VOL. 13 (4) DECEMBER 1989 103

AUSTRALIAN BIRD WATCHER 1989, 13 , 103-113

Plumages and Moult of the Little Eagle Hieraaetus morphnoides

by S.J.S. DEBUS, P.O. Box 1015, Armidale N.S.W. 2350

Summary The plumages, age criteria and moult of the Little Eagle Hieraaetus morphnoides were investigated from museum skins, captive birds and field studies in north-east New South Wales. Characteristics of juveniles, second-year birds and adults of both morphs are discussed: these relate mainly to the colour of the head and underparts (juveniles more rufous than adults of their respective morphs); the amount of black streaking on the crown, crest and underparts (heaviest in adults); the colour and contrast of the median upper-wing coverts and scapulars (paler and more prominent in adults); the presence of a uniform translucent trailing edge to the wings and tail in juveniles; and the colour of soft parts (irides changing from dark brown to reddish brown or orange-brown; cere, gape and feet tending to fade from cream or pale yellow to off-white). First-year birds show no wing or tail moult until c. 12 months old. Older birds show descendent, interrupted, symmetrical primary moult and convergent, symmetrical retrix moult, or jumbled and sometimes asymmetrical primary and rectrix moult. A rare, previously undescribed rufous morph in adults is a 'red' version of the dark morph but with the under­ wing pattern of the light morph. The proportion of dark and light birds varies geographically, with the highest proportion of dark birds on the humid east coast of Australia. Light x light adults produce light young, and dark x light adults produce light or dark young. It is suggested that light birds are homozygous, most (moderately) dark birds are heterozygous, and the few exceptionally dark ('black') birds are also homozygous.

Introduction The plumage stages, age criteria and moult of many Australian raptors, including the Little Eagle Hieraaetus morphnoides, are poorly understood. The ability to distinguish age classes in raptors is useful for conservation purposes (e.g. Ridpath & Brooker 1986), and the study of moult reveals the time taken to attain each plumage class (e.g. Brooke et al. 1972). Such knowledge enables population trends to be monitored from the proportion of birds in each age class. This paper presents data on plumages, age criteria and moult of the Little Eagle derived from studies of birds in the field, in captivity and in museum collections, and supplemented by the literature and by data generously provided by colleagues.

Methods Field studies Since 1980 I have observed eight fledgling Little Eagles of the light morph (all progeny of light x light parents), and one fledgling of the dark morph (progeny of light male x dark female), at distances down to 15m through 8 x 40 binoculars. Since 1980 I have also kept a tally of sightings (total 300) of each morph of the Little Eagle. This is based on casual observations and transect counts in the north-eastern part of New South Wales bounded by the Queensland border, Warialda, Narrabri, Coonabarabran, Singleton and Sydney (effectively from the North-West Slopes and Hunter Valley eastwards to the coast).

Museum studies I examined 70 Little Eagle specimens from collections in eastern Australia (Queensland Museum, Australian Museum, Museum of Victoria, South Australian Museum, Australian National Wildlife Collection in Canberra, and University of New England, Armidale). Sixteen of these were identifiable as juveniles including six (5 light, 1 dark) that were clearly fledglings from their collection dates and plumage AUSTRALIAN 104 DEBUS BIRD WATCHER

