Male birds are apt to sing a jaunty tune and sport some pretty plumage, making them prominent targets for population studies. But a survey of bird demographics reveals that male birds generally outnumber females – dramatically so in endangered species – meaning that real population sizes could be much smaller than estimates which assume an equal sex ratio.
Paul Donald at the UK Royal Society for the Protection of Birds analysed the sex-ratio data of 173 species documented in the literature. He found that 112 were male-biased, with males outnumbering females by 30 to 35 per cent Ibis, () on average.…
