Changes over 26 Years in the Avifauna of the Bogotá Region, Colombia: Has Climate Change Become Important?

High Neotropical mountains are among the most threatened ecosystems by climate change and this problem could be accentuated in cities where temperatures are higher. However, there are few data of long-term avifaunal changes in Neotropical cities, and the potential impact of climate change has yet to be addressed. Using data from 26 years of Audubon's Christmas Bird Counts (CBCs) in the Bogotá area (ca. 2,600–3,100 m in Colombia's eastern Andes), we analyze long-term changes of the avifauna using linear regressions corrected for species' habitat preferences and compared urban and rural sites. For the CBC we followed the National Audubon Society's methodology in which birds are counted over a 24-h period within a fixed circle 24 km in diameter. We recorded 235 species in the Bogotá circle with an average of 122 spp/year, including 46 boreal migrants, three endemic species, and four endemic subspecies, two globally and four locally threatened species. Species richness was higher in rural than in urban areas and most species were associated with native forest and scrub and wetlands. Among the species that were analyzed for changes in time 31% increased, 20% decreased, and 49% did not change. Strong fluctuations or changes in abundance were more frequent in urban than rural environments. Many of the species that increased or became established during the CBC interval came from lower elevations or the warmer, drier parts of the region beyond the count circle. By contrast, the lower elevational limits moved to higher elevations in several species that decreased. Climate change with its related effects represented the factor associated with the most changes in abundance. Other potential causes were direct human actions, mostly associated with urbanization, and “natural” successional changes in vegetation; predation by feral dogs and cowbird parasitism also affected several species negatively. Observations indicate that these factors will continue into the future, and the effects of climate change and urbanization in particular will probably intensify. The Bogotá CBC has provided much valuable information for Neotropical urban ornithology and its practice should be encouraged in other Latin American cities and should definitely continue in Bogotá for many years to come

Cambios en la avifauna de un relicto de bosque en la franja periurbana de Bogotá a lo largo de catorce años

A lo largo de varios siglos, la vegetación nativa de la parte plana de la Sabana de Bogotá ha sido casi completamente sustituida por cultivos, potreros y urbanizaciones. El último relicto de esta vegetación es un pequeño bosque (ca 10 ha), ubicado en la Hacienda Las Mercedes en el borde norte de la ciudad de Bogotá. El tamaño reducido y aislamiento del bosque, agravado por el crecimiento descontrolado de vegetación invasiva (lianas y zarzamora silvestre) ha generado la pérdida de muchas especies. Sin embargo, en los últimos años el bosque ha sido objeto de acciones de rehabilitación y actualmente la zona está inmersa en una reserva en donde se prevén programas de restauración más amplios. Con el objetivo de evaluar los cambios en la comunidad de aves para estimar los efectos de las acciones de restauración, se registró la avifauna presente en 2001-2002 y en el 2014, mediante registros visuales y auditivos en puntos fijos en el bosque. En el primer censo se encontraron 27 especies de bosque y en el segundo 30, y las abundancias relativas de por lo menos la tercera parte de ellas también aumentó en los 13 años, indicando un resultado positivo en la recuperación del bosque. Los resultados resaltan la capacidad de recuperación de los ecosistemas degradados y la importancia de continuar con las acciones de restauración en el área de reserva.The native vegetation of the Sabana de Bogota’s flat area has been replaced by agricultural lands, pastures and urbanizations over the years. The last relict of this native vegetation is a small forest (ca 10 ha) at Hacienda Las Mercedes, in the northern border of Bogota. The forest’s small size and isolation from other areas of natural vegetation have resulted in the loss of many species. The problem was exacerbated by uncontrolled growth of invasive vegetation (vines and wild blackberry). However, in recent years restorative action including control of these vegetation has been undertaken and the forest is now immerse in a natural reserve where more restorative actions are being planned. Using point count stations the authors recorded all the birds seen and heard in 2001-2002 and in 2014 in order to evaluate the changes in the bird community and estimate the effects of the restorative actions. We recorded 27 forest species in the first census and 30 in the second. The relative abundance of at least 1/3 of the species also increased indicating a positive result in the forest restoration. The results highlight the capacity of degraded ecosystems to recover and the importance of continuing the restorative actions in the reserve area

Changes over 26 Years in the Avifauna of the Bogotá Region, Colombia: Has Climate Change Become Important?

High Neotropical mountains are among the most threatened ecosystems by climate change and this problem could be accentuated in cities where temperatures are higher. However, there are few data of long-term avifaunal changes in Neotropical cities, and the potential impact of climate change has yet to be addressed. Using data from 26 years of Audubon's Christmas Bird Counts (CBCs) in the Bogotá area (ca. 2,600-3,100 m in Colombia's eastern Andes), we analyze long-term changes of the avifauna using linear regressions corrected for species' habitat preferences and compared urban and rural sites. For the CBC we followed the National Audubon Society's methodology in which birds are counted over a 24-h period within a fixed circle 24 km in diameter. We recorded 235 species in the Bogotá circle with an average of 122 spp/year, including 46 boreal migrants, three endemic species, and four endemic subspecies, two globally and four locally threatened species. Species richness was higher in rural than in urban areas and most species were associated with native forest and scrub and wetlands. Among the species that were analyzed for changes in time 31% increased, 20% decreased, and 49% did not change. Strong fluctuations or changes in abundance were more frequent in urban than rural environments. Many of the species that increased or became established during the CBC interval came from lower elevations or the warmer, drier parts of the region beyond the count circle. By contrast, the lower elevational limits moved to higher elevations in several species that decreased. Climate change with its related effects represented the factor associated with the most changes in abundance. Other potential causes were direct human actions, mostly associated with urbanization, and "natural" successional changes in vegetation; predation by feral dogs and cowbird parasitism also affected several species negatively. Observations indicate that these factors will continue into the future, and the effects of climate change and urbanization in particular will probably intensify. The Bogotá CBC has provided much valuable information for Neotropical urban ornithology and its practice should be encouraged in other Latin American cities and should definitely continue in Bogotá for many years to come. © 2017 Stiles, Rosselli and De La Zerda