British Birds VOLUME 73 NUMBER4 APRIL 1980

Breeding biology of the Little Owl

David Glue and Derick Scott

A century has elapsed since the first of the Little Owls introduced into Britain bred successfully, yet comparatively little has been published about the species' breeding biology

his paper combines the findings of intensive local studies of Little Owls TAthene noctua at 14 nests by DG in Hampshire during 1962-70, and at a further 22 nests by DS in Lincolnshire and North Nottinghamshire during 1950-77, with information from 549 cards submitted to the BTO's Nest Records Scheme during 1939-75.

Distribution of records The Little Owl is not indigenous to Britain, although it can be found across Europe north to Denmark. Introductions to Yorkshire in 1842 failed, and to Kent during 1874-80 met with only partial success. Releases with lasting consequences were in Northamptonshire during 1888-90, and in Yorkshire,

[Bril. Birds 73: 167-180, April 1980] 167 168 Breeding biology of the Little Owl Hampshire and Hertfordshire in the 1890s (Witherby & Ticehurst 1908). From these and later centres, there followed a population explosion, mainly during 1910-30 (documented by Witherby et al. 1940). Subsequently, the range expanded more slowly, though with local decreases, until today the Little Owl is accepted as a characteristic member of the avifauna of rural southern Britain, having bred at some time in all the historic English and Welsh counties. During 1968-72, an extensive effort was made to confirm breeding in as many 10-km squares as possible for The Atlas (Sharrock 1976). The results (fig. 1) indicate that the Little Owl now breeds widely over most of England and much of Wales, being absent chiefly from the higher ground of northern England, the southwest peninsula, and parts of central and west Wales. In Scotland, where breeding was first proved in Berwickshire in 1958, The Atlas shows a small population still confined to the lowlands in the south­ east, with breeding confirmed only as far north as Midlothian. There have been few confirmed sightings of Little Owls in Ireland, and no attempt at nesting. The 549 nest records under review come from 41 counties which cover most of the breeding range as shown by The Atlas (see table 1). Ten counties supplied 20 or more records, ranging from Kent and Essex in the southeast, and Devon and Somerset in the southwest, to Lancashire and Yorkshire in the north. Warwickshire provided the highest county total of 112 records, the bulk resulting from a survey, by D. R. Cooper, J. Hardman and R.J. Juckes during 1968-71, of the avian predators on 2,320 ha of mixed farmland in the southwest of the county. The chronological sequence of nest records indicates a marked increase in recording effort in recent years caused by a greater interest in the smaller birds of prey and the stimulus of Atlas fieldwork: 1936-45, 3; 1946-55, 80; 1956-65, 105; 1966-75,361.

Breeding habitat The Little Owl has successfully occupied a wide range of habitats in Britain (table 2), but breeds chiefly on agricultural land, particularly where there is plenty of timber, whether in the form of well-established hedgerows, copses,

Table 1. Regional distribution of BTO nest record cards of Little Owls Athene noctua, 1939-75 Regions are secondary divisions of the Euring code Region No. of counties No. of nests % of total nests

Southwest England 7 107 19.5 Southeast England 10 157 28.6 Eastern England 5 32 5.8 Central England 9 147 26.8 Northern England 6 89 16.2 Wales 4 17 3.1 Ireland 0 0 0 Scotland 0 0 0

41 549 100.0 Breeding biology of the Little Owl 169

Figure 1. Breeding distribution of the Little Owl Athene noctua in Britain and Ireland during 1968-72 (reproduced, by permission, from The Atlas ofBreeding Birds in Britain and Ireland) .The smallest dots indicate possible breeding, medium dots probable, and largest dots confirmed breeding, within each 10-km square orchards or woods. On a local scale, the population appears to be very unevenly distributed across the current breeding range—including the prime habitat, farmland—and merits a detailed study to determine the limiting factors. Within Hampshire, for instance, 'clusters' of pairs at points along river valleys suggest local preferences for damp pasture, 170 Breeding biology of the Little Owl

Table 2. Breeding habitats of 486 Little Owls Athene noctua in England and Wales, 1939-75

