AVIFAUNA OF THE MIDDLE IRVINGTONIAN FAIRMEAD LANDFILL LOCALITY, MADERA COUNTY, CALIFORNIA

Situated on the Chowchilla River alluvial fan along State Route 99 north of Madera, California at 37º03’50”N, 120º11’52”W, Fairmead Landfill has yielded thousands of specimens since the initial fossil discovery there in May 1993. The site preserves a middle Irvingtonian, 0.78 Ma to 0.55 Ma, biota consisting of 56 taxa (27 mammals, 4 birds, 3 reptiles, 2 amphibians, 1 fish, 1 bivalve, 1 gastropod, 1 plant macrofossil, 16 diatoms). Among the finds are seven bird specimens, representing at least four taxa. These include a small goose cf. Branta sp. (MCPC A1102 synsacrum, MCPC A1103 left distal humerus), a pygmy goose cf. Anabernicula sp. (UCMP 140414 right distal humerus, UCMP 141403 right humerus, UCMP 194432 right humerus), a diving duck cf. Aythya sp. (UCMP 194433 right tarsometatarsus), and a burrowing owl Athene sp. (MCPC A1300 left distal tarsometatarsus). Fairmead Landfill fossils occur in distal alluvial fan channel, distal fan overbank flood or sheetflood, and marsh / lacustrine deposits of the upper unit of the Turlock Lake Formation. The avifauna is dominated by waterfowl, likely a reflection of the depositional environment yielding these particular specimens. All but one of the waterfowl specimens (MCPC A1102) were recovered during excavations in 1993 from predominantly clay and sandy clay inferred to have been deposited in a marsh / lacustrine setting, which is the least common depositional environment at Fairmead Landfill. The waterfowl specimens came from a relatively narrow stratigraphic zone 13.0 m to 14.5 m below ground surface in a 15 m x 45 m area. Co-occurrence of pond turtle (Clemmys marmorata) shell fragments with the waterfowl supports a slough or slow moving water body setting, although pond turtles also are common in streams. The specimen of Athene sp. lacks field data. However, the presence of this burrowing owl is consistent with a predominantly open-country, grassland habitat indicated by the fauna, which is dominated by large grazers and mixed feeders such as horse (Equus sp.), large camel (Camelops sp.), Columbian mammoth (Mammuthus columbi), Harlan’s ground sloth (Paramylodon harlani) and Irvington pronghorn (Tetrameryx irvingtonensis).