condition. Details of plumage and soft parts (if described by the collectors) were noted for each specimen. Moult details were noted for 48 post-juvenile specimens. Captive studies In March 1986 I obtained an injured female Little Eagle for rehabilitation after it had received veterinary treatment at Taronga Zoo, Sydney. This bird had accidentally lost (and regrown) several tail feathers in January, but it had all the characteristics of a juvenile (first-year) bird including symmetrical fault bars across all its original rectrices, fresh, evenly worn primaries and secondaries and no sign of moult. It was released in April 1987 after it moulted. Details of plumage, soft parts and moult were kept from written descriptions, colour photographs, the collection and labelling of moulted flight and tail feathers, and examination of the bird in the hand for missing or growing feathers. In June 1987 I received an injured adult male Little Eagle. It was in the final stages of regrowing several flight and tail feathers; it moulted one dorsal and one ventral body feather during the following two months before it was transferred to another facility. Terminology Because it was clearly established that Little Eagles are either light or dark at fledging and remain so after moulting, the term 'morph' (a lifelong condition) is used in preference to 'phase' (a transitory stage); the criterion for classification as dark or light is the under-wing pattern (see Debus 1984). A rare rufous morph in adults (not to be confused with juveniles of the light morph) is described. A standardised terminology for colour description is desirable, therefore where possible the names of colours used here are those in Smithe (1975) with identifying numbers. Primary feathers are numbered from the innermost (1) to outermost (10), and rectrices are numbered from the central (1) to outermost (6) on right (R) and left (L) sides. Moult terminology follows Brooke et al. (1972). Results First-year plumage Light morph: The juvenile plumage of the light morph is described in some detail by Whitlock (1909) and Hall (1974), and illustrated by colour photographs in Cupper & Cupper (1981, p. 173), Egerton (no date, p. 26) and Trounson & Trounson (1987, plate 7, p. 10). Juveniles differ from adults of the light morph by their more rufous head and underparts, 'warmer' rufous cast to the upperparts and darker, less contrasting 'shoulder' band (median upper-wing coverts) and scapulars. Many juveniles have a rufous wash to the oblique band on the under-wing (museum specimens). Juveniles have little or almost no black streaking on the head (cheeks, crown and crest), and have thin streaks on the underparts (dark feather shafts only). They also have pale tips to the secondary coverts, secondaries, inner primaries and rectrices. Some juveniles have pale rufous terminal spots on the lesser upper-wing coverts. At fledging, the iris is dull, dark brown (grey-brown in nestlings), and the cere, gape and toes cream to pale yellow. In some older first-year birds, the cere and toes are pale blue-grey (museum data). Some fledglings are rufous to the under-tail coverts (pers. obs.), whereas some museum specimens, the nestling described by Hall (1974) and the juvenile photographed by Trounson & Trounson (1983, Plate 7, p. 10) are paler on the belly. The captive bird held by me was at c. 7 months old paler on the belly than wild fledglings I have seen. These differences may be a result of feather wear and/or individual variation. VOL. 13 (4) DECEMBER 1989 Plumages and Moult of the Little Eagle 105

Dark morph: There are no detailed descriptions of the juvenile plumage of the dark morph, but a colour photograph of a feathered nestling is provided in Morcombe (1986, p. 138). This bird is darker reddish brown (amber, colour 36) on the head and underparts than juveniles of the light morph (cinnamon-rufous, colour 40); it has less streaked head and underparts and darker, less contrasting upper-wing coverts than adults of the dark morph. The juvenile dark morph observed by me resembled fledglings of the light morph but was slightly darker and duller rufous (tawny, colour 38) on the head and underparts and had dark brown (not white) wing linings. Compared to the adult dark morph, it had a darker (though still discernible) fawn band across the upper-wing coverts and more rufous, less heavily streaked head and underparts. It was no darker below than some adults of the dark morph, and in fact it was not as dark on the breast as its mother. A juvenile male of the dark morph agrees with the above dark juveniles in its rich tawny (colour 38) head and underparts and dark (fawn, colour 25) upper­ wing coverts; it had little black on the head and crest but it had more prominent dark shaft streaks on the underparts than juveniles of the light morph (P. Slater unpubl. photographs). Two juvenile females of the dark morph were not as 'red' as this bird (P. Slater unpubl. data). Museum specimens reveal that dark juveniles may have prominent (though narrow) breast streaks, pale rufous spots on the lesser upper-wing coverts, and pale tips to the secondary coverts, secondaries, inner primaries and rectrices. None of these specimens was any darker on the breast than dark adults of the same sex in museum collections. A colour photograph of a dark bird of the New Guinean form H.m. weiskei in flight (Pruett-Jones & Pruett-Jones 1981, p. 21) appears to show a juvenile: it has an unmarked tawny head, yellow gape and feet and uniform translucent trailing edge to wings and tail. This bird, misidentified in the caption as a Whistling Kite Haliastur sphenurus, resembles dark juveniles of the Australian form except that it appears to have a zone of heavier black streaks on the breast.

