Exactly where a species occurs on the planet is a critical piece of information for its conservation. Our goal in Birds of the World is to provide accurate and up-to-date range information for every species, and in each species account, you’ll find some form of range map. But exactly which type of range map can depend on a number of factors. In this article we describe the rationale for inclusion of the various range map types in BOW. You can find range maps in several places in Birds of the World: on both the Introduction and Distribution pages in long format accounts; and on the right-hand side of the three-column layout for every short format account.
These maps offer a rather traditional depiction of a species range, with seasonal occurrence represented as colored polygons. These maps are similar to what you’d find in any field guide, and they offer a quick, though often coarse, overview of where a species occurs. Our goal is to have a basic range map like this for every species in Birds of the World, but at the outset there are some gaps. Due to taxonomy mismatches, some taxa that BOW considers a species never had a basic range map that adequately represented the taxon’s range. In cases where we are either lacking a basic range map altogether, or the range map we have does not adequately cover the current taxon’s range, we have opted to instead show the ‘eBird Range Map’ (see below).
These maps depict frequency of occurrence based on eBird observational data as 100 or 20km grids. Higher frequencies denote higher occurrence–in other words, you’re more likely to find the bird in the deeper purple shaded zones. By clicking through to eBird to explore further, you can enable negative data, which shows where observation data exist and the species was not recorded–a critical point. Zooming in farther reveals the actual underlying data points for each observation, and their associated checklists and media. Because eBird is underpinned by the same taxonomy as Birds of the World, these eBird range maps are available for all taxa (as well as subspecies groups). In cases where a basic range map doesn’t exist today, you’ll find the eBird range map.
For many North American breeders we are showcasing the new abundance/range maps coming out of the eBird science team at the Lab. These maps are more detailed than anything previously generated, and they represent the best in class for a static range map covering the full annual cycle of a species. There is a set of species that are more international in distribution, for which we have restricted this Abundance map to the Distribution page and instead shown the more global range-wide basic map on the species intro page (See Barn Swallow or Golden Eagle as examples).
Our goal is to create a more uniform user experience for range maps moving forward, with the same set of maps available for all taxa. In the meantime we’ll continue to feature the best of what is at hand.