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j RaptorRes. 32(2):126-135 ¸ 1998 The Raptor ResearchFoundation, Inc.

A POSSIBLE NEW OF THE PHILIPPINE HAWK-(SPIZAITUS PHILIPPENSIS) AND ITS FUTURE PROSPECTS

MONIKA PRELEUTHNER AND ANITA GAMAUF 1 KonradLorenz-Institute for ComparativeEthology, Austrian Academy of Sciences,Savoyenstrafle. l a, A-1160 Vienna, Austria

ABSTRACT.--Onthe basisof 19 study skinsfrom eight different museum collections,five captive , and 67 field observations(cumulative observation time 6.8 hr), we here describe a possiblenew sub- speciesof the Philippine Hawk-Eagle($pizagtus philippensis pinskeri). This new subspeciesis restrictedto the rain forestsof the southernpart of the Philippine Archipelago.Its altitudinalrange reachesfrom 0-1900 m and it occursat leaston , ,and .The population sizeof S.p. philippensis is estimatedto be 200-220 pairs, that of S. p. pinskeridoes not exceed 320-340 pairs.We emphasizethe current treats to the entire speciesdue to the ongoing destructionof its natural rain forest habitat. KEYWOADS: PhilippineHawk-Eagle, Spiza6tus philippensis; new subspecies; marphology; distribution; conser- vation;.

Una posiblenueva subespeciede Spiza•¾usphilippensis y su futuro RESUMEN.--Conbase en 19 pieles de estudiode 8 coleccionesdiferentes, 5 avesen cautiverioy 67 observacionesde campo (tiempo de observaci6nacumulado 6.8 horas), describimosuna posiblenueva subespeciede $pizagtusphilipensis (S. p. pinskeri).Esta nueva subespecie esfft restringida a los bosquesde 11uviadel sur del archipi61agode las Filipinas.Su rango altitudinal es de 0-1900 m y se encuentra en Mindanao, Samary Negros.E1 tamafio estimadode la poblaci6n de S.p. philippensises de 200-220 pares, el de S. p. pinskerino excede a los 320-340 pares. Enfatizamoslas actualesamenazas para la especie entera debido a la continuada destrucci6n del habitat natural, el bosque de 11uvia. [Traducci6n de C6sar M•trquez]

Taxonomically, birds of prey are well studied. new subspecieshave been added during this cen- Although only a few new have been re- tury, three from and two from cently discovered, the number of accepted spe- Central and South America. cies has increased because some subspecieshave In 1993-94, we assessed the habitat use and been raised to speciesstatus (Peters 1931, Brown behavior of 21 speciesof raptors in the Philip- and Amadon 1969, Mayr and Cottrell 1979, pines. As part of this ecomorphological study Weick 1980, Amadon and Bull 1988, Sibley and (Gamauf et al. 1998), we measured specimens in Monroe 1990). According to the recent compi- 13 museum collections worldwide. One part of lation of del Hoyo et al. (1994), the order com- the project focused on the endemic Philippine prises302 speciesand 702 subspecies.Within the Hawk-Eagle (Spiza•¾usphilippensis Gurney in Spizab'tus(Vieillot 1816), 10 species (in- Gould 2 (1863)). Because it is a forest-dwelling cluding 20 subspecies)have been described.Five specieswith low population densities,the hawk- eagle is difficult to study and information on its • Presentaddress: Museum of Natural HistoryVienna, 1. population size and habitat use is rather limited ZoologicalDivision-- Collection, Burgring 7, A-1014 (McGregor 1909, Delacour and Mayr 1946, Ama- Vienna, Austria. don 1953, Brown and Amadon 1969, Mallari 2 Since Peters (1931) the authorshipfor S. philippensis 1992, Danielsen et al. 1993). We searched in var- usuallywas credited to Gould. The specificname togeth- er with a descriptionsatisfying the criteria for availability ious museum collections (17 were contacted by was publishedverbatim as proposedby Gurney, who ac- mail, 13 visited personally), but preserved spec- cording to Art. 50(a) ICZN (1985) should be cited as the imens were availablein only eight collections.Al- author. though the Philippine Hawk-Eagle has been con-

