Intersexual variation in the foraging ecology of sexually monochromatic Western Wood-Pewees

Abstract

Investigators generally pool observations of males and females in studies of the foraging behavior of sexually monochromatic songbirds. However, such pooling can obscure possible intersexual differences. We compared the foraging behavior of male and female Western Wood‐Pewees (Contopus sordidulus), a sexually monochromatic species, in the Sierra Nevada Mountains of California during the breeding seasons of 2007 and 2008. We recorded 143 foraging observations (male N= 74, female N= 69). Overall, mean foraging rates of females (2.8 attacks/min) were higher (P < 0.001) than those of males (1.1 attacks/min). In addition, female foraging rates were significantly higher during incubation than during the nest building, nestling, and fledgling periods. When foraging, males perched higher above ground than females (means = 17.1 and 6.7 m, respectively). Differences between male and female Western Wood‐Pewees in foraging rates and perch heights suggest that males may spend more time on vigilance while females focus on foraging quickly during incubation and when feeding nestlings. Because metrics such as foraging attack rates are sometimes used as indicators of habitat quality and we found that rates can differ between the sexes and among nesting stages, investigators should consider the possibility of such differences when assessing habitat quality, especially for sexually monochromatic species of birds.

Diet of moulting Swainson's Thrushes (Catharus ustulatus) and Tennessee Warblers (Leiothlypis peregrina) at a stopover site during fall migration measured with fecal DNA metabarcoding

“…Species and moult status had no significant effect although there was some evidence that sex (within species) impacted arthropod-related diet ( p = 0.05). Sexual segregation of micro-foraging habitat has been observed in several songbirds while on their wintering grounds 49 , 50 and breeding grounds 51 – 53 . Differences in foraging height, rates, and substrate contribute to these distinct niches 49 , 51 .…”

“…Sexual segregation of micro-foraging habitat has been observed in several songbirds while on their wintering grounds 49 , 50 and breeding grounds 51 – 53 . Differences in foraging height, rates, and substrate contribute to these distinct niches 49 , 51 . Since insect families shift significantly from ground level to canopy and between plant species in temperate forests 54 , a similar distribution in foraging strategy may reflect this difference in diets between the sexes.…”

Sexual niche partitioning in two species of New Guinean Pachycephala whistlers

“…During the breeding season, females may preferentially forage near nests while males prefer other microhabitats (e.g., higher or more exposed perches) that allow vigilant territorial behavior (Morse , Franzreb , Holmes , Petit et al , Morimoto and Wasserman ). Sex differences in foraging strata may result if male vigilance posts and nests (attended primarily by females) consistently differ in their vertical placement (Franzreb , Holmes , Petit et al , Fogg et al ). If true, then differences between the sexes in foraging behavior should be apparent only during the breeding season.…”