J. Raptor Res. 42(4):273–280 E 2008 The Raptor Research Foundation, Inc.

BREEDING BIOLOGY AND DIET OF THE LONG-LEGGED ( RUFINUS) IN THE EASTERN JUNGGAR BASIN OF NORTHWESTERN

YI-QUN WU School of Life Science, Lanzhou University, Lanzhou, Gansu 730000 China

MING MA Xinjiang Institute of Ecology and Geography, Chinese Academy of Science, Urumqi 830011 China

FENG XU Institute of Zoology, Chinese Academy of Science, Beijing 100080 China

DIMITAR RAGYOV Central Laboratory of General Ecology, Bulgarian Academy of Sciences, Sofia 1113 Bulgaria

JEVGENI SHERGALIN International Wildlife Consultants (U.K.) Ltd., P.O. Box 19, Carmarthen, SA33 5YL U.K.

NAI-FA LIU1 School of Life Science, Lanzhou University, Lanzhou, Gansu 730000 China

ANDREW DIXON2 International Wildlife Consultants (U.K.) Ltd., P.O. Box 19, Carmarthen, SA33 5YL U.K.

ABSTRACT.—The eastern Junggar Basin in northwest China is a potential area of sympatry for breeding Long-legged (Buteo rufinus) and Upland Buzzards (B. hemilasius). However, during a breeding season survey in 2005, the Long-legged Buzzard was the only recorded present in this semidesert region. The minimum breeding density within our survey area was 0.19 breeding pairs/100 km2 and all nests were located either on rock faces or clay cliffs. There was little overlap in the location of Long-legged Buzzard and Golden nest sites, possibly as a result of interspecific competition. We present here information on clutch size (mean 5 3.3 eggs), brood development, and fledging success (0.7 chicks per breeding pair), as well as on the diet during the breeding season. Mammalian prey, especially the great gerbil (Rhombomys opimus), made up most of the diet of Long-legged Buzzards.

KEY WORDS: Long-legged Buzzard; Buteo rufinus; China; diet; reproductive rate.

BIOLOGI´A REPRODUCTIVA Y DIETA DE BUTEO RUFINUS EN EL ESTE DE LA CUENCA DE JUNGGAR DEL NOROESTE DE CHINA

RESUMEN.—El este de la cuenca de Junggar en el noroeste de China es un a´rea de potencial simpatrı´a entre Buteo rufinus y B. hemilasius. Sin embargo, durante un muestreo realizado en la e´poca reproductiva del an˜o 2005, B. rufinus fue la u´nica especie registrada en esta regio´n semidese´rtica. La densidad mı´nima de individuos reproductivos en nuestra a´rea de muestreo fue de 0.19 parejas reproductivas/100 km2 y todos los nidos se encontraron en paredes de rocas o en acantilados de barro. Hubo poca sobreposicio´n en las ubicaciones de los nidos de B. rufinus ydeAquila chrysaetos, probablemente como resultado de competencia

1 Email address: [email protected] 2 Email address: [email protected]

273 274 YI-QUN ET AL.VOL. 42, NO.4

interespecı´fica. En este estudio presentamos informacio´n sobre el taman˜o de la nidada (media 5 3.3 huevos), el desarrollo de la nidada, el e´xito de emplumamiento (0.7 polluelos por pareja reproductiva) y la dieta durante la e´poca reproductiva. Los mamı´feros, especialmente Rhombomys opimus, representaron la mayor parte de la dieta de B. rufinus. [Traduccio´n del equipo editorial]