Broad habitat type No. of nests %

FARMLAND 361 (74.3%) Lowland pasture 125 25.7 Mixed farmland 122 25.1 Arable farmland 63 13.0 Water meadows/wet pasture 33 6.8 Hill pasture 18 3.7 WOODLAND 59 (12.1%) Extensive orchard 37 7.6 Parkland 13 2.7 Open deciduous woodland 9 1.8 GARDENS AND HABITATIONS 51 (10.5% ) Sewage-farm 14 2.9 Rural garden 9 1.9 Quarry, gravel-pit, colliery 6 1.2 Golf course 5 1.0 Miscellaneous* 17 3.6 HEATH AND MOOR 6 (1.2%) Heather-grass moor 3 0.6 Lowland heam and common 3 0.6 WETLANDS 6(1.2%) Freshwater marsh, carr 6 1.2 COASTAL 3 (0.6%) Rocky headland, coastal cliff 2 0.4 Offshore island 1 0.2

TOTALS 486 100.0 *Miscellaneous includes cemetery 3, industrial waste ground 3, allotments 2, suburban garden 2, disused airfield 2, castle 2, hospital grounds I, reservoir 1, disused railway 1 especially water-meadows, although, elsewhere, open country bordering woodland, tree-dotted parkland, wooded hamlets and areas of chalk down- land support more pairs than surrounding terrain (DG). It is not unusual for pairs to breed in close proximity. In north Nottinghamshire in 1975, two nests in willows Salix were just 240 m apart; another two pairs nesting in a haystack and an ash Fraxinus excelsior were 320 m apart in 1977-78. Most Little Owls become confiding during the breeding season and, with caution, allow close observation, although as a rule the species will not tolerate blatant and persistent disturbance at the roost or the nest. This probably accounts for the owl's general affinity for open country, private land and areas with limited access to the public, breeding so often as it does on farmland and parkland, at sites such as sewage-farms and golf courses, and often in the vicinity of ruins, abandoned settlements and isolated buildings. Those birds which occupy residential or industrial land do so where suitable ground is available nearby, usually in the form of playing fields, cemeteries or waste ground. Within its breeding range in Britain, the Little Owl avoids many upland areas, 85% of the nests studied being below 400 feet (122 m) (table 3). Treeless areas such as sand-dunes, reclaimed saltings, sea cliffs and islands are sometimes occupied; so are upland pasture and improved moorland, Breeding biology of the Little Owl 171 Table 3. Altitudinal distribution of 355 nests of Little Owls Athene noctua in England and Wales, 1939-75 Altitude in feet (metres) No. of nests %

0-200 (0-61) 214 60.3 201-400 (61-122) 88 24.8 401-600 (122-183) 32 9.0 601-800 (183-244) 17 4.8 801-1,000 (244-305) 3 0.8 1,001-1,250 (305-381) 1 0.3

TOTALS 355 100.0 the highest nests being found at 1,000 feet (305 m) in the Rossendale Valley, Lancashire, and 1,050 feet (320 m) near Keighley, Yorkshire. Nesting site The most frequently used nesting place in lowland Britain is a hole in a deciduous tree, at an average height above the ground of only 10 feet (3 m) (table 4); in fact, 92% of the 526 nests examined in detail were in trees. Hollow oaks Quercus (24%) and ash (23%) were those most regularly occupied, diough the large number of fruit trees (18%) and willows (15%) used emphasises a strong local association with orchards and pollarded timber. Spherical holes and vertical cracks leading to chambers in the main trunk (37%) and lateral branches (23%) of mature trees with decaying heart- wood are die chief sites used (267 nesting trees examined, table 5). Certain sites in trees are used more often by the Little Owl than by any of the other three regular tree-nesting owls: in particular, holes in the bole, narrow side

Table 4. Tree sites of 482 nests of Little Owls Athene noctua in England and Wales, 1939-75 Under 'HEIGHT OF NEST' a, b, c, d and e correspond respectively to: 1-5 feet (0.3-1.5 m), 6-10 (1.8-3.0), 11-20 (3.4-6.1), 21-30 (6.4-9.1) and 31-40 (9.4-12.2)

HEIGHT OF NEST Average nest height No. of nests a b c d e in feet (m)

Oak Quercus 105 15 39 45 4 2 11(3.4) Ash Fmxinus excelsior 100 12 42 43 3 0 11(3.4) Fruit trees* 75 29 38 8 0 0 6(1.8) Willow Sttlix 63 19 35 9 0 0 7(2.1) Elm Ulmus 55 5 19 30 1 0 12(3.7) Beech Fagus sjilvatka 10 1 2 5 2 0 13 (4.0) Other trees** 20 7 5 7 1 0 10 (3.0) Unidentified trees 54 15 20 17 2 0 9(2.7)

TOTALS 482 103 200 164 13 2 10(3.0)

