Enigmatic declines in bird numbers in lowland forest of eastern Ecuador may be a consequence of climate change

John G Blake; Bette A Loiselle

doi:10.7717/peerj.1177

Enigmatic declines in bird numbers in lowland forest of eastern Ecuador may be a consequence of climate change

PeerJ. 2015 Aug 11:3:e1177. doi: 10.7717/peerj.1177. eCollection 2015.

Authors

John G Blake¹, Bette A Loiselle²

Affiliations

¹ Department of Wildlife Ecology and Conservation, University of Florida , Gainesville, Florida , USA.
² Department of Wildlife Ecology and Conservation and Center for Latin American Studies, University of Florida , Gainesville, Florida , USA.

Abstract

Bird populations have declined in many parts of the world but most of those declines can be attributed to effects of human activities (e.g., habitat fragmentation); declines in areas unaffected by human activities are not common. We have been sampling bird populations at an undisturbed site in lowland forest of eastern Ecuador annually since 2001 using a combination of mist nets and direct observations on two 100-ha plots. Bird numbers fluctuated on both plots during the first 8 years but did not show a consistent pattern of change. Since about 2008, numbers of birds on both plots have declined; capture rates in 2014 were ∼40% less than at the start of the study and observation rates were ∼50% less. Both understory and canopy species declined in abundance. Overall, insectivores showed the most pronounced declines but declines varied among trophic groups. The period from 2008 onward also was a period of stronger La Niña events which, at this study site, are associated with increased rainfall. The mechanism for the declines is not known but likely reflects a combination of reduced reproductive success coupled with reduced survival associated with changing climate.

Keywords: Birds; Climate change; Conservation; Ecuador; Long-term; Neotropics; Population declines; Tropical.

Grants and funding

Different parts of this research have been funded by The National Science Foundation (IBN-0235141), National Geographic Society (7113-01), Fulbright US Scholars Program, University of Missouri-St. Louis, University of Florida, and personal sources. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.