The Long-legged Buzzard (Buteo rufinus) is a pa- mented ( and Perrins 1998), but incubation is learctic species with a breeding range extending thought to last 28–30 d (Ferguson-Lees and Christie from northern Africa (B. r. cirtensis), southeastern 2001), and the nestling period about 40–46 d Europe and through to north- (Cramp and Simmons 1979, Ferguson-Lees and western China (Ferguson-Lees and Christie 2001). Christie 2001), though Vatev (1987) reported a The nominate subspecies rufinus, the race that oc- nestling period of 49–53 d. To our knowledge, pub- curs in northwestern China, has plumage character- lished data on breeding success of this species are istics similar to those of the Upland Buzzard (Buteo not available. hemilasius), which breeds in southern , Mon- We here describe the breeding biology, including golia, and south to the -Qinghai Plateau, and the diet, of Long-legged Buzzards in semidesert the two taxa are considered by some authors to be habitat on the eastern fringe of the Junggar Basin conspecific (e.g., Meinertzhagen 1954). However, in northwestern China. As this region is a potential recent molecular and morphological analysis has overlap zone for Long-legged and Upland buzzards, indicated that these two taxa are distinct (Krucken- we also describe the characteristics of the nesting hauser et al. 2004), and they are perhaps best treat- . ed as allospecies. Long-legged and Upland buzzards exhibit variable plumage morphs with light, inter- METHODS mediate, and dark variants occurring in both taxa; The Junggar Basin semidesert covers an area of consequently they can be indistinguishable in the over 304 000 km2 and lies between the mountain field (Naoroji and Forsman 2001, Rasmussen and massifs of the Tian Shan and Altay Shan of northern Anderton 2005). Xinjiang in northwestern China. We undertook a The breeding range of the Upland Buzzard has survey of breeding raptors in a 5150-km2 study area reportedly expanded westward in recent years to the on the eastern edge of the Junggar Basin, Xinjiang southern foothills of the Altai range in (Fig. 1). We recorded locations of all large-raptor and along the eastern border with China to the nest sites found in our survey area using a GPS mountains of Tarbagatay and Dzhungarskiy Alatau (Garmin GPS 60, Olathe, KS U.S.A.) Using Google (Gavrilov and Gavrilov 2005, Wassink and Oreel Earth Pro, we then created a convex polygon to 2007). Consequently, with the exception of the Bor- encompass all these nest sites in order to define ohoro and Bogda mountains to the south, the the boundary of our study area. Two teams of three breeding range of the Upland Buzzard potentially people surveyed the region using 4WD vehicles encompasses the Junggar Basin of northwest China. from 17 April to 29 June 2005 (Fig. 2). It was possi- Hybridization between Upland and Long-legged ble to drive across the plains and along dry buzzards has been reported from eastern Kazakh- river valleys in the regions with hills. We surveyed all stan, the evidence for which was based on tarsal the major dry river valleys of the mountainous re- scale patterns and feathering (Pfander and Schmi- gions within our survey area, and all outcrop areas galew 2001). of the desert plains. In addition, surveys on foot The breeding ecology of Long-legged Buzzards were made of hilly regions that could not be ac- has been sparsely recorded (but see Vatev 1987, cessed by vehicle. Although our search area was ex- Shevtsov 2001, Vetrov 2002, Domashevsky 2004, tensive, it was not possible make a complete survey Syzhko 2005). Across its range, the species nests of the entire study area. on crags and low rocks, occasionally on the ground Within our study area, the landscape of the south- on steep slopes or flatter areas, in trees and on hu- ern plain was predominantly flat, poorly vegetated man-made objects such as utility poles. Egg-laying sand and gravel semidesert with outcropping insel- typically occurs from March to May and the typical bergs and mesas with clay cliffs ranging in height clutch size is 3–4 eggs. The lengths of the incuba- from 5–20 m. North of this plain lay a band of ba- tion and nestling periods have not been well docu- saltic hills of friable rocks dissected by numerous DECEMBER 2008 BREEDING AND DIET OF LONG-LEGGED BUZZARD 275

of the landscape rose from 450 m in the desert plain in the southwest of our study area to 2150 m in the Baytik Shan foothills in the northeast. Plumage features, especially tail markings and the degree of tarsal feathering of the attendant birds were noted wherever possible; incubating birds were considered to be females. Each was classified as one of three color morphs: light, intermediate, and dark (Ferguson-Lees and Christie 2001). Nests con- tents were checked by climbing to nests at intervals during the breeding season, to record hatching and fledging date and nest success. We inspected each nest an average of four times (range 3–7 visits) over the nesting period, with an average interval of 12 d between visits. All nests were photographed and the Figure 1. Location of the 5150-km2 survey area (shaded construction materials noted. Nest and vertical cliff polygon) in the eastern Junggar Basin, Xinjiang, China. height were visually estimated to the nearest meter. Egg lengths and widths were measured with cali- dried river beds where vertical cliff faces, ranging in pers, and each egg was weighed with a spring scale. height from 5–25 m, were located. North of this Chicks were photographed at each nest visit and band of hills was a flat gravely plain with few rock measurements were made of mass and tarsus length. outcrops and little vegetation. The northeastern sec- Prey remains were gathered at or near active nests tor of our study area included the foothills of the during nest inspection visits and identified to spe- Baytik Shan bordering , where there were cies level using reference material held in the mu- numerous cliff faces up to 50 m high. The altitude seum at the Xinjiang Institute of Ecology and Geog-

