A population of about 15 pairs of Grey Phalaropes was studied during one season. Observations were made of behaviour and feeding habits at all stages in breeding.
Females advertized to males with Circle Flights over the breeding grounds, and became gregarious and mutually intolerant during the latter part of the season. Females also took the initiative in courtship, but males defended the pair bond against intruders and incubated the eggs. Pair bonds were believed to be stable until after egg-laying. Descriptions are given of ritual activities and the context in which they were witnessed. Courtship Touching followed intrusion by a strange female, expelled by the male's Driving Flight. Rattling occured at moments of general excitement. None of these rituals appeared to be pre-copulatory. A ceremony leading to the selection of a nest site, in which the female takes the initiative, is described for the first time. Females deserted their mates during incubation. A qualitative model is proposed to explain the variability in the time between laying and female desertion, in terms of opportunities for polyandry and risk of nest predation.
For food, the birds depended largely on a rich supply of chironomid midges, though aquatic larvae and spiders were also important, particularly early in the season. Three feeding techniques were distinguished and some assessment was made of the profitability of each, in the light of data on feeding rates.
The mating system (monogamous role reversal) is believed to have evolved from the habit of double-clutching. It is proposed that a factor in the emancipation of females and their assumption of the courtship initiative is the small size and fragmented distribution of breeding groups, in which sex ratios tend to be unequal.