Exposing hidden endemism in a Neotropical forest raptor using citizen science

Abstract

Gaps in our knowledge of the geographical distribution of species represent a fundamental challenge to biogeographers and conservation biologists alike, and are particularly pervasive in the tropics. Here we highlight the case of the Rufous-thighed Kite Harpagus diodon, a South American raptor commonly mapped as resident across half the continent. Recent observations at migration watch points have indicated it may be partially migratory in the southernmost parts of its range. To investigate this possibility, we collated contemporary and historical specimen records, published sight records and 'digital vouchers'photographs and sound-recordings archived online (from citizen science initiatives)and explored the spatiotemporal distribution of records. We were unable to trace any documented records of this species from Amazonia during the austral summer (October-March), or records from the Atlantic Forest biome during the peak of the Austral winter (June-August), and all proven breeding records stem from the Atlantic Forest region. We compared this pattern with that of a 'control' species, the congeneric Double-toothed Kite H. bidentatus, again using specimens and digital vouchers. For this species we found no evidence of seasonality between biomes and can disregard spatiotemporal variation in observer effort as a cause of seasonal biases. We consider that all populations of Rufous-thighed Kites are fully migratory, wintering in Equatorial forests in the Amazonian basin. We provide evidence that this pattern was previously obscured by erroneous undocumented records and poor or erroneous specimen metadata, and its discovery was primarily facilitated by digital vouchers. This discovery requires a reassessment of the species' global conservation status as an Atlantic Forest breeding endemic, threatened by habitat loss and degradation, as it was previously considered to be resident across large swathes of undisturbed Amazonian Forest on the Guiana Shield. The bulk of the digital voucher data used to elucidate this pattern were extracted from a Brazilian citizen science initiative WikiAves, which may serve as a model for collating biodiversity data in megadiverse countries and help catalyse environmental awareness.

Evidence for longitudinal migration by a “sedentary” Brazilian flycatcher, the Ash-throated Casiornis

“…I found no evidence for the occurrence of this species in Amazonia outside the period from April to October, suggesting that Ash‐throated Casiornises are only seasonal visitors to this biome, whereas at least some individuals are present year‐round in the Caatinga. Given extensive historical and contemporaneous sampling of both Amazonia and the Cerrado (e.g., Lees and Martin , Supplemental Fig. S1), I do not believe these results reflect differences in observer effort.…”

“…Ornithologists should continue to critically re‐examine spatiotemporal patterns in the distribution of tropical birds and expect to find more evidence for partial migration in ostensibly “sedentary” species, which may substantially alter perception of their conservation status. Care should be taken to check for any discrepancy between the spatiotemporal distribution of vouchered and un‐vouchered records, particularly in the case of cryptically similar species (Lees and Martin ).…”

“…Different data sources present different sources of bias and care is needed in their interpretation. Specimen records and digital vouchers are less prone to identification error than sight records (e.g., Lees and Martin ), but only complete checklist data or targeted surveys can provide robust data on species absences (Munson et al. ).…”

“…The 4‐month period from June to September was considered the peak dry/non‐breeding season. The 4 months between the wet and dry seasons (April–May and October–November) were designated as the migration periods, following the rationale of Lees and Martin (). This treatment of records resulted in three approximately equal‐length seasons.…”

Four decades after Belton: a review of records and evidences on the avifauna of Rio Grande do Sul, Brazil

“…Both birding and (especially) wildlife photography are fast-growing activities that have gained many enthusiasts in Brazil through the development of digital databases (e.g., WikiAves), specific events (e.g., Avistar and Festival Brasileiro de Aves Migratórias), and specialized magazines (e.g., Passarinhando and Uru). Besides being powerful tools for environmental education (Farias, 2007), these hobbies have great potential for generating large volumes of useful data (see Dickinson et al, 2010), for example, by nourishing national databases of bird records, which are key for spatial and temporal analysis, as well as for careful conservation planning (Giorgi et al, 2014;Lees & Martin, 2014;Pegas & Castley, 2014;Callaghan & Gawlik, 2015). Continuing Belton's legacy, and now making broad use of public-access databases nourished by both amateur and professional birders, we provide here the fifth update of the checklist of the birds of RGS.…”