Figure 2. Distribution of nest sites in our survey area: Long-legged Buzzard (N), (&), Saker Falcon (n) and unoccupied nests of buzzards/ (+). The range of basaltic hills running diagonally across the survey area is shaded light grey and the foothills of the Baytik Shan in the northeast is shaded dark grey. 276 YI-QUN ET AL.VOL. 42, NO.4 raphy, Urumqi. Pellets were also collected but a de- mediate phase and two as intermediate phase. tailed analysis of their contents was not undertaken; Light-phase birds had light buff or straw-colored thus, the identified prey remains from pellets were heads, light-colored chests with brown streaks that used to supplement the prey-remains data. We tended to be heavier on the belly and had brown adopted a conservative method for counting prey upper parts. Intermediate birds had similar mark- frequencies; all body parts from each prey and pel- ings but were darker brown (less rufous), especially let collection were assigned to the minimum num- around the head, and more heavily streaked on the ber of possible individuals. underside. Seven females had rufous tails typical of We defined an occupied nest as one with evi- Long-legged Buzzard; one had a white tail with dence that eggs had been laid and birds occupying brown bars. We were able to examine the tarsi of these sites were regarded as breeding pairs. We in- four light-phase females and all were unfeathered cluded nests found after hatch. However, any nests (including the female with the white-and-brown that may have failed (leaving no evidence of egg- barred tail). The plumage type was recorded for laying) prior to discovery were not included in our only six males: one was a light-phase bird, one total of breeding pairs. light-to-intermediate, one intermediate, and two We defined the number of fledged young as the dark phase. Dark-phase birds were entirely dark number of chicks directly observed to have success- brown with white, heavily barred tails. We were able fully fledged or the number of nestlings that were at to observe the tarsi on one dark-phase male: they least 32 d old at the final nest visit. At the first post- were unfeathered and typical for Long-legged Buz- hatch nest visit, chick development was assessed in zard. Thus, at six nests the phenotypic characteris- situ and from photographs by comparison with a 14- tics of both adults were consistent with Long-legged stage sequential series of photographs illustrating the Buzzard and at four additional nests the phenotypic development of a Saker Falcon (Falco cherrug)chick. characteristics of the female were consistent with The ‘‘growth stages’’ from 1 to 5 were then calibrated Long-legged Buzzard. We saw no noticeably larger to an age-in-days class (growth stage 1 5 1–2 d; 2 5 3– buzzards in the survey region to suggest that Upland 5d;35 6–8 d; 4 5 9–11 d and 5 5 12–14 d). To Buzzards were present, breeding, or hybridizing assign an estimated age to each chick, we also consid- with Long-legged Buzzards in the area. ered relative masses within each age class. After the Spatial Distribution and Features of Nests. Most age of a chick was first estimated, its age at subsequent available rock faces had a stick nest present, built visits was determined by adding the number of days either by buzzards or eagles; thus, the distribution elapsed between visits. Based on these assessments, we of nests (Fig. 2) is a good indicator of the geograph- plotted chick mass and tarsus length vs. age and fitted ical dispersion of suitable rock faces. In our survey a regression line to the data using Excel. area we located 10 active nesting territories, giving a minimum breeding density of 0.2 breeding pairs/ RESULTS 100 km2. Most of the active nests were located on We found 10 nests of Long-legged Buzzards with- cliffs of dry river valleys in a band of basaltic hills in the study area, as well as 9 nests of Golden Eagles bisecting the study area, though two were located (Aquila chrysaetos) and 6 of Saker Falcon. We also on clay cliffs of inselbergs and mesas in the desert found 192 additional nest structures likely built by plain to the south of these hills (Fig. 2). The mean eagles or hawks but not occupied at the time of the nearest neighbor distance (NND) between occu- survey. Of the 10 nests of Long-legged Buzzards, pied nest sites was 10.3 km (minimum 5 5.6 km). eight were found when they contained eggs, one The height of nesting cliffs ranged from 8 to was found after the chicks had hatched, and one 24 m, with nests located at heights of 6–18 m above was found on 1 June