Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by ...Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by habitat loss and hunting,its population size is thought to have declined from 1800 individuals 20 years ago to less than 1000.However,a recent study on Negros estimated 3564 individuals across three core forest blocks.This study aims to quantify the Visayan Hornbill population size in and around the Northwest Panay Peninsula Natural Park(NWPPNP)on Panay,the largest contiguous low-elevation forest landscape remaining across its range,and its broad habitat associations across a gradient of environmental degradation.Methods:Hornbills were surveyed using 10-min distance sampling point counts(n=367)along transects(average length 1.1 km).Environmental variables were recorded along transects,while habitat was classified into primary forest,secondary forest,plantation,or open habitat.Distance software was used to estimate population densities stratified by habitat,with the overall population estimate taken as a mean of habitat density estimates weighted by habitat area.Using generalized linear mixed models,hornbill occurrence was modelled using combinations of nine environmental variables as main and two-way fixed effects.Results:Surveys covered 204.4 km^(2) of the 374.8 km^(2) Northwest Panay Peninsula.Hornbills were not recorded in plantations or open habitats.Hornbill density was significantly higher in primary forest(17.8 individuals/km~2±26.9%CV)than in secondary forest(3.7 individuals/km^(2)±33.2%CV;z=15.212,P<0.001).The overall population estimate for the NWPPNP and environs is 2109 individuals,and 2673 individuals for the entire Northwest Panay Peninsula.Hornbill presence was best explained by a model including distance from the Park boundary alongside five interaction effects and transect as a random effect.Distance,and the interaction between distance and medium-sized trees were significant predictors of hornbill presence.Conclusions:Our study evidences the habitat preference of the Visayan Hornbill,highlights the importance of the NWPPNP for the species'conservation,and provides strong evidence for re-assessing the global population size.展开更多
Knowledge of breeding success and its limiting factors is crucial in assessing species’conservation needs.As cavity-nesters,parrots are particularly influenced by the availability of suitable cavities and low breedin...Knowledge of breeding success and its limiting factors is crucial in assessing species’conservation needs.As cavity-nesters,parrots are particularly influenced by the availability of suitable cavities and low breeding output,whether due to natural processes or trapping.On the island of Sumba,Indonesia,the Critically Endangered Citron-crested Cockatoo(Cacatua citrinocristata)has the added problem of co-existing with an unusually rich hole-nesting bird community in a forested environment much constrained by habitat loss.We monitored 95 nesting cavities of cockatoos and their competitors and potential nest-predators,over one to four breeding seasons,using a combination of camera-traps,direct checks on nest contents,and observations from the ground.Competition for suitable cavities was intense among three large parrot species,two owls and a hornbill.Visitation rates by potential competitors were higher at unoccupied cavities than at those containing active nests,reflecting the guarding behaviour of the occupants.The Endangered Sumba Hornbill(Rhyticeros everetti)dominated observed direct confrontations and was the most frequent visitor to active parrot nests,suggesting a further role as a potential nest-predator.Cockatoos prospected many cavities but rarely then attempted to nest:instead the sites were usually occupied by other cavity-nesters,or by bees.At the few cavities where cockatoos did breed,predation pressure was likely low,and observed success rate high(10 successful of 15 nests),although the low number of nests found early in the breeding cycle suggests that some may have failed before detection.Intense competition for cavities suggests a shortage of suitable nest-sites,the need for preservation of old hole-bearing trees and a role for nestboxes.Accessible,known,safe artificial nest-sites would also provide opportunities to assess the scale of nest-site shortage,allow camera placements to study productivity,exclude some competitors and predators,and prevent illegal trapping.Especially given continued trapping pressure,the species would benefit from targeted local awareness-raising and law enforcement,with the whole endeavour backed up by longer-term forest restoration.展开更多
