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2 August 2024 Diet Overlaps between the Sexes in Breeding American Oystercatchers
Lyn A. Brown, Erica Nol
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Abstract

Sexual dimorphism in bill size can lead to sex-specific foraging strategies. All 12 extant species of oystercatchers (Haematopus spp.) have sexually dimorphic bills, and most oystercatcher species show intersexual niche partitioning in diet, where males and females eat different prey species in different proportions. Intersexual niche partitioning in diet has not been examined in American Oystercatchers (Haematopus palliatus). This study tested for intersexual niche partitioning in diet in a population of American Oystercatchers breeding on two barrier islands in coastal Virginia, U.S.A. in 2022 and 2023. Diet composition, prey size selection, and foraging areas were compared between the sexes (n = 31 males and n = 28 females). Unlike other oystercatcher species, male and female American Oystercatcher diets overlapped by 99%. Both sexes took similar-sized prey across the seven prey species and shared use of 59% of feeding areas. Previous studies on other oystercatcher species may have found intersexual niche partitioning in diet because of highly competitive environments due to high population density or low prey availability. In contrast, the present study in the Virginia barrier islands that found diet overlap between the sexes may be due to a low competitive environment from low breeding densities and sufficient prey abundance.

Lyn A. Brown and Erica Nol "Diet Overlaps between the Sexes in Breeding American Oystercatchers," Waterbirds 47(1), 1-12, (2 August 2024). https://doi.org/10.1675/063.047.0105
Received: 19 November 2023; Accepted: 22 April 2024; Published: 2 August 2024
KEYWORDS
coastal Virginia
foraging strategies
Haematopus
intersexual competition
niche partitioning
niche utilization theory
Reverse Sexual Dimorphism
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