126 JUNE1998 NEWPHILIPPINE I'-IAWK-EAGLE SUBSPECIES 127

Figure 1. Top---holotypeof Spizag•usphilippensis pinske•i (USNM, CatalogNo. 578113). Bottom--Typical adult rep- resentativeof Spizak?usphilippensis philippensis (AMNH, Catalog No. 459 063).

sidered to be monotypic, we found a striking di- Although the morphological differentiation chotomy in the 19 museum specimens we ex- appeared clear-cut, the typical disyllabic calls are amined. The differences in size, plumage very similar and there is no proof that there is patterns, and coloration were found to be cor- any reproductive barrier between the two related with the geographic origin of the speci- morphs. Since the degree of genetic isolation is mens whether they were of northern or southern unknown, we propose to recognize the northern portions of the Philippines. The distinction was and southern populations as two distinct subspe- consistentlyobserved in skins, captive birds, and cies rather than separate species.The type spec- individuals in the wild. On the basis of our com- imen (The Natural History Museum--Tring, BM parisons, we concluded that there are two mor- 1955.6.N.20.424, type location substituted phologically different and geographically sepa- by Swann and Wetmore 1945) is herein recog- rated populations of hawk- in the Philip- nized as a representative of the northern nomi- pines. notypical subspeciesS. p. philippensisGurney in 128 PRELEUTHNERAND GAMAUF VOL. 32, No. 2

Table 1. Holotype and paratypemeasurements of S. p. pinskerisubsp. nov. in comparisonto the nominotypicalform dependent on age and sex. Number of studyskins are given in parentheses.F = female, M = male. * = P < 0.05, ß* = P < 0.01 (t-test).

SPIZA•TUS PHILIPPENSIS PINSKEILI SUBSP. NOV.

AGE CLASS SEX SPECIMENS ADULTF (3) 1 ADULTM (2) 2 JUVENILE MEASUREMENT(mm) i __+SD RANGE ,• ñ SD RANGE M (1) F (1) Bodylength 609.0 _+1.0 608.0-610.0 543.5 _+41.5 502.0-585.0 550.0 -- Wing length 365.5 -+ 15.5 350.0-381.0 326.0 -- 336.0 378.0 I•pp's distance 92.5 --- 7.8 87.0-98.0 77.0 _+7.1 72.0-82.0 87.0 93.0 Number of notchedprimaries 8.7 + 0.6 8.0-9.0 8.0 -- 8 9 Length of centraltail 244.0 -+ 5.7 234.0-248.0 211.0 -+ 5.0 208.0-215.0 216.0 232.0 Length of outermosttail f•ather 253.0 --- 5.0 248.0-258.0 214.0 + 15.6 203.0-225.0 221.0 240.0 Lengthof hind toe 26.9 -+ 3.2 24.5-30.5 22.9 - 1.2 22.0-23.7 23.5 30.0 Length of middle toe 50.9 -+ 2.7 49.3-54.0 44.5 _+3.5 42.0-47.0 49.5 44.2 Length of hind claw 36.9 _+1.5 35.6-38.5 30.7 _+1.0 30.0-31.4 34.6 36.2 Length of middle claw 24.7 + 1.1 23.9-26.0 21.8 -+ 1.1 21.0-22.5 23.0 25.0 Tarsuslength 82.5 +- 1.3 81.5-84.0 74.7 ___6.4 70.2-79.2 68.0 88.0 Bill length with cere 40.9 -+ 2.1 38.7-42.9 36.5 +- 1.0 35.8-37.2 40.8 41.5 Bill width of distaledge of cere 29.4 +- 1.0 28.3-30.0 28.6 + 2.6 26.7-30.4 29.5 31.8 Bdl depth 24.8 -+ 0.5 24.3-25.3 20.5 + 0.4 20.2-20.8 -- 23.8 Holotypeincluded. Subadult included.

