Abstract

An analysis of sex ratio in adult birds of 196 species showed that of 308 reliable estimates, most were male-biased. Primary sex ratio (at fertilization and in clutches) was equal, but during later life it became biased due to sex-specific mortality. A surplus of males is maintained at all ages since gaining independence. Higher survival rate of males as compared with females is common, but in many populations the deviation from the equal ratio does not reach the level of significance. The most probable explanation of different bias in sex-specific mortality rate in birds and mammals (higher mortality in female birds and male mammals) is their respective sex determination systems. In both classes, the mortality rate is higher in the heterogametic sex, but in birds these are the females, and in mammals, males. Sex ratio starts to be male-biased at a very early age, soon after fledging. The higher level of natal dispersal in females in conjunction with them being heterogametic may result in their greater mortality as compared with males.

中文翻译：

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鸟类种群的性别比和性别特异性存活率：综述

摘要

对 196 种成年鸟类性别比例的分析表明，在 308 种可靠估计中，大多数是雄性偏见。主要性别比例（受精和受精时）是相等的，但在晚年，由于性别特异性死亡率，它变得有偏差。自获得独立以来，所有年龄段的男性都保持着过剩。与女性相比，男性的存活率较高是常见的，但在许多人群中，与等比的偏差并未达到显着水平。鸟类和哺乳动物性别特异性死亡率（雌性鸟类和雄性哺乳动物死亡率较高）的不同偏差的最可能解释是它们各自的性别决定系统。在这两个类别中，异配性别的死亡率较高，但在鸟类中这些是雌性，在哺乳动物中是雄性。性别比例在很小的时候就开始偏向男性，在羽翼丰满后不久。与雄性相比，雌性较高的出生分散水平以及异配性可能导致她们更高的死亡率。