Editing Common buzzard (section)

==Breeding==
[[File:Buteo buteo -Scotland -pair-8 (1).jpg|thumb|A pair of common buzzards in [[Scotland]].]]

===Nesting territories and density===
Home ranges of common buzzards are generally {{cvt|0.5|to|2|sqkm}}.<ref name= Brown/> The size of breeding territory seem to be generally correlated with food supply.<ref name= Brown/><ref name= Kruger>Krüger, O. (2004). ''The importance of competition, food, habitat, weather and phenotype for the reproduction of Buzzard Buteo buteo''. Bird Study, 51(2), 125–132.</ref> In a German study, the range was {{cvt|0.8|to|1.8|sqkm}} with an average of {{cvt|1.26|sqkm}}.<ref name= Schindler/> Some of the lowest pair densities of common buzzards seem to come from [[Russia]]. For instance, in [[Kerzhenets Nature Reserve]], the recorded density was 0.6 pairs per {{cvt|100|sqkm}} and the average distance of nearest neighbors was {{cvt|3.8|km}}.<ref>Novikova, L. (2009). ''Number and Distribution of the Common Buzzard in the Kerzhenskiy State Nature Reserve, Russia''. Raptors Conservation, (16).</ref> The [[Snowdonia]] region of northern [[Wales]] held a pair per {{cvt|9.7|sqkm}} with a mean nearest neighbor distance of {{cvt|1.95|km}}; in adjacent [[Migneint]], pair occurrence was {{cvt|7.2|sqkm}}, with a mean distance of {{cvt|1.53|km}}.<ref>Dare, P. J., & Barry, J. T. (1990). ''Population size, density and regularity in nest spacing of Buzzards Buteo buteo in two upland regions of North Wales''. Bird Study, 37(1), 23–29.</ref> In the [[Macizo de Teno|Teno massif]] of the [[Canary Islands]], the average density was estimated as 23 pairs per {{cvt|100|sqkm}}, similar to that of a middling continental population.<ref name= Rodriguez>Rodríguez, B., Siverio, F., Rodríguez, A., Siverio, M., Hernández, J. J., & Figuerola, J. (2010). ''Density, habitat selection and breeding biology of Common Buzzards Buteo buteo in an insular environment''. Bird Study, 57(1), 75–83.</ref> On another set of islands, on [[Crete]] the density of pairs was lower at 5.7 pairs per {{cvt|100|sqkm}}; 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.<ref>Tzortzakaki, O., Simaiakis, S., & Xirouchakis, S. (2012). ''Abundance of common buzzards (Buteo buteo) in olive monocultures in the island of Crete''. Journal of Biological Research, 17, 44.</ref> In the Italian [[Alps]], it was recorded in 1993–96 that there were from 28 to 30 pairs per {{cvt|100|sqkm}}.<ref name= Sergio/> In central Italy, density average was lower at 19.74 pairs per {{cvt|100|sqkm}}.<ref>Cerasoli, M., & Penteriani, V. (1996). ''Common Buzzards (Buteo buteo) in Central Italy''. J. Raptor Res., 30(3), 130–135.</ref> Higher density areas are known than those above. Two areas of [[the Midlands]] of [[England]] showed occupancies of 81 and 22 territorial pairs per {{cvt|100|sqkm}}. High buzzard densities there were associated with high proportions of unimproved pasture and mature woodland within the estimated territories.<ref name=Sim/> Similarly high densities of common buzzards were estimated in central [[Slovakia]] using two different methods, here indicating densities of 96 to 129 pairs per {{cvt|100|sqkm}}.<ref name= Sotnar2>Šotnár, K., & Topercer, J. (2009). ''Estimating density, population size and dynamics of Common Buzzard (Buteo buteo) in the West Carpathian region by a new method''. Slovak Raptor Journal, 3, 1–12.</ref> 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 {{cvt|22|sqkm}} in [[Czech Republic]] seems to surely exceed even those densities. The Czech study hypothesized that fragmentation of forest in human management of lands for [[Mouflon|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.<ref name= Sim/><ref>Voříšek, P. (2000). ''An extremely high population density of common buzzard (Buteo buteo) in Biosphere Reserve Pálava (Czech Republic) and its possible causes''. Buteo, 11, 51–56.</ref>

In the North-Estonian [[Neeruti Landscape Conservation Area|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.{{Citation needed|date=February 2023}}

