respectively). Great and Wreathed Hornbills at Khao Yai
had a slightly longer breeding cycle reported by Poonswad
et al. (1987) (121 and 127 days, respectively) than those of
Budo. The Bushy-crested Hornbill had a similar breeding
cycle to the Brown Hornbill Ptilolaemus tickelli of Khao
Yai at 92 days (Poonswad et al. 1987). There was no
comparative information on the breeding cycle for Helmeted
and White-crowned Hornbills (Kemp 1995).
Among the total of 498 chicks fledged, Great Hornbills
dominated the entire population. Generally, the
Great Hornbill has a heavier average body mass than the
Rhinoceros Hornbill (3,006 and 2,580 g, respectively;
Kemp 1995) and may be dominant over the Rhinoceros
Hornbill. However, nesting of the large-size species could
be limited by the nest entrance size. This indicated that the
large-size cavities are available and well-suited to Great
Hornbills. During the breeding season, Great Hornbill
breeding pairs may tolerate human disturbances better than
the other species, but the slow resilience of the populations
of the other species could be the consequence of severe
poaching in the past and, perhaps, the species were already
rare in the area. Limitations on the Helmeted Hornbill