Sex allocation in Savi's warblers Locustella luscinioides: multiple factors affect seasonal trends in brood sex ratios

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Neto, JM (Author) Other; Hansson, B (Author) Other; Hasselquist, D (Author) Other

Journal

Title: Behavioral Ecology and Sociobiology

Vol. 65

Pages: 297-304

ISSN: 0340-5443

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 13 Citations

Scopus - 15 Citations

Other information

Authenticus ID: P-002-VB8

DOI: 10.1007/s00265-010-1046-5

Abstract (EN): Sex allocation theory predicts that whenever the relative fitness of sons and daughters differ, females should invest more in the sex with the greatest fitness return. In this study, we evaluated the influence of various ecological factors on the brood sex ratio (BSR) of Savi's warblers (Locustella luscinioides) across several breeding seasons. There was a slight but significant female production bias at the population level, which is consistent with the 'local resource competition' hypothesis, as the breeding density is very high and females are more prone to disperse. We found that there was a significant decline in BSR during the breeding season, but no influence of male size, female size, social status nor extra-pair paternity were detected. The seasonal decline in BSR was further evaluated by assessing the within- and between-female effects, which indicated that multiple factors were operating simultaneously in our study population. First, there was a significant within-female decline in BSR, which was consistent with the decline in female condition due to the reproductive effort associated with multiple brooding (supporting the Trivers and Willard hypothesis). Second, a significant decline in BSR with the laying date of first clutches of different pairs indicated that male and/or female qualities are also associated with the seasonal variation in BSR. Finally, a comparison between the sex of the youngest nestling with the remaining ones did not suggest any bias, indicating that females do not compensate for the increased mortality of the last nestling (caused by asynchronous hatching) by producing a male from the last laid egg.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8