NESTING BIOLOGY AND BEHAVIOR OF THE MADAGASCAR

J RaptorRes.34(2):120-125
¸ 2000 The Raptor ResearchFoundation, Inc.
NESTING
BIOLOGY
AND
HARRIER-HAWK
BEHAVIOR
OF THE
MADAGASCAR
(POLYBOROIDES RADIATUS) IN
NORTHEASTERN
MADAGASCAR
RUSSELL THORSTROM
ThePeregrine
Fund, 566 WestFlyingHawk Lane, Boise,1D 83709 U.&A.
GIUSEPPE LA MARCA
Via Plinio, 9, 20129-Milano, Italy
ABSTRACT.--We
studied the endemic MadagascarHarrier-Hawk (Polyboroides
radiatus)during the 1998
breeding seasonon MasoalaPeninsula,northeastern Madagascar.One nestingpair wasobservedfrom
courtshipto 1 wk into the post-fiedging
period (September-January).
Copulationsstarted25 d prior to
egg layingand peaked7 d before egg laying.Two eggswere laid and the female and male incubated
for 61.6% and 35.5% of 189.8hr of nestobservations,
respectively.
Incubationlasted39 d from laying
to hatchingof the first egg.Both eggshatchedbut the second-hatched
youngdied from siblicideat 7
d of age.The survivingyoungfledgedat 50 d of age.Frogs(Boophis
and Platypelis
spp.),geckos( Uroplatus
and Homopholis
spp.)and nestlingbirdswerethe mostnumerouspreytaken,representing
82% of 160
identified prey items.
K•Y WORDS: MadagascarHarrier-Hawk;Polyboroidesradiatus;nestingbiology;
behavior;,
siblicid•,
foodhabits.
Biologiade anidacitn y comportamientode Polyboroides
radiatusen el norestede Madagascar
RESUmEN.--Estudiamos
al endtmico Polyboroides
radiatusdurante la estacitn reproductivade 1998 en la
Peninsulade Masoala,noreste de Madagascar.Una pareja en anidaci6n fue observadadesdeel cortejo
hastauna semanadesputsde que los pichonespudieron volar (Septiembre-Enero).Las ctpulas com-
enzaron25 diasantesde la posturade huevosy su pico ocurri6 7 diasantesde la postura.La nidada
fue de doshuevos,la hembray el machoincubaronel 61.6% y el 35.5% respectivamente
de las 189.8
horas de observacitn en el nido. La incubacitn tttvo una duraci6n de 39 dias desdela posturahastala
eclositn del primer huevo. Los dos huevoseclosionaron,el segundopichtn fue eliminado por su
hermano a los sietedias de edad. E1pichtn sobrevivientepudo volar a los 50 diasde edad. Las ranas
(Boaphis
y Platypelis
spp.)geckos(Uroplatus
y Homopholis
spp)y pichonesde avesfueron las presasmas
abundantesrepresentando
el 82% de las 160 presasidentificadas.
[Traducci6n de Ctsar Marquez]
Langrand 1990, del Hoyo et al. 1994). Existinginformation comesmainly from incidental and anecdotal observations(Dee 1986, Milon et al. 1973)
and data on food habits (Goodman and Pidgeon
1991, Karpanty and Goodman 1999), but litfie is
known of its breeding biology (Langrand 1990, del
(Thorstrom et al. 1995, Rent de Roland et al. 1996, Hoyo et al. 1994). Here, we report on the nesting
Berkelman 1996, Rent de Roland in press,Thor- biologyof the MadagascarHarrier-Hawk in an unstrom 1999, Thorstrom and Rent de Roland in
disturbed lowland tropical forest of northeastern
press). The genus Polyboroides
containstwo species, Madagascar.
