Shifts in resident bird communities associated with cloud forest patch size in Central Veracruz, Mexico

Abstract

ABSTRACT. Avian communities in cloud forests have high levels of endemism and are at major risk given the accelerated rate of habitat fragmentation. Nevertheless, the response of these communities to changes in fragment size remains poorly understood. We evaluated species richness, bird community density, community composition, and dominance as indicators of the response to fragment size in a fragmented cloud forest landscape in central Veracruz, Mexico. Medium-sized fragments had statistically higher than expected species richness and more even communities, which may be a reflection of the intermediate disturbance hypothesis, in which mediumsized fragments are exploited by both forest and disturbance-associated species. Bird density also reached higher values in mediumsized fragments, which may indicate a carrying capacity in this habitat. However, large cloud forest fragments had a distinct taxonomic and functional composition, attributable to an increased number of understory insectivore species and canopy frugivores. By comparison, omnivorous species associated with human-altered habitats were more abundant in smaller fragments. Hence, although medium-sized cloud forest fragments had higher species richness and high bird density, large forest tracts maintained a distinct avian community composition, particularly of insectivorous and frugivorous species. Furthermore, the underlying response to fragmentation can only be properly addressed when contrasting several community attributes, such as richness, density, composition, and species dominance. Therefore, cloud forest conservation should aim to preserve the remaining large forest fragments to maintain comprehensive avian communities and avoid local extinctions.Changements dans les communautés d'oiseaux résidents associés à la dimension des îlots de forêts de nuages dans le centre du Veracruz, Mexique RÉSUMÉ. Les communautés aviaires des forêts de nuages (c.-à-d., les forêts humides de montagne) ont un degré d'endémisme élevé et sont très menacées considérant le rythme accéléré de la fragmentation de l'habitat. Néanmoins, la réponse de ces communautés en réaction aux changements de la dimension des îlots demeure largement inexpliquée. Nous avons évalué la richesse spécifique, la densité des communautés aviaires, la composition des communautés et la dominance spécifique comme facteurs pouvant expliquer la réponse à la dimension des îlots dans un paysage fragmenté de forêts de nuages dans le centre du Veracruz, Mexique. Les îlots de taille moyenne ont montré une richesse spécifique attendue plus élevée statistiquement que les autres îlots et des communautés plus uniformes, résultat qui pourrait s'expliquer par l'hypothèse de perturbation intermédiaire selon laquelle les îlots de taille moyenne sont exploités autant par des espèces forestières que des espèces associées aux perturbations. Les valeurs de densité aviaire ont aussi été plus élevées dans ces îlots, ce qui pourrait indiquer que ce milieu a atteint sa capacité de support. Toutefois, les grands îlots de...

Impacts of habitat change and protected areas on alpha and beta diversity of Mexican birds

“…Here, we have demonstrated the importance of strictly protected areas for globally declining species. Our results were mirrored elsewhere in Mexico, in both the Lacandona rain forest of Chiapas and the cloud forest of Veracruz, where larger, undisturbed stretches of forest were valuable for specialists (Carrara et al, 2015) and threatened (Rueda-Hernandez et al, 2015) bird species, whereas habitat generalists benefited from more fragmented landscapes. S4).…”

“…In addition to those observed in this study (see Table S3), the SGBR's strictly protected areas are also the only parts of the reserve where vulnerable (IUCN Red List) and highly sensitive (particularly to hunting) species such as Great Curassows Crax rubra, Bearded Wood-partridges Dendrortyx barbatus and Military Macaws Ara militaris nest. Our results were mirrored elsewhere in Mexico, in both the Lacandona rain forest of Chiapas and the cloud forest of Veracruz, where larger, undisturbed stretches of forest were valuable for specialists (Carrara et al, 2015) and threatened (Rueda-Hernandez et al, 2015) bird species, whereas habitat generalists benefited from more fragmented landscapes.…”

Impacts of Habitat Degradation on Tropical Montane Biodiversity and Ecosystem Services: A Systematic Map for Identifying Future Research Priorities

“…Although fragmentation is well-known for reducing gene flow, it has far-reaching consequences at all ecological levels, including ecosystem services. In general, fragmentation has a negative impact on communities; resulting in a decline in species richness (e.g., Borgella et al, 2001;Kumar and O'Donnell, 2007;Hundera et al, 2013;Mohandass et al, 2014;Rovero et al, 2014), and changes in species composition in response to fragmentation has also been consistently reported (e.g., Larrea and Werner, 2010;Mohandass et al, 2014;Rueda-Hernandez et al, 2015;García-Martínez et al, 2017;Herrera-Paniagua et al, 2017). However, some studies have highlighted that certain spatial characteristics such as fragment area and isolation have no effect on abundance, density or diversity (Muriel and Kattan, 2009;Ulrich et al, 2016).…”

“…While the extent of degradation may lead to conflicting results, deeper examination of species functional traits, which are indicators of habitat use, reveal that some groups within a community are more affected than others. For instance, two avian studies independently concluded that understory insectivores and canopy frugivores were more sensitive to fragmentation than other functional groups (Kattan et al, 1994;Rueda-Hernandez et al, 2015). Thus, within-community differences should be accounted for in future fragmentation research in TMF.…”

“…Species richness estimates and related indices assume all species perform the same roles, but high species richness does not necessarily beget high functional diversity (Stuart-Smith et al, 2013). For example, while bird species richness and density in medium-sized fragments were higher than larger fragments in Mexican TMFs, larger fragments had a distinct functional composition, with a greater proportion of understory insectivore species and canopy frugivores (Rueda-Hernandez et al, 2015). Furthermore, functional diversity may be a better predictor of ecosystem function than species richness or abundance indices (Gagic et al, 2015).…”