THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF • THE RAPTOR RESEARCH FOUNDATION, INC.

VOL. 34 DECEMBER 2000 NO. 4

J. RaptorRes. 34(4) :249-261 ¸ 2000 The Raptor Research Foundation, Inc.

A PARTIAL POST-JUVENILE MOLT AND TRANSITIONAL PLUMAGE IN THE ( BADIUS) AND GREY FROG ( A CCIPITER SOLOENSIS)

MARC HERREMANS AND MICHEL LOUETTE RoyalMuseum for CentralAfrica, Department Zoology, Leuvensesteenweg 13, B-3080 Tervuren,Belgium

ABSTRACT.--Molthas been poorly studied in the . Examination of museum specimens showedthat there are three age-relatedplumages in the Shikra (Accipiterbadius) and Grey Frog Hawk (A. soloensis)similar to the pattern known in the (A. brevipes).The juvenile plumage with its distinctively-spottedunderside is replacedby a transitionalpost-juvenile plumage during a partial contour molt between 4-10 mo of age. More feathers on the ventral side than on the dorsal side are replaced during this first contour molt, which is arrested at variousstages of incomplete feather replace- ment. Usually, a significantpart of the ventral pattern changesfrom spotted to barred, whereby the barring is on averagemore prominent than in adults. The early development of a transitional post- juvenile plumage might be related to early sex signaling.The adult plumage replacesthe transitional post-juvenileplumage during a completemolt at about one year of age. In the subspeciesA. b.poliopsis of the Shikra, which has almost no sexual dimorphism in the adult plumage, the transitional plumage is uncommon and very poorly developed. KEYWORDS: Shikra;Accipiter badius;Grey b?og Hawk; Accipiter soloensis;Levant Sparrowhawk; Accipiter brevipes;contour molt;, transitional post-juvenile plumage.

Muda parcial postjuvenil y de transicionde plumaje en Accipiterbadius y Accipitersoloensis RES0MEN.--Lamuda ha sido poco esmdiada en las Accipitridae. E1 examen de especimenesde museo demostr6 que hay tres plumajesrelacionadas con la edad en Accipiterbadius yen A. soloensissimilar al patr6n conocido en A. brevipes.E1 plumajejuvenil con su distintivosalpicado por debajo es remplazado por un plumaje de transici6npostjuvenil durante una muda parcial entre los 4-10 mesesde edad. Mas plumas del costadoventral queen el dorsal son remplazadasdurante esta muda, la cual se detiene en varias etapas del reemplazo incompleto de plumas. Usualmente una parte insignificante del patr6n ventral cambia de salpicadoa barrado, en donde el barrado es en promedio mas prominente queen los adultos. E1 desarrollo temprano de un plumaje postjuvenil de transici6n puede estar relacionado con serialessexuales tempranas. E1 plumaje adulto reemplaza al plumaje post-juvenilde transici6n dur- ante una muda completa al afio de edad. En la subespecieA. b. poliopsisla cual tiene un dimorfismo sexualen el plumaje adulto, el plumaje transicionales poco comfin y pobremente desarrollado. [Traducci6n de C6sar M'/rquez]

The molt of flight feathers has been studied in ally undergo a complete molt taking several some speciesof Accipiter(e.g., A. gentilis,A. nisus, months during the second year of life (Hartley A. cooperii,A. striatus, A. melanoleucus,A. badius; 1976, Fischer1980). In the EurasianSparrowhawk Stresemann and Stresemann 1966, Hartley 1976, (A. nisus),the best-studiedspecies, adults molt dur- Fischer 1980, Newton and Marquiss1982, Schmitt ing the breeding seasonin summer.Juveniles also et al. 1982, Henny et al. 1985), but body molt is undergo a complete molt that lastsseveral months lesswell-documented. The larger goshawksgener- during late summer and can continue into the sec-

