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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 2. June 2012 
TABLE 1. Prey items observed at die Harpy Eagle nest, Belize, 2010-2011. 
Species 
Common name 
n 
Percent 
Didelphis marsupialis 
Common opossum 
4 
23.5 
Nasua narica 
White-nosed coatimundi 
3 
17.6 
Alouatta pigra 
Yucatan black howler monkey 
3 
17.6 
Crax rubra 
Great Curassow 
2 
11.8 
Ateles geoffroyi 
Central American spider monkey 
1 
5.9 
Potos flavus 
Kinkajou 
1 
5.9 
Tamandua mexicana 
Northern tamandua 
1 
5.9 
Anhinga anhinga 
Anhinga 
1 
5.9 
Iguana iguana 
Green iguana 
1 
5.9 
Totals 
17 
100 
confirmed the presence of a nestling that we 
estimated to be 4-5 weeks of age. 
We made 601 hrs of focal observations over 
71 days between late January and May 2011. 
Observation periods lasted an average of 6 days, 
beginning just after sunrise and ending before 
sunset. The juvenile fed on 40 of the 71 
observation days (56.3%) and spent a total of 
48 hrs of its time feeding (8.03%). Feeding was 
coupled with the juvenile’s submissive begging 
posture (wings held down) and calling. Behaviors 
other than feeding observed consisted of stand¬ 
ing (4.6 hrs/day. 35%>) and sleeping or resting 
(3.7 hrs/day, 27%). All other behaviors accounted 
tor 1% or less oi the bird's behavior per day. Prey 
items delivered to the nest were variable with 
common opossum ( Didelphis marsupial is), just 
slightly more common than white-nosed coatimun- 
di ( Nasua narica) and Yucatan black howler 
monkey ( Alouana pigra ) (Table I ). We observed 
one prey item delivered every 2.04 days at the 
juvenile's approximate age of 4 months, increasing 
to one delivery every 3.33 days at 6 months 
(Table 2). The adult female provided nearly all of 
the food (female: n = 14. 82%; male: n = 3. 18%). 
We also made periodic observations of the female 
cutting, collecting, and bringing green branches to 
the nest trom an adjacent Ceiba pentandra tree. 
We placed an Argos System/CLS Satellite 
GPS-PPT (Global positioning system-platform 
transmitter terminal) transmitter and VHP trans¬ 
mitter on the juvenile Harpy Cagle on 14 April 
2011 to track its post-fledging movements in 
cooperation with experts from The Peregrine 
Fund, Boise, Idaho, USA. The hope was to follow 
die young eagle for up to 3 years to map Harpy 
Cagle territory size and habitat. We predicted this 
procedure would have little or no effect on the 
feeding and care of the young, but decided not to 
place any device on the adults as they currently 
represent the only known breeding pair of Harpy 
Cagles in Beli/,e. The juvenile was released into 
the nest after deploying the satellite transmitter 
The parents made only one feeding attempt after 
transmitter deployment on 17 April 2011. after 
which neither adult was observed at the nest 
Between 2 and 14 May 2011, after finding the 
juvenile perched, branching, and/or Hying 5-30 m 
front the nest on low branches (< 3 m), we 
decided the parents were not returning and we had 
to feed the Hedged eagle or watch it die. We used 
a technique similar to that used for the 'soft 
release' of a captive-bred eagle (Muela et ul 
2003). We followed only the feeding protocol, 
which consists of (ceding the eagle at a designated 
location behind a blind so the bird does not 
associate food with people. Our goal was to feed 
the bird until it could start to hunt by itself and 
then gradually reduce the food provided to wean 
the bird and encourage hunting. 
We provided three dead Domestic Chicken 4 
(Callus gallus) to the juvenile from 15 to 25 May 
2011. The young eagle fed on each chicken until all 
of the body parts were consumed. We provided 
TABLE 2. Mean prey delivery rates per age (by month 1 
of the juvenile Harpy Eagle in Belize including one 
delivery after placement of the satellite transmitter at the 
onset of the 7th month. 
Juvenile age 
Mean delivery rate 
n 
4 months 
2.04 
7 
5 months 
2.33 
5 
6 months 
3.33 
4 
Post transmitter 
4 
1 
Overall average 
2.93 
17 
