SHORT COMMUNICATIONS 
389 
TABLE 3. Coefficients for Pearson’s correlation 
analysis between principal components and variables for 
Brown Pelicans nesting on Gaillard Island. Alabama. 
PCI 
PC II 
Julian date of arrival 
0.929** 
-0.039 
Ground height DV 
-0.206 
0.916** 
Low heiaht DV 
0.107 
0.937** 
Moderate height DV 
0.764* 
0.565 
Tall height DV 
0.628 
-0.239 
Nest density 
-0.788* 
0.195 
Nests on ground 
-0.961** 
0.003 
1 P < 0.02 ** P £ 0.001 
Both egg and hatching success increased with 
earlier arrival dates, lower vegetation density in 
the layer 2-3.5 m above ground, higher nest 
density, and more nests on the ground. Hatching 
success increased as the vegetation density in the 
layer <1 m above ground and vegetation density 
in the layer 1-2 ni above the ground decreased. 
Arrival date was positively related to vegetation 
density between I and 2 m above the ground, It 
was negatively related to the interaction term of 
the first two vegetation layers (ground height DV 
N low height DV). The vegetation density 
between I and 2 m above the ground increased 
as arrival date became later and the interaction 
between the first two vegetation layers decreased, 
indicating those arriving first chose sites with 
little to no vegetation on the ground but some 
vegetation above the ground. It is not surprising 
that year had no effect on egg or hatching success. 
The study was conducted for 2 years which is not 
sufficiently long to draw conclusions regarding 
year effects on Brown Pelican nesting ecology. 
The more successful Brown Pelicans on Gail- 
bad Island arrived earliest and selected sites with 
less dense vegetation within I m of the ground. 
This provided more room to nest on the ground, 
but with some cover above the ground. Lower 
vegetation densities were selected first and nests in 
those areas were more successful. This could be 
•elated to size of Brown Pelicans. They must 
incubate eggs, sit on the nest w hen not incubating, 
and land on the nest or take flight from the nest 
(Shields 2002). Dense vegetation does not allow 
M, mc or all of these actions. Clumsy landings of 
Brown Pelicans can crush eggs or knock them 
from nests (Maxwell and Kale 1977). These 
problems were minimized by nesting in less dense 
vegetation. Vegetation in which nesting occurred 
ceases to be a factor when nests were on the 
ground. Egg and hatching success increased 
significantly in those quadrats with a high per¬ 
centage of nests on the ground. Another benefit to 
those nesting on the ground is predator avoidance. 
Nestling Brown Pelicans from ground nests are 
able to leave the nest and return earlier than those 
nesting in vegetation above die ground - as early 
as 3 weeks after hatching (Shields 2002). These 
nestlings could leave the nest to avoid predation 
(from avian predators) at a much earlier age than 
those from nests above the ground. Selecting for 
ground nests, but with vegetation above ground 
level provides thermoregulatory benefits (Grant 
1982) and cover from avian predators. Gaillard 
Island is free of mammalian and reptilian preda¬ 
tors. The only predators of Brown Pelican eggs and 
young arc gulls and wading birds. Ground nests 
under the cover of vegetation hides eggs and 
chicks from predators hunting from the air. 
Another factor that may affect nest-site selection 
and productivity is age of the nesting birds. We 
collected no data on age, hut Blus and Keahey 
(1978) have shown that older Brown Pelicans have 
the greatest nest success. A longer study would be 
needed to show these effects. 
Brown Pelicans are now flourishing along the 
Gulf Coast of Alabama. However, with develop¬ 
ment of coastal areas, the ephemeral nature of 
spoil islands, natural disasters, and man-made 
disasters in the Gulf of Mexico, their future is 
uncertain. This study provides insight into nest 
preference and the relative success rates of 
microhabitats at nest sites. This study also 
provides important baseline data tor future studies 
on the breeding ecology of Brown Pelicans in the 
Gulf of Mexico. 
ACKNOWLEDGMENTS 
Funding for this project was provided by the Slate Lands 
Division of the Alabama Department of Conservation and 
Natural Resources, the NOAA Office of Ocean and Coastal 
Resource Management (# NA05NOS4191091), and 
NOAA’s Northern Gulf Institute (DlSL-01 Education and 
Outreach). 
LITERATURE CITED 
Blus, L. J. and J. A. Keahey. 1978. Variation in 
reproductivity with age in the Brown Pelican. Auk 
95: 128-134. 
Grant. G. S. 1982. Avian incubation: egg temperature, nest 
humidity, and behavioral thermoregulation in a hot 
environment. Ornithological Monographs Number 30. 
IMHOF, T. A. 1976. Alabama Birds. Second Edition. 
University of Alabama Press, Tuscaloosa, USA. 