249 25O HERREMANS AND LOUETTE VOL. 34, NO. 4

Figtire 1. Ventral aspectof the pitimagesof the Levant Sparrowhawk(Accipiter brevipes). From left to right,juvenile (BMNH 1965.M.1087), October,Israel; transitionalmale (BMNH 1934.1.1.1221),June, (note bold stripesremain from the juvenile pitimageand tail feathersjuvenile); adult male (BMNH 1956.57.13),May, Caucasus;adult female (BMNH 1934.1.1.1220), May, Iran. Photograph courtesyof the BMNH. ond year of life (Stresemannand Stresemann1960, (Cramp and Simmons 1980, Forsman 1999). Juve- 1966, Newton and Marquiss1982). During this first niles, however,undergo a partial contour molt on molt, all the juvenile plumage is replaced by the the wintering grounds in Africa when only about adult plumage, except for the odd feather which six months old, and return to the breeding allowsone to identify second-yearbirds during the grounds in a transitional post-juvenile plumage. next year (Newton and Marquiss 1982). The mi- Adult plumage is acquired during a complete molt gratory Sharp-shinned(A. striatus)and Cooper's in summer at about one year of age; some (A. cooperiz) similarly molt directlyfrom the carry over somejuvenile feathersfor the next molt juvenile plumage to the adult plumagewith a com- (Cramp and Simmons 1980, Clark and Yosef1998, plete molt during the first summer after hatching Forsman 1999). The transitional plumage, which (Mueller et al. 1979, 1981). on the underside has a striking mixture of boldly Like the European Sparrowhawk, adult Levant streakedjuvenile feathers and barred adult type Sparrowhawks(A. brevipes)start a complete molt feathers (Fig. 1; Clark and Yosef 1998, Forsman during the breeding seasonin summer and com- 1999) is kept only for about half a year,from winter plete it in autumn, generally before migration until summer. DECEMBER2000 JUVENILEMOLT IN SMALLACCIPITERS 251

Molt information for the Shikra (A. badius) is African (Louette 2000, Herremans et al. scantyand contradictory.The Asian race A. b. cen- 2001), we became aware of the existence in several chroidesis said to follow the general pattern of the of the smaller species of a distinct transitional (Cramp and Simmons plumage, kept for a short period between the typ- 1980). Thiollay (1975) mentionedthat A. b. sphen- ical juvenile and adult plumage. Herein, we de- urusin the Ivory Coast only adoptsadult plumage scribethis transitionalpost-juvenile plumage in the in the course of the second year. According to Shikra and Grey Frog Hawk with reference to the Friedmann (1930), there is an immature plumage similar and better-documentedpattern in the Le- with variable underside pattern, and Zimmerman vant Sparrowhawk. We report on aspects of the et al. (1996) describedan immature plumage re- molt sequencerelevant to the development of the sulting from a first molt. Verheyen (1953) rejected transitionalplumage, and on its possiblefunction. the existenceof an immature plumage betweenju- METHODS venile and adult in A. b. polyzonoidesin the Congo. Similarly, Schmitt et al. (1982) did not find any We examined the plumagesof the Grey Frog Hawk at the Natural History Museum (BMNH), Tring, and stud- indication of an intermediate plumage in this race ied the two African and four Asian subspeciesof the Shik- in South Africa, where the name Little Banded ra in the Royal Museum for Central Africa (RMCA), Ter- Goshawkis commonly used, despite the fact that vuren, and BMNH collections: 148 A. b. polyzono•des they documented a partial post-juvenilecontour (), 119 A. b. sphenurus(northcentral Af- molt. rica), 150 A. b. dussumieri(, Bangladesh),115 A b. poliopsis(northeastern India to Thailand and Vietnam), The Shikra and Grey Frog Hawk (alsocalled Chi- 43 A. b. cenchroides(Azerbaijan to northwestern India), nese Goshawk;A. soloensis)are excellent speciesfor and 32 A. b. badius (southwestern India, Sri Lanka) We the study the sequence of plumages on museum noted the stateof the plumage (juvenile/adult) separate- skins,because they have contrastinglydifferent pat- ly for the contour feathers on uppersides,undersides, and rectricesand checkedfor active molt of primaries terning on the undersidebetween the juvenile and and tail feathers. Contour feather renewal was estimated adult: boldly spotted and striped in the juvenile in percent (mostly in stepsof 10%) for the dorsal and and finely barred (or mainly plain in the Grey Frog ventral side separately.Sample sizes differed because Hawk) in the adult. Tail feathersare boldly banded some specimenswere undated while, in others, the state of preparation precluded the assessmentof contour molt in juveniles, and particularly the inner and outer extent, or limited extent in transitional birds precluded pair have reduced markingsin the adult. Plumage the comparisonof ventral barring with that of adults classificationis further facilitatedby discretebreed- ing seasons,and discretebreeding and nonbreed- RESULTS ing rangesin the Grey Frog Hawk. The migratory Similar to the pattern that develops in the Le- Grey Frog Hawk and the Asian racesof the Shikra vant Sparrowhawk,juveniles of the migratory Grey breed in spring (Ali and Ripley 1983), while in Af- Frog Hawk undergo a partial body molt during rica the Shikra breedslate in the dry and early in their first winter in southeastern Asia and Wallacea. the wet season,although this means in different They replace a varying amount of contour feathers months of the year at oppositesides of the equator and return to the breeding grounds in China in a (Elgoodet al. 1973, Smeenkand Smeenk-Enserink transitional, post-juvenileplumage with a mixture 1977, Brown et al. 1982, Allan 1997). The extent of juvenile and adult-type feathers, most conspic- of movements differs in the Shikra. The northcen- uous on the underside because of the differences tral African race A. b. sphenurusis migratory in in pattern: bold barring versusalmost plain rufous- , where it moves north after breeding buff (Fig. 2). In general, the post-juvenilecontour to molt (Elgoodet al. 1973). It seemsto be more molt appearsto advancein parallel on both ventral resident in the eastern part of its range (Brown et and dorsal sides.The averageindividual difference al. 1982, del Hoyo et al. 1994). The southern Af- between the extent of renewal of ventral and dor- rican race A. b. polyzonoidesdoes not undertake a sal feathers was insignificant (0.25 +- 3% (+-SE, regular migration, but is highly nomadic, particu- range = -20%-20%; N = 12). We are not certain larly in the dry season(Allan 1997). Of the four of timing of the completemolt in adultsbut it may Asian races, only the westernmostA. b. cenchroidesterminate on the wintering grounds as evidenced is migratory (Blanford 1895, King et al. 1978, Ali by an undated adult from Jilolo Island (Moluccas) and Ripley 1983, del Hoyo et al. 1994). and two adults taken on Java that were growing During work on plumages and ecology of some outer primaries. However, an adult collected on 12 252 HERREMANSAND LOUETTE VOL. 34, No. 4

