Kittiwakes have been studied in detail at North Shields, Tyne and Wear, England since 1954. I investigated die effect of mate change (due to divorce or mate death) on reproductive performance. Below average productivity in the year of divorce and in the preceding year, coupled with a low adult survival rate in the year following divorce, suggested birds which divorced were poorer quality individuals than birds which retained their mate. Productivity was reduced if one or both members of a pair were in their last year of life and was indicative of a decline m fitness. Dispersal, breeding and the importance of nest site tenacity to mate retention were studied when kittiwakes were prevented from returning to their original nest sites in 1991. In 1991, extensive non-breeding (57%) and low productivity resulted. Of die birds which bred, 54 (83%) nested in the immediate colony area and only 11 moved to other colonies. Despite moving site, many birds retained their mate of the previous breeding season. In the following year, a further 61 kittiwakes moved and nested at other colonies and about a third retained theu" mate. This, and other evidence, suggests that individual recognition is important in mate retention. Reproductive performance, in relation to nest position in the colony and proxunity to other nesting pairs, was compared with a kittiwake colony at Marsden, NE England. Productivity was highest at the centre of the colonies and, at the edge, was highest for pairs which nested adjacent to another pair. It is suggested that social stimulation, arising from nesting adjacent to another pair, advanced the date of laying. Adult attendance at the nest during chick-rearing was monitored at Marsden in three years. During comparable time periods ui 1991 and 1993,93% and 75% of die broods, respectively, were attended by an adult, compared to only 51% during the same period in 1992. Attendance decreased in relation to hatching date, chick age and brood size and increased with parental age and/or quality.