Gould (1863). We propose that the southern ventral side is divided into three regions showing subspeciesbe designated a new subspeciesSpi- different colors. The upper breast is white with zagtusphilippinsis pinskeri subsp. nov. bold longitudinal, black streaksedged with tawny olive (S30: 5339,M50). The adjoining area is clearly DESCRIPTION separatedfrom the upper breastand carries a taw- Holotype. It is an adult female that weighed ny olive (S30: 5339,M50) band with some white, 1281.2 g and wascollected on 16 May 1963 by D.S. spotted . The lower belly as well as the Rabor in the Car-Can-Mad-LanArea, del feathered legs and the undertail covertsare con- Sur,Mindanao, Philippines (elevation 330-700 m). trastingly barred, from dark clove brown (5339: Originally, this specimenwas in the collection of M70, C99) to blackishand white. The wings are Silliman UniversityNatural History Museum (Cat- short and roundish with tips extending less than alog No. 35020), but it is now in the U.S. National halfway to the tailtip. Like the lower belly, the un- Museum, SmithsonianInstitution (USNM, Catalog derwing coverts are finely barred clove brown No. 578113,Fig. 1). (5339:M70, C99) to blackishand white. The up- Description of Holotype. The holotype of S. p. perparts beginning at the hind neck are uniform pinskeriis very colorful (Fig. 1). The head and brownish olive (S80: Y80, M 30). The long tail has crown show a pale olive btfff (S10: Y10, MOO) (no- the same color. A broad black subterminal bar is menclature taken from Ridgway [1912], color separatedby a broader unmarked zone from five codes from Kiippers [1984]) with a background narrower bars. The cere and bill are sooty black color of blackish streaks which are more bold on (S90: Y20, MOO) and the toes yellow (faded in the the crown. The head contrasts with the deep specimen). brownish olive (S80: Y80, M30) back. The long, Measurements of the holotype are as follows: prominent crest consistsof 4-5 black feathers of body length 608 mm, wing length 350 mm, Kipp's unequallength (longest7 cm). The throatis white, distance(primary projection) 87 mm, number of divided by a bold, black median stripe and bor- notched primaries 9, length of central tail feather dered by black, lateral moustache stripes com- 240 mm, length of outermosttail feather 248 mm, posed of fine black streaks.The plumage on the length of hind toe 25.6 mm, length of middle toe JUNE1998 NEW PHILIPPINEHAWK-EAGLE SUBSPECIES 129

Table 1. Extended.

SPIZAt•TUSPHILIPPENSIS PHILIPPENSIS GURNEY IN GOULD (1863) ADULTF (4) ')ADULT M (6) e JUVENILEM (2)

• + SD RANGE • + SD RANGE / + SD RANGE

618.0 + 16.6 601--634 563.3 + 22 543--587 -- -- 399.0 --+ 1.0'* 398--400 358.0 + 7.3** 352--372 358.0 -- 104.0 --+ 5.5 98--108 92.8 --+ 5.5 86--99 87.0 -- 8.3 + 0.6 8--9 8.2 --+ 0.4 8--9 8.5 --+ 0.1 8--9 246.8 + 11.5 236-249 222.3 + 11.6 208--236 247.0 -- 257.7 + 5.9 251--262 232.7 + 7.9 222--245 249.0 -- 29.3 + 1.7 27.8--31.6 25.0 + 1.4 23--27 26.9 --+ 0.8 26.3--27.4 50.6 --+ 3.4 47--55 46.0 + 3.3 43.0--49.5 47.6 --+ 1.1 46.8--48.3 38.7 --+ 2.0 37.0--40.7 34.6 --+ 0.7** 33.8--35.7 32.5 + 1.3 31.5--33.4 26.8 + 1.2' 25.2--28.0 25.4 -----1.0'* 24--27 24.3 + 0.4 24.0--24.5 86.8 + 5.6 81--94 81.7 -----2.0 79--84 -- 80.1 45.6 --+ 2.1 44.3--48.1 40.7 --+ 1.4' 39.5--42.5 39.3 --+ 1.9 37.9--40.6 30.3 --+ 4.0 29.0--35.6 27.1 + 1.0 25.5--28.3 28.4 --+ 0.1 28.3--28.4 25.0 + 1 23.6-25.9 21.2 + 1.0 20.3--22.4 20.5 --