Figure2. Ventralaspect of the plumagesof the GreyFrog Hawk (Accipitersoloensis). From left to right,jnvenile (BMNH 73.5.12.1593),no date,Batchian; transitional male (BMNH 1934.6.20.1),April, China(note underside predominantlyboldly blotched and tail feathersjnvenile); transitional male (BMNH 1903.7.3.94), May, China (note that fewerjnvenile barsremain on lowerunderside and thigh feathers);adult female (BMNH 1905.12.24.955), May,China (note faintly barred on lowerunderside); adult male (BMNH 1914.5.1.69),March, China (plain rufous and whiteunderside with marginalindication of barring).Photograph courtesy of the BMNH.

October in Thailand had old outer primaries but 1). Recently-fledgedjuveniles had been collected the otherswere newly-grownfeathers, suggesting in November and January. From March onwards, that most of the molt occursduring summer and some juveniles had molted body feathers. From autumn on the breeding grounds (immatures do May to October, body molt advancement showed normally return in transitional plumage to the great individualvariation, but wasnever completed breeding grounds,and it is unlikely that this (Fig. 3). Because most birds examined had no had remained in its winter quarters).Adults may growingfeathers when collected,molt was appar- start molting on the breeding grounds,suspend ently arrestedbefore completion.Replacement of molt during migration, and completeit in winter. the juvenile plumage started on the ventral side The fact that some specimensshowed a contrast with the upper throat.Molt on the uppersidemost- betweenworn inner and new outer seriesof pri- ly startedin the neck and the upper parts of the maries seemed to confirm the existence of molt mantle, or on the head. In 44 of 47 transitional suspension. birds, replacement was more advancedon the ven- In the southern African race of the Shikra (A. b. tral than dorsal side, while three birds had molted polyzonoides),the typicaljuvenile plumage (boldly to a similarextent ventrallyand dorsally.None of marked below and brown with rusty edgesabove) the birds that had replacedpart of their juvenile was found unmolted from November-July(Table plumagehad alreadystarted to molt primariesor 2000 JUVeNILe:MOLT t• SMPd•LACCIPITERS 253 254 HERREMANSAND LOUETTE VOL. 34, NO. 4

polyzonoides sphenurus lOO 100 [] ventral 9o

8o 80

7o 70 6o 9o60 I[l I Eldorsal 5o 4o I 40 30 30

o •' • 0 -- II ß I MARAPR MAY JUN JULAUG SEP OCT SEP OCTNOV DEC JAN FEBMAR APR MAY 2 8 12 9 5 I 6 2 1 2 4 8 8 1 2 1 o dussumieri poliopsis • 80 80 .• 70 70 133 60 60 5O 5O

40 40

ß

: 100 .... T 100 AUG SEP OCT NOV DEC JAN FEB MAR APR MAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP I 4 5 5 3 5 4 3 4 2 1 3 6 14 4 3 3 I I I I