[[File:Buteo buteo (553474414).jpg|thumb|left|A territorial dogfight between three buzzards in the [[Azores]].]]
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.<ref name= Ferguson-Lees/><ref name= Brown/> In them, common buzzards generally engage in high circling, spiraling upward on slightly raised wings. Mutual high circling by pairs sometimes go on at length, especially during the period prior to or during breeding season. In mutual displays, a pair may follow each other at {{cvt|10|-|50|m}} in level flight. During the mutual displays, the male may engage in exaggerated deep flapping or zig-zag tumbling, apparently in response to the female being too distant. Two or three pairs may circle together at times and as many as 14 individual adults have been recorded over established display sites.<ref name= Ferguson-Lees/><ref>Forsman, D., & Solonen, T. (1984, January). ''Censusing breeding raptors in southern Finland: methods and results''. In Annales Zoologici Fennici (pp. 317–320). Finnish Academy of Sciences, Societas Scientiarum Fennica, Societas pro Fauna et Flora Fennica and Societas Biologica Fennica Vanamo.</ref> 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 {{cvt|30|m}}, with dive drops of up to at least {{cvt|60|m}}. 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.<ref name= Ferguson-Lees/><ref>Negro, J. J., & Galván, I. (2018). ''Behavioural Ecology of Raptors''. In Birds of Prey (pp. 33–62). Springer, Cham.</ref> 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.<ref name= Brown/><ref>Simmons, R. E., & Mendelsohn, J. M. (1993). ''A critical review of cartwheeling flights of raptors''. Ostrich, 64(1), 13–24.</ref> 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 [[Polyandry in animals|polyandrous]] trio of buzzards nesting in the [[Canary Islands]].<ref>Barrientos, R., & López-Darias, M. (2006). ''A case of a polyandrous trio of Eurasian buzzards (Buteo buteo) on Fuerteventura Island, Canary Islands''. Journal of Raptor Research, 40(4), 305–306.</ref>

===Nests===
Common buzzards tend to build a bulky nest of sticks, twigs and often [[Calluna|heather]]. Commonly, nests are up to {{cvt|1|to|1.2|m}} across and {{cvt|60|cm}} deep. With reuse over years, the diameter can reach or exceed {{cvt|1.5|m}} and weight of nests can reach over {{cvt|200|kg}}.<ref name= Ferguson-Lees/><ref name= Brown/> Active nests tend to be lined with greenery, most often this consists of broad-leafed foliage but sometimes also includes [[Juncaceae|rush]] or [[seaweed]] locally. Nest height in trees is commonly {{cvt|3|to|25|m}}, usually by main trunk or main crutch of the tree.<ref name= Ferguson-Lees/><ref name= Brown/><ref name= Cramp/> In [[Germany]], trees used for nesting consisted mostly of [[Fagus sylvatica|red beeches]] (''Fagus sylvatica'') (in 337 cases), whereas a further 84 were in assorted [[Quercus|oaks]].<ref name= Rockenbauch>Rockenbauch, D. (1975). ''Zwölfjährige Untersuchungen zur Ökologie des Mäusebussards (Buteo buteo) auf der Schwäbischen Alb''. Journal für Ornithologie, 116(1), 39–54.</ref> Buzzards were recorded to nest almost exclusively in [[Pinus|pines]] in [[Spain]] at a mean height of {{cvt|14.5|m}}.<ref name= Zuberogoitia/> Trees are generally used for a nesting location but they will also utilize crags or bluffs if trees are unavailable.<ref name= Brown/> Buzzards in one English study were surprisingly partial to nesting on well-vegetated banks and due to the rich surrounding environment habitat and prey population, were actually more productive than nests located in other locations here.<ref>Austin, G. E. (1992). ''The distribution and breeding performance of the buzzard Buteo buteo in relation to habitat: an application using remote sensing and geographical information systems'' (Doctoral dissertation, University of Glasgow).</ref> Furthermore, a few ground nests were recorded in high prey-level agricultural areas in the [[Netherlands]].<ref>Jonkers, D. A., & Roodhart, J. (2003). ''Grondnest van Buizerd Buteo buteo op bruggetje''. De takkeling, 11(3), 234–236.</ref> In the Italian [[Alps]], 81% of 108 nests were on cliffs.<ref name= Sergio/> The common buzzard generally lacks the propensity of its Nearctic counterpart, the [[red-tailed hawk]], to occasionally nest on or near manmade structures (often in heavily urbanized areas) but in Spain some pairs recorded nesting along the perimeter of abandoned buildings.<ref>Castillo-Gómez, C., & Moreno-Rueda, G. (2011). ''A record of a Common Buzzard (Buteo buteo) nesting in an abandoned building''. Journal of Raptor Research, 45(3), 275–277.</ref> 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.<ref name= Brown/><ref name= Selas3>Selas, V. (2001). ''Breeding density and brood size of Common Buzzard Buteo buteo in relation to snow cover in spring''. Ardea, 89(3), 471–479.</ref>