•Fruit trees include apple Malm domtstka (63), pear Pyruspyraskr (7), cherry Pnams avium (4) and plum Pnams domestics (1). **Other trees: field maple Actr campesirt (4), hawthorn Crataegus memgyaa (3), horse-chestnut Atsadwhippocastamm (2), poplar Populus (2), alder Ahwgiutimsa (i), sycamore Actrpseudoptatams (I), holly Ilex awptifolium (I), haze! Cmylw avellaim (I), hornbeam Carpuw benUus {1), walnutJ*J/«JW rtgkt (1), elder Samhmm! nigra (1),lime Tilie mrdata (l), sv/ett chestnut Castmua sativa (1). (A hollow, dead Scots pine Pimis syimtris occupied in north Lincolnshire in 1969 was the only coniferous tree recorded.) 172 Breeding biology oj the Little Owl

Table 5. Position of nest in 267 trees occupied by Little Owls Athene noctua in England and Wales, 1939-75

Position of nest No. of nests %

Main trunk: cleft, crack or cavity 98 36.7 Hollow branch; split or cavity 61 22.9 Pollarded tree: cavity or branch cluster 38 14.2 Snapped-ofF trunk or decaying stump; vertical hollow 24 9.0 Tree bole or among roots 23 8.6 Wooden nestbox 14 5.2 Fallen trunk or branch: crack or cavity 7 2.6 Old nest of Magpie Pica pica or drey of grey squirrel Sciurus carotinensis 2 0.8

TOTALS 267 100.0 limbs, fallen boughs, spaces between the washed out roots of standing trees, and enclaves formed by clusters of branches in pollarded trees. The Little Owl often nests and hunts over much the same ground as the Barn Owl Tyto alba, even sharing the same nest tree on occasions and breeding successfully as little as 2 m apart. The former, however, is better equipped to exploit many more lower, smaller cracks and cavities in smaller trees (table 4): apple Malus domestica, pear Pyrus pyraster, field maple Acer campestre and hawthorn Crataegus monogyna, with hollow-trunk and branch diameters as little as 8 inches (20 cm). On occasions, cavities with an extremely narrow entrance are used, sometimes too small to allow access by an adult human arm. This habit, coupled with a preference for deep, winding cavities, can make observation of the breeding cycle very difficult. Ten nest chambers measured ranged from 4 to 18 inches (10-50 cm) in width, averaging 8 inches (20 cm), though a further two nest scrapes were situated in one of several small side pockets to chambers 36 inches (90 cm) in width. Most chambers were reached by narrow passages usually 18-48 inches (0.5-1.3 m) long, and averaging 32 inches (80 cm) for the 74 measured, though a few were considerably longer, with two or more exits. The Little Owl will use nest sites below ground level and in buildings, particularly where diere is a shortage of suitable trees. Six nests were in rock clefts or burrows of rabbits Oryctolagus cuniculus in coastal cliffs (2), laneside banks (2), an inland crag (1) and a quarry face (1). On Bardsey Island in Gwynedd, the few resident pairs nest in rabbit holes and in dry-stone walls. Elsewhere, Little Owls have nested in gravel- and sand-pit tunnels (Hamp­ shire) and inside stacked peat on moorland (South Yorkshire). Hollow trees may be shared by other species, a point well illustrated by a decaying ash tree in north Nottinghamshire in 1968, where three species bred successfully: Kestrels Falco tinnunculus occupied a hole near the tree crown (10 m), Little Owls a hole in the side of the trunk (4 m), and Wrens Troglodytes troglodytes ivy Hedera Mix near the tree base. There were five instances of chambers being used that had been excavated initially by woodpeckers: three by Great Spotted Dendrocopos major and two by Green Picus viridis. 100. Male Little Owl Athene noctua carrying male ghost swift moth Hepialus hutnuli. Nottinghamshire, June 1972 (Derick Scott) Man-made structures of various types held 35 (7%) of the nests examined, comprising barns (13), outbuildings such as an army hut, a garden potting shed, and a sewage-farm store (7), cattlesheds, stables and a piggery (5), derelict farmhouses (4), disused industrial buildings (3), hay• stacks (2) and a ruin (1). Regular nesting places included cavities in a roof or a wall, often under loose slates or tiles, among dislodged straw bales, sometimes inside chimneys or ventilation shafts or between receptacles such as wooden boxes, stone jars or pipes.

