Strix aluco Tawny Owl

BWP Update Vol. 3 No. 1, 2001, 000–000

Strix aluco Tawny Owl D. Bosuil F. Chouette hulotte G. Waldkauz I. Allocco R. Obyknovennaq neqsyt_ S. Ca´rabo comu´n S. Kattuggla Strix aluco Linnaeus, 1758 Polytypic. Nominate aluco Linnaeus, 1758, Europe from Belgium, Netherlands, German Rheinland, Vosges, Jura, and Alps east to c. 35°E in central European Russia, Ukraine, and Crimea, south to Italy (including Sicily) and Balkans; siberiae Dementiev, 1933, Ural mountains and western Siberia, intergrading with nominate aluco between 35 and 55°E in central European USSR; sylvatica Shaw, 1809, Britain, France (except extreme east), Iberia, western and central Turkey, Levant, and (probably this race) Greece (contrary to previous statement no proof of this race being present in southern Italy); mauritanica Witherby, 1905, north-west Africa; willkonskii Menzbier, 1896, Caucasus, Transcaucasia, north-east Turkey, and north-west Iran east along southern Caspian to western Kopet Dag (Turkmeniya); sanctinicolai Zarudny, 1905, Zagros mountains in western Iran, intergrading with sylvatica in northern Iraq. Extralimital: five races in central and eastern Asia from eastern Afghanistan and Tien Shan through Himalayas to China, Korea, and Taiwan.

Paolo Galeotti_ | Dipartimento di Biologia Animale, Universita` di Pavia, Italy Summary. Most sections are updated with the results of recent studies (mostly 1985–99), including much information on population size, food, behaviour, voice, and measurements. Three new sections on Survival, Parasites and diseases, and Conservation have been added. Field characters. See BWP Vol. 4, p. 526 Habitat. (Updates BWP Vol. 4, pp. 526–7) Strictly arboreal. In breeding range mainly complementary to Ural Owl Strix uralensis but in oceanic as well as continental upper and lower middle latitudes, from fringe of boreal through temperate and steppe to Mediterranean and related montane zones, avoiding unduly windswept, rainy, frosty, or arid climates and large unbroken forests, wetlands, naked rocky terrain, and treeless plains. Mainly in lowlands, but in Scotland nests up to c. 550 m (Baxter and Rintoul 1953) and in Alps to c. 1600 m, exceptionally to 1900 m in western–central Alps (Schifferli et al. 1980, Cucco and Beltramino 1988). Ranges up to 2350 m in Turkey. In Turkestan (Russia), in broadleaf mountain forests up to similar altitude, nesting in rock clefts (Dementiev and Gladkov 1951a). In Britain, mostly in deciduous or mixed woodlands, tree-dotted farmland, parks, large gardens, and churchyards; often in built-up areas, even inner London. Not uncommon in mature coniferous plantations and exceptionally in open country. In Italy, all kind of tree habitats including olive and poplar groves, _

riparian woods, coastal pinewoods of Pinus domestica, and Mediterranean scrub; occurs also in rocky areas (Penteriani and Pinchera 1988), mixed farmland, and built-up areas, even inner Rome and Milan (Galeotti 1990, 1993, Galeotti and Sacchi 1996). In Russia, rare in taiga zone, where occurs in coniferous forests; abundant in broadleaf forests and parks, orchards, and cultivated lands in central parts of range, nesting chiefly in hollow trees, especially oak Quercus, lime Tilia and birch Betula, up to c. 10 m above ground (Dementiev and Gladkov 1951a). Requires richly structured habitat with plenty of look-out posts for hunting in sparse woodland, clearings, avenues, cemeteries, hedges, and gardens, especially among mature trees and with some preference for access to water. In urban areas strongly prefers monuments, parks, and avenues (Galeotti 1990); in rural areas nests in deciduous woodlots but hunts over open farmland along network habitats or near buildings (Cesaris 1988, Hardy 1992, Redpath 1995a). In upland spruce forest selects older stages and broadleaved areas (Gill 1992). In southern Asia ranges up to 4250 m in Himalayas and occupies oak, pine, and fir forest, sometimes living above

Correspondence: Dipartimento di Biologia Animale, Universita` di Pavia, Piazza Botta 9, I-27100 Pavia, Italy. E-mail: [email protected]

 Oxford University Press 2001

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Fig. 1. Strix aluco Tawny Owl distribution within the west Palearctic: brown = resident breeding. Reprinted unamended from Concise Edition of BWP.

