Open AccessAbsence of seasonal variation in great tit offspring sex ratios
Author(s) -
Verboven Nanette,
Käkelä Minna,
Orell Markku
Publication year - 2002
Publication title -
journal of avian biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.022
H-Index - 76
eISSN - 1600-048X
pISSN - 0908-8857
DOI - 10.1034/j.1600-048x.2002.330203.x
Subject(s) - biology , offspring , parus , sex ratio , juvenile , avian clutch size , reproduction , seasonal breeder , hatching , demography , sex allocation , zoology , ecology , population , pregnancy , genetics , sociology
When the timing of breeding affects the reproductive value of sons and daughters differently, parents are expected to increase their fitness by changing the offspring sex ratio during the course of the breeding season. Previous studies have shown that in great tits Parus major hatching date has a stronger effect on the fitness of juvenile males than on that of juvenile females. We tested whether this difference was reflected in a seasonal decline in the proportion of sons per breeding attempt. Although offspring sex ratio was more variable than would be expected from a binomial distribution, there was no significant relationship between the proportion of sons and the laying date of the clutch. Moreover, individual females did not adjust the sex ratio of their offspring following an experimental delay of breeding. This study therefore fails to demonstrate adaptive seasonal variation in great tit offspring sex ratios.