Second-year plumage Light morph: After moulting, the captive female held by me had changed little in colour except that there was more black on the crown; her median upper-wing coverts were still dark although each feather had a small pale area at the tip, and she had lost most of the rufous spotting on the lesser upper-wing coverts. Upon release, about half way through her second year, this bird had a light brown iris, cream cere, greyish-white toes and bluish-white gape (iris dark brown and toes pale yellow when received). A captive male about half way through his second year had some black on the crown and crest, pale median upper-wing coverts, almost no rufous spots on the lesser upper­ wing coverts, light brown irides, cream cere and pale grey toes (pers. obs.); in his first year his underparts were more extensively rufous (B. Kubbere pers. comm.). Another captive bird remained rufous on the breast after its first moult, but assumed a black crown and crest (P. & J. Olsen unpubl. data.).

Dark morph: I obtained no data on dark birds after their first moult. One captive juvenile (rufous with dark under-wings) assumed a rich, dark chestnut on the breast and a black crown and crest after its first moult (P. & J. Olsen unpubl. data) . One post-moult specimen (AM 0.32185) may be a sub-adult: it is rufous on the head and entire underparts (like a juvenile light morph) but with heavy black streaks and dark under-wings, and it has an old and worn feather (R6) among its mostly new rectrices; its eyes were noted as brown and its feet as bluish-white. AUSTRALIAN 106 DEBUS BIRD WATCHER

Adult dark morph Little Eagle in flight. Plate 29 Photo: David Whelan

Adult plumage The adult plumage of the light and dark morphs has been adequately described and illustrated by colour photographs elsewhere (e.g. Cupper & Cupper 1981, Hollands 1984). [Note that the 'adult' in Trounson & Trounson (1987, Plate 6, p. 10) is the same bird photographed at the same time as the juvenile in their Plate 7 (D. Trounson pers. comm.); both show juvenile characters]. Apart from the head colour, adults of both morphs are similar on the upperparts, varying from medium to very dark brown on the back and wings. Although somewhat variable, the most obvious features of adult birds are the heavy black crown and crest, dark facial streaks, prominent pale 'shoulder' band (median upper-wing coverts) and scapulars, and darker/thicker streaks on the breast than in juveniles. The wing coverts tend to grey (drab-grey, colour 119D) rather than the fawn (colour 25) of juveniles. Birds greater than one year old (i.e. 2+) may also show moult or a mixture of old and new feathers (see below); this removes the effect of a uniform, translucent trailing edge to the wings and tail (pale feather tips) that is evident in juveniles in flight. In both morphs there is some variation in the intensity of the colour of the underparts. The light morph may have a white belly, though some adults retain a rufous wash. The dark morph varies from 'deep sandy' (Pizzey 1980) through 'russet' (Hollands 1984) to dark brown. For example, one exceptionally dark ('black') individual was antique brown (colour Jl) with heavy black crown and broad black streaks on the breast; its under-wing coverts were mostly sepia (colour 119) with dark grey (colour 82) under primary coverts (J. Klapste unpubl. photographs). An incubating female appeared dark brown, almost black, when flushed from the nest (P. Olsen). In most dark birds, the background colour is medium brown but the dark appearance is accentuated by the heavy black streaking (pers. obs.). In such birds, the brown leading edge of the under-wing (lesser coverts) is somewhat mottled, producing a darker oblique band (solid brown wing lining). In the darkest birds the under-wing, apart from the flight feathers, is uniformly dark. VOL. 13 (4) DECEMBER 1989 Plumages and Moult of the Little Eagle 107

Juvenile light morph Little Eagle, dorsal view. Note pale border to secondary coverts, secondaries, inner primaries and tail. Plate 30 Photo: David Whelan

Juvenile light morph Little Eagle, ventral view. Note uniform translucent trailing edge to wings and tail, and strong rufous wash to pale oblique band on under-wing in this individual. Plate 31 Photo: Rex Davies/BOCA AUSTRALIAN 108 DEBUS BIRD WATCHER

Within each morph, some of the colour variation seems related to sex. For instance in light pairs, females tend to have more rufous smudging and darker streaks on the breast than males (pers. obs.; see Cupper & Cupper 1981, p. 172). Similarly, dark females tend to be darker on the breast than males (pers. obs.; Cupper & Cupper 1981, p. 171 top right; Hollands 1984, first 2 plates), though occasional exceptionally dark individuals of both sexes occur (pers. obs.).

