Common Buzzard

The first formal description of the common buzzard was by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Falco buteo. The word buteo is Latin for a buzzard. It should not be confused with the Turkey vulture, which is sometimes called a buzzard in American English. The Buteoninae subfamily originated from and is most diversified in the Americas, with occasional broader radiations that led to common buzzards and other Eurasian and African buzzards. The common buzzard is a member of the genus Buteo, a group of medium-sized raptors with robust bodies and broad wings. The Buteo species of Eurasia and Africa are usually commonly referred to as "buzzards" while those in the Americas are called hawks. Under current classification, the genus includes approximately 28 species, the second most diverse of all extant accipitrid genera behind only Accipiter. DNA testing shows that the common buzzard is fairly closely related to the red-tailed hawk (Buteo jamaicensis) of North America, which occupies a similar ecological niche to the buzzard in that continent. The two species may belong to the same species complex. Three buzzards in Africa are likely closely related to the common buzzard based on genetic materials, the Mountain buzzard (Buteo oreophilus), Forest buzzards (Buteo trizonatus) and the Madagascar buzzard (Buteo brachypterus), to the point where it has been questioned whether they are sufficiently distinct to qualify as full species. However, the distinctiveness of these African buzzards has generally been supported. Genetic studies have further indicated that the modern buzzards of Eurasia and Africa are a relatively young group, showing that they diverged at about 300,000 years ago. Nonetheless, fossils dating earlier than 5 million year old (the late Miocene period) showed Buteo species were present in Europe much earlier than that would imply, although it cannot be stated to a certainty that these would have been related to the extant buzzards.

Some 16 subspecies have been described in the past and up to 11 are often considered valid, although some authorities accept as few as seven. This highly individually variable race is described below. This is a relatively large and bulky race of buzzard. In males, the wing chord ranges from and the tail from . In comparison, the larger female has a wing chord measuring and tail length of . In both sexes, the tarsus measures in length. In southern Norway, the mean weight of males was reportedly , while that of females was . British buzzards were of intermediate size, 214 males averaging and 261 females averaging . Cramp and Simmons (1980) listed the mean body mass overall of nominate buzzards in Europe overall as in males and in females. This race differs from a typical intermediate of the nominate in being a darker, colder brown both above and below, closer to the darker individuals of the nominate. It averages smaller than most nominate buzzards. The wing chord of males ranges from while that of females ranges from . The eastern vulpinus group includes: ]] *B. b. vulpinus: The steppe buzzard breeds as far west as eastern Sweden, in the southern two-thirds of Finland, eastern Estonia, much of Belarus and Ukraine, eastward to the northern Caucacus, northern Kazakhstan, Kyrgyzstan, much of Russia to Altai and south-central Siberia, Tien Shan in China and western Mongolia. B. b. vulpinus is a long-distance migrant. It winters largely in much of eastern and southern Africa. Less frequently and often very discontinuously, steppe buzzards winter in the southern peninsulas of Europe, Arabia and southwestern India in addition to some parts of southeastern Kazakhstan, Uzbekistan and Kyrgyzstan. In the open country favoured on the wintering grounds, steppe buzzards are often seen perched on roadside telephone poles. It at one time was considered a separate species due to differences in size, form, colouring and behaviour (especially in regards to migratory behaviour) but is genetically indistinct from nominate buzzards. Furthermore, the steppe buzzard engages in extensive interbreeding with the nominate race, causing typical characteristics of the two races to mix. The zone of integration runs from Scandinavia through the European continent to the Black Sea, including any part of the overlapping ranges in Sweden, Finland, Estonia, Latvia, Lithuania, western Ukraine and eastern Romania. At times, the fertile hybrids of these two races have been erroneously proposed as races such as B. b. intermedius or B. b. zimmermannae. Intergrade buzzards are commonest where the grey-brown type of pale morphs of vulpinus are predominant. Weights of migrant birds appear to be lower than at other times of year for steppe buzzards. Two surveys of migrant buzzards during their huge spring movement in Eilat, Israel showed 420 birds averaged and 882 birds averaged . In comparison, weights of wintering steppe buzzards was higher, averaging in 35 birds in the former Transvaal (South Africa) and in 160 birds in the Cape Province. Weights of birds from Zambia were similar. *B. b. menetriesi: This race is found in southern Crimea through the Caucasus to northern Iran and possibly into Turkey. This race has traditionally been listed as a resident race, but some sources consider it a migrant to eastern and southern Africa. Compared to the overlapping steppe buzzard subspecies, it is larger (roughly intermediate between the nominate race and vulpinus) and is duller in overall colour, being sandy below rather than rufous and lacking the bright rufous on the tail. Wing chord is in males and in females. Buzzards found on the islands of Cape Verde off of the coast of western Africa, once referred to as the subspecies B. b. bannermani, and Socotra Island off of the northern peninsula of Arabia, once referred to as the rarely recognized subspecies B. b. socotrae, are now generally thought not to belong to the common buzzard. DNA testing has indicated that these insular buzzards are actually more closely related to the long-legged buzzard (Buteo rufinus) than to the common buzzard. Subsequently, some researchers have advocated full species status for the Cape Verde population, but the placement of these buzzards is generally deemed unclear.