Figure 3. Progressof the post-juvenilebody-molt on the dorsal and ventral side in subspeciesof the Shikra (Accipiter badius).Monthly valuesfor medians of ventral shownin dark bars, dorsal molt stagein white bars, and ranges in thin lines. Numbers under the figtire indicate monthly sample sizes.

secondaries. One bird with well-advanced contour the ventral side of the transitional post-juvenile molt in June had new inner and outer tail feathers plumage tended to be broader and more rusty in on both sides,but none growing. Most juveniles, color than in adults (Table 2; Fig. 4). Birds therefore, acquire a transitional second plumage changed from transitional plumage into full, adult by a partial molt of the body feathers only, retain- plumage through a complete molt when about 1 ing most remiges and rectrices.The extent of this year old, almost synchronous with the molt of partial contour molt is highly variable individually adults. Adults undergomg a complete molt from (Fig. 3). A single second-year bird (BMNH one definitive plumage to the next were collected 1910.7.1.108)was collectedin November molting from December (early stages)to May (lateststages). directly from a much-wornjuvenile plumage to a Recently-fledgedyoung of A. b. sphenuruswere fully adult plumage, apparently without having de- dated February-September. Juveniles with transi- veloped transitionalplumage. Despitewide individ- tional plumage appeared from September onwards ual variation, the barring of the new feathers on (Table 1). The contour molt never completed, with DECEMBER2000 JUVENILEMOLT IN SMALLACCIPITERS 255

Table 2. Intensity of ventral barring of the lransitional, age (Table 1; Fig. 3). Despite the great individual post-juvenileplumage compared to adult plumagein sub- variation in extent of the contour molt, replace- speciesof the Shikra (Acdpiterbadius). ment was less extensive than in the African races (Fig. 3). Four birds had very worn juvenile plum- MEAN AD ages in February and April, indicating that they < MAX P:l < P:l < plumage, but would have molted directly from MAX AD a AD b MEAN AD ( MIN mDd worn, juvenile plumage to adult plumage with a A. b. polyzonoides complete molt (Table 1), similar to the few exam- Males 6 5 5 0 ples in the other racesmentioned above.All of 37 Females 17 11 3 0 transitionalbirds had molted more extensivelyven- A. b. sphenurus trally than dorsally.Again, new feathers of the tran- Males 5 5 2 0 sitional plumage tended to be more prominently Females 8 4 4 0 barred than in the adult plumage (Table 2; Fig. 6). No transitional birds were found during the com- A. b. dussumieri plete molt into adult plumage, but this molt is like- Males 7 8 2 0 ly to be synchronouswith that of adults, which oc- Females 3 6 2 0 curs shortly after breeding, from June-November • Barring of post-juvenileplumage heavier (broader and more (Table 2). contrasting) than the maximum barring in adults. •' Barring of post-juvenileplumage in betweenthe heaviestand In A. b. poliopsis,recently-fledged juveniles were average barring of adults. dated April-September. Few juveniles developed •'Barring of post-juvenileplumage in between the averageand transitional plumage, and if so, mostly did so to a weakestbarring of adults. small extent, making it sometimesdifficult to dis- d Barring of post-juvenileplumage poorer developedthan weak- tinguish between transitional molt and accidental est barring of adults. feather replacement (Table 1; Fig. 3). When 6-12- mo old, most juveniles had heavily-worn,juvenile great variation in the extent of renewal among in- plumage, without any sign of transitional post-ju- dividuals (Fig. 3). In general, we suspecta tenden- venile plumage (Table 1). Consequently,the bar- cy for a lessextensive transitional plumage than in ring of the transitionalplumage could not be com- A. b. polyzonoides(Fig. 3). Of 30 transitionalbirds, pared to that in the adult plumage. One juvenile 26 had molted more extensivelyventrally than dor- (BMNH 87.11.1.165)was in completemolt in June, sally; three had progressedequally and one had changing feathers directly from a very worn juve- the upperside more extensivelymolted. One sec- nile plumage to the adult plumage. All of the in- ond-yearbird (RMCA 102759)was molting directly dividuals with worn plumage that were collected from a much-worn juvenile plumage to the adult fromJanuary-June (Table 1) were expected to fol- plumage with a complete molt, apparentlywithout low the samepattern. Birds in transitionalplumage having developeda transitionalpost-juvenile plum- underwent a complete molt to adult plumage in age. In it, the bars on the underside of the transi- April, May, and August, possibly slightly earlier tional plumage tended to be more stronglymarked than the molt in adults,which occurredJune-Sep- than those of adults (Table 2; Fig. 5). One bird tember, after breeding (Table 1). collected in February and severalmore collected Specimens of A. b. cenchroidesand nominate A. between May and September were undergoing a b. badiuswere limited. Several specimens of both complete molt from transitional post-juvenile races were in transitional plumage (Table 1). Of plumage to full adult plumage and, therefore, five transitional A. b. cenchroides,one had 80% of when about one year old. Adults undergoing com- the ventral plumage renewed by December, anoth- plete molts from one adult plumage to another er 60% by February,and the remainder had <15% were collected from May (early stages)to Decem- new feathers. All five transitional A. b. badius had ber (latest stages). >20% renewedfeathers ventrally, and three had In A. b. dussumieri,recently-fledged juveniles 70-90% renewed.The limited data suggestedthat, were dated June-July and juveniles in fresh plum- among the Asian races, A. b. badiusmay develop age were found until October. From August on- the most extensive transitional plumage, while wards, birds started to develop transitional plum- molt extent in the migratory A. b. cenchroidesap- 256 HERR•MANS AND LOUETTE VOL. 34, NO. 4