after young had apparently ground. Of the 10 nests, two faced south to south- died or been taken. In the last case, the nest was west, five faced west to northwest and three north to stained and held prey remains, indicating that northeast. Typically, there were several alternate chicks had been present, but the early date and nests in a breeding range. The outer nest structures absence of fledglings in the area suggested failure; were made mainly of sticks from locally occurring we categorized this as a failed breeding attempt. desert shrubs, such as Chenopodium spp., Ephedra Species Identification. Plumage type was record- spp., Atraphaxis spp., Calligonium spp., Halimoden- ed for all 10 breeding females, six of which were dron spp., and Tamarix spp., with fine twigs and classified as light-phase birds, two as light-to-inter- sprays in the shallow inner cup. The nest cups were DECEMBER 2008 BREEDING AND DIET OF LONG-LEGGED BUZZARD 277 lined with varying amounts of debris (e.g., shreds and bags of polythene, rags, pieces of cloth, cardboard, paper, string, nylon chord, pieces of gazelle skin, fur and wool). Additional items of debris were added to the nests during the incubation and nestling periods. Clutch Size, Laying Date, and Hatching Success. The mean clutch size at nests found with eggs was 3.3 (range 2–4 eggs, N 5 8 clutches). Eggs were off- white, variably marked with red-brown blotches and the mean egg size of eight clutches was 56 3 43 mm (range 53–62 3 42–45 mm). Mean egg mass was 68.2 g (N 5 25 eggs in eight clutches). The first- egg date was known for one clutch found during laying and estimated for six more by back-dating from chicks that could be accurately aged (assum- ing a 31-d incubation period; Harrison and Castell 1998). The mean first-egg date was calculated as 8–9 April (N 5 7 clutches). Of the eight nests found with eggs, four clutches failed to hatch (50% hatching success), despite the fact that the adults continued to incubate well be- yond the estimated 31-d incubation period. Of the four clutches in which eggs hatched, three con- tained one unhatched egg each. Nestling Development and Fledging Success. Shortly after hatching, the chicks weighed ca. 65 g and were covered with fine off-white down; they had greenish-yellow ceres, pale yellow unfeathered tarsi, and dark brown irises. In their second week, the chicks had grayish down. In the third week, the pins of the primary feathers began to emerge. In the Figure 3. Mass increase (A) and tarsus growth (B) of Long- fourth week, the primary feathers started to emerge legged Buzzard nestlings. Data points are not independent, from the pins and the ceres had changed to green as nestlings were measured two or three times each. or blue-grey. In the fifth week, the chicks were well- feathered other than the crown, breast, and belly, Four of five broods exhibited asymmetric chick the covert feathers being rufous-brown with dark development, primarily as a result of incubation be- centers; ceres were greenish and the irises had gun before clutch completion. In one case, the de- changed color from dark brown to green-brown. gree of developmental asymmetry diminished as In the sixth week, only a little down remained chicks aged, but in two nests it resulted in brood around the forehead, tarsi were still bare and yellow reduction when the smallest chick in each nest died with large transverse scales on the anterior surface, in the third week after hatching. At one of these and the irises were olive green. The chicks left the nests, two additional chicks of the initial brood of nest when they were 40–45 d old. four disappeared during the fifth week. At the other We measured tarsus length and body mass of 13 nest exhibiting brood reduction, the two remaining nestlings from five different nests. Biometric data chicks died in the fourth or fifth week after hatch- was obtained for each chick two or three times dur- ing. Overall, four of the 10 nests fledged at least one ing the nestling period; however, we have treated chick, with a mean fledged brood of 0.7 chicks per repeat measurements of the same chicks as inde- breeding pair (N 5 10) and 1.8 chicks per successful pendent samples because of the small sample size. nest (N 5 4) where a successful nest was defined as We recorded a linear increase in mass from 4–39 d one that fledged at least one young. of age (Fig. 3A), but tarsus growth slowed after ca. Diet. Prey remains and pellets yielded 50 prey 28 d of age (Fig. 3B). items, comprising 13 species of , birds 278 YI-QUN ET AL.VOL. 42, NO.4

