Genetic relatedness, parentage and behavioural ecology of colonial and cooperative-breeding birds. My research combines the study of animal behaviour and population biology with the examination of molecular genetic markers. The main areas of research are: the evolution of complex social systems in birds; parental care patterns and mate choice; and genetic effects of environmental mutagen loads as estimated by DNA fingerprint mutation rates. To understand the evolution of communal social system we focus on two communal bird species. In Pukeko, a gallinaceous bird inhabiting New Zealand, groups of one to three males and similar numbers of females raise young at a single nest. Sexual access to laying females is shared among sexually mature males. In contrast, smooth-billed anis, a crotophagid bird of Central and South America, engage in a system of social pairs sharing a single nest and competing for access to the incubated clutch of eggs. Females bury each other’s eggs in the structure of the nest. We have detected mutant fragments of DNA in multi-locus mini-satellite profiles of herring gull families. High levels of polycyclic aromatic compounds (PAC) are associated with steel production facilities and automobile emissions. Rates of genetic mutations are being determined for gull colonies with varying levels of PACs.