SummaryThis five month study involved the daily observation of the contents of 83 occupied Fairy MartinHirundo arielnests under a large culvert near Murwillumbah N.S.W. Nest building occurred from July until 16 November. The average time taken to build nests was 30 days. Eggs were laid between 1 August and February. Clutch size varied from two to five and averaged 3.5 eggs. The range of egg sizes and colours are given. Incubation averaged 13.8 days (range = 11–17) and each pair successfully hatched an average of 3.3 nestlings early in the season and 3.0 nestlings later in the season. Clutch size, incubation period, hatching rate and the average number of hatchlings fledged from each brood, all declined in the last part of the season. The natal pterylosis, feather growth and growth rate of the chicks is described. Nestlings took an average of 22.5 days (range 14–30) to depart their nests. Predation and interspecific nest competition are recorded.