49.3 mm, length of hind claw 35.6 mm, length of width of the bill (Table 2). Bird hunters typically middle claw 24.4 mm, tarsuslength 84.0 mm, bill have longer claws on their middle toes (positive length with cere 41.1 ram, bill width of distaledge correlation) and shorter hind claws, their bill is of cere 30.0 mm, and bill depth 24.3 mm. shorter and the cross-sectionof the bill (reflected Measurementsfrom Museum Specimens.We ob- in the width of the bill) is more roundish com- tained measurements on 42 morphometric char- pared to the mammal hunters. This suggeststhat acters from 19 museum specimensof Philippine members of the bigger S. p. philippensismay have Hawk-Eagles,14 of which were prominent and dis- a higher proportion of mammals in their diet criminative characters (Table 1). Despite the pro- whereas S. p. pinskerimay preferentially feed on nounced sexualdimorphism, the measurementsof birds (Rochon-Duvigneaud 1952, Wattel 1973, S. p. pinskerigive clearly smaller valuesthan those Brown 1976, Hertel 1995, Gamauf et al. 1998). of S. p. philippensis.This finding wascorroborated ETYMOLOGY by discriminant function analysis (Fig. 2) which separatedboth speciesin both sexes.The clearest Scientific Name. The proposed new subspecies discriminating feature found was the size of the is named in honor of Prof. Dr. Wilhelm Pinsker, feet and bill, although the distinction held even Institute for Medical Biology,University of Vienna, when wing measurementswere included. All spec- for his excellent scientific work as well as his emi- imens were correctly classifiedand there was no nent skill in the guidance of his studentsas a teach- multivariate overlapping of the groups. er. We wish to emphasizeour gratitude for the in- Discriminant function 1 (DF 1) concerned char- valuablehelp he has given to both of us. actersrelated to the mode of handling and killing English (German) Names. According to the geo- the prey as well as indirecdy to prey size. The graphical distribution of the two subspecies,we length of the bill wasloaded the higheston axis 1, propose the name Southern Philippine Hawk-Ea- followedby the length of hind clawand the length gle (Stidlicher Philippinenhaubenadler) for S. p. of the hind toe. DF 2 was correlated with charac- pinskeri and Northern Philippine Hawk-Eagle ters describingthe killing apparatusbut also with (N6rdlicher Philippinenhaubenadler) for the the type of prey (especiallybirds vs. mammals).It nominotypical subspeciesS. p. philippensis. wasdominated by the length of the clawsof middle Paratypes.The three specimensfrom Mindanao toe and hind toe and secondarilyby the length and are herein designatedparatypes: 130 PRELEUTHNERAND GAMAUF VOL. 32, NO. 2

4.5

2.5 Spizadtus p13.philippensis

0.5

Spizadtusphilippensis pinskeri subsp. nov. 0 -1.5

-3.5

-4.9 -2.9 -0.9 1.1 3.1 5.1 7.1

Discriminant function 1

Figure2. Separationof S.p. philippensis (N = 12,round symbols) and S. p. pinskeri (N = 7, squaresymbols) according to discriminantfunction analysis of 5 morphologicalvariables (bill length,bill width, length of the hind toe, hind claw and middle claw).

1. Adult male collectedon 30January 1964 by D.S. [UMZC], Copenhagen, Denmark, Catalog No. Rabor at Tucay, Mt. Matutum, South , 936). Mindanao (Museum of Natural History, Univer- 3. Immature female (we determined it to be a sity of the Philippines at Los Barios [UPLB], male) collected on 30 October 1946 by D.S. Ra- Philippines,Catalog No. 108). bor at Maduum Tagurn, del Norte, Min- 2. Subadult male collected on 12 March 1953 by danao (Field Museum of Natural History E Solomonsenat Talacogon,, [FMNH], Chicago, IL U.S.A., Catalog No. Mindanao (University Museum of Zoology 1247).

Table2. Canonicaldisciminant analysis of four hawk-eaglegroups (S. p. philippemi.•,& p. pinskeri,males and females). Shownare loadingson discriminantfi•nction axes and resultsof univariateF-tests.

