768 
THE WILSON JOURNAL OF ORNITHOLOGY . Vol 124. No. 4. December 2012 
until mid January 2012. Observations were usually 
made by the same observer (ALB) and were a,I 
libitum with all activities in the nest observed and 
noted. Thus, we achieved continuous observation for 
6 hrs/day. Observations were primarily front 06(X) 
(sunrise) until 1200 hrs, and at a lower frequency 
from LOO to 1900 hrs. The activities recorded 
included: parental care and incubation, nestling/ 
fledgling development, hunting sessions, provision¬ 
ing sessions, and agonistic interactions. We built a 
camouflaged blind 40 m from the nest from which to 
make observations and not disturb the birds 
Occas'ona 1 observations were made until 15 January 
S ' r , ay m the nest area - We used Zeiss 
X a 42 binoculars, and a Canon PowerShot SX20 
camera to describe and document observations and , 
digital recorder Panasonic RR-US 470 to record calls 
and Raven Pro 1.4 (Bioacoustics Research Pre^rn 
0 prodllce tlle spectrograms. Vegetation 
n Tk-°" 0WS M ™ Boreal Curd n 
RESULTS 
blest Location and Description—Tho n 
bellied Hawk pair was first known to be in'The 
area on 14 September 2011. However the pair 
and a juvenile had been observed in the v. o 
at the end of September. 1 yearZitT^ 
was looted because of the aggressive behavior 
the female m response to hum-m r, 1 
perched high S T “ ^ 
direction of the observer's position ' n 
du ri „: 20,1 
cons,meted ,8 m above ground Tvefl^ The 
incubation and brooding, only when taking find 
from the male or attacking potential predators and 
intruders. The male remained close (10-20 m) to 
the nest at all times when the female was off Ik 
nest. 
Only one nestling survived and. at the end of 
the sixth week <5 Nov 2011; - 42 days), wcfound 
the remains o| the oldest nestling on the ground 
30 m from the nest. The surviving nestling left the 
nest at the end of the seventh week 49da )m 
when its first flight was observed, The fledging 
had a black cap and malar streaks, rufous cheeks 
neck and breast, and a white throat and middle- 
breast with the pattern of black streaks complete 
mi the underparts in the eighth week (- 55 day., 
1 ig. ID). The lledgling stayed close to the rest 
om 'he' eighth until the twelfth week, venturing 
up to 300 m from it. 
blest Defense .-Both the female and male 
elended the nest, but while the former defended 
up to a radius ol —50 m, the latter seemed to 
defend a zone from -50 to 200 m. The female 
was observed chasing a Grey-headed Kite (Up- 
Union cayanensis) and a Southern Crested Cara¬ 
cul a ( C a meant pUtncus). Her aggression was 
strongest towards the Grey-headed Kite with three 
observed body contacts. She grabbed the kite with 
jc* jaws on his back on one occasion, and Hew in 
1 11 °clion ol the conifer canopy and continued 
to do so until -50 m from the nest. 
he aggressiveness of the female against 
raptors or humans continued throughout the 
nesting period, from incubation until fledgling. 
, e ’otinued to demonstrate this behavior after 
hr., « 7 r “ uuve ground level in u,> ° , g,ing lcfl lfle nest until the tenth weel 
■ nC es ,° 1 lc ‘ cano Py of a young Parana Pin * *?° St " ,atc * lm £ w hen aggressive behavior began t£ 
close ,o he top of the tee. and wasTuTou dedTT T™' *» ‘<4* Performed this betavio, 
dense foltage. The nes, .. .... . . noundeJ ,n the twelfth week and i, watt difficult to find her 
oi the fledgling in the nesting area. 
i" ^'ao”d 
Sticks that ranged front 0.5 to‘cT b, '7^ “ d 
(Ftg. 1A. B). The inside of te „es, L " 
°n 26 Sep 2011 and wc „ b sTrv cd aT e ^ 
newly hatched nestling (Fij , , TL*" “ d a 
rounded oval shape md L ‘ ™ Cgg had a 
e white ™ 
were overall beige in color , nes t ||n gs 
nrent was followed for -dOday, oSff h' Vd ° P ‘ 
Incubation and Nest lino n # 
female incubated the cZ The 
during the period ofobsem,lots r d ? a " d ' 
nest 96% of the time. She Tft d ° n lhe 
short periods (12 + 974 ° 10 nesl on, y for 
/4 m,n ’ n = 14) during 
.. *- .. . uicj. 
c also observed the male attacking potential 
predators (Grey-headed Kite and Southern Crest- 
l a,ac ara) on two occasions at a distance 
ctween 50 and 200 m of the nest. Other raptors 
wtn_ observed close to the nest but appeared to be 
tolerated within the defended area. These included 
£■ I low-headed Caracara (Milvago chimachimi). 
<>ai sic e Hawk (Buieo magnirostris ), Plumbeous 
1 c (Ictinia plumhea). and Swallow-tailed Kite 
anon is fo/ftcatus). These species were prob- 
, yUaled ' n l he nest area because they were 
,a - v 0 served flying above the canopy. A 
m side Hawk approached the nest closely on 
<- occasion and perched on a branch at a 
