Knowledge gaps and biases in the Pantanal indicate future directions for ornithological research in large wetlands (vol 163, pg 784, 2021)

While taxonomic and biogeographical biases are often acknowledged, those for certain biological responses and species traits are routinely overlooked, generating major gaps in knowledge and conservation of biodiversity. Biases in research on birds - an over-sampled, diverse vertebrate class - may be readily detectable, and wetlands are important species-rich ecosystems in which to identify biases and research gaps for birds. The Pantanal, one of the world's largest wetlands, is globally relevant for bird conservation. In this wetland, we determined spatial, temporal, taxonomic and biological response-related biases in ornithological studies to guide future research in this ecosystem and, ultimately, in major global wetlands. Avian research was geographically biased, with 61 studies conducted in the Brazilian Pantanal and only one in Bolivia. Most studies were concentrated near urban centres, with poorly explored areas in the central Pantanal. Research was also over-represented during the dry season when field conditions are more favourable, but such temporal bias may hamper migration studies. Considering their richness, some families were studied disproportionately more (e.g. Jacanidae) or less (e.g. Tyrannidae). Some species (e.g. Wood Stork Mycteria americana and Yellow-billed Cardinal Paroaria capitata) were included in > 25% of studies, whereas a relatively low number of threatened bird species were studied. Behaviour was the most studied response, followed by abundance and reproduction, which were considered for > 65% of species studied. We conclude that further research needs to be focused on unexplored areas and periods, less detectable species, and ecological processes (e.g. interspecific interactions). Additionally, our results can provide useful information to better address future work and bird conservation actions in other large wetlands. For example, major gaps detected here constitute a primary roadmap to guide research in under-sampled regions, such as the Canadian peatlands and Tonle Sap Lake. Specifically, more studies on waterbirds in highly diverse wetlands from low-income countries (e.g. Okavango and Sundarban Delta) may help to disentangle the essential functional role provided for these species and to prioritize conservation actions in regions with limited research capacity.