CHARACTER AxIS 1 AxIs 2 F P Lengthof hind toe 0.255 -0.067 4.610 <0.05 Lengthof hind claw 0.430 - 1.294 17.512 <0.00001 Lengthof middleclaw -0.119 1.819 10.136 <0.001 Bill lengthwith cere 0.508 0.459 16.199 <0.0001 Bill width of distaledge of cere 0.175 0.289 2.208 n.s. Percentvariance explained 62.1 37.2 JUNE 1998 NEW PHILIPPINEHAWK-E^GLE SUBSPECIES 131

The three remaining specimensfrom the south- vary betweenmouse grey (S70:YI0, M10) to chae- ern population were collected in Samar and Ne- tura drab (S80: Y30, M30). The uppertail coverts gros. One was an adult female collected by D.S. are also white. The cere and bill are sooty black Rabor on 6 April 1957 at Matuguinao, Samar (S90: Y20, MOO) and together with the black lores (FMNH, CatalogNo. 247 377). The secondwas an they form a dark mask. The toes in living birds are adult male (we determined it to be a female) col- yellow as in adults, whereas the eye coloration lected on 21 December 1955 by D.S. Rabor at Bas- changesfrom dark grey in juveniles to bright lem- ey, Bayawan, (UPLB, CatalogNo. on crome (S00: Y90, M30) in subadults (at least in 107) and the third specimenwas an immature fe- Basic III) and adults. male collectedon I August 1871 by A. Everett at The median and lesser wing coverts are white Nueva Valencia, Negros Oriental (Tweeddale Col- and form a broad band on the upper side of the lection, The Natural History Museum [BMNH], wing. The secondariesare deep mouse grey (Y40: Tring, Herts, U.K., CatalogNo. 87.11.1.333). M30, C50), the primariesblackish. Both are heavily Description. In adults of S. p. pinskeri,the colors barred with 7-9 relatively fine bars. In soaring of the head and nape vary from ivory (S00: YI0, birds, a narrow white sickle-like panel is seen in M10) to pale olive grey (S20: Y00, MOO) or dark backlighting along the base of the primaries. On olive buff (S30: Y50, M20) with more or less fine the mousegrey (S70: YI0, M10) to chaeturadrab black shaft streaks. These shaft streaks can become (S80:Y30, M30) coloredtail, 6-7 barsare regularly very bold so that the crown appearsblack suchas spaced or one broad subterminal bar is discern- the specimenfrom Samar.The black occipitalcrest ible. has a maximum length of 8 cm. The throat is al- Specimens Examined. Including the holotype, ways completely white. The upper breast has a sevenstudy skinsof S. p. pinskeriwere available.In white ground color with pronounced black streaks, addition, two captive birds were examined at the in some casesespecially at the distal side of the Breeding Center of the Conser- body edgedwith tawnyolive (S30:Y99, M50). The vation Program Foundation in Toril, Davao. Sixty color of the lower breast and flanks is more vari- individuals were observed in the field on the able, ranging from yellow ocher (S20: Y80, M20) of Mindanao. For comparisons, measurements to cinnamon(S20: Y70, M40), claycolor (S30:Y60, were taken from 12 skinsof representativesof S. p. M50) or tawny olive (S30: Y99, M50) with more or philippensis (five including the holotype from lesspronounced bars.This pattern appearsonly in BMNH--Tring, three from the DMNH, one from adult birds, which are at least in their fourth cal- the CMNH, one from the RNMS, one from the endar year. The lower belly and the legs are in- AMNH, and one from the FMNH). Ten of these variably barred clove brown (Y99: M70, C99) to 12 birds come from Luzon but the origins of the black and white. Back varies between raw umber other two specimenscould not be traced. We also (Y99: M70, C80), brownish olive (S80: Y80, M30) studied three captivebirds, one in the - or sepia (S80: Y99, M40). The cere and bill are logical Garden and two at the Wildlife Research sootyblack (S90: Y20, MOO) in studyskins and liv- Center in Manila. In Luzon, we observed the nom- ing birds. The unfeathered toes are apricot yellow inotypical subspecieseight times. The cumulative (S00: Y60, M20) to lemon crome (S00: Y90, M30) observationtime for both subspeciesin their nat- in living birds, bright lemon crome are also the ural habitat was 6.8 hr during three field trips to eyes. the Philippines (January-April 1993, November Sincejuvenile hawk-eaglesare difficult to distin- 1993-February 1994, and March-July 1994). The guish from other species,we give a rather detailed study of plumage changesin captive birds was es- account of the plumage pattern. The juvenile sential for age determination. plumage is white at the ventral side, also on head Diagnosis.The proposed new subspeciescan be and neck, except the long black crest feathers. distinguishedfrom S. p. philippensisby the smaller Only one youngbird, observedand photographed size of both sexes(Table 1), and by the different at Mr. Kitanglad, Mindanao, had dark grey flanks. plumage coloration and plumage patterns on the The leathered legs are white with fine warm buffy head, breast and belly. In contrastto S. p. pinsken, (S20: Yõ0, M20) bars on the tibiotarsus. There is a the head of S. p. philippensisis raw sienna (S30: Y80, gradual change in color from the white head to M50) to brown (S40: Y99, M50) with broad the dark back. The broadly pale-edged feathers blackishstreaks and the throat is mainly fine ivory 132 PRELEUTHNERAND GAMAUF VOL. 32, No. 2

