Using multiple data sources to investigate foraging niche partitioning in sympatric obligate avian scavengers

Journal Article · Thu Jan 03 04:00:00 EST 2019 · Ecosphere

DOI:https://doi.org/10.1002/ecs2.2548· OSTI ID:1614636

Byrne, Michael E. ^[1]; Holland, Amanda E. ^[2]; Turner, Kelsey L. ^[3]; Bryan, A. Lawrence ^[2]; Beasley, James C. ^[3]

---

1. Savannah River Site (SRS), Aiken, SC (United States). Savannah River Ecology Lab. (SREL); DOE/OSTI
2. Savannah River Site (SRS), Aiken, SC (United States). Savannah River Ecology Lab. (SREL)
3. Savannah River Site (SRS), Aiken, SC (United States). Savannah River Ecology Lab. (SREL); Univ. of Georgia, Athens, GA (United States)

As carrion feeders competing for a limited and ephemeral resource, avian scavengers are ideal model organisms to study mechanisms of niche partitioning. Previous work has focused on observations of species’ interactions at carcasses, and although fruitful, the inclusion of behavior beyond that at carcasses, such as movement patterns, could yield a more comprehensive understanding of mechanisms of foraging niche partitioning. Our goal was to assess how differences in physiological, morphological, and social characteristics between sympatric black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) manifest interspecific variation in movement patterns, foraging habitats, and carcass use to reduce direct competition. Both species are obligate scavengers that co-occur across much of the New World. Turkey vultures are solitary foragers with enhanced olfactory capabilities and wings optimized for energy-efficient low-altitude soaring. Black vultures are aggressive, heavier bodied, and forage socially. We assessed interspecific variation in carcass exploitation using experimental carcass trials encompassing a range of habitats, carcass sizes, and seasons, and used GPS telemetry to compare how soaring conditions influenced daily space use and diurnal patterns of movement activity for each species. Turkey vultures occurred more often at small (i.e., rabbit) carcasses, and those obscured by forest cover than black vultures, and were the first vultures recorded at 94% of carcasses visited by both species. Both species increased movement rates and daily ranges when soaring conditions were favorable; however, turkey vultures had higher travel rates regardless of soaring conditions. Our results suggest the olfactory sense of turkey vultures allows them to locate smaller and visually obscured carcasses more efficiently than black vultures, facilitated by wing morphology that allows them to forage over large areas efficiently. Socially foraging black vultures appear specialized at locating larger carcasses in open habitats, which does not require as much foraging flight as turkey vultures. Our study illustrates how inclusion of movement ecology into niche partitioning studies provides a more complete understanding of the mechanisms of coexistence in avian scavenger guilds. This approach may provide important information to guide conservation efforts, such as supplemental feeding, of imperiled vulture species.

• Research Organization: Univ. of Georgia, Athens, GA (United States)
• Sponsoring Organization: USDOE Office of Environmental Management (EM)
• Grant/Contract Number: EM0004391
• OSTI ID: 1614636
• Journal Information: Ecosphere, Journal Name: Ecosphere Journal Issue: 1 Vol. 10; ISSN 2150-8925
• Publisher: Ecological Society of America
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
60 APPLIED LIFE SCIENCES
Cathartes aura
Coragyps atratus
Environmental Sciences & Ecology
black vulture
movement ecology
niche differentiation
resource specialization
telemetry
turkey vulture.