The National Park of Nameri holds large populations of hornbill species. Great Pied Hornbill and Wreathed Hornbill are the most common species, which are frequently seen in the evening, when large flocks are flying to their roosting trees. Large numbers of hornbills are an indication of a healthy primary forest ecosystem: as a cavity breeder, these birds need enough big trees with natural cavities for nesting to hold a viable population.