Breeding season There is normally little activity until the end of January or beginning of February, when males begin marking their territories. These are usually quite small in area, averaging 87 acres (35 ha) on water-meadows in Hampshire and 95 acres (38 ha) on mixed farmland in Warwickshire (eight and 11 territories mapped respectively). Marking is achieved by the males singing from some favourite tree, telegraph post, or fence post within the territory. The main activity does not start until March, when it is possible to hear as many as six males competing with each other (DS). 174 Breeding biology ojthe Little Owl

101. Male Little Owl Athene noctua with two 3V2-week-old young at nest-hole, Nottingham• shire, June 1973 (Derick Scott) The Little Owl has a great variety of call notes, but during courtship the male utters a loud 'hooo-oo, hooo-oo' and the female shrieks and yelps in answer. The male usually flies round and round the perching female, often quite close to their nest site. Before copulation they face each other on a tree branch or a fence, where the male bobs up and down, weaving and dancing before her. She in turn bobs up and down and then slightly opens and flutters her lowered wings before copulation. Occasionally, the two owls pursue one another in flight with great agility, the male sometimes hovering above the sitting female. Both pair-bond and site-tenacity appear strong, though a long-term marking study is needed. Ringed adults caught by hand at the nest or in mist-nets regularly over three and four years indicate that some individuals do occupy the same territory in successive years; since pairs are frequently recorded during winter, it seems likely that, as a general rule, the pair-bond is unbroken as long as both partners survive. Certain 'traditional' nest sites Breeding biology of the Little Owl 175

Little Owl Athene noctua

120

100

80 i 60

40

20 1—™~i

^12-21 22-31 1-10 11-20 21-30 1-10 11-20 21-30 31-9 10-19 March April May June Figure 2. First-egg laying dates at 357 nests of Little Owls Athene noctua in England and Wales, 1939-77, Mean laying date 28th April have now held Little Owls for over 25 years. The recovery oi ringed Little Owls at the nest during their first summer indicates an early maturity, though it is not uncommon to find non-breeding and unmated individuals on territory through the breeding season. First-egg dates were calculated for nests where the timing of egg-laying, egg-hatching or young fledging was known, or where the young could be accurately aged. Data from 357 nests show (fig. 2) that the Little Owl has a highly synchronised laying period: the shortest breeding season of any of the five owl species breeding regularly in Britain. Laying is almost ex­ clusively confined to April and May, 83% of the clutches being started between 11th April and 10th May (mean 28th April, including any repeats). The laying season spans 16th March (Lincolnshire in 1950) to 19thJune (Lincolnshire in 1967). The latest laying date marks the only instance of a second brood. At a traditional nest site in Lincolnshire, three young fledged from the first clutch started on 12th April, then a further two young hatched from a second clutch in the same nest on 18th July and left on 19th August. Today, second broods are rare, contradicting earlier statements suggesting that they are 'occasional' (e.g. Walpole-Bond 1938, Fisher 1951). Lost clutches are not often replaced. Three replacement clutches were confirmed in the present study and a further three cases are known from egg-collectors operating in the 1930s and 1940s. All were laid in the original nest.

Clutch size Clutches were considered complete when two or more visits made to an active nest during incubation over 48 hours apart showed no increase in the number of eggs. From 268 nests, clutches of three and four eggs are shown 176 Breeding biology oj the Little Owl

102. Little Owl Athene noctua about to feed earthworm to 3¥2-week-old young, Nottingham• shire, June 1973 {Derick Scott) to be usual, two and five occasional, one, six and seven rare (table 6), though clutches of eight have been recorded (Witherby et al. 1940). Re• placement clutches were of three (five occasions) or four (once) eggs. Little Owl eggs are white, broad ellipse in shape, with no gloss. They are usually laid on consecutive days in a crude scrape, there being no de• termined attempt at nest construction. Incubation is by the female alone, and normally begins when the first egg is laid, but sometimes not until the clutch is completed. Estimates of the length of the incubation period vary (e.g. 24-25 days, Campbell & Ferguson-Lees 1972; 28-29 days, Witherby et al. 1940), the present study indicating that the eggs may hatch between 28 and 33 days. During this time, and from hatching up to the fourteenth to sixteenth day, the female leaves the nest for brief periods only, relying on the male for food.