The iris of breeding adults is reddish brown to orange-brown, e.g. amber (colour 36); two museum specimens had golden-brown irides, and one bird had a dull yellow iris (Hall 1974). The cere, gape and toes of adults tend to be off-white, sometimes with a blue-grey tinge, though there are occasional exceptions with cream or pale yellow soft parts (Hall 1974; museum data). The plumage of captive adult light birds (sandy with rufous streaks on the breast and a black-streaked crown and crest) has remained unchanged except for blacker crown, crest and streaks on the underparts (P. Olsen unpubl. data). The plumage of a captive dark morph held by P. Olsen (brown with black streaks on the breast, black crown and crest) has also remained unchanged except for blacker crown and crest (P. Olsen unpubl. data; pers. obs.). Some of these changes may relate to fresh versus worn plumage, and birds may also change gradually from juvenile to full adult plumage over several years. Rufous morph One specimen (ANWC 40476) differs from all others examined in that it appears as dark as the dark morph on the underparts, though redder (raw umber, colour 23 on the breast to amber, colour 36 on the belly), but it has the under-wing pattern of a light morph. An adult male, it has a solid black crown and heavy black streaks on the underparts. In the field, such a bird could be mistaken for the dark morph unless the under-wing is seen. I have no information on the juvenile plumage of this morph, which appears to be a heavily pigmented variant of the light morph. I have not seen a bird in this plumage in the field, although the above specimen came from New South Wales. It appears to occur at low frequency in the population (one in 70 specimens; none recognised in ) 300 sightings). Moult The captive first-year female held by me started moulting in mid July and finished in mid March, eight months (c. 250 days) later. Moult started with the head and scapulars (July) then spread to the under-tail coverts, back, throat (August), median upper-wing coverts (September), breast, flanks (late September/early October), primary coverts (moulted descendently), lesser upper-wing coverts (October), under-wing coverts (November), alulae (December), wing lining, axillaries and secondary coverts (January). Primary moult was descendent, symmetrical and almost complete (P1 to P8 then P10, skipping P9). It started in late August and finished in mid February, six months later. Successive feathers were lost about two weeks (inner primaries) to a month (outer primaries) apart, but corresponding feathers in each wing were in phase by 2-7 days. Secondary moult was three-centred, ascendent, somewhat asymmetrical and incomplete. It started in mid November and finished in mid March, four months later. Some feathers were lost from the outer, middle and inner secondaries; some middle and inner secondaries were out of phase, and 11 (out of 13) were :Jst from the left wing versus nine from the right. Rectrix moult was symmetrical, convergent and incomplete, lasting 2V2 months (mid November to early February). Left and right were in phase by 1-2 days or so; the sequence was 1, 6, 2. Only six of 12 rectrices moulted, these being original feathers and not those that were prematurely replaced when the bird was injured. VOL. 13 (4) DECEMBER 1989 Plumages and Moult of the Little Eagle 109

