Unexpected Limb Proportions in a Pleistocene Population of Eastern Meadowlark (Sturnella magna) from the Bahamas
Jessica A. Oswald1,2,*, David W. Steadman1, and Janet Franklin3
1Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA. 2Biology Department, University of Nevada Reno, Reno, NV 89557, USA. 3Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.*Corresponding author.
Caribbean Naturalist, No. 68 (2019)
The most abundant fossil songbird (Passeriformes) from late Pleistocene sites in the Bahamas is Sturnella magna (Eastern Meadowlark). Today, S. magna comprises ~15 subspecies found in grasslands of North, Central, and South America, but nowhere in the West Indies except Cuba. Species distribution models suggest that several combinations of subspecies from Mexico, Central America, and Cuba have the greatest per-area climatic suitability for the ice-age Bahamas. Based on skeletal measurements, the 10 modern subspecies of S. magna that we were able to study in detail are not well differentiated from each other. This pattern generally holds true for the extirpated Bahamian meadowlark as well, with 2 exceptions: shorter distal wing element (carpometacarpus) than in S. m. magna, and shorter distal leg elements (tibiotarsus, tarsometatarsus) than in 7 modern subspecies. The distal leg proportions are opposite to expectations based on studies of other volant island birds, whereby the Bahamian meadowlarks would be expected to have had relatively longer legs than continental forms. The shorter distal leg elements may be related to a reduced need for running speed in an insular setting because of the rugged karst terrain.