Brood size and breeding success The female feeds the newly-hatched young; only rarely is she assisted by the male. At some nests during this stage, the male will call the female off the

Table 6. Numbers and sizes of 268 clutches of Little Owls Athene noctua Data from 182 BTO nest records collected throughout England and Wales combined with 86 records from local study in Lincolnshire and Nottinghamshire (DS) CLUTCH SIZE Average 1 2 3 4 5 6 7 clutch size

BTO nest records 2 20 75 69 13 1 2 3.45 Lincs./Notts. 1 6 20 36 22 1 0 3.87

TOTALS (268) 3 26 95 105 35 2 2 3.59 % 1 10 35 39 13 1 1 — Breeding biology of the Little Owl 177 nest and transfer the food to her. She in turn flies back to the nest and feeds the young. From about the fourteenth day until fledging, both sexes share in the feeding. The main feeding time is from dusk to midnight, with a break of two hours before a resumption of feeding activity until dawn. Little hunting takes place during the day, and food items are rarely brought to the nest in daylight. After about 12-14 days, the young produce hunger cries: a con• tinuous wheezing sound. Later, they utter tongue-clicking noises similar to those produced by other owls. During times of anxiety or excitement, the male often gives a sharp, repetitive 'kek-kek-kek-kek' call near the nest, the female sometimes answering with a rather grating 'shar'. Estimates of the length of the fledging period vary: Witherby et al. (1940) gave 'about 26 days' (apparently based on a single record), but most authors suggest "iVi-A^h weeks. Such variations are probably caused by the tendency for some unfledged young to leave the shelter of their nest cavities before they are fully grown and while they are still largely incapable of flight. Young may be found hiding among the roots of the nest after as few as 14 days. Many such young are capable of returning unaided to the nest and eventually fledging, but this behaviour has an adverse effect on their survival chances. The present study shows that young fledge (i.e. leave the nest more or less fully developed and capable of flight) after 30-35 days, and the majority after 32-34 days, but it is not unknown for broods to stay as long as 43 days, though they are probably capable of leaving before this. Confirmed brood sizes were defined as those where the young were observed to fly or were thought capable of leaving the nest when last seen. The average brood size at 241 nests was 2.40 (table 7), one, two or three young being usual, five the maximum. Of 477 eggs laid, at least 269 103. Male Little Owl Athene noctua about to feed moth to 3y2-week-old young, Nottingham• shire, June 1973 (Derick Scott) 178 Breeding biology of the Little Owl

Table 7. Sizes of 241 broods of Little Owls Athene noctua

Data from 167 BTO nest records collected throughout England and Wales combined with 74 records from local study in Lincolnshire and Nottinghamshire (DS)

BROOD SIZE Average 12 3 4 5 brood size

BTO nest records 38 55 54 15 5 2.36 Lincs./Notts, 12 24 32 4 2 2.46

TOTALS (241) 50 79 86 19 7 2.40 % 21 33 36 8 3 — hatched, and 234 young flew. From 156 clutches started, 43 (28%) failed during laying, involving 108 eggs, a further 41 (26%) failed during the incubation or fledging periods, but 72 (46%) raised one or more young (table 8). Complete losses of clutches and, to a lesser extent, of broods were frequent, but, of the 113 clutches completed (table 8), 32 (28%) raised the full clutch to produce flying young. The causes of 52 failures are known: eggs taken by man (14), Magpie Pica pica (1), fox Vulpes wipes (1), stoat Mustela erminea (1), hedgehog Erinaceus europaeus (1); young taken or killed by man (6), fox (1), stoat (1), common rat Rattus norvegicus (1); adults shot by man (4), killed by stoat (1), by domestic cat Felis 'domestica' (1); nest chamber deliberately blocked by man (4); tree felled (3); eggs infertile or addled (2); nest cavity collapsed (2); hay bales dislodged (2); eggs and young saturated by rain (2); deserted after disturbance by machinery (2); nest tree struck by lightning (1); nest in willow taken over by Shelducks Tadoma tadorna (1). It is disturbing to note continued deliberate destruction of breeding Little Owls at many sites. Deemed undesirable earlier this century because of alleged attacks on poultry and game-birds, an exhaustive study by Hibbert-Ware (1936-37) demonstrated that the diet is composed chiefly of insects such as beetles and moths, earthworms, small rodents and a few

Table 8. Outcome of 1 IS completed clutches of Little Owls Athene noctua in England and Wales, 1939-75

'BROOD SIZE' refers to number successfully leaving nest; totals in italics are those where all eggs resulted in fledged young

Clutch Number of No. failing to BROOD SIZE size clutches hatch or fledge 12 3 4 5

12 17 — 2 15 6 4 5 3 57 19 6 13 19 4 31 12 3 4 7 5 5 7 2 0 2 1 0 2 6 0 0 0 0 0 0 0 7 1 10 0 0 0 0