The captive adult male held by me in June-August 1987 showed incomplete, jumbled and asymmetrical primary moult, with a mixture of old and new feathers. The secondaries showed incomplete, asymmetrical, three-centred moult, with very old and worn outermost feathers (almost two yers old?). The rectrices showed incomplete, asymmetrical, jumbled moult with old and new feathers including one that was very old and worn (almost two years old?). This bird was in fresh plumage in late May 1989 (pers. obs.). Other evidence was obtained that primary moult is usually descendent, and that primary and retrix moult is incomplete in a given year. Captive Little Eagles moult fewer flight and tail feathers annually than would be expected if moult is complete (P. & J. Olsen unpubl. data). Post-juvenile specimens in which moult was not active (no missing or growing feathers) showed a mixture of old and new primaries and rectrices. In some cases, very worn feathers amongst fresh and less worn feathers appeared to be almost two years old (i.e. three generations of primaries and rectrices present). Non-moulting specimens had inner primaries old and outer primaries new (8 birds), inner primaries new and outer primaries old (6 birds), or fresh (inner), old (middle) and normal (outer) primaries in an obviously descending sequence (1 bird). Three symmetrically moulting specimens had increasingly fresh primaries from Pl to P4, 5 or 6, with P5, 6 or 7 growing and P6, 7 or 8 to PlO old; two others had fresh, normal and old primaries in an obviously descending sequence. Twenty specimens (9 moulting) showed a jumbled mode of primary replacement; in 13 of these, primary moult was asymmetrical. For the rectrices, eight specimens showed the symmetrical, convergent mode. of feather replacement, 19 showed the jumbled mode (18 of these assymetrical), two showed a symmetrical, possibly three-centred mode and four showed no discernible pattern. These last four birds and two showing the jumbled mode had 1-2 very worn feathers (almost two years old?) in otherwise complete tails. My captive second-year female and two museum specimens (1 male, 1 female) had new rectrices up to 10 mm longer than old rectrices, even allowing for feather wear; the latter also had descendent, symmetrical primary moult with new inner feathers (male) or symmetrical primary moult and convergent, symmetrical rectrix moult (female), which suggests that they were also second-year birds. It appears that adults may have slightly longer tails than juveniles. Little information was obtained on the timing of moult. Twenty of 48 post-juvenile specimens were in active moult: eight males (one in October, November and February, two in January and April, one undated) and 12 females (one in September, November, February, March and May, two in April, three in December, two undated). Two adult females hand-held for banding purposes had fresh inner primaries (Pl to P4 or 5) and old outer primaries (P5 or 6 to PlO), but no missing or growing feathers, at the end of May (pers. obs.). Observations of breeding birds revealed some females in active primary moult early in the nestling period (November-December) and some males starting primary moult later in the nestling period (December-January) at Armidale (pers. obs.). Among the post-juvenile museum specimens, there were females not in active primary or tail moult from all months except February-April inclusive, and males not in active primary or tail moult in August-November inclusive (no specimens for March or May-July). It appears that in adults, partial wing and tail moult starts during the breeding cycle and (in southern latitudes) is arrested in late autumn and winter. Age criteria The following age criteria have been identified for Little Eagles of the light and dark morphs, and may apply to the rufous morph. AUSTRALIAN 110 DEBUS BIRD WATCHER

Head: usually with few black streaks in juveniles; black or black-streaked crown and crest (in particular) in adults. 'Shoulder' band (median upper-wing coverts): dark (fawn) and usually not contrasting strongly with back and wings in juveniles; pale (grey) and prominent in adults. Applies to a lesser extent to scapulars. Breast streaking: in the light morph, indistinct in juveniles and confined to dark feather shafts; often distinct in adults, sometimes broader (dark stripe down the vane either side of the shaft). In some dark juveniles, streaks confined to dark feather shafts; other dark juveniles resemble dark adults in this character though vane stripes often broader in adults. Lesser upper-wing coverts: spotted rufous in some juveniles; this character is lost during the second year and is absent in adults. Pale tips to secondary coverts, secondaries, inner primaries and rectrices: readily visible in most juveniles, appearing as a uniform translucent trailing edge to the wings and tail in flight. This pale border is absent or broken in adults, which have some worn flight and tail feathers. Iris: grey-brown in nestlings, dark dull brown in fledglings, dark brown in first-year birds, light brown in second-year birds and reddish brown to orange-brown in breeding adults; occasionally paler (older birds?). Cere, gape and/or feet: often cream to pale yellow in first-year birds; occasionally so in adults though usually pale grey or bluish white in older birds (2+ ). Moult: first-year birds show no wing or tail moult, and moult into essentially adult plumage at the beginning of their second year. Second-year birds show descendent, interrupted primary moult and convergent rectrix moult (both symmetrical). Older bird show these moult modes, or jumbled and sometimes asymmetrical primary and rectrix moult.