the Africa Harrier-Hawk (P. typhus)which is con- STUDY AREA AND METHODS
fined to mainland Africa and the MadagascarHarThe west coast of the Masoala Peninsula is roadless and
rier-Hawk (P. radiatus)which occursonly on Mad- composedof a mosaicof slash-and-burnclearings,secagascar.The latter speciesis common throughout ondary growthand primary rain forests.The maturelowMadagascarbut has been little studied (Dee 1986, land rain forest of the Masoala Peninsula has a canopy
Our knowledge of African tropical raptors,mainly from the southern subtropics,has increasedin
recent yearsbut the raptors endemic to the western Indian Ocean islands are still poorly known
(Virani and Watson 1998). During the last decade
several studies have focused on Malagasyraptors
120
JUNE2000
MADAGASCAR
HARRIER-HAWK
NESTINGBIOLOGY
121
height near 30 m with emergent trees, high fioristic diversity and steep mountainous topography (Guillaumet
1984). Elevationsrange from 0-1200 m. Averageannual
period with dry branchesmaking up the remaining
10.3% (21). The female contributed 79.8% (162)
rainfall recorded at Andranobe Field Station (AFS) was and the male 20.2% (41) of the greenery through6049 mm from 1991-96 (range = 4468-7002 mm) out the breeding period. Both the male and female
(Thorstromet al. 1997). Monsoonrainsand cyclonesoc- were observedconstructingthe nestduring all daycur betweenDecember and March, but rain falls steadily light hours (0500-1700 H), but most of the conbetween April and August. September to November are
the driest monthsreceiving,on average,481 mm (8%) struction took place in the morning hours between
of the annual rainfall recorded during 1991-96 (Thor- 0600-1100 H; 82% of the nesting material wasaddstrom et al. 1997).
ed to the nest before
Daily observationswere made at a harrier-hawknest
from 0500-1700 H, initially from the ground and later
the last deliveryof greenery to the nest on 7 January 1999, two daysafter the young fledged from
from a tree hide, with 10X binoculars from distances of
25-45
m. Observations
from
the hide were also made
using a 16-48X spottingscope.Data collectedincluded
notes on adult and nestling behavior, nest attendance
and identification of prey and provisioning rates. The
length, breadth and depth of the nest were measured
with a metric tape and nest height wasmeasuredwith a
plumb line from the nest to the ground. Nest tree height
was estimated in meters above the nest height.
Egg volume was estimated from the equation V =
0.51LB2, whereL is the length and B the breadthof the
the
1200
H. The
female
made
nest tree.
We observed 167 prey items delivered by the
male and female to the nest from courtship to the
post-fiedging period. The harrier-hawks had a
broad diet delivering at least 15 different taxa during the nesting period. Prey wasalwayscarried and
exchanged at the foot of the nest by the male to
the female. Of these, 160 were identified
at least
to classlevel. Frogs (Boophisand Platypelisspp.) toegg (Hoyt 1979).The equation(V•gest- Vsmanest/Vsm•n½st)
was used to calculate the percent difference in volume
between the two eggsin the nest (Edwardsand Collopy
1983).
RESULTS
The pair of MadagascarHarrier-Hawks nestedin
a tree near one of the main research trails, approximately 2.0 km north of AFS, from 1991-98
(Borge 1992). The nest was a large, stick structure
approximately18 m above the ground within the
canopyand slightlybelow a ridge on a north facing
slope. The pair fledged one young every year the
taled 31.3% (50), lizards (Uroplatus
and Homophohs
spp.) 23.8% (38), birds ( Otusrutilusand Couaspp.),
mainly nestlings (Phyllastrephusspp. and Coua
spp.), 26.9% (43), and rodents (Eliurusspp. and
Rattus spp.) and lemurs (Lepilemurmustelinusand
Microcebus
spp.) 17.5% (28) of the identified prey
items. Of interest
was the occurrence
of 7 lemurs
and the pair constructeda new nest 50 m north-
delivered during the nestling period by both the
male and female. Nestling birds accounted for
86% of the 43 avian prey items delivered during
the nestling period. The male delivered 131 prey
items from courtship to the post-fledgingperiod
and the female delivered 36 prey items from the
beginning of incubation to the post-fledgingperi-
east of the old nest site. In 1996, this nest measured
od.
76 X 72 cm, with 7 cm interior and 47 cm exterior
We observed the pair for 152.4 hr during the
courtship period which lasted from the first week
nest was observed. In 1995, the nest tree fell down
depths. Two other nestswere located in 1998 2530 km to the east of AFS. They had lengths and
widthsmeasuring85 X 50 cm and 90 X 70 cm and
interior depths of 5 and 9 cm and exterior depths
of 45 and 46 cm. Nest heights were 30.8 and 31.9
m and nest tree heights were 33 and 36 m.
