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1 September 2012 Potential Factors Affecting Nest Initiation Date, Clutch Size and Nest Success in the Plumage Dimorphic Reddish Egret
Zachary Holderby, William Simper, Brock Geary, M. Clay Green
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Abstract

Plumage dimorphism is common in the family Ardeidae with one morph possessing all-white plumage and the alternate morph being darkly colored. The effects of plumage morph and colony site on nest initiation date, clutch size and total nest success of the plumage dimorphic Reddish Egret in the Laguna Madre region of Texas were examined. Color morph did not significantly affect nest initiation date (Julian date - Dark morph: 109.88 (S.D. 26.56), White morph: 100.82 (25.85), Mixed-morph: 113.29 (27.55); ANOVA: F(2,158)= 0.199, P = 0.820) although nest initiation date was different between nesting colonies (Julian date - Rabbit Island: 125.14 (S.D. 18.05); Zigzag Island: 87.15 (19.07); ANOVA: F(1,158) = 5.732, P = 0.018). Overall mean (±S.E.) clutch size was 3.29 ± 0.05 and differed between colony sites but not between color morphs. Model selection analysis using logistic exposure revealed that neither plumage morph nor colony site had a significant effect on nest success. Mayfield total nest success was estimated at 85.10% ± 5.4% (n = 171), results which are similar to nesting success estimates in other heron species. The lack of effect of color morph on timing of nest initiation, clutch size and nest success suggests other factors may influence the maintenance of color dimorphism in Reddish Egrets.

Zachary Holderby, William Simper, Brock Geary, and M. Clay Green "Potential Factors Affecting Nest Initiation Date, Clutch Size and Nest Success in the Plumage Dimorphic Reddish Egret," Waterbirds 35(3), 437-442, (1 September 2012). https://doi.org/10.1675/063.035.0308
Received: 21 October 2011; Accepted: 7 March 2012; Published: 1 September 2012
KEYWORDS
Egietta rufescens
logistic exposure
nest initiation
nest success
polymorphism
Reddish Egret
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