Long-term monitoring of breeding successes of Great Hornbill (Buceros bicornis) and Rhinoceros Hornbill (Buceros rhinoceros) using artificial nest boxes in Budo-Su-Ngai Padi National Park, Thailand

Nest boxes are a conservation tool for increasing the availability of nests. The efficacy of nest boxes can be assessed by examining the breeding parameters of birds in nest boxes to see whether data are comparable with tree cavities. The hornbill artificial nest research was conducted in Budo-Su-Ngai Padi National Park, Thailand since 2003. This project aims to increase the breeding propensity of two large species of hornbills; the Great Hornbill (Buceros bicornis) and the Rhinoceros Hornbill (Buceros rhinoceros) that coexist in the study area, by utilizing nest boxes. The nest boxes were constructed from fiber-reinforced plastic. There were two designs; small nest box: 50 x 49 cm at base and 95 cm height, and large: 65 x 70 cm at base and 95 cm height. Twenty nest boxes were installed between 2004 and 2006. These nest boxes were monitored from 2004 to 2021. The study results indicated that the proportion of nest occupancy of Great Hornbill breeding in natural nests was higher than nest boxes: 48.9% and 31.4%, respectively (the two binomial proportions test gives: Zc= 4.01, P < 0.0006 < α = 0.05). The results also showed that the Great Hornbill prefers to select a large nest box than a small one: 37.3% and 17.3%, respectively (the two binomial proportions test gives: Zc = 3.4, P < 0.00068 < α = 0.05). Eight nest boxes so far have been utilized by hornbills: six by Great Hornbill with 58 nesting successes and two by Rhinoceros Hornbill with 1 nesting success. The average life cycle of the fiberglass nest box is about 11.38±4.23 SD years. The study results suggest that reproduction parameters of hornbills in nest boxes are different from natural cavities in many aspects. Our two target species do not equally benefit from nest boxes