Table 1. Frequency and percentage of prey items in the et al. 1999, Gombobaatar et al. 2003, A. Dixon un- diet of breeding Long-legged Buzzard in the eastern publ. data). Dark-phase individuals are probably in- Junggar Basin, northwestern China. separable with certainty in the field; however, typical Upland Buzzards tend to be noticeably larger than

PREY TAXA N (%) Long-legged Buzzards (Naoroji and Forsman 2001). The species we found breeding in the semidesert Mammals habitats of the eastern Junggar Basin was consistent Rhombomys opimus 24 (48) with Long-legged Buzzard. Gazella subgutturosa 3 (6) Though there was some degree of overlap, the Lepus capensis 3 (6) egg sizes we found in our study were on average Birds smaller than those reported for Upland Buzzards Apus apus 1 (2) in Dementiev et al. (1966), further supporting our Podoces hendersoni 1 (2) conclusion that the species breeding in the eastern Rhodopechys mongolicus 3 (6) Junggar Basin was Long-legged Buzzard. None of Chlamydotis undulata 1 (2) the chicks had feathered tarsi, whereas the tarsi of Alectoris chukar 1 (2) Columba rupestris 1 (2) Upland Buzzard chicks are normally covered for at Columba livia (dom.) 1 (2) least two-thirds of their length with down (then feathers); furthermore, the down of Upland Buz- Reptiles zard nestlings is typically darker grey, the irises of Eryx tataricus 9 (18) feathered chicks are a lighter green and the ceres Teratoscincus przewalskii 1 (2) become more yellow as nestlings age rather than Laudakia stoliczkana 1 (2) greener (A. Dixon unpubl. data). However, differ- Total 50 (100) ences in the color development of nestling ceres may be related to diet rather than species-related and reptiles (Table 1). The breeding season diet of differences (e.g., Negro et al. 1998). The large, Long-legged Buzzards was dominated by mammals transverse scales on the anterior surface of the tarsi (60% of prey items), with the remainder birds conformed with the description given for Long-leg- (18%) and reptiles (22%). ged Buzzards by Dementiev et al. (1966). According The great gerbil (Rhombomys opimus) was the most to Pfander and Schmigalew (2001) the presence of common prey species (Table 1). The goitered ga- large transverse scales on the tarsus can be used to zelles (Gazella subgutturosa) were almost certainly distinguish Long-legged from Upland buzzards; scavenged from the many carcasses of dead however, Upland Buzzards breeding in central Mon- in our study area and it is possible that these pieces golia can also exhibit a similar pattern (A. Dixon of fur-covered skin were picked up as nest lining unpub. data). material rather than food. Bird feather remains In 2005, we also found breeding buteonine hawks found at nest sites included Common Swift (Apus that were also consistent with Long-legged Buzzards apus), a migrant species in the study area. Other in the southern foothills of the Chinese Altay Shan than a homing pigeon (Columba livia dom.), all oth- and on the northern and western edge of the Jung- er bird species were residents, including recently gar Basin. We saw no large buzzards in northern fledged chicks of Mongolian (Rhodopechys Xinjiang that had phenotypic characteristics that mongolicus) and nestlings of Mongolian Ground-Jay were inconsistent with Long-legged Buzzard. This (Podoces hendersoni). suggests that the western extension of the breeding range of Upland Buzzards into eastern Kazakhstan, DISCUSSION where the species is now a common breeder in the From our experience identifying Long-legged Zaysan region and Tarbagatay hills (Gavrilov and Buzzards in the Balkans and Turkey (AD and DR) Gavrilov 2005, Wassink and Oreel 2007), has prob- and Upland Buzzards in central and northern Mon- ably proceeded along the Altai mountain chain and golia (AD) and Qinghai (AD and MM), we conclude not extended into the semidesert region of north- that the species are not easily separable in the field, ern Xinjiang. The easternmost breeding limit of as light-morph Upland Buzzards can frequently ex- Long-legged Buzzard and the westernmost breeding hibit rufous plumage tones including pale rufous limit of Upland Buzzard in western Mongolia are tails and sometimes have unfeathered tarsi (Ellis not clear. Maps in Ferguson-Lees and Christie DECEMBER 2008 BREEDING AND DIET OF LONG-LEGGED BUZZARD 279