s of Africa are extremely easy to mistake for juvenile common buzzards of the steppe race that come to winter in Africa.]] The common buzzard is often confused with other raptors especially in flight or at a distance. Inexperienced and over-enthusiastic observers have even mistaken darker birds for the far larger and differently proportioned golden eagle (Aquila chrysaetos) and also dark birds for western marsh harrier (Circus aeruginosus) which also flies in a dihedral but is obviously relatively much longer and slenderer winged and tailed and with far different flying methods. Also buzzards may possibly be confused with dark or light morph booted eagles (Hieraeetus pennatus), which are similar in size, but the eagle flies on level, parallel-edged wings which usually appear broader, has a longer squarer tail, with no carpal patch in pale birds and all dark flight feathers but for whitish wedge on inner primaries in dark morph ones. Pale individuals are sometimes also mistaken with pale morph short-toed eagles (Circaetus gallicus) which are much larger with a considerably bigger head, longer wings (which are usually held evenly in flight rather than in a dihedral) and paler underwing lacking any carpal patch or dark wing lining. While less individually variable in Europe, the honey buzzard is more extensively polymorphic on underparts than even the common buzzard. The most common morph of the adult European honey buzzard is heavily barred and rufous on the underside, quite different from the common buzzard, however the brownish juvenile much more resembles an intermediate common buzzard. Honey buzzards flap with distinctively slower and more even wing beats than common buzzards. The wings are also lifted higher on each upstroke, creating a more regular and mechanical effect, furthermore their wings are held slightly arched when soaring but not in a V-shape. On the honey buzzard, the head appears smaller, the body thinner, the tail longer and the wings narrower and more parallel-edged. The steppe buzzard race is particularly often mistaken for juvenile European honey buzzards, to the point where early observers of raptor migration in Israel considered distant individuals indistinguishable. However, when compared to a steppe buzzard, the honey buzzard has distinctly darker secondaries on the underwing with fewer and broader bars and more extensive black wing-tips (whole fingers) contrasting with a less extensively pale hand. Wintering steppe buzzards may live alongside mountain buzzards and especially with forest buzzard while wintering in Africa. The juveniles of steppe and forest buzzards are more or less indistinguishable and only told apart by proportions and flight style, the latter species being smaller, more compact, having a smaller bill, shorter legs and shorter and thinner wings than a steppe buzzard. However, size is not diagnostic unless side by side as the two buzzards overlap in this regard. Most reliable are the species wing proportions and their flight actions. Forest buzzard have more flexible wing beats interspersed with glides, additionally soaring on flatter wings and apparently never engage in hovering. Adult forest buzzards compared to the typical adult steppe buzzard (rufous morph) are also similar, but the forest typically has a whiter underside, sometimes mostly plain white, usually with heavy blotches or drop-shaped marks on abdomen, with barring on thighs, more narrow tear-shaped on chest and more spotted on leading edges of underwing, usually lacking marking on the white U across chest (which is otherwise similar but usually broader than that of vulpinus). In comparison, the mountain buzzard, which is more similar in size to the steppe buzzard and slightly larger than the forest buzzard, is usually duller brown above than a steppe buzzard and is more whitish below with distinctive heavy brown blotches from breasts to the belly, flanks and wing linings while juvenile mountain buzzard is buffy below with smaller and streakier markings. The steppe buzzard when compared to another African species, the red-necked buzzard (Buteo auguralis), which has red tail similar to vulpinus, is distinct in all other plumage aspects despite their similar size. The latter buzzard has a streaky rufous head and is white below with a contrasting bold dark chest in adult plumage and, in juvenile plumage, has heavy, dark blotches on the chest and flanks with pale wing-linings. Jackal and augur buzzards (Buteo rufofuscus & augur), also both rufous on the tail, are larger and bulkier than steppe buzzards and have several distinctive plumage characteristics, most notably both having their own striking, contrasting patterns of black-brown, rufous and cream.

The common buzzard is found throughout several islands in the eastern Atlantic islands, including the Canary Islands and Azores and almost throughout Europe. It is today found in Ireland and in nearly every part of Scotland, Wales and England. In mainland Europe, remarkably, there are no substantial gaps without breeding common buzzards from Portugal and Spain to Greece, Estonia, Belarus and Ukraine, though are present mainly only in the breeding season in much of the eastern half of the latter three countries. They are also present in all larger Mediterranean islands such as Corsica, Sardinia, Sicily and Crete. Further north in Scandinavia, they are found mainly in southeastern Norway (though also some points in southwestern Norway close to the coast and one section north of Trondheim), just over the southern half of Sweden and hugging over the Gulf of Bothnia to Finland where they live as a breeding species over nearly two-thirds of the land. The common buzzard reaches its northern limits as a breeder in far eastern Finland and over the border to European Russia, continuing as a breeder over to the narrowest straits of the White Sea and nearly to the Kola Peninsula. In these northern quarters, the common buzzard is present typically only in summer but is a year-around resident of a hearty bit of southern Sweden and some of southern Norway. Non-breeding populations occur, either as migrants or wintering birds, in southwestern India, Israel, Lebanon, Syria, Egypt (northeastern), northern Tunisia (and far northwestern Algeria), northern Morocco, near the coasts of The Gambia, Senegal and far southwestern Mauritania and Ivory Coast (and bordering Burkina Faso). In eastern and central Africa, it is found in winter from southeastern Sudan, Eritrea, about two-thirds of Ethiopia, much of Kenya (though apparently absent from the northeast and northwest), Uganda, southern and eastern Democratic Republic of the Congo, and more or less the entirety of southern Africa from Angola across to Tanzania down the remainder of the continent (but for an apparent gap along the coast from southwestern Angola to northwestern South Africa).

