Abstract
The continued loss, fragmentation, and degradation of forest habitats are driving an extinction crisis for tropical and subtropical bird species. This loss is particularly acute in the Atlantic Forest of South America, where it is unclear whether several endemic bird species are extinct or extant. We collate and model spatiotemporal distributional data for one such “lost” species, the Purple-winged Ground DoveParaclaravis geoffroyi, a Critically Endangered endemic of the Atlantic Forest biome, which is nomadic and apparently dependent on masting bamboo stands. We compared its patterns of occurrence with that of a rare “control” forest pigeon, the Violaceous Quail-DoveGeotrygon violacea, which occurs in regional sympatry. We also solicit information from aviculturists who formerly kept the species. We find that the two species share a similar historical recording rate but can find no documentary evidence (i.e., specimens, photos, video, sound recordings) for the persistence of Purple-winged Ground Dove in the wild after the 1980s, despite periodic sighting records, and after which time citizen scientists frequently documented the control species in the wild. Assessments of the probability that the species is extant are sensitive to the method of analysis, and whether records lacking documentary evidence are considered credible. Analysis of the temporal sequence of past records reveals the extent of the historical range contraction of the Purple-winged Ground Dove, while our species distribution model highlights the geographic search priorities for field ornithologists hoping to rediscover the species—aided by the first recording of the species vocalizations which we obtained from interviews with aviculturists. Our interviews also revealed that the species persisted in captivity from the 1970s until the 1990s (up to 150 birds), until a law was passed obstructing captive breeding efforts by private individuals, putting an end to perhaps the best chance we had to save the species from extinction.
Highlights
Understanding the magnitude of global biodiversity loss is a fundamental goal for conservation, but ascertaining whether a species is extinct or extant becomes extremely problematic the rarer a species becomes (Diamond, 1987)
The 37,000 banded birds from Argentina include no records of either target species, while of 956,360 birds banded in Brazil, there are 29 Violaceous Quail-Doves, of which 21 were from the Atlantic Forest, and no Purple-winged Ground Doves
We present the first attempts to model the geographic range of the Purple-winged Ground Dove, document its range contraction, describe novel aspects of its life history, and make a quantitative appraisal of its continued persistence
Summary
Understanding the magnitude of global biodiversity loss is a fundamental goal for conservation, but ascertaining whether a species is extinct or extant becomes extremely problematic the rarer a species becomes (Diamond, 1987). Local and Global Red Lists reporting extinctions must balance this uncertainty, given that failure to report an extinction leads to conservative estimates of the current extinction crisis and false reporting of extinction may lead to the withdrawal of conservation support for a still-extant Critically Endangered (CR) taxon (Collar, 1998). Red Lists tend to be conservative, so missing species are in many cases not formally listed as extinct for decades after the last sighting. The problem of ascertaining species persistence is most acute in the humid tropics where species richness and extinction rates are highest and where field surveys have traditionally been least intense (Butchart et al, 2018). In many cases, it may be important to find methodologies to make better use of existing occurrence data (Newbold, 2010)
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