基金funded by the Mohamed bin Zayed Species Conservation Fund(project 192514132)Bristol Zoological SocietyDK was employed by Bristol Zoological Society to oversee the project,and HM,BT and AF worked as contractors for Bristol Zoological Society during the survey duration。
文摘Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by habitat loss and hunting,its population size is thought to have declined from 1800 individuals 20 years ago to less than 1000.However,a recent study on Negros estimated 3564 individuals across three core forest blocks.This study aims to quantify the Visayan Hornbill population size in and around the Northwest Panay Peninsula Natural Park(NWPPNP)on Panay,the largest contiguous low-elevation forest landscape remaining across its range,and its broad habitat associations across a gradient of environmental degradation.Methods:Hornbills were surveyed using 10-min distance sampling point counts(n=367)along transects(average length 1.1 km).Environmental variables were recorded along transects,while habitat was classified into primary forest,secondary forest,plantation,or open habitat.Distance software was used to estimate population densities stratified by habitat,with the overall population estimate taken as a mean of habitat density estimates weighted by habitat area.Using generalized linear mixed models,hornbill occurrence was modelled using combinations of nine environmental variables as main and two-way fixed effects.Results:Surveys covered 204.4 km^(2) of the 374.8 km^(2) Northwest Panay Peninsula.Hornbills were not recorded in plantations or open habitats.Hornbill density was significantly higher in primary forest(17.8 individuals/km~2±26.9%CV)than in secondary forest(3.7 individuals/km^(2)±33.2%CV;z=15.212,P<0.001).The overall population estimate for the NWPPNP and environs is 2109 individuals,and 2673 individuals for the entire Northwest Panay Peninsula.Hornbill presence was best explained by a model including distance from the Park boundary alongside five interaction effects and transect as a random effect.Distance,and the interaction between distance and medium-sized trees were significant predictors of hornbill presence.Conclusions:Our study evidences the habitat preference of the Visayan Hornbill,highlights the importance of the NWPPNP for the species'conservation,and provides strong evidence for re-assessing the global population size.
基金funded by Zoologische Gesellschaft für Arten-und Populationsschutz (Fond fur bedrohte Papageien and Strunden Papageienstiftung)supported by a scholarship of the German Academic Exchange Service (DAAD Doktorandenstipendium)Loro Parque Fundacion
文摘Knowledge of breeding success and its limiting factors is crucial in assessing species’conservation needs.As cavity-nesters,parrots are particularly influenced by the availability of suitable cavities and low breeding output,whether due to natural processes or trapping.On the island of Sumba,Indonesia,the Critically Endangered Citron-crested Cockatoo(Cacatua citrinocristata)has the added problem of co-existing with an unusually rich hole-nesting bird community in a forested environment much constrained by habitat loss.We monitored 95 nesting cavities of cockatoos and their competitors and potential nest-predators,over one to four breeding seasons,using a combination of camera-traps,direct checks on nest contents,and observations from the ground.Competition for suitable cavities was intense among three large parrot species,two owls and a hornbill.Visitation rates by potential competitors were higher at unoccupied cavities than at those containing active nests,reflecting the guarding behaviour of the occupants.The Endangered Sumba Hornbill(Rhyticeros everetti)dominated observed direct confrontations and was the most frequent visitor to active parrot nests,suggesting a further role as a potential nest-predator.Cockatoos prospected many cavities but rarely then attempted to nest:instead the sites were usually occupied by other cavity-nesters,or by bees.At the few cavities where cockatoos did breed,predation pressure was likely low,and observed success rate high(10 successful of 15 nests),although the low number of nests found early in the breeding cycle suggests that some may have failed before detection.Intense competition for cavities suggests a shortage of suitable nest-sites,the need for preservation of old hole-bearing trees and a role for nestboxes.Accessible,known,safe artificial nest-sites would also provide opportunities to assess the scale of nest-site shortage,allow camera placements to study productivity,exclude some competitors and predators,and prevent illegal trapping.Especially given continued trapping pressure,the species would benefit from targeted local awareness-raising and law enforcement,with the whole endeavour backed up by longer-term forest restoration.
