Towards reconciliation of the four world bird lists: hotspots of disagreement in taxonomy of raptors

Abstract

There are currently four world bird lists referenced by different stakeholders including governments, academic journals, museums and citizen scientists. Consolidation of these lists is a conservation and research priority. In reconciling lists, care must be taken to ensure agreement in taxonomic concepts-the actual groups of individual organisms circumscribed by a given scientific epithet. Here, we compare species-level taxonomic concepts for raptors across the four lists, highlighting areas of disagreement. Of the 665 species-level raptor taxa observed at least once among the four lists, only 453 (68%) were consistent across all four lists. The Howard and Moore Checklist of the Birds of the World contains the fewest raptor species (528), whereas the International Ornithological Community World Bird List contains the most (580) and these two lists are in the most disagreement. Of the disagreements, 67% involved owls, and Indonesia was the country containing the most disagreed upon species (169). Finally, we calculated the amount of species-level agreement across lists for each avian order and found raptor orders spread throughout the rankings of agreement. Our results emphasize the need to reconcile the four world bird lists for all avian orders, highlight broad disagreements across lists and identify hotspots of disagreement for raptors, in particular.

Keywords: bird of prey; checklist; raptor; taxonomic concept; taxonomy; world bird list.

Figure 1.

Map of countries in which the four taxonomic concepts applied to the scientific name T. alba occur. The Venn diagram illustrates the colour symbology of the countries where lists consider birds circumscribed under the name T. alba to occur. eBird, the eBird/Clements Checklist of the Birds of the World; HBW, HBW & BirdLife International; IOC, the IOC World Bird List; HM, the Howard and Moore Complete Checklist of the Birds of the World. White areas in the Venn diagram are combinations that do not occur. For example, there are no countries where only IOC and HM consider T. alba to occur. To determine where a given list places T. alba, examine the colours contained within the circle ascribed to that list in the Venn diagram. Therefore, the countries where HM considers T. alba to occur are in blue and purple. By contrast, the countries where IOC considers to harbour T. alba are in purple only. Note that eBird and HM agree where T. alba occur at the country level and thus share a circle in the Venn diagram. However, eBird and HM disagree over which populations within India are T. alba or T. deroepstorffi. Thus, even though all lists agree that something named T. alba exists, they do not all agree on the populations to which that name refers. (Online version in colour.)

Figure 2.

Comparison of the species-level taxonomic concepts for raptors across the four world bird lists. Percentages indicate the number of concepts that are shared by a given pair of lists. The total number of concepts per list is given parenthetically.

Figure 3.

Families of raptors and circles representing the number of species level taxonomic concepts (saturation) and the proportion of disagreed upon species concepts (size) for each family. Note that darker circles indicate more total concepts and larger circles indicate more disagreed upon concepts. Per family, the numbers of disagreed upon concepts are on top, and the bottom number is the total amount of concepts. For example, Strigidae is the darkest circle, so has the most total concepts, and is the third largest in size, so has a moderately high proportion of disagreements. (Online version in colour.)

Figure 4.

Map of the number of disagreed upon species-level taxonomic concepts of raptors per country. (Online version in colour.)

Figure 5.

Proportion of agreed upon species-level taxonomic concepts per avian order. We consider concepts to be agreed upon only if they occur at the species level across all four lists. Names of raptor orders are in orange and identified by asterisks. Saturation indicates the number of taxonomic concepts per order ranging from 1 (Leptosomiformes and Opisthocomiformes, lightest) to greater than 600 (Passeriformes, darkest). Here, we use the Howard and Moore taxonomy at the order level, except that we separate Cathartiformes from Accipitriformes, for the ease of comparison. (Online version in colour.)