Frequency of colour morphs Of300 sightings of Little Eagles in the study area (north-east N.S.W.), 230 (77%) were light and 70 (23%) were dark (3.3:1 in favour oflight). Even within this region I have formed the subjective impression that the proportion of dark birds increases from west to east, from drier to more humid areas. The ratio in New South Wales generally is 4.5:1 in favour oflight birds (36light and 8 dark in museum collections). Other data indicate geographical variation in the ratio of colour morphs. P. Slater (in !itt.) supplied the following information: in five years in the Kimberley region (W.A.) he saw many light birds but no dark birds; the ratio in south-western Australia is about 15:1 in favour oflight; in coastal south-east Queensland there are about equal numbers of the two morphs. In north-western Victoria 'most' birds are light (D. Baker-Gabb); on the Southern Tablelands of New South Wales the ratio in the field is about 6:1 in favour of light and 3:1 (n=9) in local captive birds (J. & P. Olsen unpubl. data); in coastal south-eastern Queensland dark birds predominate (Czechura 1985). Museum data generally support this: there is one dark specimen from the Kimberley; all South Australian specimens (n= 6) are light; there are six light to two dark fron: Victoria (n=8); and four light to one dark from Queensland (n= 5). Among museum specimens, light males outnumber dark males by 2.7:1 (16:6, n=22) whereas light females outnumber dark females by almost 5:1 (38:8, n=46). This supports my field impression that dark males are more common than dark females, and raises the possibility of sex-linkage. VOL. 13 (4) DECEMBER 1989 Plumages and Moult of the Little Eagle 111

Genetics of colour morphs In my experience (n=8 fledglings) and that of others (e.g. Cupper & Cupper 1981, p. 172, 173 top), light x light parents always produce offspring of the light morph. Light x dark parents produce either light or dark young: in one mixed pair, the young was light one year and dark the next (Slater 1983); in another pair (light female, dark male), one young was light and the other was dark (two siblings: Morcombe 1986, p. 138 and unpubl. data); the single young of a dark male x light female was light in two successive years (Bollen 1989). A dark female x light male pair produced a dark juvenile (pers. obs.); another dark female x light male pair produced a fledgling that appeared indistinguishable from a light juvenile, but I could not see its under­ wing pattern to be certain that it was a light bird. Limited results are inconclusive for dark x dark parents, which seems a rare combination: a dark pair produced a chick with white down (Cupper & Cupper 1981, p. 171 top, Hollands 1984 and unpubl. photographs). Some dark juveniles have white down (Morcombe 1986, p. 138); dark chicks of the related Booted Eagle H. pennatus have white, grey or brown down (Smeenk 1974, Steyn & Grobler 1985).

Discussion On present information it is possible to recognise only two age classes of the Little Eagle in the field: juvenile (first year) and older (2 +). Plumage differences between juveniles and others are of degree, and become increasingly difficult to detect with increasing distance from the observer. The picture is complicated by feather wear (bleaching), for instance in juveniles approaching their first moult. From a small sample the pattern of moult in the Little Eagle agrees well with that of other eagles Aquila and Hieraaetus and large buzzards Buteo, for instance: post­ juvenile moult starting on the head; primary moult descendent, symmetrical and interrupted in second-year birds, and becoming jumbled in adults; secondary moult three-centred, ascendent and sometimes asymmetrical in second-year birds; rectrix moult symmetrical and convergent in second-year birds and becoming three-centred or jumbled and often asymmetrical in adults; and incomplete primary and rectrix moult in a given year (see Brooke et al. 1972, Cramp & Simmons 1980, Schmitt et al. 1987). A larger sample of captive, known-age birds is needed. However, nutrition in captivity may influence the timing and completeness of remex moult (cf. Brooke et al. 1972). The captive female held by me was fed ad libitum on freshly killed rabbits and gained weight; this may have caused more rapid and complete primary replacement than in her wild counterparts. Inadvertently, she also went without food for ten days towards the end of her primary moult, which may have increased the moult interval of her outer primaries and caused the retention of P9. Stress, for example injury or change of location in mid moult, may cause moult in captive raptors to stop and not start again until the next moulting period (J. Olsen pers. comm.). The age criteria and moult of the Little Eagle resemble those of the closely related Booted Eagle (see Cramp & Simmons 1980, Clark 1988) . Differences between juvenile and adult Booted Eagles are minor, and of degree (as in the Little Eagle); adult plumage is apparently attained at the first complete moult. In the larger Bonelli's Eagle H. fasciatus, in which there is greater difference between adult and juvenile, adult plumage is attained over several years (Cramp & Simmons 1980) and apparently over two complete moults. It seems likely that Little Eagles gradually attain full adult plumage over two (or perhaps more) incomplete annual moults. Moult may also slow down with age, so that old birds are in a state of continuous, gradual moult as suggested by the few adult specimens with missing or growing primaries (cf. Brooke et al. 1972). The change from descendent to jumbled moult in old birds may represent a slowed AUSTRALIAN 112 DEBUS BIRD WATCHER

