight.
© Copyright Nick Rossiter 2003-2007