tree-line and nesting on ground under overhanging rock by streams or in holes in cliffs in ravine (Bates and Lowther 1952, Ali and Ripley 1969). Adaptability to close proximity of man shown in various parts of range. Distribution. (Updates BWP Vol. 4, p. 527) See Fig. 1. Colonized Finland in late 19th century; recent range expansion in Belgium, Netherlands, Norway, Italy, and Ukraine; decrease reported in Denmark, Moldova, and Albania. B. Bred Isle of Man 1961 (Sharrock 1976), otherwise absent from there and Isle of Wight. Recent increase in range as a result of upland area reafforestation (Petty and Saurola 1997). N. In 19th century, restricted to east, south, and centre; from c. 1925 colonized much of remainder of country and still spreading in north and coastal dunes. N. Bred near 66°N 1969 (Haftorn 1971). F. First proved breeding 1878; range expanded in 1920s and especially 1930s (Merikallio 1958). I. Widespread from north to south including Sicily; absent from most of Apulia, all Sardinia, and other islands; from early 1960s colonized

many towns and cities. G. May breed Samos, Rhodes, and Kos but no proof. Reported to be spreading north. R. Spreading north in southern Kareliya in 1950s (Neufeldt 1958). C. No adequately documented records of breeding (??????? 1966, Stewart and Christensen 1971) or even of occurrence. S. Probably regular breeder in north-west, questionable Damascus area; recorded further inland at Deir ez-Zor, March 1979, and Palmyra Oasis, October 1988. Accidental. Balearic Islands, Canary Islands. Beyond west Palearctic, breeds discontinuously east to China and Korea, south to northern Iran and Himalayas. Population. (Updates BWP Vol. 4, pp. 527–8) Well known except for North Africa. Generally common and increasing throughout range. European population in mid-1990s estimated at 400 000–800 000 pairs (Petty and Saurola 1997) of which some 50% occur in Russia, Germany, France, Poland, and Italy. Decline in Denmark, Albania, and Moldova. B. Declined 19th century due to human persecution (Alexander and Lack 1944). Increased over

Strix aluco 3 much of England, Wales, and southern Scotland from c. 1900 to 1930 (until c. 1950 some areas); apparently stable since (Parslow 1973) and then estimated 10 000–100 000 pairs (Parslow 1973) or 50 000–100 000 pairs (Sharrock 1976). These figures probably over-optimistic since recent estimates gave >20 000 pairs in 1988–91. Recent increase in density as a result of upland area re-afforestation (Petty and Saurola 1997). F. 10 000–100 000 pairs in early 1970s (Yeatman 1976). Increased to 50 000–150 000 pairs. B. c. 3000 pairs in early 1970s; 5000–7000 pairs 1989–91. L. c. 800 pairs in early 1970s (Lippens and Wille 1972); increased to 1000–1200 pairs. N. Estimated 2500–3000 pairs 1977 (Teixeira 1979); increased to 4000–5500 pairs 1979–85 mainly because of range extension but formerly aided by afforestation. G. Estimated >20 000 pairs in early 1980s (Rheinwald 1982); c. 94 000 pairs in mid-1980s; c. 18 000–25 000 pairs in east in early 1980s (Mikkola 1983). D. 4000–5000 pairs in 1980s; stable or decreasing. N. 10 000–30 000 pairs 1970–90. S. c. 10 000 pairs (Ulfstrand and Ho¨gstedt 1976); decreased in 1960s (probably because of pesticides), but has recovered since; 10 000–20 000 pairs in late 1980s. F. Estimated 2000 pairs; increased to 1500–2500 pairs in late 1980s (Merikallio 1958). E. Rare in 19th century, but upward trend until 1960s, since when marked decline. c. 500 pairs in early 1970s (Randla 1976), 1000–1200 pairs in 1991. L. 15 000–25 000 pairs in 1980s. L. Over 1500 pairs. P. c. 70 000 pairs. Increase noted in centres of large towns in 1970s. C R. 6000–9000 pairs 1985–9. S. 2500–3000 pairs 1973–94. H. 2000–2500 pairs 1979–93. A. Common and widespread; data insufficient, but probably increasing. S. 5000– 6000 pairs 1985–93. S. Over 50 000 pairs 1975. Recently 45 000–61 000 pairs. P. 1000–10 000 pairs 1978–84. Algarve: uncommon. I. Very common and rapidly increasing from late 1970s, when legal shooting ended; previous figures (5000–10 000 pairs) underestimates; recent figures (1990–9) suggest 45 000–70 000 pairs, locally very abundant. A. Rare. 2000–4000 pairs in 1962. G. Previously thought uncommon, now 10 000–20 000 pairs. F Y. No data. C. 20 000–25 000 pairs. S. 1000–5000 pairs. B. 500–5000 pairs. R. 3000–9000 pairs 1986–92. R. Common in central areas; rare in taiga, Crimea, north-west Caucasus, and Talysh plain (Dementiev and Gladkov 1951). 10 000–100 000 pairs 1975–90. B. 8500–12 000 pairs in 1990. U. 6000–7000 pairs in 1988. M. 650–800 pairs in 1989. T. 5000–20 000

