Current population status of four endemic Caribbean forest birds in Montserrat

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Laura Bambini
James R. Daley
Calvin Fenton
Gerard A.L. Gray
Glenford James
Lloyd Martin
Stephen Mendes
Steffen Oppel

Keywords

Forest birds, Montserrat, Population trends

Abstract

Abstract Deforestation is a major cause of biodiversity loss across the world, but in the Caribbean region the fate of many forest species is poorly known despite ongoing forest loss. Bird populations in Montserrat were affected by the loss of more than 50% of the island’s forest cover since 1995 when the Soufrière Hills Volcano started erupting. Today, Montserrat’s bird populations appear to be stable but little is known about the status of many of the species. We report on the current popula­tion trajectories of four endemic Caribbean forest birds found in Montserrat: Bridled Quail-Dove (Geotrygon mystacea), Forest Thrush (Turdus lherminieri), Brown Trembler (Cinclocerthia ruficauda), and Montserrat Oriole (Icterus oberi). We estimated abun­dance from repeated count surveys around 67 sampling points during 2011–2016 using binomial mixture models and conclude that the Forest Thrush is the most common species (1,174 individuals in 2016; 95% credible interval: 624–2,178), with Bridled Quail-Dove (411; 250–853), Montserrat Oriole (323; 221–510), and Brown Trembler (246; 150–541) less common. Low precision in the estimates limits inference about population trends, but the Montserrat Oriole appears to have increased between 2011 and 2016 (trend estimate = 0.161; 0.032–0.298). We recommend that the current monitoring is continued on an annual basis to understand population trajectories of forest birds. Continued protection of the remaining forests is critical to maintain stable populations of the forest bird species in Montserrat.

Keywords forest birds, Montserrat, population trends

 

Resumen Estado poblacional actual de cuatro especies de aves de bosque endémicas del Caribe en Montserrat—La defores­tación es la causa principal de pérdida de la biodiversidad en todo el mundo; pero en la región del Caribe el destino de muchas especies forestales es poco conocido pese a la pérdida continua de bosques. Las poblaciones de aves en Montserrat fueron afectadas por la pérdida de más del 50% de la cobertura boscosa de la isla desde que en 1995 entrara en erupción el volcán Soufrière Hills. Actualmente, las poblaciones de aves de Montserrat parecen estar estables, aunque se conoce poco sobre el estado de muchas de las especies. Ampliamos la información existente sobre los estados poblacionales de cuatro especies de aves de bosque endémicas del Caribe que se encuentran en Montserrat: Geotrygon mystacea, Turdus lherminieri, Cinclocerthia ruficauda y Icterus oberi. La abundancia fue estimada a partir de conteos repetidos en 67 puntos de muestreo durante el periodo 2011–2016 usando modelos binomiales mixtos y concluimos que Turdus lherminieri es la especie más común (1.174 individuos en 2016, intervalos de confianza del 95%: 624–2.178), en cambio, Geotrygon mystacea (411; 250–853), Icterus oberi (323; 221–510) y Cinclocerthia ruficauda (246; 150–541) fueron mucho menos comunes. La baja precisión en las estimaciones limita las infe­rencias sobre las tendencias poblacionales, pero Icterus oberi parece haber aumentado entre el 2011 y el 2016 (estimación de tendencia = 0,161; 0,032–0,298). Recomendamos que el monitoreo actual se continúe anualmente para entender las tendencias poblaciones de las aves de bosque. La protección continua de los bosques remanentes es crucial para mantener estables las poblaciones de estas aves en Montserrat.

Palabras clave aves de bosque, Montserrat, tendencias poblacionales

 

Résumé État actuel de la population de quatre espèces d’oiseaux endémiques des forêts caribéennes de Montserrat—La dé­forestation est une cause majeure de la perte de biodiversité à travers le monde, mais dans la région Caraïbe, le sort de nom­breuses espèces forestières est peu connu malgré la disparition progressive des forêts. Les populations d’oiseaux de Montserrat ont été affectées par la perte de plus de 50% de la couverture forestière de l’île depuis 1995, lorsque le volcan de la Soufrière est entré en éruption. Aujourd’hui, les populations d’oiseaux de Montserrat semblent stables, mais l’état de conservation de nombreuses espèces est peu connu. Nous présentons les tra­jectoires actuelles des populations de quatre oiseaux endé­miques des forêts caribéennes de Montserrat : la Colombe à croissants (Geotrygon mystacea), la Grive à pieds jaunes (Tur­dus lherminieri), le Trembleur brun (Cinclocerthia ruficauda), et l’Oriole de Montserrat (Icterus oberi). Nous avons estimé leur abondance en utilisant un modèle binomial mixte, à partir de comptages répétés de 2011 à 2016 autour de 67 points d’échantillonnage, et nous concluons que la Grive à pieds jaunes est l’es­pèce la plus commune (1.174 individus en 2016, intervalle de confiance à 95% : 624-2.178), suivi de la Colombe à croissants (411 ; 250-853), de l’Oriole de Montserrat (323 ; 221-510) et du Trembleur brun (246 ; 150-541) l’espèce la moins fréquente. La faible précision des valeurs estimées limite la capacité à prédire les tendances des populations, mais l’Oriole de Montserrat semble avoir augmenté entre 2011 et 2016 (estimation de la tendance = 0,161 ; 0,032-0,298). Nous recommandons que le suivi actuel se poursuive sur une base annuelle afin de comprendre l’évolution des populations d’oiseaux forestiers. La protection continue des forêts restantes est essentielle au maintien de la stabilité de l’avifaune forestière de Montserrat.

Mots clés Montserrat, oiseaux forestiers, tendances démographiques

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