title: Sex differences in digestive traits in sexually size-dimorphic birds: Insights from an assimilation efficiency experiment on black-tailed godwit.
abstract: Digestive assimilation efficiency is considered a trait with important implications for animal ecology. However, practically all studies have ignored the importance of sex differences in food assimilation efficiency (AE). Here, we investigated sex differences in dietary and physiological parameters in the Black-tailed Godwit Limosa limosa limosa feeding on rice seeds, a species with sexual dimorphism in body size and body mass. Gross daily food intake, gross energy intake, gross energy output and metabolizable energy intake did not vary significantly between sexes, but godwit females showed lower faeces energy density and higher AE than males. Mass-specific AE was similar in males and females, and the difference in AE could be attributed to the females' greater body mass. We suggest that a differential AE could play a role in explaining sex differences in habitat or micro-habitat selection during the non-breeding season in bird species with sexual dimorphism in size. Finally, we addressed the question about assimilation efficiency accuracy in models that estimate prey acquisitions by declining shorebirds as the Black-tailed Godwit.
authors.affiliation: Conservation Biology Research Group, Area de Zoología, Universidad de Extremadura, Avenida de Elvas s/n, 06071 Badajoz, Spain. fquesada@unex.es
authors.forename: Francisco
authors.initials: F
authors.lastname: Santiago-Quesada
authors.forename: José A
authors.initials: JA
authors.lastname: Masero
authors.forename: Noelia
authors.initials: N
authors.lastname: Albano
authors.forename: Auxiliadora
authors.initials: A
authors.lastname: Villegas
authors.forename: Juan M
authors.initials: JM
authors.lastname: Sánchez-Guzmán
mesh_terms: D000821:Animal Feed; D000818:Animals; D001717:Birds / Q000033:anatomy & histology*; D015992:Body Mass Index; D049628:Body Size / Q000502:physiology*; D004032:Diet; D004063:Digestion / Q000502:physiology*; D002149:Energy Intake; D005260:Female; D008297:Male; D012275:Oryza; D012639:Seeds; D012727:Sex Characteristics; D013045:Species Specificity