The common buzzard is a typical Buteo in much of its behaviour. It is most often seen either soaring at varying heights or perched prominently on tree tops, bare branches, telegraph poles, fence posts, rocks or ledges, or alternately well inside tree canopies. Buzzards will also stand and forage on the ground. In resident populations, it may spend more than half of its day inactively perched. Furthermore, it has been described a "sluggish and not very bold" bird of prey. It is a gifted soarer once aloft and can do so for extended periods but can appear laborious and heavy in level flight, more so nominate buzzards than steppe buzzards. In Israel, migrant buzzards rarely soar all that high (maximum above ground) due to the lack of mountain ridges that in other areas typically produce flyways; however tail-winds are significant and allow birds to cover a mean of .

, where buzzards have one of the largest raptor migrations in the world.]] The common buzzard is aptly described as a partial migrant. The autumn and spring movements of buzzards are subject to extensive variation, even down to the individual level, based on a region's food resources, competition (both from other buzzards and other predators), extent of human disturbance and weather conditions. Short-distance movements are the norm for juveniles and some adults in autumn and winter, but more adults in central Europe and the British Isles remain on their year-around residence than do not. Even for first year juvenile buzzards dispersal may not take them very far. In England, 96% of first-years moved in winter to less than from their natal site. Southwestern Poland was recorded to be a fairly important wintering grounds for central European buzzards in early spring that apparently travelled from somewhat farther north, in winter average density was a locally high 2.12 individual per square kilometer. In Bulgaria, the mean wintering density was 0.34 individual per square kilometer, and buzzards showed a preference for agricultural over forested areas. Similar habitat preferences were recorded in northeastern Romania, where buzzard density was 0.334–0.539 individuals per square kilometer. The nominate buzzards of Scandinavia are somewhat more strongly migratory than most central European populations. However, birds from Sweden show some variation in migratory behaviours. A maximum of 41,000 individuals have been recorded at one of the main migration sites within southern Sweden in Falsterbo. In southern Sweden, winter movements and migration was studied via observation of buzzard colour. White individuals were substantially more common in southern Sweden rather than further north in their Swedish range. The southern population migrates earlier than intermediate to dark buzzards, in both adults and juveniles. A larger proportion of juveniles than of adults migrate in the southern population. Especially adults in the southern population are resident to a higher degree than more northerly breeders. The entire population of the steppe buzzard is strongly migratory, covering substantial distances during migration. In no part of the range do steppe buzzards use the same summering and wintering grounds. Steppe buzzards are slightly gregarious in migration, and travel in variously sized flocks. This race migrates in September to October often from Asia Minor to the Cape of Africa in about a month but does not cross water, following around the Winam Gulf of Lake Victoria rather than crossing the several kilometer wide gulf. Similarly, they will funnel along both sides of the Black Sea. Migratory behavior of steppe buzzards mirrors those of broad-winged & Swainson's hawks (Buteo platypterus & swainsoni) in every significant way as similar long-distance migrating Buteos, including trans-equatorial movements, avoidance of large bodies of waters and flocking behaviour. Between 150,000 and nearly 466,000 Steppe Buzzard have been recorded migrating through Israel during spring, making this not only the most abundant migratory raptor here but one of the largest raptor migrations anywhere in the world. Migratory movements of southern Africa buzzards largely occur along the major mountain ranges, such as the Drakensberg and Lebombo Mountains. The onset of migratory movement for steppe buzzards back to the breeding grounds in southern Africa is mainly in March, peaking in the second week. In last 50 years, it was recorded that nominate buzzards are typically migrating shorter distances and wintering further north, possibly in response to climate change, resulting in relatively smaller numbers of them at migration sites. They are also extending their breeding range possibly reducing/supplanting steppe buzzards.

Resident populations of common buzzards tend to vocalize all year around, whereas migrants tend to vocalize only during the breeding season. Both nominate buzzards and steppe buzzards (and their numerous related subspecies within their types) tend to have similar voices. The main call of the species is a plaintive, far-carrying pee-yow or peee-oo, used as both contact call and more excitedly in aerial displays. Their call is sharper, more ringing when used in aggression, tends to be more drawn-out and wavering when chasing intruders, sharper, more yelping when as warning when approaching the nest or shorter and more explosive when called in alarm. Other variations of their vocal performances include a cat-like mew, uttered repeatedly on the wing or when perched, especially in display; a repeated mah has been recorded as uttered by pairs answering each other, further chuckles and croaks have also been recorded at nests. Juveniles can usually be distinguished by the discordant nature of their calls compared to those of adults.