===Reproduction and eggs===
[[File:The birds of the British Isles and their eggs (8263824243).jpg|thumb|The much plainer egg of the common buzzard contrasted with that of the [[European honey buzzard]].]]
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.<ref name= Ferguson-Lees/><ref name= Brown/> Eggs are usually laid in 2 to 3-day intervals. The clutch size can range from to 2 to 6, a relatively large clutch for an accipitrid. More northerly and westerly buzzard usually bear larger clutches, which average nearer 3, than those further east and south.<ref name= Ferguson-Lees/><ref name= Brown/><ref name= Rodriguez/> In Spain, the average clutch size is about 2 to 2.3.<ref name= Zuberogoitia/> From 4 locations in different parts of Europe, 43% had clutch size of 2, 41% had size of 3, clutches of 1 and 4 each constituted about 8%.<ref>Holdsworth, M. (1971). ''Breeding biology of Buzzards at Sedbergh during 1937–67''. British Birds, 64, 412–420.</ref> 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.<ref name= Austin/> 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 {{cvt|49.8|-|63.8|mm}} in height by {{cvt|39.1|-|48.2|mm}} in diameter with an average of {{cvt|55|x|44|mm}} in 600 eggs. In the race of ''vulpinus'', egg height is {{cvt|48|-|63|mm}} by {{cvt|39.2|-|47.5|mm}} with an average of {{cvt|54.2|x|42.8|mm}} in 303 eggs.<ref name= Brown/> 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.<ref name= Ferguson-Lees/><ref name= Brown/><ref name= Swann/> The female does most but not all of the incubating, doing so for a total of 33–35 days.<ref name= Ferguson-Lees/><ref name= Brown/> 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.<ref name= Brown/>

===Development of young===
[[File:Buteo nestling juedischer Friedhof.JPG|thumb|right|Two young buzzard nestlings.]]
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 {{cvt|45|g}} in body mass.<ref name= Ferguson-Lees/><ref name= Brown/><ref name= Cramp/> Often the youngest nestling dies from starvation, especially in broods of three or more.<ref name= Brown/> In nestlings, the first down replaces by longer, coarser down at about 7 days of age with the first proper feathers appearing at 12 to 15 days. The young are nearly fully feathered rather than downy at about a month of age and can start to feed themselves as well. The first attempts to leave the nest are often at about 40–50 days, averaging usually 40–45 in nominate buzzards in Europe, but more quickly on average at 40–42 in ''vulpinus''. Fledging occurs typically at 43–54 days but in extreme cases at as late 62 days. Sexual dimorphism is apparent in European fledglings, as females often scale about {{cvt|1000|g|lb}} against {{cvt|780|g|lb}} in males.<ref name= Brown/><ref name= Cramp/><ref name= Tyack>Tyack, A. J., Walls, S. S., & Kenward, R. E. (1998). ''Behaviour in the post‐nestling dependence period of radio‐tagged Common Buzzards Buteo buteo''. Ibis, 140(1), 58–63.</ref> 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.<ref name= Ferguson-Lees/><ref name= Brown/><ref name= Cramp/> Radio-tracking suggests that most dispersal, even relatively early dispersals, by juvenile buzzards is undertaken independently rather than via exile by parents, as has been recorded in some other birds of prey.<ref>Walls, S. S., Mañosa, S., Fuller, R. M., Hodder, K. H., & Kenward, R. E. (1999). ''Is early dispersal enterprise or exile? Evidence from radio-tagged buzzards''. Journal of Avian Biology, 407–415.</ref> 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.<ref name= Tyack/><ref name="Walls"/> Juvenile buzzards are subordinate to adults during most encounters and tend to avoid direct confrontations and actively defended territories until they are of appropriate age (usually at least 2 years of age).<ref name= Cramp/> This was the case as well for steppe buzzard juveniles wintering in southern Africa, although in some cases juveniles were able to successfully [[Kleptoparasitism|steal prey]] from adults there.<ref>Herremans, M. (2001). ''Age-related differences in abundance and habitat occupation of Steppe Buzzards, Buteo buteo vulpinus, in the Western Cape Province, South Africa''. Ostrich-Journal of African Ornithology, 72(1–2), 105–108.</ref>
[[File:Common Buzzard fledgling in Pinus nigra 2010-06-16.jpg|thumb|left|A common buzzard recent fledgling in a pine tree.]]