to warm buffy (S20: Y60, M20) with fine dark rately. Due to particular morphological features, streaks.The breast is ochraceous-tawny(S30: Y90, especiallythe short, broad and round wings, the M50) and the belly somewhat darker, antique Philippine Hawk-Eagleis well adapted for rainfor- brown (S40: Y99, M50) to cinnamon-brown (S40: est habitats.These apparent adaptationsdo not al- Y90, M50). The bold black streaks on the breast low long-distanceflights acrossopen habitats as it are lesscontrastful. Individuals of S. p. philippensis is actuallythe casebetween Luzon and Samar (Ga- have fine whitish bars on the cinnamon-brown mauf et al. 1998). Therefore, disruption of the (S40: Y90, M50) to clove brown (Y99: M70, C99) gene flow by sucha geographicbarrier could have feathered legs and undertail coverts.Almost all il- led to genetic isolation between the northern and lustrationsof Philippine Hawk-Eaglesfound in the southern populations and subsequentlyto the di- hterature (e.g., Walden 1875, Brownand Amadon vergence into separate subspecies.This isolation 1969, Weick 1980, del Hoyo et al. 1994) depict rep- processis enhanced by further subdivisionof the resentativesof S. p. philippensis.One exception is extant populations through the fragmentation of the individual shown in dupont (1971), which the habitat. matcheswith S. p. pinskeriin the most important To explain the sizedifferences between S. p. pin- characters.To our knowledge,only a single pho- skeriand S. p. philippensiswe have to take into con- tograph by M.C. Witmer published in Gonzales siderationinteractions and competition with other and Rees (1988) showsan adult S. p. pinskeri(cap- species.One reason for the smaller size of S. p. tive bird at the Philippine Eagle captive breeding pinskericould be niche separationwith respectto center, Barracatan, Toril, ; R.S. Kennedy other sympatric eagles also specialized for the pers. comm.). hunting of large mammalsand birds. In the south, The morphological traits and differencesin col- two larger eagle species exist, the Changeable or patterns do not vary clinally from north to Hawk-Eagle (Spizak•usdrrhatus) and the Philippine south. Our data indicate that the boundary be- Eagle (Pithecophagajefferyi). In contrast, on the tween the subspeciesruns along the San Bernar- northern island Luzon, only the Philippine Eagle dino Channel which separatesLuzon and Samar is larger than the Philippine Hawk-Eagle.The Ru- by a distanceof lessthan 20 km. Within the Phil- fous-belliedEagle (Hieraaetuskienerii) comes next ippines, this line is also known to separatetaxa of in size, a specieswhich has been recorded from other vertebrates (birds, mammals, reptiles) with the whole Philippine Archipelago.Thus, both sub- limited ability to disperseacross saltwater channels speciesfit approximately into the respectivesize (Heaney 1986, ICBP 1992). gap between their food competitors.The size dif- Effects of the Pleistocenehistory, with repeated ference to its larger competitor is greater in S. p. land bridge connectionsbetween many of the is- philippensisthan in S. p. pinskeri.The wider niche lands, may serve as an explanation for the present reflects the larger body size and the more pro- distribution pattern (Hauge et al. 1986). Growth nounced sexual size dimorphism in S. p. philippen- and recessionof continental glaciers during the sis (Fig. 2). Pleistocenewere associatedon a global basiswith ACTUAL SITUATION AND FUTURE PROSPECTS changesin sea level and temperature. In the late middle Pleistocene(about 160000 yr ago), sealev- Habitat and Distribution. We found the Philip- el was about 160-180 m below the present level. pine Hawk-Eaglein large, continuousareas of dip- The shallow (140 m) be- terocarp rainforests.It definitely prefers extensive