The common buzzard is a generalist predator which hunts a wide variety of prey given the opportunity. Their prey spectrum extents to a wide variety of vertebrates including mammals, birds (from any age from eggs to adult birds), reptiles, amphibians and, rarely, fish, as well as to various invertebrates, mostly insects. Young animals are often attacked, largely the nidifugous young of various vertebrates. In total well over 300 prey species are known to be taken by common buzzards. Furthermore, prey size can vary from tiny beetles, caterpillars and ants to large adult grouse and rabbits up to nearly twice their body mass. Mean body mass of vertebrate prey was estimated at in Belarus. At times, they will also subsist partially on carrion, usually of dead mammals or fish. Hunting in relatively open areas has been found to increase hunting success whereas more complete shrub cover lowered success. A majority of prey is taken by dropping from perch, and is normally taken on ground. Alternately, prey may be hunted in a low flight. This species tends not to hunt in a spectacular stoop but generally drops gently then gradually accelerate at bottom with wings held above the back. Sometimes, the buzzard also forages by random glides or soars over open country, wood edges or clearings. Perch hunting may be done preferentially but buzzards fairly regularly also hunt from a ground position when the habitat demands it. Outside the breeding season, as many 15–30 buzzards have been recorded foraging on ground in a single large field, especially juveniles. Normally the rarest foraging type is hovering. A study from Great Britain indicated that hovering does not seem to increase hunting success.

.]] A high diversity of rodents may be taken given the chance, as around 60 species of rodent have been recorded in the foods of common buzzards. In southern Scotland, field voles were the best-represented species in pellets, accounting for 32.1% of 581 pellets. In southern Norway, field voles were again the main food in years with peak vole numbers, accounting for 40.8% of 179 prey items in 1985 and 24.7% of 332 prey items in 1994. Altogether, rodents amount to 67.6% and 58.4% of the foods in these respective peak vole years. However, in low vole population years, the contribution of rodents to the diet was minor. Common voles were the main foods recorded in central Slovakia, accounting for 26.5% of 606 prey items. The common vole, or other related vole species at times, were the main foods as well in Ukraine (17.2% of 146 prey items) ranging east to Russia in the Privolshky Steppe Nature Reserve (41.8% of 74 prey items) and in Samara (21.4% of 183 prey items). In Belarus, voles, including Microtus species and bank voles (Myodes glareolus), accounted for 34.8% of the biomass on average in 1065 prey items from different study areas over 4 years. Other rodents are taken largely opportunistically rather than by preference. Several wood mice (Apodemus ssp.) are known to be taken quite frequently but given their preference for activity in deeper woods than the field-forest interfaces preferred, they are rarely more than secondary food items. All four ground squirrels that range (mostly) into eastern Europe are also known to be common buzzard prey but little quantitative analysis has gone into how significant such predator-prey relations are. Rodent prey taken have ranged in size from the Eurasian harvest mouse (Micromys minutus) to the non-native, muskrat (Ondatra zibethicus). Other rodents taken either seldom or in areas where the food habits of buzzards are spottily known include flying squirrels, marmots (presumably very young if taken alive), chipmunks, spiny rats, hamsters, mole-rats, gerbils, jirds and jerboas and occasionally hearty numbers of dormice, although these are nocturnal. Surprisingly little research has gone into the diets of wintering steppe buzzards in southern Africa, considering their numerous status there. However, it has been indicated that the main prey remains consist of rodents such as the four-striped grass mouse (Rhabdomys pumilio) and Cape mole-rats (Georychus capensis). Other than rodents, two other groups of mammals can be counted as significant to the diet of common buzzards. One of these main prey types of import in the diets of common buzzards are leporids or lagomorphs, especially the European rabbit (Oryctolagus cuniculus) where it is found in numbers in a wild or feral state. In all dietary studies from Scotland, rabbits were highly important to the buzzard's diet. In southern Scotland, rabbits constituted 40.8% of remains at nests and 21.6% of pellet contents, while lagomorphs (mainly rabbits but also some young hares) were present in 99% of remains in Moray, Scotland. The nutritional richness relative to the commonest prey elsewhere, such as voles, might account for the high productivity of buzzards here. For example, clutch sizes were twice as large on average where rabbits were common (Moray) than were where they were rare (Glen Urquhart). In northern Ireland, an area of interest because it is devoid of any native vole species, rabbits were again the main prey. Here, lagomorphs constituted 22.5% of prey items by number and 43.7% by biomass. While rabbits are non-native, albeit long-established, in the British Isles, in their native area of the Iberian peninsula, rabbits are similarly significant to the buzzard's diet. In Murcia, Spain, rabbits were the most common mammal in the diet, making up 16.8% of 167 prey items. Similarly, in different areas and the mean weight of brown hares taken in Finland was around . One young mountain hares (Lepus timidus) taken in Norway was estimated to about . The other significant mammalian prey type is insectivores, among which more than 20 species are known to be taken by this species, including nearly all the species of shrew, mole and hedgehog found in Europe. Moles are taken particularly often among this order, since as is the case with "vole-holes", buzzards probably tend to watch molehills in fields for activity and dive quickly from their perch when one of the subterranean mammals pops up. The most widely found mole in the buzzard's northern range is the European mole (Talpa europaea) and this is one of the more important non-rodent prey items for the species. This species was present in 55% of 101 remains in Glen Urquhart, Scotland and was the second most common prey species (18.6%) in 606 prey items in Slovakia. In Bari, Italy, the Roman mole (Talpa romana), of similar size to the European species, was the leading identified mammalian prey, making up 10.7% of the diet. The full-size range of insectivores may be taken by buzzards, ranging from the world's smallest mammal (by weight), the Etruscan shrew (Suncus etruscus) to arguably the heaviest insectivore, the European hedgehog (Erinaceus europaeus). Mammalian prey for common buzzards other than rodents, insectivores, and lagomorphs is rarely taken. Occasionally, some weasels such as least weasel (Mustela nivalis) and stoat (Mustela erminea) are taken, and remains of young pine martens (Martes martes) and adult european polecats (Mustela putorius) was found in buzzard nest. Numerous larger mammals, including medium-sized carnivores such as dogs, cats and foxes and various ungulates, are sometimes eaten as carrion by buzzards, mainly during lean winter months. Still-borns of deer are also visited with some frequency.