Figure 4. Ventral aspectof the plumagesof the Shikra (Accipiterbadius polyzonoides). From left to right, juvenile male (BMNH 1911.12.23.430),January, Zambia; transitionalfemale (BMNH 1950.50.125), April, Namibia (note limited replacement and new feathers more prominently barred than in adult); transitionalfemale (BMNH 80.1.30.3), no date, Zambia (note only some barring from juvenile plumage remaining on flanks and thighs,juvenile tail, and replaced feathers on underside more prominently barred than in adult); adult female (BMNH 1932.5.10.598), March, Tanzania;adult male (BMNH 94.6.16.170),no date, Zambia.Photograph courtesy of the BMNH.

pears more similar to A. b. dussumieri.There were and all tail feathers are heavily banded. A transi- too few specimensto compare the post-juvenile tional plumage occurs in the second half of the barring with that of adults. Adults had been col- first year of life during which time remiges, most lected from nestswith eggs in April for A. b. cen- of the rectrices,and most of the larger upper wing chroides,and molt in adults also followed breeding coverts are retained from the juvenile plumage, in this race (Table 1). From the timing of appear- but between 4-10 mo of age some of the body ance of juveniles in the population and molt in feathersare replaced. New featherson the upper- adults (Table 1), it appeared that the same molt side resemble the adult type, while those on the pattern alsoapplied to the nominate race A. b. bad- underside become barred with a tendencyfor wid- ius. er, bolder barring than in adults. The extent of the partial contour molt is highly variable between in- DISCUSSION dividuals and taxa, and somejuveniles do not de- In A. brevipes,A. soloensis,and A. badius,juvenile velop transitionalplumage at all, particularlythose birds in nestling plumage have undersides with of the race A. b. poliopsisof the Shikra. In it, the large rufous-brown spots and stripes, and broad transitional plumage is replaced by adult plumage barring on the flanks; the upperside has rusty during a complete molt when one year old, more brown edges to a generally dark brown plumage or less synchronouswith the complete molt of DECEMBER2000 JUVENILEMOLT IN SMALLACCIPITERS 257

Figure 5. Ventral aspectof the plumagesof the Shikra (Accipiterbadius sphenurus). From left to right,juvenile male (RMCA 109477),July, Ethiopia; transitional male (RMCA 102.759),May, Uganda (note somespots from juvenile plumage left, tail juvenile and heavilybanded, and more distinctlybarred undersidethan adult); adult male (RMCA 95921), August,D.R. Congo (note lessdistinctly barred than female and unmarked outer tail feathers); transitional female (RMCA 102.736),June, Kenya(note somespots left fromjuvenile plumage, tail juvenile and heavilybanded, and more prominentlybarred than adult); adult female (RMCA 103.515), November,D.R. Congo (note more dis- tinctly barred than adult male, but lessthan post-juvenilefemale, unmarked outer tail feathers).

