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Breeding Biology of Five Species of Herons in Coastal Florida

George R. Maxwell, II and Herbert W. Kale, II
The Auk
Vol. 94, No. 4 (Oct., 1977), pp. 689-700
DOI: 10.2307/4085265
Stable URL: http://www.jstor.org/stable/4085265
Page Count: 12
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Breeding Biology of Five Species of Herons in Coastal Florida
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Abstract

The breeding biology of the Louisiana Heron, Snowy Egret, Cattle Egret, Little Blue Heron, and the Great Egret was studied on Riomar Island, a 2.8-ha mangrove island in Indian River County, Florida from March through May 1973. The Louisiana Heron and Cattle Egret nests were built increasingly more distant from the shoreline as the breeding season advanced. Nests of the Little Blue Heron were not horizontally stratified and the seasonal differences in siting of the Snowy Egret and Great Egret nests were not significant. The Louisiana Heron nests showed vertical stratification and were built significantly higher as the season advanced. Snowy Egret and Great Egret nests were built at lower elevations in midseason, but later nests were at the same height as the earlier nests. The heights of Cattle Egret and Little Blue Heron nests did not change during the season. The Louisiana Heron, Snowy Egret, Cattle Egret, and Great Egret completed clutches the last week of March and the first week of April. Little Blue Herons completed their clutches the second and third weeks in April. The louisiana Heron, Snowy Egret, and Cattle Egret laid eggs on the average at slightly greater than 2-day intervals and the Little Blue Heron and Great Egret at slightly less than 2-day intervals. All five laid replacement clutches when the original clutch was destroyed. Little Blue Heron clutches were significantly larger than Snowy Egret and Great Egret clutches. Louisiana Heron clutches were significantly larger than Great Egret clutches. Incubation began after the first egg was laid in most Snowy Egret, Cattle Egret, and Great Egret nests and was delayed until after the second egg in Louisiana Heron and Little Blue Heron nests. The time interval between hatching of successive eggs in the clutch increased in all species except the Little Blue Heron, which showed a decrease in interval. Nests failures were caused mainly by Brown Pelicans, whose clumsy landings at or near their own nests knocked eggs from nearby heron nests or crushed them. Still nesting success of the Riomar herons was better than any reported in the literature. The Little Blue Herons had the highest nest success because of their relative isolation from the other nesting species.

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