Title: Aspects of the breeding biology of the Cattle Egret (Bubulcus ibis) in Montserrat, West Indies, and its impact on nest vegetation
Author: Arendt, W.J.; Arendt, A.I.;
Source: Colonial Waterbirds 11(1): 72-84.
Publication Series: Scientific Journal (JRNL)
Description: Aspects of the Cattle Egret's reproductive ecology and habitat use in an insular environment were studied on Montserrat, West Indies. Average size of 290 nests (17.9 cm) was smaller than sizes reported in the literature and was attributed to a paucity of available nesting materials. We measured 330 eggs to determine: egg volume (24,117.04 mm3), fresh egg weight (24.4 g), egg weight loss during incubation (2.9 g), pipping egg ("star pips" only) weight (21.5 g), egg length (45.56 mm), egg breadth (32.22 mm), and a speciesspecific egg weight constant Kw (= 0.506) (where Kw is fresh egg weight divided by egg length times the square of the egg breadth or W/LB2). Comparative data suggest that clutch-size in this species increases with latitude, but egg size does not. Nest placement within the vegetation and within the colony (core vs. peripheral sites) was studied to compare differential habitat use by nesters. Four nest placement parameters were compared for core nests and peripheral nests: nest height (1.8 m vs 2.4 m), distance from trunk (0.4 m vs 0.6 m), distance from the distal end of the branch (0.89 m vs 0.77 m), and (nearest neighbor distance 52.4 cm vs 56.4 cm). We hypothesized that under keen interspecific competition for nest sites in mixed-species heronries, each species should be forced into a narrower habitat niche (narrower vertical stratification and horizontal partitioning of habitat) than if it nests in monospecific colonies but only nest height substantiated the hypothesis. The Cattle Egret may be having a deleterious impact on the small tidal mangrove forest ecosystem found at Fox's Bay, Montserrat in conjunction with a multiplicity of environmental and ecological factors, including natural storms, wood-cutting, over-grazing by farm animals, reduced flooding, siltation, and soil compaction.
Keywords: Bubulcus ibis, Cattle Egret, clutch size, competition for nest sites, ecosystem, egg, habitat destruction, habitat use, islands, Montserrat, Neotropics, reproductive ecology, vegetation, West Indies.
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Arendt, W.J.; Arendt, A.I. 1988. Aspects of the breeding biology of the Cattle Egret (Bubulcus ibis) in Montserrat, West Indies, and its impact on nest vegetation. Colonial Waterbirds. 11(1): 72-84.
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