adults. Adults are uniformly bluish-greydorsally al. (1982) indicated that the Shikra might breed at (dark slate in A. b. soloensis)and have barring on one year of age, while Thiollay (1975) suggested the underside (almost plain in soloensis);females that somebirds do not breed at age one. Zimmer- are generally more prominently barred than man et al. (1996) felt that the race A. b. sphenurus males. At least some tail feathers of adults have re- might breed in transitionalplumage but no cases duced banding. Adult plumage is replaced by a of it were observedin A. b.polyzonoides by Tarboton complete molt followingbreeding. (2000). We lack information on whether birds may or Schmitt et al. (1982) found that half of the 20 may not breed when 1 year old and in transitional juveniles caughtin South Africa were undergoing plumage. In migratory speciessuch as the Levant solelya contour molt in April and May, mostlikely Sparrowhawkand Grey Frog Hawk, transitional the partial contour molt of the post-juvenileplum- birds migrate to the breeding grounds. Brown et age we report here. The fact that a bird they clas- 258 HERREMANSAND LOUETTE VOL.34, NO. 4

Figure6. Ventralaspect of theplumages of theShikra (Accipiter badius dussumieri). From left to right,juvenile female (BMNH85.8.19.487), no date,India; transitional male (BMNH 85.8.19.481), Octobex; India (notesome spots from juvenileplumage left, tailjuvenile and heavilybanded, and moredistinctly barred traderside than adult); adult male (BMNH 1949.WHI.1.223), March, India (noteunderside less distinctly barred than female and unmarkedouter tail feathers);transitional female (BMNH 85.8.19.508), March, Nepal (note many blotches left from the juvenile plumage, tail juvenileand heavilybanded, and ventrallymore prominentlybarred than adult);transitional tkmale (BMNH 1949.25.87),Novembex; Rawalpindi, Pakistan (note a tkwblotches left from the juvenile plumage and more promi- nentlybarred than adult); adult tkmale (BMNIf 86.3.25.79),December, India (note •nore distinctly barred than adult malebut lessthan transitional female, and reduced markings on outertail feathers).Photograph courtesy of the BMNH.

siftedas a juvenile in May wasrecaptured a year The individualthey caughtmay have showedcom- later in adult plumageshould not be seenas proof plete, adult plumageadding further evidencethat for the absenceof an intermediate plumage. In the transitionalplumage is retainedfor onlyabout fact, their observationsfit exactlythe plumagese- half a year and is replacedby the adult plumage quence we present here. A bird in recognizable in synchronywith the molt of breedingadults. We juvenile plumage in May, whether or not the re- found several specimensfor the different taxa placementof bodyfeathers has started, is expected molting from transitionalplumage to adult plum- either to be in the transitionalplumage or to have age with a complete molt at about the same time molted recently from the transitional to the adult as adults undergo the complete post-breeding plumageby next May. Schmittet al. (1982) did not molt. This meant that the transitionalplumage is recognizethe barred transitionalplumage as dif- only worn for about half a year. Some transitional ferent from the adult and, thereft)re, identified the birds may molt slightlyahead of adultswith non- bird as an adult when recapturingit a year later. breeding birds molting earlier. DECEMBER2000 JUVENILEMOLT IN SMALLACCIPITERS 259

