Tim Birkhead

“One of the most remarkable of all ornithological discoveries was the realisation that birds in temperate regions undergo enormous seasonal changes in their internal organs...Perhaps the most far-reaching discovery relating to these changes was the finding in the 1970s that parts of the brain also varied in size across the year...The centres in the avian brain that control the acquisition and delivery of song in male birds shrink at the end of the breeding season and grow again in the following year.”