mobs a buzzard. Buzzards will readily prey on crows, especially their fledglings.]] When attacking birds, common buzzards chiefly prey on nestlings and fledglings of small to medium-sized birds, largely passerines but also a variety of gamebirds, but sometimes also injured, sickly or unwary but healthy adults. While capable of overpowering birds larger than itself, the common buzzard is usually considered to lack the agility necessary to capture many adult birds, even gamebirds which would presumably be weaker fliers considering their relatively heavy bodies and small wings. On the contrary, in southern Scotland, even though the buzzards were taking relatively large bird prey, largely red grouse (Lagopus lagopus scotica), 87% of birds taken were reportedly adults. They also prey on a wide size range of birds, ranging down to Europe's smallest bird, the goldcrest (Regulus regulus). Other assorted avian prey has included a few species of waterfowl, most available pigeons and doves, cuckoos, swifts, grebes, rails, nearly 20 assorted shorebirds, tubenoses, hoopoes, bee-eaters and several types of woodpecker. Birds with more conspicuous or open nesting areas or habits are more likely to have fledglings or nestlings attacked, such as water birds, while those with more secluded or inaccessible nests, such as pigeons/doves and woodpeckers, adults are more likely to be hunted.

but was flushed from its catch.]] prey in Armenia.]] The common buzzard may be the most regular avian predator of reptiles and amphibians in Europe apart from the sections where they are sympatric with the largely snake-eating short-toed eagle. In total, the prey spectrum of common buzzards include nearly 50 herpetological prey species. In studies from northern and southern Spain, the leading prey numerically were both reptilian, although in Biscay (northern Spain) the leading prey (19%) was classified as "unidentified snakes". In Murcia, the most numerous prey was the ocellated lizard (Timon lepidus), at 32.9%. In total, at Biscay and Murcia, reptiles accounted for 30.4% and 35.9% of the prey items, respectively. Findings were similar in a separate study from northeastern Spain, where reptiles amounted to 35.9% of prey. In Bari, Italy, reptiles were the main prey, making up almost exactly half of the biomass, led by the large green whip snake (Hierophis viridiflavus), at 24.2% of food mass. However, in at least one case, the corpse of a female buzzard was found envenomed over the body of an adder that it had killed. In some parts of range, the common buzzard acquires the habit of taking many frogs and toads. This was the case in the Mogilev Region of Belarus where the moor frog (Rana arvalis) was the major prey (28.5%) over several years, followed by other frogs and toads amounting to 39.4% of the diet over the years. In central Scotland, the common toad (Bufo bufo) was the most numerous prey species, accounting for 21.7% of 263 prey items, while the common frog (Rana temporaria) made up a further 14.7% of the diet. Frogs made up about 10% of the diet in central Poland as well.

When common buzzards feed on invertebrates, these are chiefly earthworms, beetles and caterpillars in Europe and largely seemed to be preyed on by juvenile buzzards with less refined hunting skills or in areas with mild winters and ample swarming or social insects. In most dietary studies, invertebrates are at best a minor supplemental contributor to the buzzard's diet. For wintering steppe buzzards in Zimbabwe, one source went so far as to refer to them as primarily insectivorous, apparently being somewhat locally specialized to feeding on termites. Stomach contents in buzzards from Malawi apparently consisted largely of grasshoppers (alternately with lizards). Fish tend to be the rarest class of prey found in the common buzzard's foods. There are a couple cases of predation of fish detected in the Netherlands, while elsewhere they have been known to have fed upon eels and carp.

