The breeding biology of the co-operatively breeding White-throated Brown Hornbill (Anorrhinus austeni) in north-east India

We documented the breeding biology of the cooperatively breeding Brown Hornbill Anorrhinus austeni. We found ten nests from 2017 to 2020. The nesting season was from early March to mid-July. The mean (± SE) nesting duration was 95.4 (± 2.3) days with a range from 92 to 99 days. Overall nesting success was high (91.6%). Most successful nests (83%) produced one chick, with the remaining 17% producing two chicks. Visitation and food delivery rates were higher in the post-hatching period compared to the pre-hatching period. There was inter-annual variation in the food delivered at nests, with a higher proportion of animal matter recorded in 2018 compared to 2019. The mean (± SE) number of helpers at Brown Hornbill nests was 2.2 (± 1.6), ranging from zero to five, and helpers (adult males or juveniles) assisted in bringing food and guarding nests. There was no relationship between number of helpers and nesting success or the number of chicks. The role of helpers may be related to ensuring nesting success through greater vigilance or by enhancing food finding and food delivery, however there may be no incremental advantage from having more helpers. Helpers may also be constrained by limited breeding opportunities and therefore may defer their own breeding and instead, assist the adult pairs. Further research with marked individuals would be required to better understand the role of helpers, and the factors determining the evolution of cooperative breeding behaviour in this species.

Link: https://iucnhornbills.org/wp-content/uploads/2023/08/HNHC_Volume-4_full_online.pdf