In 1998, we made observationstotaling 677 hr
from courtship (September) to the post-fledging
period (January) at the nest nearest to AFS. We
observed 203 items of nesting material delivered
to the nest throughout the nesting period. Of
them, 90 (44.3%) were deliveredduring courtship,
31 (15.3%) during incubation, 81 (39.9%) during
the nestlingperiod and 1 (0.5%) during the postfledgling period. Green branchesmade up 89.7%
(182) of the greenery delivered during the nesting
of Septemberto 7 October 1998. During this period, the female made 64 deliveriesof nesting ma-
terial consistingof 57 green sprigs and 7 dead
branches. The male delivered 24 green sprigsand
3 dead branches.We observed80 copulationsduring the 4-wk courtship period. The earliest copulation wason 13 September1998, 25 d before egg
laying,and copulationswere mostfrequent 7 d before egg laying on 1 October 1998. On that day,
we observed the pair copulate eight times during
a 10.5 hr nest observationperiod. A total of 76
copulations totaling 1634 sec was observed for an
averagecopulation time of 21.5 sec (range = 10.534.0 sec). The duration of copulations gradually
increasedfrom 13.0 sec 25 d prior to egg laying to
122
THORSTROM AND LA MARCA
34.0 sec 5 d prior to egg laying and subsequently
tapered off with no copulationswere observedafter the first egg waslaid. Copulationsoccurred at
the nest and on perches of the nest tree and nearby trees. During copulations both sexesexhibited
the red facial flushing described by Thurow and
VOL. 34, No. 2
519 pieces of food while the younger nestling received only 59 pieces.After the younger nestling
died in the nest, the female ate most of it and fed
some to the survivingnestling.
The
female
was the
sole attendant
at the
nest
during the nestling period and she brooded the
Both
nestling,fed it and deliveredgreenery76 times(66
sexesgavea high, shrill call during copulations.We green sprigsand 10 dry branches). The female also
observed the male feed the female 24 prey items. delivered 28 prey items consistingof 14 (50%)
Fifty percent (12) were frogs, 12.5% (3) lizards, geckos (Uroplatusspp. and Homopholisspp.), 5
12.5% (3) rodents, 8.33% (2) birds, 4.17% (1)
(18%) birds,4 (14%) frogs,3 (11%) lemursand 2
snake and 12.5% (3) unidentified items.
(7%) rats.During this period, the male only delivIn 1994 and 1996, 2 two-eggclutcheswere mea- ered prey to the female and nestling. The female
sured and weighed. In 1994, the first egg weighed alwaysvocalized a high "pe-ee-ee-ee" (Langrand
46.0 g and measured57.0 X 42.3 mm and the sec- 1990) at the nest or near the nest as the male arond eggweighed47.0 g and measured54.4 X 41.2 rived with food. The male delivered greenery only
min. In 1996, the first egg weighed 48.0 g and mea- once. The male delivered 80 prey items that consured49.6 X 38.8 and the secondeggweighed59.0 sisted of 33 (41%) birds, 15 (19%) rodents, 14
g and measured54.5 • 41.6 min. The percent dif- (18%) lizards,12 (15%) frogs,4 (5%) lemurs and
ference in volume between the two eggs in 1994 2 (2.5%) unidentifieditems.The youngfledgedon
was 10.5% and in 1996 was 26.1% (i = 18.4% +
5 January 1999, at 50 d of age.
0.05, -1SE). The eggs were buff, marbled and
We observed the young for 40.4 hr during the
spotted with reddish-brown
post-fledging period from 6-14 January. During
Nest observationstotaled 189.8 hr during incu- this period, the female delivered I green branch
bation, from 8 October-16 November. One egg and spent2.9% of the time at the nest.The female
was laid on 8 October and the second egg waslaid delivered7 preyitemsconsisting
of 5 geckos,I frog
Black (1981) for the African Harrier-Hawk.
between
10-12
October.
The
female
delivered
and
I
unidentified
item.
