Sexing of juvenile Montagu’s Harrier
tributed and less evenly spaced, creating a pale‘boomerang’ (like in juvenile Pallid Harrier
C macrourus) more often than in juvenile male.
The dark secondaries are darker on the underside
and, on average, also darker on the upperside,with more obvious dark bars. On the upperwing,
the primaries are generally darker, with a less grey
wash and less obvious pale primary base; consequently, in flight, there is a less obvious contrast
between the dark secondaries and the pale primary base. As already described, the axillaries andthe greater underwing-coverts have distinct darkmarks. Only rarely, these marks are less distinct,
with a pattern similar to that of juvenile male. The
white rump-patch is normally more extensive,
broader than in juvenile male. The tail is in mostcases darker than in juvenile male, with darker
rectrices having darker and more obvious bars,
especially on the outer rectrices. The central rectrices never show a grey wash as in juvenile male.
Bare parts
The iris is distinctly darker than in juvenile male,ranging from dark-brown to warm-brown or

blackish-brown. In nestlings, the iris is perhaps
similarly coloured as the pupil or a shade paler;after fledging, the iris becomes gradually palerbut, throughout the first year, it is still brown (cfClarke 1996, Forsman 1999).
Acknowledgements
I thank Daniele Aliffi, Maurizio Azzolini, Valerio
Cappello, Carmela Cardelli, Roberto Gildi,
Marcello Grussu, Carmelo Iapichino and Marco
Preziosi for their help; and the bird hospitals I
visited for permitting me to photograph the injured Montagu’s Harriers in their care.
References
Clarke, R 1996. Montagu’s Harrier. Chelmsford.
Forsman, D 1995. Field identification of female andjuvenile Montagu’s and Pallid Harriers. Dutch
Birding 17: 41-54.
Forsman, D 1999. The raptors of Europe and the Middle East: a handbook of field identification. London.
Lontkowski, J 1995. Die Unterscheidung von KornCircus cyaneus, Wiesen- C. pygargus und Steppenweihe C. macrourus. Limicola 9: 233-275.

Andrea Corso, via Camastra 10, 96100 Siracusa, Italy (f.corso@isabenergy.inet.it)

Juvenile plumage of Javan Crested
Honey Buzzard, with comments on
mimicry in south-eastern Asian
Pernis and Spizaetus species
S (Bas) van Balen, Resit Sözer, Vincent Nijman, Rona Dennis, Eric Meijaard & Paul R JepsonOn 16 October 1995, when travelling between Pelabuhanratu and Bogor, West Java,
Indonesia, Rona Dennis and Eric Meijaard discovered an immature raptor at a roadside bird
market. Initially, the bird was thought to be an
immature Javan Hawk-eagle Spizaetus bartelsiand, because of the protected status of raptors inIndonesia in general and of this rare raptor endemic to Java in particular, it was photographed192

for documentation and identification purposes.
Three weeks later, the bird was still present andPaul Jepson took additional photographs. However, examination by Bas van Balen and Reflit
Sözer of the taken photographs showed that itwas not an immature Javan Hawk-eagle or another Spizaetus (or Hieraaetus) eagle but a juvenile Javan Crested Honey Buzzard Pernis ptilorhyncus ptilorhyncus, another (very) rare raptor[Dutch Birding 21: 192-198, 1999]

