Carcasses provide resources not exclusively to scavengers: patterns of carrion exploitation by passerine birds

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Abstract
Carrion provides energy transfer to food webs as a primary trophic resource for many taxa. Ecological relationships around this pulsed resource are highly complex and are influenced by many factors, including those related to its availability and the management of carcasses by humans. In recent years progress has been made in understanding the scope, implications and value of carrion ecology, mainly using scavenger birds and arthropods as study models. However, carrion is important for other facultative scavengers, and even for other non‐scavenger species, which may be influenced by the onset of the resources generated. The objective of this study was to evaluate the patterns of attendance of passerine birds, including the non‐scavengers, at carrion inputs in order to divulge the importance of this resource, its relationship to other species, and to reveal its ecological implications. Individuals of the Corvidae family, recognized facultative scavengers, showed a similar trophic behavior to obligate scavenger raptors regarding the selection of carcass characteristics (i.e., format, scattering, biomass), the surrounding landscape and spatiotemporal conditions. Furthermore, corvids mismatched their presence with vultures, benefitting through commensalism from the generation of residual small pieces and scraps. The non‐scavenger passerines avoided simultaneous presence with vultures and delayed their attendance to carcasses from the time of input. Non‐corvid passerines profited from carrion opportunistically, especially through predation on scavenger arthropods. Thus, their appearance was linked to seasons and conditions with an increased abundance of invertebrates, and coincided with periods of higher energy demand (migration and wintering). Similarly, inter‐specific competition in carrion exploitation as well as a decrease in abundance of arthropods may determine the segregation between non‐corvid passerines and scavenger raptors.

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