moult with successive moult cycles overlapping (inner primaries starting to shed before outer primary moult from the previous cycle is complete, cf. Brooke et al. 1972, Cramp & Simmons 1980). The time taken for the irides of Little Eagles to change colour is also poorly known. Much information on plumage and age criteria could be obtained from captive birds (e.g. rehabilitation projects); bird banders could also assist by recording or photographing details of plumage, moult and soft parts of birds captured and subsequently recovered. A rufous morph has been described for the Booted Eagle, which also has light and dark morphs like the Little Eagle (Clark 1988, 1989). Although combining features of both light and dark morphs, the rufous Booted Eagle is considered not strictly intermediate because its under-wing pattern is different from that of the others (pale leading edge, dark oblique band). The rufous morph of the Little Eagle also combines some features of both light and dark morphs, but in an unusual manner that is not strictly intermediate. From similar results for light x light and dark x light pairs in the Booted Eagle (Steyn-& Grobler 1985) and the genetics of the colour morphs in Eleonora's Falcon Falco eleonorae (Cade 1982), I suggest that pale Little Eagles are homozygous, that most (moderately) dark birds (so-called 'intermediates') are heterozygous and that the few very dark birds ('black') are also homozygous. Further data are needed on dark x dark Little Eagle pairs to see if they produce young that are variously light, dark or 'black' as adults, and to determine the down and juvenile plumage colour of homozygous dark young. Assuming a single pair of allelic genes with incomplete dominance as postulated for Eleonora's Falcon (Cade 1982) and a population of four light to one dark (heterozygous) Little Eagles, about 2% of resulting offspring would be homozygous dark ('black'). In such a population, assuming random mate selection, there would be 16 light x light pairs for every eight mixed pairs and one dark x dark pair. Field observations support these figures: around Armidale, only two in over 30 pairs have been dark x dark; in over 300 sightings, fewer than 10 birds have been very dark ('black'). These aspects of the Little Eagle's morphology deserve specific study. The existence of a rufous morph complicates the picture, and raises the possibility that the genetics of the colour morphs are more complex than in Eleonora's Falcon. The Little Eagle may well be better treated as polymorphic; it remains to be seen whether there is any correlation between environment and the frequency of the different morphs, other than the prevalence of the dark morph in humid regions as is already apparent. The rufous morph may prove to be frequent in desert areas, as seems to be the case with the rufous morph Booted Eagle which is rarely reported in boreal regions, but is apparently frequent in the Middle East (cf. Holmgren 1984, Ullman & Undeland 1985, Clark 1988, 1989).

Acknowledgements I am most grateful to the following people for generously providing information and/or photographs: David Hollands, Jerry Klapste, Michael Morcombe, Liz Notley, Penny & Jerry Olsen, Peter Slater, Donald Trounson and David Whelan. Walter Boles, John Calaby, Zoltan Enoch, Belinda Gillies, Wayne Longmore, Rory O'Brien, Shane Parker and Richard Schodde provided access to museum specimens in their care. Literature was kindly provided by Bill Clark, David Noakes, Lyle Smith and Patricia White (RAOU Librarian). I am grateful to Bob Harden & John Robertshaw (Zoology Dept, University of New England) for the use of facilities for holding the two captive Little Eagles, and the following people for assistance with the care, transport and/or VOL. 13 (4) DECEMBER 1989 Plumages and Moult of the Little Eagle 113

feeding of the birds: Chris Baker, Pam Bristol, Peter Debus, Sarah Dick, Mal Dywer (NPWS), Liz Notley (Taronga Zoo) and Fred Spiteri. A steady food supply for the eagles was facilitated by Shane Andrews and Malcolm Rowe and storage was facilitated by Stuart Green, all of the University of New England. A permit to keep the birds was provided by the N.S.W. National Parks & Wildlife Service. Finally, I thank David Baker-Gabb and Penny & Jerry Olsen for comments on drafts of this paper.