Juvenile plumage of Javan Crested Honey Buzzard
endemic to Java which, according to del Hoyo etal (1994), may be close to species threshold.
As no descriptions or illustrations of the juvenile plumage of Javan Crested Honey Buzzard
are available in the literature, and in view of its
confusing resemblance to the immature plumageof the sympatric Javan Hawk-eagle, it seems useful to publish the compiled description of thephotographed juvenile Javan Crested Honey
Buzzard and to discuss its identification. Furthermore, it seems appropriate to comment on mimicry in south-eastern Asian Pernis and Spizaetus
species.
The data presented in this article are largely
derived from observations done during field studies by the authors throughout the Indonesian partof the ranges of Crested P ptilorhyncus andBarred Honey Buzzards P celebensis (ie, Bali,
Java, Kalimantan, Sulawesi and Sumatra) in the
period of 1980-98.
Description
The description is based on the photographs
taken of the juvenile Javan Crested Honey Buzzard. Also, comparisons were made with skins ofJavan and other Crested Honey Buzzards in thecollections at the National Museum of Natural
History, Leiden, the Netherlands, and at the Museum Zoologicum Bogoriense, Bogor, Indonesia.
Head long and narrow, with long anderect crest. Tail (very) short, apparently still growing.
Bill weak. Tibia feathered (‘trouser’); tarsus short (about
as long as middle toe) and unfeathered, talon slightly
curved.
HEAD Forehead with white frontal band. Crown muchdarker than in any Javan Hawk-eagle, forecrown predominantly sooty-black and hindcrown (especiallymore central part) distinctly paler and browner. Crest
sooty-black, shorter feathers with brown tip and longer
ones with whitish tip. Nape and rest of neck buffbrown, feathers with dark centre (shaft-streak) (approaching buff-cinnamon of underparts). Lore whitish,
lore-feathers seemingly scaly (not clearly visible on thephotographs). Ear-coverts brownish, with black ‘crescent’ below eye and black spot at rear edge, and surrounded by white line, running from rear corner of eye
down around ear-coverts to base of bill. Chin and throat whitish, showing traces of black outline or mesial
stripe typical of adult Javan Crested Honey Buzzard(chin- and throat-feathers seemed to be damaged orwere moulting).
UPPERPARTS Dark brown, feathers with pale brownish
fringe.
UNDERPARTS Plain buff-cinnamon, feathers with slightly darker shaft-streak. ‘Trouser’ pale buff to whitish.
WING Primaries blackish-brown. Secondaries, tertials
and wing-coverts dark brown with pale brown fringe.
STRUCTURE

TAIL Undertail-coverts buff-cinnamon. Base of under-side of tail white (rest of tail hardly visible on photographs).
BARE PARTS Iris brown, no obvious contrast with pupil.
Orbital ring white to dirty-white. Upper mandible greyish; lower mandible whitish, greyish towards tip; cerebright yellow. Tarsus and foot pale yellow, talon black.

Identification
The unfeathered tarsus and the long narrow headexcluded the possibility that the photographed
raptor was a Javan Hawk-eagle or anotherSpizaetus (or Hieraaetus) eagle. In fact, the shortunfeathered tarsus, the long narrow head withthe weak bill and the yellow cere only fitted
Crested Honey Buzzard. The long, sooty-blackand pale-tipped crest was typical of juvenile
Javan Crested Honey Buzzard. Presumably, it
was a recently fledged bird on account of the‘simultaneously growing’ crest-feathers and ‘very
short’ tail (Kees Roselaar pers comm). The partly
sooty-black head and the plain buff-cinnamon
underparts strongly resembled those of immature
Malaysian Crested Honey Buzzard P p torquatus(of which skins were studied at Museum Zoologicum Bogoriense). The white pattern on the headis also found in immature Siberian Crested
Honey Buzzard P p orientalis. Apart from thelong crest, Javan and Malaysian Crested Honey
Buzzards differ from the almost-crestless Siberian
Crested Honey Buzzard by the structure of thefeathers of the upperneck: broad and rounded inJavan and Malaysian Crested Honey Buzzards
and long and lanceolate in Siberian Crested
Honey Buzzard (M E G Bartels in litt in van
Heurn & van Heurn 1923).
The sooty-black pattern on the head and thesooty-black crest were more like an adult Blyth’s
Hawk-eagle S alboniger or even a Rufous-bellied
Eagle H kienerii but the buff-brown neck (including the nape) made the bird look more like a
Javan Hawk-eagle, especially when seen fromaside or from behind.
Status on Greater Sundas
As already mentioned, Javan Crested Honey
Buzzard is endemic to Java. There are only twoskins of Javan Crested Honey Buzzard among the
50 skins of Crested Honey Buzzard in the Bartels
collection from Java brought together between
1898 and 1942 (René Dekker pers comm), suggesting that Javan Crested Honey Buzzard has
always been (very) rare. However, van Heurn &van Heurn (1923) reported the presence of noless than 14 skins (and one egg) of Javan Crested
193