tween southern Luzon and may primary, or well-structured,old secondaryforests havebeen dry during this period, allowingfree ex- which were selectivelylogged 20-30 yr ago. Occa- change throughout much of the archipelago(Hea- sionally even transitional stagesto semi-openhab- ney 1985) and alsoto the large Visayanislands like itats are used.With respectto altitude, S.p. pinsken Negros. At the end of the Pleistocene,about 18 000 was observed from almost sea level up to 1900 m. yr ago, sealevel had risen to 120 m below the pres- Of the 11 from which the specieshas ent coastline covering the channel with a body of been recorded so far (Dickinson et al. 1991, water 20 m depth that cut off the connection be- Brookset al. 1992, Evanset al. 1993a, 1993b), only tween the islands.Thus, the separationof the two the main island Luzon is inhabited by S. p. philip- subspeciesmust have happened after the geo- pensiswith certainty.Mindanao, Negros,and Samar graphical isolation, which cannot be dated accu- are doubtlesslypopulated by S. p. pinskerias docu- JUNE1998 NEWPHILIPPINE HAWK-EAGLE SUBSPECIES 133 mented by study skins.Individuals recorded from south of province. Around Asaclat (35 and probably also from , ,Si- km• 500-900 m), we found two pairs (5.7 pairs/ quijor, and more recentlyfrom (Hornskov 100 km • and in Don Mariano Perez (32 km • 400- 1995) presumablybelong to S. p. pinskeri.No un- 1100 m) one pair (3.1 pairs/100 km=. Basedon equivocalevidence for the occurenceof either sub- this survey,we estimatedthe size of the S. p. philip- speciesis known so far from .The only pensispopulation on Luzon to be about 200-220 museum specimen labeled as "Philippine Hawk- pairs.For S.p. pinskeri,we surveyedfour studyareas Eagle" from the localityPalawan was a misidenti- in Mindanao. In the lowland forests of PRI (former fled ChangeableHawk-Eagle (Staatliches Naturhis- PICOP) (Surigaodel Sur, 58 km2, 90-180 m), we torisches Museum Braunschweig, Catalog No. found 3-4 pairs (5.2-6.9 pairs/100 km• and in 14158, collector Dr. C. Platen). In general, infor- Carmen-Cantilan(, 27 km• 80-540 mation on the distribution of the Philippine Hawk- m) one pair (3.7 pairs/100 km=. At the gentle Eagle (and other bird species)is still insufficient slopeon the Dalwanganside of Mt. Kitanglad (Bu- and further studies are needed. kidnon, 38 km • 900-1800 m), we found three Conservation. Most current threats to raptors in pairs (7.9 pairs/100 km2) and on the steep slope the tropical forest belt are related to habitat de- on the Barracatan side of Mt. Apo (Davao City, 25 struction (Kennedy1986, Thiollay 1994). Owing to km• 950-1800 m) we found one pair (4 pairs/100 the construction of new roads for timber harvest- km=. Thus, in the total 7500 km= of closedcanopy ing, often in a very damagingway, the final destruc- forest available,we estimated the number of pairs tion is conducted by shifting cultivatorswho enter may be about 320-340. the region illegally. An additional threat arises In the world list of threatened birds (Collar et from the fact that the Philippines are one of the al. 1994), the Philippine Hawk-Eagle is listed as most densely populated countries in Southeast Vulnerable with a high risk of extinction in the Asia, with more than 65 million people on 300 000 wild within the medium-term future. Based on our km 2. recent investigations,the estimatedmaximal num- Dickinson et al. (1991) have presented data on ber of mature individuals is <1200, a population the extent of forestsremaining on the major island size clearly below the criterion of <2500 set by groups.They found that only the major islands BirdLife International for endangered species.Ac- possesssufficiently large forestedareas. According cording to this criterion the classificationof the to