If the transitional plumage is only retained for Recently, a second-yearplumage was described about half a year, are the feathers molted during from the South American Gray-bellied Hawk (A. the first year replaced again in the subsequent poliogaster),a specieswith a unique juvenile plum- molt to adult plumage, or is all replacement part age (Whittaker and Oren 1999). We found a sec- of the same molt cycle, with part of the contour ond-year plumage with broader ventral barring molt shiftedhalf a year forwards?Is the transitional than in adults in the Mayotte of the plumage, therefore, a distinct plumage, or is it Frances' Sparrowhawk (Accipiterfrancesiae brutus, merely part of a protractedmolt process?A pattern Herremans et al. 2001). A transitional plumage, af- of a protracted molt with advancedcontour molt ter a partial contour molt, is also more frequent m would be similar to that found in severallong-dis- the Black-shouldered Kite (Elanus caeruleus)than tance migrants (e.g., wadersin the Calidris, previously known (Herremans 2000). The occur- Cramp and Simmons 1983) and in some rence of early, partial post-juvenilemolts in small (Hirundo spp., Delichonspp., Riparia spp.) and war- raptors seemsto be associatedwith a distinctiveju- biers (Acrocephalusspp., Locustellaspp., Hippolais venile plumage with the underside pattern differ- spp., Sylviaspp., Jenni and Winkler 1994), which ing from that of adults. There are regions in the start a contour molt when still on the breeding world where several accipiters,with essentiallythe grounds during the northern summer, but post- samejuvenile plumage co-occur (e.g., King et al. pone the replacementof most remigesand rectri- 1978, Zimmerman et al. 1996), and molt into a ces of the same molt cycleuntil arrival on the win- more adult-like plumage may be essentialfor prop- tering grounds some months later. In accipiters,if er speciesrecognition before they can enter the feathers of the transitional plumage are not re- breeding population. However, interspecific pres- placed after half a year, there should be birds in suresmay not be the main force behind the early the population with new, adult-type rectrices and molt, becausethe phenomenon also existswhere two generations of contour feathers with under- no confusing juveniles of other species co-occur sides showing a mixture of worn, prominently (e.g., on Mayotte Island: Herremans et al. 2001). barred feathers from the transitional plumage, and At this point we are uncertain how it functions but fresh, less barred, adult feathers. We have not the underside plumage is probably important in found such birds in collections. Furthermore, be- social communication in accipiters. Under this cause markings on the undersidesof transitional functional hypothesis, it is important that the birds were on average more prominent, we con- adult-like ventral plumage be acquired before the cluded that the molt at age one included all feath- start of the next breeding season. In the well- ers. We found no evidencein the Accipiterliterature marked race of the Shikra (A. b. poliopsis),the sex- of a possible split molt, whereby replacement of ual differentiation in ventral colors and patterning body feathers significantlyprecedes that of flight of adults is minimal and less than in the other rac- feathers during the same molt cycle. In the Eur- es and the transitional, post-juvenile plumage is asian Sparrowhawk,replacement of the primaries poorly developed.Possibly, the developmentof the spans the entire molt period and no significant transitional plumage functions as an early indica- body molt occurs outside the period of primary tion of the individual's sex and, because of the replacement (Newton and Marquiss 1982). How- poor sexual plumage dimorphism of adults, there ever, it has a rather variable plumage with poorly- is no functional need for young A. b. poliopszsto differentiated adult and juvenile patterns (Nilsson change plumage at an early stage. Individual vari- 1992, Engstrtm and Edelstam 1995). Although it ation in the development of the post-juvenilemolt is the best studied Accipiterspecies, it may thus be might be dependent on condition and age, and an unfortunate choice as the standardfor the ge- the extent could alsovary between years. Molt var- nus illustrating plumage sequences. iation could, therefore, offer juveniles opportuni- The transitionalplumage in the three accipiters ties to advertisetheir sex, age, and individual qual- we studied clearly showeda separate,intermediate ity. Age and quality have been demonstrated to feather generation between juvenile and adult have important impact on breeding performance plumages(Humphrey and Parkes1959). It results in the Eurasian Sparrowhawk (Risch 1998), and it from its own, albeit partial and individually-variable is likely that early advertisementof sex and quality contour molt, giving a plumage type which is dif- for young birds entering their first breeding season ferent from that of adults. is ultimately beneficial for their reproductive per- 260 HEP,m•s AND LOUETTE VOL. 34, No. 4

