Harmonizing spatial scales and ecological theories to predict avian richness and functional diversity within forest ecosystems.

Classic ecological theory has proven that temperature, precipitation and productivity organize ecosystems at broad scales and are generalized drivers of biodiversity within different biomes. At local scales, the strength of these predictors is not consistent across different biomes. To better translate these theories to localized scales, it is essential to determine the links between drivers of biodiversity. Here we harmonize existing ecological theories to increase the predictive power for species richness and functional diversity. We test the relative importance of three-dimensional habitat structure as a link between local and broad-scale patterns of avian richness and functional diversity. Our results indicate that habitat structure is more important than precipitation, temperature and elevation gradients for predicting avian species richness and functional diversity across different forest ecosystems in North America. We conclude that forest structure, influenced by climatic drivers, is essential for predicting the response of biodiversity with future shifts in climatic regimes.

Effects of forest fragmentation on avian breeding activity.

Biodiversity declines and ecosystem decay follow forest fragmentation; initially, abundant species may become rare or be extirpated. Underlying mechanisms behind delayed extirpation of certain species following forest fragmentation are unknown. Species declines may be attributed to an inadequate number of breeding adults required to replace the population or decreased juvenile survival rate due to reduced recruitment or increased nest predation pressures. We used 10 years of avian banding data, 5 years before and 4 years after fragment isolation, from the Biological Dynamics of Forest Fragments Project, carried out near Manaus, Brazil, to investigate the breeding activity hypothesis that there is less breeding activity and fewer young after relative to before fragment isolation. We compared the capture rates of active breeding and young birds in 3 forest types (primary forest, fragment before isolation, and fragment after isolation) and the proportion of active breeding and young birds with all birds in each unique fragment type before and after isolation. We grouped all bird species by diet (insectivore or frugivore) and nesting strategy (open cup, cavity, or enclosed) to allow further comparisons among forest types. We found support for the breeding activity hypothesis in insectivorous and frugivorous birds (effect sizes 0.45 and 0.53, respectively) and in birds with open-cup and enclosed nesting strategies (effect sizes 0.56 and 0.44, respectively) such that on average there were more breeding birds in fragments before isolation relative to after isolation. A larger proportion of birds in the community were actively breeding before fragment isolation (72%) than after fragment isolation (11%). Unexpectedly, there was no significant decrease in the number of young birds after fragment isolation, although sample sizes for young were small (n = 43). This may have been due to sustained immigration of young birds to fragments after isolation. Together, our results provide some of the strongest evidence to date that avian breeding activity decreases in response to fragment isolation, which could be a fundamental mechanism contributing to ecosystem decay.

Efectos de la fragmentación del bosque sobre la actividad reproductiva de las aves Resumen Les declinaciones de la biodiversidad y el deterioro de los ecosistemas van después de la fragmentación forestal; al inicio, las especies abundantes pueden volverse raras o ser extirpadas. Todavía no se conocen los mecanismos subyacentes detrás de la extirpación retrasada de ciertas especies después de la fragmentación forestal. La declinación de las especies puede atribuirse a un número inadecuado de adultos reproductivos requeridos para reemplazar a la población o a la tasa reducida de supervivencia de los juveniles debido al reclutamiento disminuido o al incremento en la presión de depredación de los nidos. Usamos diez años de datos de anillamiento de aves, cinco años antes y cuatro años después del aislamiento por fragmentación, tomados del Proyecto Dinámica Biológica de Fragmentos de Bosque realizado cerca de Manaos, Brasil, para investigar la hipótesis de actividad reproductiva que sostiene que hay una menor actividad reproductiva y menos crías después del aislamiento por fragmentación que antes del aislamiento. Comparamos las tasas de captura de aves con reproducción activa y aves juveniles en tres tipos de bosque (primario, fragmento antes del aislamiento y fragmento después del aislamiento) y la proporción de las aves juveniles y con reproducción activa con todas las aves en cada tipo de fragmento único antes y después del aislamiento. Agrupamos todas las especies de aves según su dieta (insectívora o frugívora) y su estrategia de anidación (nido abierto, cavidad o nido cerrado) para poder realizar más comparaciones entre los tipos de bosque. Las aves con dieta insectívora y frugívora (tamaño del efecto: 0.45 y 0.53, respectivamente) y aquellas con nidos abiertos y cerrados (tamaño del efecto: 0.56 y 0.44, respectivamente) respaldaron la hipótesis de la actividad reproductora de tal manera que en promedio hubo más aves reproductoras en los fragmentos antes del aislamiento que después del aislamiento. Una gran parte de las aves de la comunidad tuvieron reproducción activa antes del aislamiento por fragmentación (72%) que después del aislamiento (11%). Sorprendentemente, no hubo una disminución significativa en el número de aves juveniles después del aislamiento, si bien el tamaño de la muestra de este grupo fue reducido (n = 43). Lo anterior pudo deberse a la continua inmigración de juveniles a los fragmentos después del aislamiento. En conjunto, nuestros resultados proporcionan algunos de los indicios más claros de que la actividad reproductiva de las aves disminuye como respuesta al aislamiento por fragmentación, lo cual podría ser un mecanismo fundamental del deterioro de los ecosistemas.

Long-term changes in avian biomass and functional diversity within disturbed and undisturbed Amazonian rainforest.

Recent long-term studies in protected areas have revealed the loss of biodiversity, yet the ramifications for ecosystem health and resilience remain unknown. Here, we investigate how the loss of understory birds, in the lowest stratum of the forest, affects avian biomass and functional diversity in the Amazon rainforest. Across approximately 30 years in the Biological Dynamics of Forest Fragments Project, we used a historical baseline of avian communities to contrast the avian communities in today's primary forest with those in modern disturbed habitat. We found that in primary rainforest, the reduced abundance of insectivorous species led to reduced functional diversity, but no reduction of biomass, indicating that species with similar functional traits are less likely to coexist in modern primary forests. Because today's forests contain fewer functionally redundant species-those with similar traits-we argue that avian communities in modern primary Amazonian rainforests are less resilient, which may ultimately disrupt the ecosystem in dynamic and unforeseen ways.

Global assessment of forest quality for threatened terrestrial vertebrate species in need of conservation translocation programs.

Conservation actions such as habitat protection, restoration, and translocations are critical actions in preventing further extinctions of threatened species. We used the 152 threatened species on the International Union for the Conservation of Nature's Red List with conservation translocations as a recommended conservation action to access the habitat quality of these species' ranges. We determined where multi-species conservation translocation and forest restoration efforts can be concentrated. To determine the habitat quality of species' ranges, we assessed forest cover, forest restoration potential, protected area status, and invasive species concerns. Forty-four percent (67 species) of species with translocations recommended have part of their range in a protected area, existing forest cover, and currently no invasive species risk. However, the majority (85 species) currently need habitat management (63 species), invasive species control (71 species), or protection (34 species). We also identified key differences between species recommended for reintroductions (115 species) and benign introductions (37 species), such as the percentage of a species' range within a protected area, in which reintroductions (median = 7.4%) had more than benign introductions (median = 0.9%). Mauritius, central Africa, eastern Australia and Himalaya regions each have areas with range overlap of three or more species recommended for translocations and forest restoration potential. For those species with CT programs in place, mean forest cover was 32% and restoration potential was 16%, suggesting potential minimum habitat requirements for initial releases. Results provide a global perspective on reintroduction and translocation needs of threatened species with evidenced-based information on habitat quality, i.e. forest restoration potential, forest cover, protected areas, and invasive species control, to aid conservation translocation scientists and ultimately improve the success of such projects.