Flight Feather Molt of Turkey Vultures

—We document the molt sequence of flight feathers in Turkey Vultures (Cathartes aura) based on studies of captive and wild birds, and examination of museum specimens. We found an unusual pattern of primary replacement, which appears to be a modified form of Staffelmauser, or stepwise wing molt. A Staffelmauser-like strategy for replacement of the secondaries is also described. These patterns of feather replacement appear to be adaptations to maintain flying performance while replacing all primaries and most secondaries during each molt. To what extent molt patterns in Turkey Vultures reflect convergent adaptation for flight, rather than ancestral characters useful for phylogenetic studies, remains unknown. Received 15 June 2009. Accepted 12 January 2010. Maintaining optimal flight performance is essential for Turkey Vultures (Cathartes aura), a species adapted for long-term soaring (Rosser and George 1986, Tucker 1987). This species locates its primary diet of carrion by detecting odor plumes while aloft, and spends most daylight hours searching for food (Owre and Northington 1961, Stager 1964). It is a migratory species that can travel hundreds or thousands of kilometers seasonally between southern wintering and northern breeding areas (Stewart 1977, Kirk and Houston 1995, Bildstein and Zalles 2001). Little is known about the molt of Turkey Vultures despite its widespread distribution and abundance (Kirk and Mossman 1998). Identifying and understanding molt processes in birds can be accomplished in several ways. Miller (1941), Stresemann (1963), and Pyle (2005) used data from museum study skins of raptors to make their basic molt sequence hypotheses. Analyzing molt patterns from study skins can be difficult and may not represent the progression of a single individual, and sample sizes of large birds are typically too low to undertake comprehensive analyses. Houston (1975) observed flight feather replacement in both captive and wild individuals of Old World vultures (Gyps), but molt in captive birds may not reflect that of wild birds (cf. Pyle 2005). Snyder et al. (1987) based their molt study of California Condors (Gymnogyps californianus) on photographs of wild birds in flight. Bloom and Clark (2001) used banding records with some recaptures to study the molt of the Golden Eagle (Aquila chrysaetos), but sample sizes of known individual birds are low in these studies. Ideally, a complete understanding of molt strategies would be based on the study of wild birds, captive individuals, and specimens; we present such an analysis of molt in Turkey Vultures.