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

Rubén Moreno-Opo,Antoni Margalida

doi:10.1890/es13-00108.1

Rubén Moreno-Opo, Antoni Margalida

Open Access

https://doi.org/10.1890/es13-00108.1

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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.

Highlights

Carrion plays a key role in food webs, and is an extensively used trophic resource providing high nutritional levels in terrestrial ecosystems (DeVault et al 2003, Leroux and Loreau 2008)
We identified 18 species of passerines and two related species (Table 2)
Factors affecting attendance to carcasses Factors determining attendance to carrion inputs were different between corvids and the rest of the passerines

Summary

Introduction

Carrion plays a key role in food webs, and is an extensively used trophic resource providing high nutritional levels in terrestrial ecosystems (DeVault et al 2003, Leroux and Loreau 2008). Carcasses are a pulsed resource whose occurrence patterns in ecosystems are subject to variable spatiotemporal predictability depending on many factors (Nowling et al 2008, CortesAvizanda et al 2009a) These are, among others, the mortality rates and their causes, the abundance, location and distribution of wild animal species, as well as the intensity and methods of their socio-economic uses (DeVault et al 2003, Deygout et al 2009, Margalida and Colomer 2012). All of these determine carrion availability, triggering adaptive changes in the morphology, behaviour, interactions, distribution and population dynamics of species linked to this resource (i.e., Wilmers et al 2003a, Selva et al 2005, Shivik 2006, Cortes-Avizanda et al 2009a, Deygout et al 2010, Margalida et al 2011)

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