Brooding behaviour in the cooperatively breeding Bell Miner (Manorina melanophrys)

Abstract

Brooding of nestlings in cooperatively breeding bird species may be disrupted by the attendance of helpers at the nest. We studied the factors that influence brooding in the cooperatively breeding honeyeater, the Bell Miner (Manorina melanophrys), and how nest attendants interacted with the bird brooding at the nest. Only the breeding female brooded nestlings, despite helpers assisting with many other aspects of the care of nestlings. The number of bouts of brooding by the female per hour was dependent upon the age and number of nestlings, ambient air temperature, and the number of Bell Miners visiting the nest. Behaviours performed by the female differed significantly between brooding and non-brooding visits. These findings are consistent with earlier studies of species with simpler biparental care. However, the complexity of meeting the nutritional and thermoregulatory requirements of nestlings in a cooperatively breeding species is demonstrated by changes in the behaviour of nest attendants when females were brooding, and by the different responses of females to different nest attendants. Nest attendants delayed visiting the nest when the female was brooding. However, if an attendant did visit the nest while the female was brooding, she was more likely to stop brooding and allow nestlings to be fed if the attendant was the breeding male, rather than a helper, irrespective of whether or not the attendants were close relatives of the nestlings.