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Title: No evidence of sex ratio manipulation by black-throated blue warblers in response to food availability
Sex allocation theory predicts that females should bias their offspring sex ratios when the fitness benefits of producing sons or daughters differ depending on rearing environment. The Trivers-Willard hypothesis proposes that whether females produce more sons or daughters depends on food availability via both intrinsic maternal condition and differing reproductive potential (typically from mating system structure) for sons versus daughters. However, tests of its key predictions are often based on untested, implicit assumptions that are difficult to quantify, especially in migratory animals. In a 5-year study, we manipulated food availability in low- and high-elevation forest to test the Trivers-Willard hypothesis in the migratory black-throated blue warbler (Setophaga caerulescens). We found that the population-wide offspring sex ratio was significantly male-biased (population mean: 0.58), which was driven by an overproduction of sons in high-elevation forest (high-quality habitat mean: 0.59). Yet, we found no effect of food availability on offspring sex ratio from either natural variation or supplemental feeding. Sex-specific developmental costs did not differ for sons and daughters reared under low and high food availability. These results suggest that female black-throated blue warblers do not manipulate offspring sex ratios in response to food availability and are not consistent with the predictions of the Trivers-Willard hypothesis. This study highlights challenges of examining mechanisms driving patterns in offspring sex allocation in migratory species for which both the costs of rearing and relative fitness benefits of sons and daughters cannot be tracked into adulthood.  more » « less
Award ID(s):
2224545
PAR ID:
10490267
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Springer Link
Date Published:
Journal Name:
Behavioral Ecology and Sociobiology
Volume:
77
Issue:
11
ISSN:
0340-5443
Subject(s) / Keyword(s):
food supplementation offspring sex allocation setophaga caerulescens sex ratio bias Trivers-Willard hypothesis
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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