TOTALS 113 41 14 24 27 5 2 Breeding biology of the Little Owl 179

104. Female Little Owl Athene noctua with four-week-old young, Nottinghamshire, July 1977 (Derick Scott) smaller birds, the latter largely common species such as Starling Sturnus vulgaris and House Sparrow Passer domesticus. Ringing recoveries provide further evidence of Little Owls shot and trapped annually by man (Glue 1971, 1973), especially at the nest. Successful young are able to fly well within a week of leaving the nest, though they are still fed by their parents for up to one month after fledging, a feature also noted in the Netherlands (Haverschmidt 1946). Dispersal usually takes place within four or five weeks, but juvenile Little Owls may still be seen with their parents into September. June to September, the four months from fledging to indepen• dence, is the testing time for the young, 60% of Little Owls ringed as nestlings being recovered then, with inexperienced youngsters found emaciated, dead beneath wires, on roads or railway lines, or killed by man (Glue 1971) and other predators. Having gained experience and secured a territory by October, first-years are better equipped to contribute to the coming breeding season.

Acknowledgements We are very grateful to all the people who submitted the BTO nest record cards that form the backbone of this paper. Dr G. Hirons and R. A. Morgan commented helpfully on the first draft of the paper, and Mrs E. Murray kindly drew fig. 2. 180 Breeding biology of the Little Owl Summary This breeding biology study of the Little Owl Athene noctua in England and Wales is based on 585 nests examined during 1939-77. The species breeds widely over much of lowland Britain, 85% of the nests being below 400 feet (122 m), but a few as high as 1,050 feet (320 m). Well-timbered farmland is the chief habitat (agricultural land holds 74% of the nests), with fewer in woodland (12%), gardens and built-up areas (10%), and only occasional pairs on heath, moor, marsh, coastal ground, tree-less hill pasture, sand-dunes and islands. Holes in deciduous trees provide 92% of the nesting places. Oaks Quercus, ash Fraxinus excelsior, willows Salix and fruit trees are the main trees occupied. Most nest chambers are reached by narrow, winding channels in hollow main trunks, lateral branches, snapped off trunks, pollarded trees or fallen boughs; rarely, the old nest of another animal is used. Ground nests (1% of the total) were usually in burrows of rabbits Oryctolagus cuniculus or rock clefts. Buildings held 7% of the nests, chiefly barns, other outbuildings and derelict farmsteads; these were mainly in upland areas lacking suitable hollow trees. The laying season extends from mid March to mid June, but the great majority of clutches are laid during late April and early May (mean for first egg, 28th April). Replacement clutches are infrequent and second broods exceptional. The clutch size ranges from one to seven eggs, though usually three or four (mean 3.59). Incubation, by the female alone, takes 28-33 days. Most broods are composed of one, two or three young (mean 2.40), and the full clutch is frequently raised to fly. The young normally fledge after 32-34 days, and disperse within four to five weeks, though may be seen with their parents into September. References CAMPBELL, B., & FERGUSON-LEES,J. 1972. A Field Guide to Birds' Nests. London. FISHER, J. 1951. Bird Recognition, vol. 2. London. GLUE, D. 1971. Ringing recovery circumstances of some small birds of prey. Bird Study 18: 137-146. 1973. Seasonal mortality in four small birds of prey. Ornis Scan. 4: 97-102. HAVERSCHMIDT, F. 1946. Observations on the breeding habits of the Little Owl. Ardea 34: 214-246. HIBBERT-WARE, A. 1936. Report on the investigation of the food of captive Little Owls. Brit. Birds 29: 302-305. — 1937-38. Report of the Little Owl Food Inquiry, 1937-38. Brit. Birds 31: 162-187,205-229, 249-264, plates 5-10. SHARROCK, J. T. R. 1976. The Atlas of Breeding Birds in Britain and Ireland. Berkhamsted. WALPOLE-BOND, J. 1938. A History of Sussex Birds, vol. 2. London. WITHERBY, H. F., JOURDAIN, F. C. R., TICEHURST, N. F., & TUCKER, B. W. 1940. The Handbook of British Birds, vol. 2. London. & TICEHURST, N. F. 1908. The spread of the Little Owl from the chief centres of its introduction. Brit. Birds 1: 335-342.

David E. Glue, Populations Section, British Trust for Ornithology, Beech Grove, Tring, Hertfordshire HP23 5NR Derick Scott, West View, Walkeringham, near Doncaster, South Yorkshire DN 10 4HZ