Collins et al. (1991), the rate (de- Philippine Hawk-Eagleas an Endangered species termined for the period 1986-90) is 1380 km'•/yr seems appropriate. for the whole Philippines. In 1988, the forested ACKNOWLEDGMENTS area with closedcanopy cover on the island of Lu- zon wasdetermined as 7621 km". Assuminga uni- The work wassupported by the Austrian ScienceFoun- form rate of deforestationover the Philippines, the dation (FWF-projectP-8889-Bio) and the IWJ, University of Agriculture, Vienna. We want to expressour sincere remaining forest habitat is roughlyestimated to be gratitudeto the Departmentof Environmentand Natural 5000 km 2. Ressources(DENR) of the Republic of the Philippines, Knowing the inhabitable area and the present the Philippine Eagle ConservationProgram Foundation, population density,we attemptedto gaugethe ac- the Haribon Foundation, Green Mindanao, the industry companiesin Carmen (Puyat Logging) and (PRI) tual populationnumber. In six studyareas, we de- as well as the Technical Aid Agency of the Federal Re- termined the number of pairs using two methods: public of Germany (GTZ) and our local guidesfor their census from exposed points (cliffs, clearings, excellent cooperation. prominent trees) and line transects.These two The authors are very much obliged to the curatorsof methods have been used successfullyin studieson the following museum collectionsfor accessto specimens in their care: The Natural History Museum (BMNH), tropical rain forest raptors (Thiollay 1989, Whita- Bird Group (Tring, U.K.), Royal National Museum of cre et al. 1992). Point censusesproved very suitable Scotland (RNMS, Edinburgh, U.K.), UniversitetsZoolo- to map the locationsof hawk-eaglessince they are giske Museum (UMZC, Kobenhavn, DK), Rijksmuseum year-roundresidents that often fly above the can- van Natuurlijke Historie (RMNH, Leiden, NL), Zoolo- opy. In each studyarea, the total time of observa- gischesMuseum der Humboldt Universit/itBerlin (ZMB, Berlin, D), Staatliches Naturhistorisches Museum Braun- tion wasat least 2 wk. The densityof the Philippine schweig (SNMB, Braunschweig, D), Naturhistorisches Hawk-Eaglein Luzon wasdetermined in two study Museum Wien (NMW, Wien, A), American Museum of areas in the Sierra Madre mountain range in the Natural History (AMNH, New York, NY U.S.A.), Smith- 134 PRELEUTHNERAND GAMAUF VOL. 32, NO. 2 sonian Institution (USNM, Washington DC, U.S.A.), DUPONT,J.E. 1971. Philippine birds. Monograph Series Field Museum of Natural History (FMNH, Chicago, IL No. 2. DelawareMuseum of Natural History, Green- U.S.A.), Cincinnati Museum of Natural History (CMNH, ville, DE U.S.A. Cincinnati, OH U.S.A.), Delaware Museum of Natural EvANs, T.D., G.C.L. DUTSON AND T.M. BROOKS. [Los.]. History (DMNH, Wilmington, DE U.S.A.), National Mu- seum of the Philippines (PNM, Manila, PH), University 1993a.Cambridge Philippines rainforest project 1991. of the Philippines at Los Barios (UPLB, Los Barios,PH), final report (study report no. 54). Birdlife Interna- and Zoological Garden Manila (Manila, PH). We are es- tional, Cambridge, U.K. pecially grateful to R. Prys-Jones,M. Walters and P. Col- , P. MAGSAL•Y, G.C.L. DUTSON AND T.M. BROOKS. ston,R. McGowan,J. FjeldsS,C. Smeenckand R. Dekker, 1993b. The conservation status of the forest birds of B. Stephan, G. Boenig, E. Bauernfeind, G.F. Barrow- ,Philippines. Forktail 8:89-96. clough and P. Sweet, D. Zusi and P. Angle, D. Willard GAMAUF, A., M. PRELEUTHNER AND H. WINKLER. 1998 and P. Baker, R.S. Kennedy and J. Brown, G. Hess, P.C. Philippine birds of prey:interrelations among habitat, Gonzales,A. Dans and R. A. Andres for their helpful co- morphology,and behavior. Auk 115:in press. operation. We are very much indebted to A. 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