Changing mates

No fewer than 11 hypotheses have been proposed to explain why socially monogamous bird species divorce. Is divorce adaptive and, if so, is it adaptive for one or for both partners? Can we determine which partner initiates mate change, and why? The recent paper by Streif and Rasa demonstrates how careful measures of changes in the breeding success of individuals and of changes in the quality of their offspring can produce clear answers to such questions.