SHORT COMMUNICATIONS 
819 
nest in that tree, whereupon the hawk flew to a 
perch above the nest and climbed down the 
upnght limbs to the nest. While the view of the 
hawk was obscured by the nest, a squirrel exited 
and ran down the tree, entering a cavity. The 
hawk, having positioned itself on top of the nest, 
began pulling the nest apart and a second squirrel 
escaped behind the hawk. The hawk became 
aware of this squirrel and w atched it run down the 
tree, but it did not attempt capture. This squirrel 
remained on the tree, but hid from sight on the 
apposite side of the tree. The hawk returned to 
decoastructing the nest until the nest was largely 
tom apart and the hawk departed. 
On the same day. at —1630 hrs. the haw k returned 
to the same oak. Less interest was show n in nests 
(which had already been tom apart), but attention 
was focused on the many cavities ol the old tree. 
Tire Red-tailed Hawk hopped among branches as it 
sought cavities that might afford refuge for squirrels. 
Each of five cavities sufficiently large to shelter a 
squirrel was probed by the bird's beak. In the case ol 
a laterally positioned larger cavity, the hawk grasped 
the edge with its talons while beating its wings to 
maintain position and probing the opening with its 
beak. These actions were search phase and not in 
response to a visible squirrel. 
The hawk again was observed tearing apart a 
nest with no effect on 2 March 2012 at 1415 hrs. 
The hawk flew to two other nests and behaved in 
the same manner. However, at the latter site the 
hawk reached into the nest, pulled out an adult 
squirrel, and quickly threw it directly to the 
concrete sidewalk (—10 m below). The squirrel 
hit the ground solidly and was immobile, and the 
hawk swooped down to the prey and secured it. 
After looking about for —1.5 min. the hawk flew 
to a limb and began to consume the prey. 
After the trees had grown leaves, 1 again 
observed the hawk tearing apart a squirrel nest 
on 30 March 2012 at 1310 hrs. A squirrel emerged 
and tied down the limb as three American Crows 
(Corvus brachvrhynchos ) and one Northern 
Mockingbird (Mimus polyglottos) arrived and 
mobbed the hawk, causing the hawk to fly 
without pursuit of the squirrel. The mobbing 
behavior, not witnessed during the winter, may 
have been related to the recent arrival and 
development of territories by the birds. 
people (i.e., synurbanized; Gliwicz et al. 1994, 
Warren et al. 2006, Parker and Nilon 2008) and were 
approachable to within 5-6 in. The elusive nature 
more typical of gray squirrels was thought to 
explain their low occurrence in the diet of Red¬ 
tailed Hawks in California (Fitch et al. 1946). 
Tree squirrels have been captured through 
cooperative hunting by mated pairs of Red-tailed 
Hawks, when the two hawks guard opposite 
sides of a tree and work together (Bent 1937). 
My observation appears to be the first docu¬ 
mented case of this aggressive behavioral adjust¬ 
ment by a Red-tailed Hawk to a localized and 
abundant urban prey source, as predators are 
expected to hunt in profitable areas (Wakeley 
1978). Squirrels were the only available prey in 
the area, and the foraging strategy I witnessed 
was focused on them. Rather than waiting to 
locale prey, the hawk at times actively attempted 
to flush, or capture, prey from their refuges. Leaf 
and slick nests usually were reconstructed by 
squirrels after an unsuccessful attack. The hawk 
had habituated to the presence of humans, but 
most (not all) of the observed foraging activity 
occurred in early morning or late afternoon when 
fewer students were on campus. 
The Red-tailed Hawk was seen 12 times using 
nest destruction as a technique of attempting to 
access prey. The hawk was observed on two other 
occasions in active search by repetitive examina¬ 
tion of eight cavities (2 in a pine. 6 in oaks). 
Predation attempts regarding nests in this study 
were not always initiated after location of prey 
from perches, which typically are used tot 
observations before a ground attack (Orde and 
Harrell 1977, Preston 1990. Leyhc and Ritchison 
2004). I witnessed successful capture ol three 
squirrels, on 23 August 2011.30 January 2012, and 
2 March 2012, but the hawk was already on the 
ground with the first two kills when observed and 
the hunting strategy used could not be ascertained. 
The 2 March 2012 observation conclusively 
documented the direct success of the nest-attack 
strategy. The successful strategy increases the 
search area actively used by a solitary Red-tailed 
Hawk to the canopy layer, and does not require 'sit- 
and-wait' predation from a perch. 
discussion 
Numerous gray squirrels on the campus of 
Henderson State University were habituated to 
ACKNOWLEDGMENTS 
I thank W. E. Stoul and an anonymous reviewer for 
helpful comments on the manuscript, and T. G. Finley and 
S. L. Russell for alerting me to the presence of the hawk on 
some important occasions. 
