I have been watching birds since I was a child. H. Mendelssohn introduced me to the scientific aspect of ornithology. The book by Niko Tinbergen, The Study of Instinct (1951), convinced me that watching birds could be an intellectual challenge. I spent most of 1955 in Oxford with Tinbergen, a year that introduced me to ethology and to the study of behaviour at the gull colony in Ravenglass. In 1970, after working as an activist for conservation in the intervening years, I spent a few months at Oxford with David Lack, who convinced me that individual selection is the only mechanism by which to interpret adaptations.

My doctoral thesis was on the social behaviour of the white wagtail Motacilla alba. I was able to show by experiments how ecological conditions, especially food distribution, shape its social system. This study started my interest in studying the relationship between ecology and social systems (Ward & Zahavi 1973).

In 1972, my student and friend, Yoav Sagi, questioned the logic of Fisher's model of mate choice. This stimulated me to develop the handicap principle as an alternative to Fisher's model. The implications of the handicap principle dramatically changed my understanding of evolution. I soon realised that the handicap principle is a necessary component in the evolution of all signals (a signal is defined as a trait that has evolved in the signaller, in order to transfer information to receivers, to affect the behaviour of the receivers in a manner that is beneficial to the signaller).