The Nesting Biology of the Grey-headed Robin Heteromyias albispecularis (Petroicidae) in Australian Upland Tropical Rainforest

Abstract

Seventy-eight nests of the Grey-headed Robin Heteromyias albispecularis were studied on the Paluma Range, north Queensland, during 1978–89 and three on the southern Atherton Tableland in 1997. Only one pair of birds attended each nest. The presumed female built, incubated, brooded and fed young, provisioning herself and being fed by her mate. The male did not feed the offspring directly. Nests took 12-15 days to build and often remained empty for 2-4 weeks before egg laying. Nests were open cups typically built upon the spiny stems of a climbing palm Calamus sp. or in the crowns of saplings, mostly < 3 m above ground. Nesting at Paluma began in late August–early September. Most (90%) clutches were incubated during September–November, with October the peak month (59%) and 81% of nestlings left the nest in November. Of 46 clutches, 56% were of two eggs and 44% of one egg (mean clutch size 1.6). Fresh eggs (1-3 days old) weighed 15% of mean adult female weight on average, and were incubated for 17-19 days in bouts averaging 6.8 min at a rate of 5.8 per h. There was little variation in nestling period between broods of one and two; the median for all broods was 12-13 (range 10-14) days. Females brooded young for 33% of diurnal observation time and fed them 9.7 times per h. Males provisioned nesting females 1.3 times per h during incubation, 5.2 times per h during the nestling stage and overall provided 47% of nestling meals indirectly. Eighty-three per cent of eggs hatched and 54% of nestlings fledged; 39% of eggs produced fledglings at a rate of 0.7 per nest. Overall nest success rate was 45%, or higher (53%) if restricted to onlythose nests whose fate was known. These findings are compared with those of other Australasian robins.