being mobbed by a pair of common buzzards over the Isle of Canna, as the eagle will sometimes prey on the buzzard.]] Common buzzards co-occur with dozens of other raptorial birds through their breeding, resident and wintering grounds. There may be many other birds that broadly overlap in prey selection to some extent. Furthermore, their preference for interfaces of forest and field is used heavily by many birds of prey. Some of the most similar species by diet are the common kestrel (Falco tinniculus), hen harrier (Circus cyaenus) and lesser spotted eagle (Clanga clanga), not to mention nearly every European species of owl, as all but two may locally prefer rodents such as voles in their diets. Diet overlap was found to be extensive between buzzards and red foxes (Vulpes vulpes) in Poland, with 61.9% of prey selection overlapping by species although the dietary breadth of the fox was broader and more opportunistic. Both fox dens and buzzard roosts were found to be significantly closer to high vole areas relative to the overall environment here. The only other widely found European Buteo, the rough-legged buzzard, comes to winter extensively with common buzzards. It was found in southern Sweden, habitat, hunting and prey selection often overlapped considerably. Rough-legged buzzards appear to prefer slightly more open habitat and took slightly fewer wood mice than common buzzard. Roughlegs also hover much more frequently and are more given to hunting in high winds. The two buzzards are aggressive towards one another and excluded each other from winter feeding territories in similar ways to the way they exclude conspecifics. In northern Germany, the buffer of their habitat preferences apparently accounted for the lack of effect on each other's occupancy between the two buzzard species. A more direct negative effect has been found in buzzard's co-existence with northern goshawk (Accipiter gentilis). Despite the considerable discrepancy of the two species dietary habits, habitat selection in Europe is largely similar between buzzards and goshawks. Goshawks are slightly larger than buzzards and are more powerful, agile and generally more aggressive birds, and so they are considered dominant. In studies from Germany and Sweden, buzzards were found to be less disturbance sensitive than goshawks but were probably displaced into inferior nesting spots by the dominant goshawks. The exposure of buzzards to a dummy goshawk was found to decrease breeding success whereas there was no effect on breeding goshawks when they were exposed to a dummy buzzard. In many cases, in Germany and Sweden, goshawks displaced buzzards from their nests to take them over for themselves. In Poland, buzzards productivity was correlated to prey population variations, particularly voles which could vary from 10 to 80 per hectare, whereas goshawks were seemingly unaffected by prey variations; buzzards were found here to number 1.73 pair per against goshawk 1.63 pair per . In contrast, the slightly larger counterpart of buzzards in North America, the red-tailed hawk (which is also slightly larger than American goshawks, the latter averaging smaller than European ones) are more similar in diet to goshawks there. Redtails are not invariably dominated by goshawks and are frequently able to outcompete them by virtue of greater dietary and habitat flexibility. Furthermore, red-tailed hawks are apparently equally capable of killing goshawks as goshawks are of killing them (killings are more one-sided in buzzard-goshawk interactions in favour of the latter). Other raptorial birds, including many of similar or mildly larger size than common buzzards themselves, may dominate or displace the buzzard, especially with aims to take over their nests. Species such as the black kite (Milvus migrans), booted eagle (Hieraeetus pennatus) and the lesser spotted eagle have been known to displace actively nesting buzzards, although in some cases the buzzards may attempt to defend themselves. The broad range of accipitrids that take over buzzard nests is somewhat unusual. More typically, common buzzards are victims of nest parasitism to owls and falcons, as neither of these other kinds of raptorial birds builds their own nests, but these may regularly take up occupancy on already abandoned or alternate nests rather than ones the buzzards are actively using. Even with birds not traditionally considered raptorial, such as common ravens, may compete for nesting sites with buzzards. In urban vicinities of southwestern England, it was found that peregrine falcons (Falco peregrinus) were harassing buzzards so persistently, in many cases resulting in injury or death for the buzzards, the attacks tending to peak during the falcon's breeding seasons and tend to be focused on subadult buzzards. Despite often being dominated in nesting site confrontations by even similarly sized raptors, buzzards appear to be bolder in direct competition over food with other raptors outside of the context of breeding, and has even been known to displace larger birds of prey such as red kites (Milvus milvus) and female buzzards may also dominate male goshawks (which are much smaller than the female goshawk) at disputed kills. .]] Common buzzards are occasionally threatened by predation by other raptorial birds. Northern goshawks have been known to have preyed upon buzzards in a few cases. Much larger raptors are known to have killed a few buzzards as well, including steppe eagles (Aquila nipalensis) on migrating steppe buzzards in Israel. Further instances of predation on buzzards have involved golden, eastern imperial (Aquila heliaca), Bonelli's (Aquila fasciata) and white-tailed eagles (Haliaeetus albicilla) in Europe. Besides preying on adult buzzard, white-tailed eagles have been known to raise buzzards with their own young. These are most likely cases of eagles carrying off young buzzard nestlings with the intention of predation but, for unclear reasons, not killing them. Instead the mother eagle comes to brood the young buzzard. Despite the difference of the two species diets, white-tailed eagles are surprisingly successful at raising young buzzards (which are conspicuously much smaller than their own nestlings) to fledging. Studies in Lithuania of white-tailed eagle diets found that predation on common buzzards was more frequent than anticipated, with 36 buzzard remains found in 11 years of study of the summer diet of the white-tailed eagles. While nestling buzzards were multiple times more vulnerable to predation than adult buzzards in the Lithuanian data, the region's buzzards expelled considerable time and energy during the late nesting period trying to protect their nests. The most serious predator of common buzzards, however, is almost certainly the Eurasian eagle-owl (Bubo bubo). This is a very large owl with a mean body mass about three to four times greater than that of a buzzard. The eagle-owl, despite often taking small mammals that broadly overlap with those selected by buzzards, is considered a "super-predator" that is a major threat to nearly all co-existing raptorial birds, capably destroying whole broods of other raptorial birds and dispatching adult raptors even as large as eagles. Due to their large numbers in edge habitats, common buzzards frequently feature heavily in the eagle-owl's diet. Eagle-owls, as will some other large owls, also readily expropriate the nests of buzzards. In the Czech Republic and in Luxembourg, the buzzard was the third and fifth most frequent prey species for eagle-owls, respectively. The reintroduction of eagle-owls to sections of Germany has been found to have a slight deleterious effect on the local occupancy of common buzzards. The only sparing factor is the temporal difference (the buzzard nesting later in the year than the eagle-owl) and buzzards may locally be able to avoid nesting near an active eagle-owl family. As the ecology of the wintering population is relatively little studied, a similar very large owl at the top of the avian food chain, the Verreaux's eagle-owl (Bubo lacteus), is the only known predator of wintering steppe buzzards in southern Africa. Despite not being known predators of buzzards, other large, vole-eating owls are known to displace or to be avoided by nesting buzzards, such as great grey owls (Strix nebulosa) and Ural owls (Strix uralensis). Unlike with large birds of prey, next to nothing is known of mammalian predators of common buzzards, despite up to several nestlings and fledglings being likely depredated by mammals. Common buzzards themselves rarely present a threat to other raptorial birds but may occasionally kill a few of those of smaller size. The buzzard is a known predator of Eurasian sparrowhawks (Accipiter nisus), common kestrel and lesser kestrel (Falco naumanni) . Perhaps surprisingly, given the nocturnal habits of this prey, the group of raptorial birds the buzzard is known to hunt most extensively is owls. Known owl prey has included Western barn owls (Tyto alba), European scops owls (Otus scops), tawny owls (Strix aluco), little owls (Athene noctua), boreal owls (Aegolius funereus), long-eared owls (Asio otus) and short-eared owls (Asio flammeus). Despite their relatively large size, tawny owls are known to avoid buzzards as there are several records of them preying upon the owls.

