Lesser Yellow-headed Vulture is recorded most often feeding on fish and reptiles (Wetmore 1965, Eitniear and McGehee 2015). In Mexico Howell and Pyle (1993) noted a flock of 30 feeding on insects behind agricultural equipment. Wetmore (1965) observed an individual flying with a large lizard in its bill. Di Giacomo (2005) provides a long list of items fed on.
Eitniear and McGehee (2017) discuss observations made of foraging Lesser Yellow-headed Vultures (Cathartes burrovianus), Turkey Vultures (Cathartes aura), and Black Vultures (Coragyps atratus) 9-30 May 1983 near Crooked Tree village at Crooked Tree Lagoon (N 17o 50' 25" W 88o 31' 25"), 55 km northwest of Belize City, Belize, Central America. Feeding observations were made using fish as bait at an established feeding sight during daylight hours (180 total observation hours) to determine foraging and competitive interactions between species. Foraging bouts totaled 3,156 min, with Lesser Yellow-headed Vultures arriving first at a provisioned carcass in 15 of 21 gatherings (71%) and Turkey Vultures arriving first the remaining 6 times (29%). Larger species (Turkey Vulture) displaced smaller species (Lesser Yellow-headed and Black Vultures) more often than expected (75 instances), and conversely, smaller species displaced larger species less often than expected (2 instances).
In addition to foraging observations Eitniear and McGehee (2017) analyzed the mandibles of 12 specimens of Turkey and Lesser Yellow-headed Vultures (at Louisiana State University Museum of Natural Sciences, Baton Rouge, LA) and concluded there was no difference in variance between Turkey Vultures and Lesser Yellow-headed Vultures in bill height (n= 24, F=0.5039, P<0.262) nor bill length (n=25, f=0.5827, P<0.3670). However, variance in bill width was significantly different (n=25, f=0.2087, P<0.01186). This study suggests that despite being smaller in size, the Lesser Yellow- headed Vulture has an advantage as it arrives at carcasses first and may have a greater ability to consume more flesh due to a larger gape width.