References Bollen, C. (1989), 'Notes on Little Eagles breeding on the Southern Tablelands of New South Wales', Aust. Bird Uiltcher 13, 65-66. Brooke, R.K., Grobler, J.H., Stuart Irwin, M.P. & Steyn, P. (1972), 'A study of the migratory eagles Aquila nipalensis and A. pomarina (Aves: Accipitridae) in Southern Africa, with comparative notes on other large raptors', Occ. Pap. Nat/ Mus. Rhodesia BS, 61-114. Cade, T.J. (1982), The Falcons of the World, Collins, London. Clark, W.S. (1988), 'The rufous morph of the Booted Eagle' in International Bird Identification, 1st edn, 21-24, International Birdwatching Center, Eilat, Israel. -- (1989), 'The rufous morph of Booted Eagle', Dutch Birding 11, 57-60. Cramp, S. & Simmons, K.E.L. (Eds) (1980), Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the ~stem Palaearctic, vol. 2, Oxford University Press, Oxford. Cupper, J. & Cupper, L. (1981), Hawks in Focus, Jaclin, Mildura. Czechura, G.V. (1985), 'The raptors of the Blackall-Conondale Ranges and adjoining lowlands, southeastern Queensland', Corella 9, 49-54. Debus, S.J.S. (1984), 'On the field characters of Little Eagles', Aust. Bird Uiltcher 10, 204-205. Egerton, L. (compiler) (no date), Favourite Australian Birds, Bay Books, Sydney. Hall, B.P. (Ed.) (1974), Birds of the Harold Hall Australian Expeditions, 1962-70, British Museum of Natural History, London. Hollands, D. (1984) , Eagles, Hawks and Falcons of Australia, Nelson, Melbourne. Holmgren, V. (1984), 'Booted Eagles in intermediate plumage seen at Eilat, Israel', Sandgrouse 6, 76-79. Morcombe, M. (1986), The Great Australian Bird Finder, Lansdowne, Sydney. Pizzey, G. (1980), A Field Guide to the Birds of Australia, Coflins, Sydney. Pruett-Jones, S. & Pruett-Jones, M. (1981), 'Hunters by day, hunters by night', Paradise (Air Niugini) 30, 21-23 (July 1981). Ridpath, M.G. & Brooker, M.G. (1986), 'Age, movements and management of the Wedge-tailed Eagle, Aquila audax, in arid Western Australia', Aust. Wildt. Res. 13, 245-260. Schmitt, M.B., Baur, S. & von Maltitz, F. (1987), 'Observations on the Jackal Buzzard in the Karoo', Ostrich 58, 97-102. Slater, P. (1983), 'Observations on the Little Eagle', Australasian Rnptor Assoc. News 4(4), 4-5. Smeenk, C. (1974), 'Comparative-ecological studies of some East African birds of prey', Ardea 62, 1-97. Smithe, F.B. (1975), Naturalist's Color Guide, American Museum of Natural History, New York. Steyn, P. & Grobler, J.H. (1985), 'Supplementary observations on the breeding biology of the Booted Eagle in Southern Africa', Ostrich 56, 151-156. Trounson, D. & Trounson, M. (1987), Australia, Land of Birds, Collins, Sydney. Ullman, M. & Undeland, P. (1985), ['Two intermediately coloured Booted Eagles Hieraaetus pennatus in Scania, 1980'], Vd'r Fdgelvarld 44, 156-158 (English summary). Whitlock, F.L. (1909), 'Notes on birds observed on the Pilbara Goldfield, north-western Australia', Emu 8, 173-194.

Received 6 February 1989 •