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Home ranges of common buzzards are generally . In a German study, the range was with an average of . The Snowdonia region of northern Wales held a pair per with a mean nearest neighbor distance of ; in adjacent Migneint, pair occurrence was , with a mean distance of . In the Teno massif of the Canary Islands, the average density was estimated as 23 pairs per , similar to that of a middling continental population. On another set of islands, on Crete the density of pairs was lower at 5.7 pairs per ; here buzzards tend to have an irregular distribution, some in lower intensity harvest olive groves but their occurrence actually more common in agricultural than natural areas. In the Italian Alps, it was recorded in 1993–96 that there were from 28 to 30 pairs per . Higher density areas are known than those above. Two areas of the Midlands of England showed occupancies of 81 and 22 territorial pairs per . High buzzard densities there were associated with high proportions of unimproved pasture and mature woodland within the estimated territories. Despite claims from the study of the English midlands were the highest known territory density for the species, a number ranging from 32 to 51 pairs in wooded area of merely in Czech Republic seems to surely exceed even those densities. The Czech study hypothesized that fragmentation of forest in human management of lands for wild sheep and deer, creating exceptional concentrations of prey such as voles, and lack of appropriate habitat in surrounding regions for the exceptionally high density. In the North-Estonian Neeruti landscape reserve (area 1250 ha), Marek Vahula found 9 populated nests in 1989 and 1990. One nest was found in 1982 and is apparently the oldest known nest that is still populated today. .]] Common buzzards maintain their territories through flight displays. In Europe, territorial behaviour generally starts in February. However, displays are not uncommon throughout year in resident pairs, especially by males, and can elicit similar displays by neighbors. Sky-dancing by common buzzards have been recorded in spring and autumn, typically by male but sometimes by female, nearly always with much calling. Their sky-dances are of the rollercoaster type, with upward sweep until they start to stall, but sometimes embellished with loops or rolls at the top. Next in the sky-dance, they dive on more or less closed wings before spreading them and shooting up again, upward sweeps of up to , with dive drops of up to at least . These dances may be repeated in series of 10 to 20. In the climax of the sky dance, the undulations become progressive shallower, often slowing and terminating directly onto a perch. Various other aerial displays include low contour flight or weaving among trees, frequently with deep beats and exaggerated upstrokes which show underwing pattern to rivals perched below. Talon grappling and occasionally cartwheeling downward with feet interlocked has been recorded in buzzards and, as in many raptors, is likely the physical culmination of the aggressive territorial display, especially between males. Despite the highly territorial nature of buzzards and their devotion to a single mate and breeding ground each summer, there is one case of a polyandrous trio of buzzards nesting in the Canary Islands.

Common buzzards tend to build a bulky nest of sticks, twigs and often heather. Commonly, nests are up to across and deep. With reuse over years, the diameter can reach or exceed and weight of nests can reach over . Buzzards were recorded to nest almost exclusively in pines in Spain at a mean height of . Furthermore, a few ground nests were recorded in high prey-level agricultural areas in the Netherlands. In the Italian Alps, 81% of 108 nests were on cliffs. Pairs often have several nests but some pairs may use one over several consecutive years. Two to four alternate nests in a territory is typical for common buzzards, especially those breeding further north in their range.