formance. Under this hypothesis,aspects such as ENGSTROM, H. AND C. EDELSTAM. 1995. Om utseendet hos differencesin territorial establishment,mating suc- sparvhCkar--dCda och levande. Anser34:195-202. cess,or recruitment into the breeding population FISCHER,W. 1980. Die Habichte. Neue Brehm-Bfichere•, at age one, may prove to be related to the extent Wittenberg/Lutherstadt,Halle-Saale, Germany. of the post-juvenilemolt. FORSMAN,D. 1999.The raptorsof Europe and the Middle East. T. and A.D. Poyser,London, U.K. Kemp (1999) demonstratedan early partial con- FRIEDMANN,H. 1930. Birds collected by the Childs Frick tour molt in the Greater Kestrel (Falcorupicoloides) expeditionto Ethiopiaand Kenyacolony. Part 1. Non- which coincided with changesin territorial behav- passerines.Smithsonian Institution, Washington,DC iors of adults. Small investmentsin a partial, post- U.S.A. juvenile molt, paralleled by changesin soft parts I4•d•TLEY,R. 1976.Some notes on the plumagesof Black (e.g., eye color) resulted in important effects on Sparrowhawks.Bokmakierie 28:61-63. communication and signaling.As in most accipi- HENN¾,CJ., R.A. OLSON,AND T.L. FLEMING.1985. Breed- ters, eye color changeswith age in the Shikrafrom ing chronology,molt, and measurementsof accipiter pale bluish-yellowin the freshjuvenile to yellowor hawks in Northeastern Oregon. J. Field Ornithol.56: orange in the transitionalplumage and bright red 97-212. in adults,with somevariation accordingto sex and HERREM^NS,M. 2000. Serial descendantprimary molt race.As in the Greater Kestrel,such changes in eye (Staffelmauser) in the Black-shouldered Kite Elanus color could contribute to age and sexual commu- caeruleus.Ringing & Migz 20:15-18. nication in the Shikra. , M. LOUETTE,AND J. STEVENS.2001. Biologyof the Frances'sSparrowhawk Accipiterfrancesiae on the Com- ACKNOWLEDGMENTS oro Islands. Ostrich72:in press. HUMPHREY,P.S. AND K.C. PARKES.1959. An approach to The staff of the Natural History Museum at Tring pro- the studyof molt and plumages.Auk 76:1-31. wded all necessaryfacilities for the study of skins, and prepared the photographsof their specimens.The paper JENNI,L. ^ND R. WINKLER.1994. Molt and aging of Eu- benefittedfrom the commentsof the refereesAlan Kemp ropean passerines.Academic Press,London, U.K. and W.S. Clark. J.-M. •andyck made the photographsof KEMP,A.C. 1999. Plumage development and visualcom- the RMCA specimensand prepared the prints. munication in the Greater Kestrel Falco rupicoloides near Pretoria, South Africa. Ostrich 70:220-224. LITERATURE CITED KING, B., M. WOODCOCK, AND E.C. DICKINSON. 1978. A ALI, S. •dqD S.D. PdPLEY.1983. Handbook of the birds of field guide to the birds of south-eastAsia. Collins, India and Pakistan,Compact Ed. Oxford Univ. Press. London, U.K. Oxford, U.K. LOUETTE,M. 2000. Evolutionaryexposition from plum- At.I2•N, D.C. 1997. Little Banded Goshawk.Pages 226- age pattern in African accipiter. Ostrich71:45-50. 227 in J.A. Harrison, D.C. Allan, L.G. Underhill, M. MUELLEP•,H.C., D.D. BEP•GER,AND G. ALLEZ.1979. Age Herremans, AJ. Tree, V. Parker, and CJ. Brown and sex differentiation in size of Sharp-shinned [EDs.], The atlas of southern African birds. Vol. I. Hawks. Bird-Banding50: 34-44. BirdLife South Africa,Johannesburg, South Africa. , --, AND--.. 1981. Age, sex, and seasonal BI•NFORD, W.T. 1895. The fauna of British India, includ- differencesin size of Cooper's Hawks.J. FieldOrnithol ing Ceylon and Burma. Vol. III: birds. Taylor and 52:112-126. Francis. London, U.K. NEWTON,I. ANDM. MARQUISS.1982. Moult in the Spar- BROWN, L.H., E.K. UPOn4, AND K. NEWMan. 1982. The rowhawk. Ardea 70:163-172. birds of Africa. Vol. I. Academic Press. London, U.K. NILSSON,L. 1992. Hur ser vuxna sparvhCkaregentligen CI•RK, W.S. AND R. YOSEF. 1998. In-hand identification ut? Anser 31:279-281. guide to Palearcticraptors. IBCE Tech. Publ. 7. Inter- RISCH, M. 1998. Der Einfluss individueller Qualit/it auf national Birdwatching Centre, Eilat, Israel. die Reproduktiondes SperbersAccipiter nisus. Disser- CP•dwP, S. ^ND K.E.L. SIMMONS. 1980. The birds of the tation abstract.J. Ornithol.139:112-113. Western Palearctic. Vol. II. Oxford Univ. Press. Ox- SCHMITT, M.B., S. B^UR, AND F. VO• M^LTITZ. 1982. Men- ford, U.K. sural data, moult, and abundance of the Little Band- --)dqD --.. 1983. The birds of the western Pa- ed Goshawk in the Transvaal. Ostrich 53:74-78. learctic. Vol. III. Oxford Univ. Press. Oxford, U.K. SMEENK,C. AND N. SMEENI•-ENSERINK.1977. Observa6ons DELHOYO, J., A. ELLIOTT,AND J. SARGATALlEDS.]. 1994. on the Shikra Accipiterbadius in Nigeria. Ardea65:148- Handbook of the birds of the world. Vol. 2. Lynx Ed- 164. icions, Barcelona, Spain. STRESEMANN,E. AND V. STRESEM^NN. 1966. Die Mauser ELGOOD,J.H., C.H. FRY,•ND RJ. DOWSETT.1973. African der VCgel.J. Ornithol.107 (Sonderheft):3-445. migrants in Nigeria. Ibis 115:1-45. STRESEM^NN,V. •ND E. STRESEMANN.1960. Die Handsch- DECEMBER2000 JUVENILEMOI,T IN SMALLACCIPITERS 261

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