distribution of Hg. Rates of accumulation have increased as much as ten-fold from pre- 
1990 conditions. Presently, no spatial distribution pattern is apparent. The Everglades 
are distinctly different in structure, function, geographical, and climatologic conditions 
from other described systems, yet the sediment profiles suggest that Hg accumulation 
in the Everglades is similar to such patterns reported elsewhere. 
1994 0 
Bancroft, G. T., A. M. Strong, R. J. Sawicki, W. Hoffman, and S. D. Jewell (1994) 
Relationships among wading bird foraging patterns, colony locations, and hydrology in the 
Everglades. In: Everglades: The Ecosystem and Its Restoration . S. M. Davis and J. C. Ogden 
(eds.) St. Lucie Press, Delray Beach, FL. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Restoration of wading bird 
breeding populations in the Everglades requires a better understanding of the 
relationships among wading bird foraging patterns, colony locations, and hydrology. To 
address this need, general foraging distribution data from systematic aerial surveys, 
specific foraging distribution data obtained from following flights, habitat data from the 
USGS orthophotomaps, hydrological data from gauges and aerial surveys, and coloney 
location, size, and sucess data from three recent studies were analyzed. Nesting great 
egrets (Casmerodius albus) and white ibises (Eudocimus albus) typically foraged within 
9 and 10 km, respectively, of their colonies. Historically, these species bred in large, 
mixed-species colonies in the mangrove zone of Everglades National Park, whereas 
currently they breed in much smaller colonies in the water Conservation Areas. The 
persisting historic colonies in the mangrove zone are surrounded by a diverse mosaic of 
habitats and generally have a smaller percentage of freshwater habitats. In the Water 
Conservation Areas, great egret and white ibis foraging distributions varied within and 
among years and were generally correlated with differences in water depth and 
distribution. Comparison of colony location and size with overall foraging distributions 
during the months overlapping breeding indicated that colony location for these two 
species was only a marginal predictor of the location of food resources at the time 
when they were feeding young. Examination of the formation, growth and decline of the 
L-67 colony in the Water Conservation Areas during the drought year 1989 showed 
that, initially, the nesting birds were feeding close to the colony. As the area dried out, 
the overall foraging distribution shifted well south of the colony. Nesting birds 
gradually had to fly farther to find foraging sites, and the colony experienced high 
levels of nest abandonment. It can be concluded that wading birds initiate nesting near 
foraging aggregations, feeding on large and concentrated prey bases near suitable 
nesting sites, at physiologically appropriate times of year. These simple cues, 
however, may no longer be adequate indicators of foraging sites that will provide food 
for the 3 - 4 months needed to complete nesting. In addition to influencing the patterns 
and timing of water flows, it is likely that water management has aggravated the 
effects of dry season rainfall by increasing the severity and duration of reversals, 
creating pulsed regulatory releases and reducing water levels so that a given rainfall 
event has a greater diluting effect. The compartmentalization of the Everglades may 
have decreased the ability of forage fish to migrate through the system, especially into 
the deeper sloughs during the dry season, thus decreasing the productivity of these 
areas for nesting wading birds. The extent of wetlands should be maximized by 
restoring degraded marshes wherever possible. The natural connectivity in the system 
should be increased by reducing compartmentalization and the critical features of 
natural hydrology should be replicated, especially in the northern ends of the Water 
Conservation Areas and Shark River Slough. Additionally, the hydrology and 
productivity of the lower Shark River Slough wetlands and the associated estuaries 
should be analyzed more thoroughly, and peak flows out of Water Conservation Area 3A 
and Shark River Slough should be increased to improve habitats in the areas from Nine 
375 