The
male
delivered
2
greeneryto the nest 18 times (17 green and I dry) frogs, I gecko and I unidentified item during this
and the male 13 times (all green branches) during period.
the incubation period. During incubation, the
DISCUSSION
male delivered 23 prey items to the female, of
which 82.6% (19) were frogs. The female also
The Madagascar Harrier-Hawk occurs throughbrought a lizard to the nest that she ate herself out Madagascar,except on the high plateau. Deafter an incubation exchange with the male. The spite the fact that it is the fourth most common
total incubation
time for the female and male was
raptor on the island (Langrand and Meyburg
116.8 (61.5%) and 67.6 (35.6%) hr, respectively 1984), it hasnot been studiedin great detail. Thorand both adults were absent from the nest for only strom and Watson (1997) found the Madagascar
2.9% (5.3 hr) of the time during incubation. The Harrier-Hawk at sevenof eight avian inventory sites
incubation period from laying to hatching of the throughout the Masoala Peninsula confirming its
first-laid egg was 39 d.
widespreadoccurrence in the rainforest of this reNest observationstotaled 294.7 hr during the gion.
nestling period from 16 November 1998, when we
For diurnal raptors in general, nest building
observedthe first hatchednestlingat 0719 H, to 5 takes place in the morning and males are mainly
January 1999. We documented asynchronous responsiblefor nest construction(Newton 1979).
hatching with at least a 2-d interval between hatch- Our results showed that harrier-hawks added most
ing of the first and second eggs.The secondegg nesting material to the nest before 1200 H but the
hatched
on 18 November
1998.
From
18-25
No-
vember, we observed the oldest young strike the
younger nestling822 timeswith its beak, eventually
leadingto its death on 25 Novemberat 7 d of age.
During the one week period of 18-25 November,
the female was observedfeeding the oldestyoung
female
was the main
nest builder.
Thurow and Black (1981) reported that breeding activity of African Harrier-Hawks in South Africa begins in late spring before summer rains begin. Tarboton and Allan (1984) were more specific
indicating that hatching coincideswith peak pro-
JUNE 2000
•AG^SCo;m HARRIER-HAWK
NESTINGBIOLOGY
duction of passerinenestlingsfrom October to December. Breeding activity of the MadagascarHarrier-Hawk was similar beginning in August and
123
eggs,e.g., the American Swallow-tailedKite (Elanoidesforficatus)in the northern Neotropics (Gerhardt et al. 1997), the Augur Buzzard(Buteoaugur)
ending in January (Tarboton 1978). Nestlings in mainlandAfrica (Gargett 1970) and the African
hatched during November when conditionswere Harrier-Hawk (Tarboton et al. 1990, del Hoyo et
at their driest and most passerineswere breeding, al. 1994). Tarboton and Allan (1984) recorded 10
and fiedging occurred during January when the 2-egg clutches of the African Harrier-Hawk in
rainy seasonhad begun.
Transvaal but seven nests contained only one
The three nestsof the MadagascarHarrier-Hawk young. A 2-eggclutch wasdocumented at the study
we studiedwere similarbut averagedslightlylarger nest of the harrier-hawkand we suspectedthat sity
nests ob(75 cm in diameter X 20 cm wide) and higher licide occurred at 8 other harrier-hawk
(10.3 m) than nestsdescribedby Tarboton and Al- served from 1991-98.
lan (1984) for the African Harrier-Hawk. Similar
Edwardsand Collopy (1983) describedtwo types
to the Transvaal region where many nests were of siblicide,obligateand facultative,in large eagles
used in consecutiveyears,the pair of harrier-hawks with asychronoushatching and a high percentage
we observedoccupied one nest site from 1991-95 of volume difference within two-egg clutches
and a newly constructedsite from 1996-98.
