SEASONAL-VARIATION IN THE SEX-RATIO OF MARSH HARRIER CIRCUS-AERUGINOSUS BROODS

被引：64

作者：

ZIJLSTRA, M ^{[1
]}

DAAN, S ^{[1
]}

BRUINENBERGRINSMA, J ^{[1
]}

机构：

[1] UNIV GRONINGEN,ZOOL LAB,POB 14,9750 AA HAREN,NETHERLANDS

来源：

FUNCTIONAL ECOLOGY | 1992年 / 6卷 / 05期

关键词：

CLUTCH SIZE; EGG SEX SEQUENCE; LAYING DATE; MORTALITY; PRIMARY SEX RATIO;

D O I：

10.2307/2390052

中图分类号：

Q14 [生态学（生物生态学）];

学科分类号：

071012 ; 0713 ;

摘要：

1. Analysis of the sexes of 2260 nestlings in 735 marsh harrier broods revealed an overall excess [sex ratio (SR) = 54.8%] of males, and a significant increase in the proportion of males with progressive laying date (d = day of the year): In [SR/(1-SR)] = -1.286 + 0.013 d. 2. We argue that it is likely that these deviations from parity are determined at ovulation rather than by differential mortality ot the sexes. This argument is based on two facts. First, the seasonal trend was most pronounced among the largest and oldest two nestlings per brood. These corresponded with the initial two eggs in 95% of the cases in a subset of 61 nests followed closely. Secondly, these initial eggs suffered least mortality. 3. We speculate that marsh harriers may benefit from producing more daughters early in the season if the probability of females breeding as yearlings declines with progressive date of birth.

引用

页码：553 / 559

页数：7