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Twenty-three nests were monitored intensively, 14 were observed at intervals of
1–2 weeks (data pooled for all 4 years), and a few nests were checked twice each
season, once to see whether they were active and once at the end of the breeding
season. Nesting success was determined by direct observation of a chick fledging
or by indirect evidence of success, such as presence of sealing plaster below the
nest, activity of the nest until the end of the breeding season, or the presence of
the family group (male, female and newly fledged chick) on or in the vicinity
of the nest. Re-use of nests by the same or different species in successive years
was also recorded, as was the presence of potential competitors or predators at
nest-trees.