Day length, reproductive effort, and the avian latitudinal clutch size gradient. Issue 6 (1st June 2013)

• Record Type: Journal Article
• Authors: Rose, Alexandra P.; Lyon, Bruce E.
• Is Part Of: Ecology. Volume 94:Issue 6(2013)
• Page Start: 1327
• Page End: 1337
• Publication Date: 2013-06-01
• Subjects: Ashmole's hypothesis -- avian ecology -- clutch size -- day length -- Lack's rule -- latitudinal gradient -- life history -- Tachycineta bicolor -- Tree Swallow; Ecology -- Periodicals; Ecology -- Periodicals; Écologie -- Périodiques; Ecologie; Écologie; Écologie animale; Écologie végétale; Ecology; Periodicals; 577.05
• DOI: 10.1890/12-0953.1
• Languages: English
• ISSNs: 0012-9658

Abstract

Abstract : Explaining latitudinal patterns in life history traits remains a challenge for ecologists and evolutionary biologists. One such prominent pattern is the latitudinal gradient in clutch size in birds: the number of eggs laid in a reproductive bout increases with latitude in many species. One intuitive hypothesis proposes that the longer days at high latitudes during the breeding season allow parents to spend more time foraging each day, which results in greater total food delivery to the brood each day, and hence more offspring produced. This day length hypothesis is virtually untested, although it was proposed nearly 100 years ago. We developed a conceptual framework for distinguishing between the day length hypothesis and the widely accepted alternative hypothesis that attributes the latitudinal gradient in clutch size to increased per capita food resources at higher latitudes. Using this framework to contrast components of reproductive effort and life history patterns in a mid‐ and high‐latitude Tree Swallow ( Tachycineta bicolor ) population provided clear evidence for the day length hypothesis, but little evidence for the alternative. Our findings suggest that the length of an animal's workday may be an important, but unappreciated, component of reproductive effort.