Juvenile plumage of Javan Crested Honey Buzzard
Honey Buzzard in the Bartels collection (now at
National Museum of Natural History). The 12
missing skins may have got lost during World War
II. Four skins of Javan Crested Honey Buzzard areat Museum Zoologicum Bogoriense. It should
also be pointed out that well-documented fieldrecords of Javan Crested Honey Buzzard are rare.
Convergent evolution or mimicry
Immature Javan Crested Honey Buzzard may
cause confusion with immature Javan Hawkeagle. Apart from the above-described similarities in plumage, the flight silhouettes are alsosimilar. Both raptors are confined to Java andhave not been recorded on any of the off-lying
islands like, for instance, Bali, Kangean and
Madura. Although few data are available, Javan
Crested Honey Buzzard and Javan Hawk-eagle
seem to be confined to primary and secondaryrain forests. Their altitudinal ranges largely overlap although, in the (upper) montane forest zone,
only Javan Hawk-eagle is recorded, albeit infrequently. Although Javan Crested Honey
Buzzard and Javan Hawk-eagle occur largely inthe same habitat and show similarities in plumage and flight silhouette, there is little resemblance in morphology or hunting and flightbehaviour. Bill, head, foot and talon differ
markedly in morphology. Javan Hawk-eagles
feed on vertebrates taken from either perches inside the forest or by soaring close to the canopy.
Javan Crested Honey Buzzards mainly prey onsocial insects, including larvae, taken both fromforest and non-forest areas. Hawk-eagles have ahigher wing-loading (tail included) than Crested
Honey Buzzards, 34-39 and 22-23 Newton per
square metre, respectively (eg, Gamauf et al
1998b). In general, a higher wing-loading is
associated with a more rapid flight (Burton1989). Javan Crested Honey Buzzard flies withdeep wing-beats and Javan Hawk-eagle withmore shallow ones (Nijman & Sözer 1998).
In conclusion, the resemblance between Javan
Crested Honey Buzzard and Javan Hawk-eagle
may represent mimicry rather than convergence,
similar to other Pernis-Spizaetus pairs discussed
below.
Mimicry in south-eastern Asian Pernis
and Spizaetus species
Despite the fact that mimicry is a frequently discussed phenomenon, it has been verified by few
studies and until now has been scarcely taken
into consideration in raptors. As pointed out by
Gamauf et al (1998a), members of the genus
194

Pernis exhibit the highest local variability inplumage colour and pattern among raptors
world-wide, including dark morphs in some taxa
(del Hoyo et al 1994). The general trend of thisvariation in Crested Honey Buzzards is for the
taxa inhabiting tropical forests to be darker ormore richly barred in adults, with a crest and a
black gorget surrounding a whitish throat to becommon; immatures are paler than adults but
browner than in the more northern taxa (Brown& Amadon 1968).
As first described for Sulawesi by Meyer &Wigglesworth (1898), in the Indo-Malayan andPhilippine archipelagos, plumage colour andpattern of geographically distinct populations of
Barred and Crested Honey Buzzards closely
resemble those of sympatric hawk-eagles, either
in adult plumage, as on Borneo and Sumatra, orin immature plumage, as on Java, or in bothplumages, as in the Philippines and on Sulawesi.
Five mimetic species pairs can be distinguished.
Similarities in these species pairs extend to flightsilhouette, presence of crest (pairs 1-4 with crestand pair 5 without crest), breast and belly coloration and tail pattern (with a broad pale bar).
1 Malaysian Crested Honey Buzzard P p torquatus(adult dark morph) and Blyth’s Hawk-eagle S alboniger: Borneo and Sumatra
2 Malaysian Crested Honey Buzzard P p torquatus(adult normal morph) and Wallace’s Hawk-eagle
S nanus: Borneo and Sumatra
3 Javan Crested Honey Buzzard P p ptilorhyncus(immature) and Javan Hawk-eagle S bartelsi (immature): Java
4 Barred Honey Buzzard P celebensis steerei/winkleri(adult and immature) and Philippine Hawk-eagle
S philippensis: Philippines
5 Barred Honey Buzzard P c celebensis (adult andimmature) and Sulawesi Hawk-eagle S lanceolatus:
Sulawesi

