Gender-related diet composition and morphometry of the Restinga Antwren, Formicivora littoralis (Aves: Thamnophilidae)

Abstract

ABSTRACT. Formicivora littoralis (Gonzaga and Pacheco, 1990), the Restinga Antwren, considered the only endemic bird species of the Restinga ecosystem (sandy plain coastal vegetation), is threatened with extinction. The scientific literature provides little information on the biology of this bird, which was discovered in 1990. We evaluate gender-related differences in the composition of the diet and morphometric measurements of this species. We tested the hypothesis that the sexes differ in what they eat and in morphometric characters. Our results revealed that the diet of the Restinga Antwren includes mainly arthropods, which is consistent with the diets of other Thamnophilidae. The lack of differences in the composition of the diet between the sexes does not support the hypothesis that habitat partitioning to avoid intraspecific competition is taking place. We found significant differences in six morphometric measurements, two in the beak and four in body size. It is possible that intraspecific differences between the sexes are a result of sexual selection, a hypothesis that needs to be tested.

Biometry of Two Sympatric Species of the Genus Hypocnemis (Aves: Thamno- Philidae) in Southwestern Amazonia

“…(Table 3). A similar situation was recorded in an endemic thamnophilid from the Atlantic forest in Brazil, the Restinga Antwren (Formicivora littoralis); for this species, some biometric measurements of the male, such as those of the beak, were found larger than those of the female (Chaves & Alves 2013). Differences between the sexes in some biometric traits may minimize the competition for resources between males and females (Selander 1966, Holmes 1986, given that distinct traits may support the exploitation of different types of resources, thus minimizing the feeding competition between the sexes (Selander 1966, Holmes 1986.…”

“…Morphological differences may also be found between the males and females of a species, a phenomenon known as sexual dimorphism (Møller & Pomiankowski 1993). In birds, this difference is primarily found in the plumage and body dimensions, although males and females may also vary in size and body mass (Berns & Adams 2010, Chaves & Alves 2013, Maccarone & Brzorad 2016.…”

Molecular sexing and intersexual differences in the morphometry of the Hangnest Tody-Tyrant Hemitriccus nidipendulus (Passeriformes: Rhynchocyclidae)

“…Gender differences in beak morphometry have also been found for the Restinga Antwren (Chaves and Alves 2013), reflecting habitat partitioning, with males foraging higher up in the vegetation than females (Chaves et al 2017), even though the two sexes had a similar diet. In addition to body size, male Restinga Antwren had larger beaks than females in two parameters -nostril-tip and beak width at the nostril (Chaves and Alves 2013). The Restinga Antwren occurs in the same habitat (sandy coastal plain) in which the Hangnest Tody-Tyrant was sampled in the present study.…”

“…The males of this thrush have larger wings than the females, which could allow them to fly faster and arrive first at their breeding grounds (Silva et al 2011). In resident species, larger wing size has been recorded in male Chestnut-capped foliage-gleaner Clibanornis rectirostris (Wied, 1831) in the Serra do Cipó National Park, in the Brazilian Cerrado savanna (Faria et al 2007), and in the male Restinga Antwren in the coastal restinga (Chaves and Alves 2013). The males of both Figure 1.…”