Foraging behaviour at carcasses in an Asian vulture assemblage: towards a good restaurant guide

Abstract

SummaryVulture populations are declining steeply worldwide. Vulture ‘restaurants’ or feeding stations are a tool for maintaining and monitoring numbers, but individual species may be disadvantaged by the effects of carcass distribution, carcass size and interspecific aggression. To test the degree to which restaurants give opportunities for each species to access the food provided, we studied behaviour and morphology in three Critically Endangered species of vulture in Cambodia: the gregariously breeding and feeding White-rumped Vulture Gyps bengalensis and Slender-billed Vulture G. tenuirostris, and the solitary Red-headed Vulture Sarcogyps calvus. We video-recorded attendance time, attendance order and dominance behaviour at different-sized carcasses. Interspecific aggression at carcasses was least frequently shown by the ‘small’ White-rumped Vulture. The relatively ‘large’ Slender-billed and ‘medium’ Red-headed Vultures showed aggression more regularly and at similar levels. However, the latter avoids conflict by waiting until Gyps vultures are no longer crowding at the carcass, although its arrival at carcasses was correlated with total number of vultures present. While more numerous than Red-headed, the two Gyps vultures are more dependent on large carcasses, which increases their vulnerability to further declines in wild large ungulate species. Body size, number of individuals, hunger levels and carcass size and availability all influence carcass attendance behaviour. An increase in the number and spatial distribution of restaurants as well as of carcass size range could boost numbers of all vulture species.

Carrion converging: Skull shape predicts feeding ecology in vultures

“…The intermediate positions of these species in morphospace as well as their proximity to non‐vulture raptors, suggest that these two species have not undergone such extreme morphological evolution as other, more specialized vultures. In addition, although the gulper assignment of Gyps tenuirostris is supported by field observations (Hille et al., 2016), this is the first morphometric study on vulture feeding types to include this taxon and confirm morphological similarities with other gulpers, including the distantly related cathartids Vultur gryphus and Gymnogyps californianus (Fig. 4).…”

“…Feeding type was assigned to each species following the classification scheme created by Hertel (1994; Table 1) and based on behavioral observations in the field (Gaengler & Clum, 2015; Hille et al., 2016; Houston, 1987; König, 1974, 1983; Kruuk, 1967; J. Burnett, pers. comms.)…”

Carrion converging: Skull shape is predicted by feeding ecology in vultures

“…The intermediate positions of these species in morphospace as well as their proximity to non-vulture raptors, suggest that these two species have not undergone such extreme morphological evolution as other, more specialized vultures. In addition, although the 'gulper' assignment of Gyps tenuirostris is supported by field observations (Hille et al, 2016), this is the first morphometric study on vulture feeding types to include this taxon and confirm morphological similarities with other 'gulpers,' including the distantly related cathartids Vultur gryphus and Gymnogyps californianus (Figure 4). Finally, it is possible to extrapolate feeding assignments to extinct species using discriminant analyses, though results should be interpreted with caution given the inability to obtain observational feeding data.…”

“…Feeding type was assigned to each species following the classification scheme created by Hertel (1994; Table 1) and based on behavioral observations in the field (Kruuk, 1967;König, 1974;König, 1983;Houston, 1987;Hille et al, 2016;Gaengler & Clum, 2015; J.…”

Analysis of skull morphometric characters in diurnal raptors (Accipitriformes and Falconiformes)

“…Larger vulture species have even larger and more hooked bills. Only the largest species (Lappet-faced Vulture and Cinereous Vulture) can tear open a big carcass, later allowing smaller vulture species to access the innards (Kruuk 1967, Schüz & König 1983, Hille et al 2016, Ballejo et al 2018). Steller's Sea Eagle, Philippine Eagle and Harpy Eagle (Harpia harpyja) have also high beaks and long culmens similar to the larger vulture species.…”