.]] The breeding season commences at differing times based on latitude. Common buzzard breeding seasons may fall as early as January to April but typically the breeding season is March to July in much of Palearctic. In the northern stretches of the range the breeding season may last into May–August. Mating usually occurs on or near the nest and lasts about 15 seconds, typically occurring several times a day. Laying dates are remarkably constant throughout Great Britain. There are, however, highly significant differences in clutch size between British study areas. These do not follow any latitudinal gradient and it is likely that local factors such as habitat and prey availability are more important determinants of clutch size. The eggs are white in ground colour, rather round in shape with sporadic red to brown markings sometimes lightly showing. In the nominate race, egg size is in height by in diameter with an average of in 600 eggs. In the race of vulpinus, egg height is by with an average of in 303 eggs. Eggs are generally laid in late March to early April in extreme south, sometime in April in most of Europe, into May and possibly even early June in the extreme north. If eggs are lost to a predator (including humans) or fail in some other way, common buzzards do not usually lay replacement clutches but they have been recorded, even with 3 attempts of clutches by a single female. The female does most but not all of the incubating, doing so for a total of 33–35 days. The female remains at the nest brooding the young in the early stages with the male bringing all prey. At about 8–12 days, both the male and female will bring prey but the female continues to do all feeding until the young can tear up their own prey.

Once hatching commences, it may take 48 hours for the chick to chip out. Hatching may take place over 3–7 days, with new hatchlings averaging about in body mass. After leaving the nest, buzzards generally stay close by, but with migratory ones there is more definitive movement generally southbound. Full independence is generally sought 6 to 8 weeks after fledging. 1st year birds generally remain in wintering area for following summer but then return to near area of origin but then migrate south again without breeding. In common buzzards, generally speaking, siblings stay quite close to each other after dispersal from their parents and form something of a social group, although parents usually tolerate their presence on their territory until they are laying another clutch. However, the social group of siblings disbands at about a year of age.

Numerous factors may weigh into the breeding success of common buzzards. Chiefly among these are prey populations, habitat, disturbance and persecution levels and interspecies competition. High breeding success was detected in Argyll, Scotland, due likely to hearty prey populations (rabbits) but also probably a lower local rate of persecution than elsewhere in the British isles. Here, the mean number of fledglings were 1.75 against 0.82–1.41 in other parts of Britain. The composition of habitat and its relation to human disturbance were important variables for the dark and light phenotypes but were less important to intermediate individuals. Thus selection pressures resulting from different factors did not vary much between sexes but varied between the three phenotypes in the population. Breeding success in areas with wild European rabbits was considerably effected by rabbit myxomatosis and rabbit haemorrhagic disease, both of which have heavily depleted wild rabbit population. Breeding success in formerly rabbit-rich areas were recorded to decrease from as much as 2.6 to as little as 0.9 young per pair. Age of first breeding in several radio-tagged buzzards showed only a single male breeding as early as his 2nd summer (at about a year of age). Significantly more buzzards were found to start breeding at the 3 summer but breeding attempts can be individually erratic given the availability of habitat, food and mates. The mean life expectancy was estimated at 6.3 years in the late 1950s, but this was at a time of high persecution when humans were causing 50–80% of buzzard deaths. In a more modern context with regionally reduced persecution rates, the lifespan expected can be higher (possibly in excess of 10 years at times) but is still widely variable due to a wide variety of factors.

.]] The common buzzard is one of the most numerous birds of prey in its range. Almost certainly, it is the most numerous diurnal bird of prey throughout Europe. Conservative estimates put the total population at no fewer than 700,000 pairs in Europe, which are more than twice the total estimates for the next four birds of prey estimated as most common: the Eurasian sparrowhawk (more than 340,000 pairs), the common kestrel (more than 330,000 pairs) and the northern goshawk (more than 160,000 pairs). In Westphalia, Germany, population of buzzards was shown to nearly triple over the last few decades. The Westphalian buzzards are possibly benefiting from increasingly warmer mean climate, which in turn is increasing vulnerability of voles. However, the rate of increase was significantly greater in males than in females, in part because of reintroduced Eurasian eagle-owls to the region preying on nests (including the brooding mother), which may in turn put undue pressure on the local buzzard population. At least 238 common buzzards killed through persecution were recovered in England from 1975 to 1989, largely through poisoning. Persecution did not significantly differ at any time due this span of years nor did the persecution rates decrease, nor did it when compared to rates of last survey of this in 1981. While some persecution persists in England, it is probably slightly less common today. Given its relative abundance, the common buzzard is held as an ideal bioindicator, as they are effected by a range of pesticide and metal contamination through pollution like other raptors but are largely resilient to these at the population levels. In turn, this allows biologists to study (and harvest if needed) the buzzards intensively and their environments without affecting their overall population. The lack of affect may be due to the buzzard's adaptability as well as its relatively short, terrestrially-based food chain, which exposes them to less risk of contamination and population depletions than raptors that prey more heavily on water-based prey (such as some large eagles) or other birds (such as falcons). Common buzzards are seldom vulnerable to egg-shell thinning from DDT as are other raptors but egg-shell thinning has been recorded. Other factors that negatively effect raptors have been studied in common buzzards are helminths, avipoxvirus and assorted other viruses.