(2001) indicate that Long-legged and Upland buz- Great gerbils, the main prey of Long-legged Buz- zards have allopatric breeding ranges and, errone- zards in the eastern Junggar Basin, are mainly active ously, that neither species breeds in the eastern during the day. However, the populations of this Junggar Basin, though the distribution map in De- social, burrowing species can exhibit marked fluctu- mentiev et al. (1966) indicates that the breeding ations, and in years of peak populations, the gerbils range of Long-legged Buzzard may extend as far can significantly damage desert vegetation and har- east as central Mongolia. bor plague (Davis et al. 2004). Consequently, the The distribution of Long-legged Buzzard nests re- species is subject to stringent pest control measures flected the relative availability of potential nesting (Deng and Wang 1984) in many arid regions of sites in our study area. Other than vertical clay and western China, including within our study area. rock faces there were few other potential nesting During the study period, great gerbils were not pres- sites for Long-legged Buzzards in our study area, ent at high densities in the study area, based on the although outside this area we also found nests built paucity of active burrows and live animals encoun- on a utility pole and in tall desert shrubs. The two tered during our field surveys (D. Ragyov unpubl. nests with southerly aspects were both on clay cliffs data). The effect of great gerbil control on predator in the desert plain, but both were in sheltered po- populations in the region is not known, but else- sitions to shade them from direct sunlight. A lack of where Buteo populations are known to respond to suitable nesting sites could not explain the absence changes in density of their favored mammalian prey of the species in the western part of the basaltic hills (e.g., Rough-legged Buzzard [B. lagopus] in Potapov and in the higher hills to the northeast of our study 1997, Upland Buzzard in Gombobaatar et al. 2003). area. In these regions, interspecific competition with Golden Eagles may be responsible for the ab- ACKNOWLEDGMENTS sence of breeding Long-legged Buzzards, as the nest This study was funded by the Environment Agency of site distribution of these two species were spatially Abu Dhabi (EAD) and National Natural Science Founda- separated (Fig. 2). Golden Eagles have been shown tion of China (NSFC; code:30470262). The comments of three anonymous referees improved an earlier version of to influence the location of the breeding sites of this manuscript. We thank Nicholas C. Fox, Mei Yu, Tian other raptors in Scotland (Fielding et al. 2003). Leilei, and Chen Ying for their assistance. Items of debris are a common feature in the nests of Long-legged Buzzard, presumably because soft LITERATURE CITED nest-lining material is not readily available in arid CRAMP,S.AND K.E.L. SIMMONS [EDS.]. 1979. The birds of habitats. We recorded no instances of nestling mor- the western palearctic, Vol. 2. Oxford University Press, tality caused by the incorporation of debris in nests Oxford, U.K. (e.g., Ellis and Lish 1999). However, complete fail- DAVIS, S., M. BEGON,L.DE BRUYN, V.S. AGEYEV, N.L. KLAS- ure of some clutches to hatch was probably caused SOVSKIY, S.B. POLE,H.VILJUGREIN, N.C. STENSETH, AND H. LEIRS. 2004. Predictive thresholds for plague in Ka- by the materials used to line the nests. On some nest zakhstan. Science 304:736–738. visits we found large pieces of cloth, cardboard, and DENG,Z.AND C.-X. WANG. 1984. control in China: polyethylene bags covering the eggs and preventing proceedings of the 11th Vertebrate Pest Conference. contact with the brood patch when an adult bird University of Nebraska, Lincoln, NE U.S.A. was incubating. Adult birds appeared to make no DEMENTIEV, G.P., N.A. GLADKOV, E.S. PTUSHENKO, E.P. SPAN- attempt to move such items and simply sat on top GENBERG, AND A.M. SUDILOVSKAYA.1966.Birdsofthe of any material that covered their eggs. Soviet Union, Vol. 1. The Smithsonian Institution, Na- Brood reduction was noted at two nests, and in tional Science Foundation, and the Israel Program for both cases mortality of the smallest chick occurred Scientific Translations, Jerusalem, Israel. in the third week after hatching. Brood reduction is DOMASHEVSKY, S.V. 2004. Materials on ecology of buzzards often regarded as an adaptation to environmental in northern Ukraine. Berkut 13:230–243. (In Russian.) ELLIS,D.AND J.W. LISH. 1999. Trash-caused mortality in shortages of food, but it can also be a direct conse- Mongolian raptors. Ambio 28:536–537. quence of hatching sequence in which the youngest ———,N.WOFFINDEN,P.L.WHITLOCK, AND P. TSENGEG. and smallest chicks are unable to compete with larg- 1999. Pronounced variation in tarsal and foot feather- er siblings for food even when it is plentiful (Sten- ing in the Upland Buzzard (Buteo hemilasius) in Mon- ning 1996). There were uneaten prey remains at golia. J. Raptor Res. 33:323–326. nests during most of our visits, suggesting that food FERGUSON-LEES,J.AND D.A. CHRISTIE. 2001. Raptors of the was not in short supply. world. Christopher Helm, London, U.K. 280 YI-QUN ET AL.VOL. 42, NO.4

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