pairs. S. 30–50 pairs in early 1980s. I. C. 250 pairs in 1980s. T. Fairly common. A. Locally common in 1970s. M. Locally common. Survival. (Updates BWP Vol. 4, p. 528) Very few young die during period of dependence in parents’ territory, but often starve quickly after being driven out (Southern 1970, Hirons et al. 1979), thus young mortality heavy in first autumn (40–50–70%; Hirons 1985). However, in Scotland, mortality of radiotagged juveniles before dispersal was c. 92% (Petty and Thirgood 1989) and 61% in Norway, due to starvation and predation by red fox Vulpes vulpes; also, significant negative effect of fledgling mass on probability of survival until dispersal (Overskaug et al. 1999). Sweden: mortality in first year of life 71.2%, in second year 44.3%, in third year 47.6% (Olsson 1958). Switzerland: mortality in first year of life 49.4%, in second and third years 24.5% (Glutz von Blotzheim and Bauer 1980). England: mortality in first year of life 52.6%, in second year 22.2%, in third year 31.8% (small sample, n = 19) (Southern 1970). West Germany: mortality in first year of life 48%. Belgium: mortality in first year of life 58%. (Delme´e et al. 1978.) For life-table see Southern (1970), for seasonal mortality see Glue (1973), and for deaths of juveniles from starvation, see Southern (1970) and Hirons et al. (1979). Oldest ringed bird in the wild: a female of 21 years 11 months, still living and successfully breeding in Switzerland in 1993 (Jeanmonod 1993). In captivity one owl reached over 27 years (Glutz von Blotzheim and Bauer 1980). Owls survive less well without territories. At Wytham, annual mortality of territorial owners c. 15% (Hirons 1985), but higher in severe winters (Southern 1970) and average tenure of territories estimated 5 years. At Pavia, over 3 years, 1995–7, turn-over of territorial males 18.7% (3 of 16 males); however, of 23 males recorded in 1986–7 (Galeotti and Pavan 1991), only 1 still present in its territory (in city centre) 10 years later. In Czechia, mortality of adult females 22% (Zva´ral 1992b). Conservation. (New section) Not globally threatened: CITES II, SPEC 4, Threat status Secure. Legally protected in all European countries. Population increase observed in most of range due to protection, re-afforestation and ability to adapt to manmodified habitats. Mortality due to collision with vehicles and wires frequent in Britain (Glue 1973), but apparently much lower than in other owl species, e.g. in Italy, of 800 owls found dead on road (1990–2000), Tawny Owl only 4.5% compared with 41% Little Owl Athene noctua, 39% Barn Owl Tyto alba and 13.5% Long-eared Owl Asio otus. In Westphalia (Germany), of 95 owls recovered on road or railway, Tawny Owl only 7.4%, while Barn

4 Tawny Owl Owl 53%, Little Owl 28.4% and Long-Eared Owl 11.6% (Illner 1992). Contamination reported with chlorinated hydrocarbons, mercury compounds, and other heavy metals used in agriculture and forestry, but extent of damage not known (Conrad 1977); lower serum CbE activity may indicate higher susceptibility to organophosphates and carbamate pesticides than herbivorous birds (Thompson et al. 1991). First-generation rodenticides, Warfarina anticoagulent, no serious threat to Tawny Owl (Townsend et al. 1981), but new rodenticides (difenacoum, bromadiolone, brodifacoum, floucomafen) fatal to captive birds (Anon. 1982). Movements. See BWP Vol. 4, pp. 528–9. Food and feeding. (Updates BWP Vol. 4, pp. 529–36) Wider range of prey than other medium-sized Strigiformes of west Palearctic. In woodland, mainly small rodents; also larger mammals (up to size of young rabbit Oryctolagus cuniculus), birds, amphibians, shrews (Soricidae), earthworms (Lumbricidae), and beetles (Coleoptera). In towns, largely birds; also small rodents and other prey as available. Normally hunts almost wholly between dusk and dawn; most activity from dusk to 22.00 hours, followed by a more variable pattern up until dawn (Redpath 1995a). Changes in daylength affect length of activity, birds leaving roost progressively earlier in relation to sunset in summer (Hardy 1992); hunting in full daylight (even in the open) quite common when young in nest (e.g. Brown 1936, Hardy 1977, Hirons 1977, Hardy 1992; see final paragraph in BWP Vol. 4). Most prey evidently located by ear. For head movements in this and other Strigidae and their possible use in localization of prey, see Lindblad (1962). Much hunting done by waiting on perch and gliding or dropping on to prey; on impact, will extend wings to cover victim or strike it (Meinertzhagen 1959). While hunting from perch, bird turns body occasionally and makes frequent short flights (at least one every 5 min), returning to same perch or another. Mean perch time 8.0 ± 0.9 min in woodland versus 14.3 ± 1.3 min in farmland. Interperch flights were twice as long in fragmented landscape as in continuous woodland: male owls in fragmented woods flew 40% further per hour than males in continuous woodland (Redpath 1995a); also, perch time positively correlated with small mammal availability in the ‘core’ woods of birds, but no difference in perch times between sexes (Redpath 1995a). Where habitat includes open ground, often also hunts in flight, 2–3 m high between bushes in marsh or grassland; flight then slow and frequently interrupted with glides; after flying in zigzag pattern over area c. 30 × 50 m, flies 100–200 m before resuming zigzag search (Nilsson 1978); may hover (Ruthke 1935). Of two birds radiotracked for 54

and 33 h, late February–early May, southern Sweden, one spent 27% of time sitting still, 40% hunting from perch, and 34% hunting in flight; other bird, 49, 9, and 42% (Nilsson 1978). However, 24 birds (10 females, 14 males) regularly radiotracked in mixed farmland and woodland, October–April, Cambridgeshire, UK, spent