H. F. Percival

Food Habits of Ring-necked Ducks Wintering in Florida

Food habits of wintering ring-necked ducks (Aythya collaris) were determined by examining gullets from 597 birds collected in 3 regions of Florida. Fifty-five of the gullets contained trace amounts of food and 148 contained >1 ml. Forty-one foods were identified. Animal matter, principally snails, chironomids, and dragonflies, occurred in 43.6% of the samples containing food. Plant foods, principally hydrilla {Hydrilla verticillata), waterlilies (Nuphar advena, Nymphaea odorata, Brasenia scherberi), and sawgrass (Cladium jamaicense), occurred in 89.1 % of the samples containing food....


Evaluation of Alligator Hatchling and Egg Removal from Three Florida Lakes

The removal of 50% annual alligator production over a 6-year period on 3 central Florida lakes did not appreciably change population size structures. On Lake Jessup, increases were found in the >0.6 m size classes, while on Lake Griffin no changes were found in any size classes. Lake Apopka experienced significant (P <0.05) declines in all size classes, but these declines resulted from unexplained and unrelated mortality and reproductive failures and not from the early age-class harvest. No change in size structure was found for the control area, Lake Woodruff.


Habitat Variables Affecting Nesting Success of the American Alligator in Florida

Five aerially estimated habitat variables and nest spacing patterns were used to develop predictive models for evaluating the status of American alligator (Alligator mississippiensis) nests on 2 lakes in central Florida. Models developed from data on 146 and 54 nests on Orange Lake and Lake Woodruff, respectively, indicated that none of the habitat variables were useful in predicting nest success. Nests occurred in clumped distributions in some years, but were not clumped in the same areas from year to year. Until more reliable methods for evaluating nest status are available, management...


Food Habits of the Common Moorhen and Purple Gallinule in North-Central Florida

The food habits of common moorhens (Gallinula chloropus) and purple gallinules (Porphyrula martinica) on a north-central Florida lake were studied through monthly analysis of gizzard contents from May 1981 through April 1982. Common moorhens consumed an average volume of 93% plant and 7% animal food, whereas purple gallinules consumed an average volume of 71% plant and 29% animal food. The major foods of the common moorhen were leaves and stems of Hydrilla verticillata, seeds of Polygonum spp., and snails, Planorbella spp. The major foods of purple gallinules were seeds of Nuphar luteum...