Sight or smell: which senses do scavenging raptors use to find food?

Abstract

Raptors are usually considered to be mainly visually dependent, and the use of other sensory modalities has rarely been studied in these birds. Here, we investigated experimentally which senses (vision and/or olfaction) Turkey vultures (Cathartes aura) and Southern caracaras (Caracara plancus) use to find hidden food. First, two identical stainless-steel perforated balls, one containing a putrefied piece of meat and the other an odorless control, were presented to birds in binary choice experiments. Both species interacted more with the smelling ball than with the control, suggesting that they were attracted by the odor of the hidden meat. In a second experiment, individuals were accustomed to eat in one specifically colored ball (blue or green). In the test phase, the meat was hidden in the opposite color with respect to the one each bird had become accustomed to. Vultures still interacted more with the smelly ball disregarding the color, while caracaras interacted equally with the two balls. The prevalence of olfaction in Turkey vultures may partly explain why they are the first raptors to find carcasses in tropical forests. In contrast, caracaras forage on the ground opportunistically, a strategy where both olfaction and sight may be involved. Our experiments suggest that both species are able to use olfactory cues for foraging. However, olfaction could be the predominant sense in Turkey vultures while olfaction and sight could play an equivalent role in Southern caracaras.Electronic supplementary materialThe online version of this article (10.1007/s10071-018-1220-0) contains supplementary material, which is available to authorized users.

Uncovering the vertebrate scavenger guild composition and functioning in the Cerrado biodiversity hotspot

“…The species that first detected more carcasses was the turkey vulture, followed by the southern caracara. These two species are not only guided by the sense of sight and hearing, like most raptors, but also have a developed sense of smell (Houston, 1985; Potier et al, 2019). It has been hypothesized that these evolutionary differences between New and Old world vulture guilds (e.g., olfactory capacities of some species) are due to the type of habitat in which they have evolved; Old World vultures are distributed in areas of open habitat, while most New World species (except the two condor species) are mainly distributed in Neotropical forests (Houston, 1985).…”

“…In the Cerrado, there are five of the seven species of the New World vultures (Cathartidae): turkey (Cathartes aura), lesser yellow-headed (C. burrovianus), greater yellow-headed (C. melambrotus), American black (Coragyps atratus), and king (Sarcoramphus papa) vultures. A characteristic feature of some of these vulture species is their developed sense of smell, as they have highly developed olfactory bulbs, which is not found in any of the Old World vulture species (Potier et al, 2019). This ability, together with the potential to fly great distances with little energy expenditure (Duriez et al, 2014), means that New World vultures are especially efficient at locating carrion even when vegetation is dense.…”

A dead giveaway: Foraging vultures and other avian scavengers respond to auditory cues

“…As a result, natural selection has shaped foraging strategies and animals' physical, physiological, or neurological adaptations to increase search efficiency and food acquisition rates (Preston, Pitchford, & Wood, 2010). In birds, many species rely on visual and/or olfactory cues while foraging (Goldsmith, 1990;Martin, 2017;Nevitt & Bonadonna, 2005;Potier, Duriez, Célérier, Liegeois, & Bonadonna, 2019). Although sound is important in the behavioral ecology of many birds (e.g., mate finding, territorial displays), few species reportedly use auditory cues during foraging (e.g., Wagner, Kettler, Orlowski, & Tellers, 2013;Onrust et al, 2017).…”

“…Avian dietary specialization differs considerably, however, as can be illustrated by the vultures inhabiting African savanna ecosystems. Unlike species of New World vultures (Cathartidae) (Potier et al, 2019), Africa's vultures (Accipitridae) reportedly have no refined olfactory senses (Houston, 1985). However, closely related species are able to use olfaction during foraging (Gilbert & Chansocheat, 2006;Nelson Slater & Hauber, 2017;Potier, 2019), indicating that it might be possible for the African species too.…”

Tritrophic interactions with avian predators: the effect of host plant species and herbivore-induced plant volatiles on recruiting avian predators

“…Further, much recent behavioral work has demonstrated that birds use odor in many important ecological contexts, such as in mate choice and species recognition (Bonadonna and Mardon 2013, Zhang et al 2013, Van Huynh and Rice 2019, kin recognition (Fracasso et al 2019), predator avoidance (Amo et al 2008, Roth et al 2008, Stanbury and Briskie 2015, Lee 2021, nesting (Petit et al 2002, Gwinner and Berger 2008, Shutler 2019, foraging (Hutchinson and Wenzel 1980, Hiltpold and Shriver 2018, Saavedra and Amo 2018a, Potier et al 2019, Potier 2020, and navigation (Pollonara et al 2015, Abolaffio et al 2018, Zannoni et al 2020. Here, we assess the ability for birds to cue in on plant volatiles to locate insect prey.…”