Breeding ecology of the Madagascar Grebe Tachybaptus pelzelnii in Bemanevika Protected Area in the northern highlands of Madagascar

Abstract

We studied the breeding ecology of the endangered Madagascar Grebe Tachybaptus pelzelnii (family Podicipedidae) at Bemanevika Protected Area, during two consecutive years (October 2020–September 2022). Two breeding units were observed: pairs and trios made up of one male and two females. Our evidence supported polygyny, over communal breeding, for the trios — the first record for the family. We counted 147 occupied nests, of which 105 were monitored during the two breeding seasons: 78 nests with pairs and 27 nests with trios. Breeding activity occurred from October to April. Nest construction lasted on average 21.4 days but nest material deliveries occurred until the end of the breeding season. Nests were placed at an average of 101.4 cm in water depth, 2.3 m from shore and 2.2 m from open water. The nest density was 0.5 and 0.4 nests per hectare during season 1 and season 2, respectively. Egg-laying occurred between mid-October and mid-March. The clutch size ranged from one to seven eggs. Incubation started with the laying of first egg and lasted on average 21.5 days. Of the 324 eggs laid in 105 nests, 121 (37.4%) hatched, and 76 (62.8%) of the hatchlings fledged (reproductive success of 0.7 young per nesting attempt). The rearing period averaged 42.8 days.