Mimic or model?
The central question now lies in identifying inwhat direction the mimicry has evolved, ie,
which species is the mimic and which is themodel. Crested Honey Buzzard as a mimic may
take advantage from the fierceness of hawk-eagle
whereas especially immature hawk-eagles asmimics may gain from the innocence of Crested
Honey Buzzards.
Gamauf et al (1998a) proposed that, at least in
the Philippines, the ‘weak’ Barred Honey Buzzard is, through its similarity, protected against
attacks by the ‘aggressive and dominant’ hawkeagles. This is because the latter would avoid
aggressive interactions with similarly colouredJuvenile plumage of Javan Crested Honey Buzzard

203-204 Javan Crested Honey Buzzard / Javaanse Wespendief Pernis ptilorhyncus ptilorhyncus, juvenile, roadsidebird market between Pelabuhanratu and Bogor, West Java, Indonesia, 16 October 1995 (Rona Dennis) 205 Javan
Crested Honey Buzzard / Javaanse Wespendief Pernis ptilorhyncus ptilorhyncus, adult, Taman Safari Zoo, Cisarua,
West Java, Indonesia, 10 December 1994 (Bas van Balen) 206 Javan Hawk-eagle / Javaanse Havikarend Spizaetus
bartelsi, immature, Taman Safari Zoo, Cisarua, West Java, Indonesia, 10 December 1994 (Bas van Balen)

195

Juvenile plumage of Javan Crested Honey Buzzard

207 Javan Hawk-eagle / Javaanse Havikarend Spizaetus bartelsi, adult, Taman Safari Zoo, Cisarua, West Java, Indonesia, 10 December 1994 (Bas van Balen) 208-209 Javan Hawk-eagle / Javaanse Havikarend Spizaetus bartelsi,
adult, bird market, Jakarta, Java, Indonesia, 5 July 1989 (Arnoud B van den Berg)

196

Juvenile plumage of Javan Crested Honey Buzzard
competitors to avert injury in escalated fights.
The coloration may protect Barred Honey Buzzard also from being attacked by other birds. A
prediction that arises from this hypothesis is thathawk-eagles would always avoid confrontations
with conspecifics whereas other raptors are normally attacked. Although hawk-eagles may appear fierce, no aggressive interactions between
Javan Hawk-eagles and other raptors were observed (cf Nijman & Sözer 1995). Also, otherbird species with good powers of flight did notseem to be alarmed by the presence of Javan
Hawk-eagles, in contrast to their reaction to patrolling falcons or accipiters (Mooney 1997).
Compared with Javan Hawk-eagle, other Indonesian hawk-eagles were less intensively studied
but no aggressive interactions between them andother raptors were observed either. The moreabundant a mimic relative to the model, the lesswell-protected a mimic is (Calow 1998). Furthermore, the model should have larger or at least
equal geographical and ecological distributions.
On Sulawesi, Barred Honey Buzzard is slightly
more abundant than Sulawesi Hawk-eagle (Meyburg & van Balen 1994) but, on Java, Javan
Crested Honey Buzzard is far less often recorded
than Javan Hawk-eagle. Siberian Crested Honey
Buzzard is an abundant visitor to Java in thenorthern winter (it is largely a passage migrant on
Borneo and Sumatra while there are no records
on Sulawesi). This abundance would make theless abundant model less useful. It must be
noted, however, that Siberian Crested Honey
Buzzards may only superficially resemble Javan
Hawk-eagles, ie, in flight but less so perched asthey lack a crest and have different coloration of
the underparts.
An alternative explanation for the observed
instances of mimicry is that the hawk-eagle isactually the mimic. Mimicking Crested Honey
Buzzards might be advantageous for hawk-eagles
because of the innocuousness of the former. This
type of mimicry was described by Jensen (inprep) to explain the mimetic relationship between Wallace’s Hawk-eagle and Malaysian
Crested Honey Buzzard on Kalimantan. Especially, immature Wallace’s Hawk-eagles would takeadvantage of this as they are ill-experienced hunters and may mislead potential prey animals inthis way (‘a wolf in sheep’s clothing’). On Java,
immature Javan Hawk-eagle may profit from theabundance of Siberian Crested Honey Buzzards
in the northern winter.
Interestingly, on Java (unlike on the otherislands), only immature Javan Crested Honey

