Sexual niche partitioning in two species of New Guinean Pachycephala whistlers

Abstract

Sex differences in foraging behavior have been widely reported in the ornithological literature, but few examples are available from tropical avifaunas. Differences between males and females in foraging behavior have been hypothesized to be a byproduct of sexual size dimorphism or a result of niche partitioning to reduce intersexual competition for food or different reproductive roles. From 2010 to 2013, I used foraging data and mist‐net capture rates from multiple study sites to examine possible sex differences in the foraging behavior of two New Guinean Pachycephala whistlers. I found that male Regent (Pachycephala schlegelii) and Sclater's (Pachycephala soror) whistlers consistently foraged in higher strata than females. It is unlikely that these differences are due to sexual dimorphism because these species exhibit little sexual dimorphism. Sex differences in foraging behavior were consistent across years and study sites and did not appear linked to breeding behavior, supporting the food‐competition hypothesis, but not the reproductive‐roles hypothesis. Male territorial defense often occurs in relatively high strata in Pachycephala whistlers, possibly influencing male foraging strata. However, male territorial behavior cannot explain why females predominately forage in lower strata. Instead, intersexual competition for food resources is likely the primary driver of differences in the foraging behavior of male and female Regent and Sclater's whistlers.

High‐resolution multi‐marker DNA metabarcoding reveals sexual dietary differentiation in a bird with minor dimorphism

“…Nevertheless, on some monomorphic seabirds species, different foraging areas have been described between sexes, especially in the beginning of the breeding period (Cleasby et al., 2015; Hedd et al., 2014; Pinet, Jaquemet, Phillips, & Le Corre, 2012). On two New Guinean whistlers, passerine species with little sexual dimorphism, vertical segregation was also found between sexes and attributed to male territory defence and intersexual food resource differentiation (Freeman, 2014). Nonetheless, it is not clear how spatial segregation translates into dietary segregation, and there seems to be little evidence of dietary segregation in monomorphic species (Catry et al., 2019; Phillips et al., 2011), despite some exceptions (Cleasby et al., 2015).…”

Nitrogen and carbon stable isotope analysis sheds light on trophic competition between two syntopic land iguana species from Galápagos

“…1 A). Intraspecific niche partitioning mechanisms are widespread in animal populations and can be interpreted as a strategy to reduce intersexual competition for food resources 70 . The isotopic pattern observed in our data is likely to reflect behavioral differences between sexes.…”

Using multi-marker DNA metabarcoding to reveal the diet of a scarce woodland bird

“…It has been suggested in some bird species that females have reduced foraging ranges in order to be closer to offspring, and as a result, may feed on more abundant or predictable items, even if these items are less nutritious (da Silva et al, 2020;Sunde, Bølstad, & Møller, 2003). Freeman (2014) found vertical segregation between the sexes of two New Guinean whistlers (Pachycephala sp., Schlegel), with little sexual dimorphism, attributed to territory defence and intersexual food resource differentiation.…”