===Breeding success rates===
Numerous factors may weigh into the breeding success of common buzzards. Chiefly among these are prey populations, habitat, disturbance and persecution levels and innerspecies competition.<ref name= Brown/> In Germany, intra- and interspecific competition, plumage morph, laying date, precipitation levels and anthropogenic disturbances in the breeding territory, in declining order, were deemed to be the most significant bearers of breeding success.<ref name="Kruger"/> In an accompanying study, it was found that a mere 17% of adult birds of both sexes present in a German study area produced 50% of offspring, so breeding success may be lower than perceived and many adult buzzards for unknown causes may not attempt to breed at all.<ref name= Kruger2>Krüger, O., & Lindström, J. (2001). ''Lifetime reproductive success in common buzzard, Buteo buteo: from individual variation to population demography''. Oikos, 93(2), 260–273.</ref> 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.<ref name= Austin/> It was found in the English [[The Midlands|Midlands]] that breeding success both by measure of clutch size and mean number of fledglings, was relatively high thanks again to high prey populations. Breeding success was lower farther from significant stands of trees in the Midlands and most nesting failures that could be determined occurred in the incubation stage, possibly in correlation with predation of eggs by [[corvid]]s.<ref name= Sim/> More significant than even prey, late winter-early spring was found to be likely the primary driver of breeding success in buzzards from southern [[Norway]]. Here, even in peak [[vole]] years, nesting success could be considerably hampered by heavy snow at this crucial stage. In Norway, large clutches of 3+ were expected only in years with minimal snow cover, high vole populations and lighter rains in May–June.<ref name= Selas3/> In the Italian [[Alps]], the mean number of fledglings per pair was 1.07.<ref name= Sergio/> 33.4% of nesting attempts were failures per a study in southwestern [[Germany]], with an average of 1.06 of all nesting attempts and 1.61 for all successful attempt. In Germany, weather conditions and rodent populations seemed to be the primary drivers of nesting success.<ref name= Rockenbauch/> In [[Region of Murcia|Murcia]] part of [[Spain]] contrasted with [[Biscay]] to the north, higher levels of interspecific competition from [[booted eagle]]s and [[northern goshawk]]s did not appear to negatively affect breeding success due to more ample prey populations (rabbits again) in Murcia than in Biscay.<ref name= Zuberogoitia/>

In the [[Westphalia]] area of Germany, it was found that intermediate colour morphs were more productive than those that were darker or lighter.<ref name= Kruger2/> For reasons that are not entirely clear, apparently fewer parasites were found to afflict broods of intermediate plumaged buzzard less so than dark and light [[phenotype]]s, in particular higher [[melanin]] levels somehow were found to be more inviting to parasitic organism that effect the health of the buzzard's offspring.<ref>Chakarov, N., Boerner, M., & Krüger, O. (2008). ''Fitness in common buzzards at the cross‐point of opposite melanin–parasite interactions''. Functional Ecology, 22(6), 1062–1069.</ref> 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.<ref name= Kruger3>Krüger, O. (2002). ''Dissecting common buzzard lifespan and lifetime reproductive success: the relative importance of food, competition, weather, habitat and individual attributes''. Oecologia, 133(4), 474–482.</ref> Breeding success in areas with wild [[European rabbit]]s was considerably effected by [[Myxomatosis|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.<ref name="Moore, N. W. 1957"/><ref>Moore, N. W. (1956). ''Rabbits, buzzards and hares. Two studies on the indirect effects of myxomatosis''. Les conséquences biologiques dues à la présence de la myxomatose.</ref><ref>Lees, A. C., & Bell, D. J. (2008). ''A conservation paradox for the 21st century: the European wild rabbit Oryctolagus cuniculus, an invasive alien and an endangered native species''. Mammal Review, 38(4), 304–320.</ref> 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.<ref>Davis, P. E., & Davis, J. E. (1992). ''Dispersal and age of first breeding of buzzards in central Wales''. British Birds, 85(11), 578–587.</ref> 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.<ref name= Mebs/> 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.<ref name= Kruger3/>