()10%). In a specieswith obligatesiblicide,the
MadagascarHarrier-Hawks broke off branches second young to hatch alwaysdies, e.g., Aquila powithin a 20-50 m radius of the nest tree. After demarina, A. verreauxiiand Stephanoaetus
coronatus
livering greenery to the nest, they frequently cut (Edwardsand Collopy 1983). In facultativesiblicioff the leavesand placed them in the nest bowl de species,the second-hatchedyoung sometimes
and then positionedthe leaflessbranch to the ex- dies, usually during food restriction, and egg volterior to form a nest rim. Green branches ap- ume differenceis (10%, e.g, A. chrysaetos,
A. aupeared to be preferred over dry branches,perhaps dax, A. rapax,A. clanga,Hieraaetusfasciatus,H. penThe African
becausethey offered both material for construct- natus, and Haliaeetus leucocephalus.
ing the nest and fresh leavesfor lining the nest Harrier-Hawk appearsto exhibit faculativesiblicide
bowl. Perhaps, the greenery provides insulation (Tarboton et al. 1990). We feel that the Madagasand protection for eggs and nestlings,and posi- car Harrier-Hawk may be more like the Swallowtioning of twigsin a nest rim createsa border for tailed Kite (Gerhardt et al. 1997) and Augur Buzmaintaining them in the center of the nest.
zard (Gargett 1970) and has obligate sublicide.
At 7 d before egglaying,we observedthe highest The mean egg volume of 18.4% for the Madagasfrequency (8 times) of copulationsduring a nest car Harrier-Hawk fell into the category associated
observation period and the average copulation with the large obligate siblicide eagles (Edwards
time graduallyincreasedto the longestduration5 and Collopy1983).
We found the MadagascarHarrier-Hawk to have
d prior to egg laying. Basedon our observations,
we suspectthat the optimum time for insemination similar reproductive parameters to the African
of harrier-hawksoccursfrom 5-7 d before egglay- Harrier-Hawk, with an incubation period of 39 d
ing. Optimum inseminationsfor a captiveNorth- compared to 35-36 d, a nestling period of 50 d
ern Goshawk (Accipitergentilis)via artificial insem- compared to 45-55 d and occurrence of siblicide,
inafion occurred 4 d before the first egg (Berry though two young may sometimesfledge (Tarbo1972). Thurow and Black (1981) observed one ton and Allan 1984, Tarboton et al. 1990, and del
pair still copulafingafter egg laying and until the Hoyo et al. 1994).
Previousinformation reported on food habitsof
nestlingwas8 d Of age. In this pair of Madagascar
Harrier-Hawks,no copulationswere observedafter the MadagascarHarrier-Hawk comes from Rand
egg laying.
(1936), who found carrion (Tenrececaudatus),spiSiblicide has been documented
for some marine
der, insects,locusts,frog, lizards,snakeand a small
birds (Proctor 1975, Anderson 1990) and large ea- mammal (Mus musculus)in the diet. Recently, in
gles,includingthe MadagascarFishEagle (Haliaee- the dry climate of extreme southeasternMadagastusvociferoides),
with a clutch sizeof two eggs(Mey- car, Goodman and Pidgeon (1991) documented
burg 1974, Edwardsand Collopy 1983, Gargett the harrier-hawkpreying on flying foxes (Pteropus
1993, Watson et al. 1996). It has been documented
rufus) and Karpanty and Goodman (1999) docufor only a few smaller birds of prey that lay two mented it feeding on adult and infant Verreaux's
124
THORSTROM AND. LA MARCA
Sifaka (Propithecus
verreauxi)during the courtship
period. In the courtship period of September
1997, we observedone partiallyeaten dwarf lemur
(Cheirogaleus
major) lying at the base of the nest
tree and, during nest observations,we documented lemurs (Microcebus
and Lepilemur)in the diet
only in the nestling period. Frogs were the predominant prey type during the courtshipand incubationperiodswhile nestlingbirdswere the major prey typestaken during the nestlingperiod. In
85 prey itemsof the AfricanHarrier-Hawk,nestling
birds composed31% of them (Thurow and Black
VOL. 34, No. 2
and ANGAP for their collaboration with The Peregrine
Fund's Project in Madagascar.This work was supported
by grants from the Disney Corporation.
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ACKNOWLEDGMENTS
We thank
R. Watson
and W. Burnham
of The
Pere-
grine Fund for makingthis studypossible.Specialthanks
to R. Watson and L. Kiff for comments on earlier dr',fits
and M. Marin of Western Foundation
of Vertebrate
Zo-
ologyfor an obscurecitation.We thank the Direction des
Eaux et For•ts, CommissionTripartite, Projet Masoala
Univ. Press, New Haven, CT U.SßAß
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Received30 July 1999;accepted7 February2000