No relationship between territory size and the risk of cuckoldry in birds.

It has been suggested that male birds adjust their territory size in order to prevent potential intruders from gaining extra-pair copulations. The risk of cuckoldry is supposed to be highest when the distance between a female and the neighbouring males is shortest. This paper describes the variation in territory size of the chiffchaff, Phylloscopus collybita, in relation to the breeding cycle. Contrary to the risk of cuckoldry hypothesis, chiffchaff territories were larger prior to the fertile period of the females and at a minimal size during the fertile period. A review of the literature shows little, if any, evidence of a peak in territory size during the fertile period of the females for most species studied. It is suggested that territoriality is in need of an operational definition. Without such a definition, it is difficult to make and test predictions about the adaptive basis of variation in territory size. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.