Implications of long-distance movements of frugivorous rain forest hornbills

Long-distance seed dispersal influences many critical ecological processes by improving chances of gene flow and maintaining genetic diversity among plant populations. Accordingly, large-scale movements by frugivores may have important conservation implications as they provide an opportunity for long-distance seed dispersal. We studied movement patterns, resource tracking, and potential long-distance seed dispersal by two species of Ceratogymna hornbills, the black-casqued hornbill C. atrata, and the white-thighed hornbill C. cylindricus, in lowland tropical forests of Cameroon. We determined fruiting phenology of 24 tree species important in hornbill diet at monthly intervals and compared these patterns to monthly hornbill census data. After capture and radio-tagging of 16 hornbills, we used radio telemetry by vehicle and fixed wing aircraft to determine the extent of long-distance movements. Hornbills exhibited up to 20-fold changes in numbers in response to fruit availability in our 25 km(2) study area. Also, hornbills made large-scale movements up to 290 km, which are larger than any movement previously reported for large avian frugivores. Together, these observations provide direct evidence that hornbills are not resident and that hornbills track available fruit resources. Our results suggest that Ceratogymna hornbills embark on long-distance movements, potentially dispersing seeds and contributing to rain forest regeneration and diversity.