Buzzards mimic immature Javan Hawk-eagle
whereas adult Javan Crested Honey Buzzards do
not seem to have a model. This may be becausea different situation is prevalent on Java, either
through the influx of Siberian Crested Honey
Buzzards, in which case the second explanation
would come in force (as there would not beenough models for the first explanation), or
because, on Java, the adult Javan Crested Honey
Buzzard’s model has gone extinct through largescale forest destruction on Java. As it is unlikelythat Blyth’s Hawk-eagle ever occurred sympatrically with Javan Hawk-eagle (both form allospecies within one superspecies) on Java, theexistence may be suspected of an unknown darkcrested hawk-eagle that stood model for adult
Javan Crested Honey Buzzard. This explanation
would still be consistent with the higher (temporary) abundance of Siberian Crested Honey
Buzzards as in ancient times the birds would be
more dispersed over the then-existing forest.
Acknowledgements
We would like to thank René Dekker for supplying information on the skins of Javan Crested
Honey Buzzard present in the collection at the
National Museum of Natural History at Leiden,
the staff of the Museum Zoologicum Bogoriense
at Bogor for allowing access to the skin collection in their care, and Kees Roselaar for commenting on an earlier version of the manuscript.
Samenvatting
JUVENIEL VERENKLEED VAN JAVAANSE WESPENDIEF, MET COMMENTAAR OP MIMICRY BIJ ZUIDOOST-AZIATISCHE PERNIS- EN
SPIZAETUS-SOORTEN In oktober-november 1995 werd
een juveniele Javaanse Wespendief Pernis ptilorhyncus
ptilorhyncus gefotografeerd op een vogelmarkt tussen
Pelabuhanratu en Bogor, West-Java, Indonesië. Javaanse Wespendief is een (zeer) zeldzame en op Java endemische roofvogel. De structuur, het verenkleed en denaakte delen van de gefotografeerde vogel wordenbeschreven. De gelijkenis van onvolwassen Javaanse
Wespendief en onvolwassen Javaanse Havikarend
Spizaetus bartelsi wordt besproken. Dit in verband met
het mogelijke bestaan van een mimetische relatie tussen Javaanse Wespendief en Javaanse Havikarend zoals
die ook wordt gevonden bij andere Pernis-Spizaetussoortparen in het Indo-Maleise gebied en op de Filippijnen. Javaanse Havikarend komt eveneens alleen op
Java voor.

References
Brown, L & Amadon, D 1968. Eagles, hawks and falconsof the world. Feltham.
Burton, P 1989. Birds of prey. New York.
Calow, P 1998. Encyclopedia of ecology and environmental management. Oxford.

197

Juvenile plumage of Javan Crested Honey Buzzard
Gamauf, A, Preleuthner, M & Winkler, H 1998a. Mimicryin south-east Asian birds of prey: Barred Honey Buzzard(Pernis celebensis) and Hawk-eagles (Spizaetus spp).
Poster presented at 22nd International Ornithological
Congress, 16-22 August 1998, Durban, South Africa.
Gamauf, A, Preleuthner, M & Winkler, H 1998b. Philippine birds of prey: interrelations among habitat,morphology, and behavior. Auk 115: 713-726.
van Heurn, F C & van Heurn, W C 1923. Over eenige
roofvogels van Sumatra’s oost-kust en enkele bijzonderheden omtrent hun voorkomen in den Archipel. Jaarb
Club Ned Vogelkd 13: 139-145.
del Hoyo, J, Elliott, A & Sargatal, J (editors) 1994. Handbook of the birds of the world 2. Barcelona.
Jensen, R A C in prep. Observations on plumage changes

in a juvenile Wallace’s Hawk-eagle Spizaetus nanus.
Meyburg, B-U & van Balen, S 1994. Raptors on Sulawesi(Indonesia): the influence of rain forest destruction andhuman density on their populations. In: Meyburg, B-U& Chancellor, R D (editors), Raptor conservation today,
Proc IV World Conf Birds Prey Owls Berlin 10-17 May
1992, Berlin, pp 269-276.
Meyer, A B & Wigglesworth, L W 1898. The birds ofCelebes and neighbouring islands. Berlin.
Mooney, N 1997. Status and conservation of Elang Jawa
(the Javan Hawk-eagle (Spizaetus bartelsi)). Hobart.
Nijman, V & Sözer, R 1995. Aggressive behaviour displayed towards the Javan Hawk-eagle. Kukila 7: 152-154.
Nijman, V & Sözer, R 1998. Field identification of theJavan Hawk-eagle Spizaetus bartelsi. Forktail 14: 13-16.

S (Bas) van Balen, Department of Terrestrial Ecology and Nature Conservation,
Wageningen Agricultural University, Bornsesteeg 69, 6708 PD Wageningen, Netherlands(bas.vanbalen@staf.ton.wau.nl)
Resit Sözer, Institute for Systematics and Population Biology / Zoological Museum,
University of Amsterdam, PO Box 94766, 1090 GT Amsterdam, Netherlands
Vincent Nijman, Institute for Systematics and Population Biology / Zoological Museum,
University of Amsterdam, PO Box 94766, 1090 GT Amsterdam, Netherlands
Rona Dennis, Velserduinweg 50, 1971 ZE IJmuiden, Netherlands
Eric Meijnaard, WWF-Netherlands, PO Box 7, 3700 AA Zeist, Netherlands
Paul R Jepson, School of Geography, Oxford University, Mansfield Road, Oxford OX1 2SB, UK

Varia
Churchill
Churchill, a small village in north-eastern Manitoba,
Canada, is often advertised as the ‘Polar Bear
Capital of the World’. It is, however, much morethan that. Because of its unique location on the
shore of Hudson Bay, where taiga and tundra converge, it is a birdwatcher’s paradise and in summer
large numbers of Beluga Whales Delphinapterus
leucas gather at the mouth of the Churchill River.
Although Churchill’s location is not extremely far
north (58:46 N), the prevailing winds coming overthe Hudson Bay, which is ice-covered for ninemonths of the year, give the place a truly ‘arctic’
look and atmosphere.
The first migrants appear in mid-April, but thepeak time of migration is late May and early June.
During the third week of June most birds start
nesting and hatching reaches its peak in early July.
Beluga Whales arrive when the river breaks up in
June, usually around the second week, and their
numbers steadily increase until there are as many as
3000 in the area by the end of July. Polar Bears
Ursus maritimus come ashore from the sea ice from198

late July to early November; their presence is almost
guaranteed during the last two weeks of October
and the first week of November. In autumn, as
many as 150 Polar Bears pass close to or eventhrough Churchill. Sometimes a lone individual oreven a mother with cubs may be present in springor early summer. Churchill’s bird list has well over
200 species, an unusual high number for such a
subarctic location. A visit during the second andthird week of June is best, when migration is still inprogress and most local birds have arrived. Becauseof the diversity of habitats, visiting birders can
expect to see a wide range of birds.
Wildfowl includes Whistling Swan Cygnus
columbianus, Snow Goose Anser caerulescens andsmall numbers of Ross’s Goose A rossii, Greenwinged Anas carolinensis and Blue-winged Teals
A discors, American Wigeon Mareca americana,King Eider Somateria spectabilis (rare), Harlequin
Duck Histrionicus histrionicus, Long-tailed Duck
Clangula hyemalis, Black Melanitta americana, Surf
M perspicillata and White-winged Scoters M deglandi and Bufflehead Bucephala albeola (rare).
Pacific Loon Gavia pacifica, American Bittern[Dutch Birding 21: 198-204, 1999]