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Too much is bad: increasing numbers of livestock and conspecifics reduce body mass in an avian scavenger

Citation

Donázar, José Antonio et al. (2020), Too much is bad: increasing numbers of livestock and conspecifics reduce body mass in an avian scavenger, Dryad, Dataset, https://doi.org/10.5061/dryad.02v6wwq0d

Abstract

Individual traits such as body mass can serve as early warning signals of changes in the fitness prospects of animal populations facing environmental impacts. Here, taking advantage of a 19-year monitoring, we assessed how individual, population and environmental factors modulate long-term changes in the body mass of Canarian Egyptian vultures. Individual vulture body mass increased when primary productivity was highly variable, but decreased in years with a high abundance of livestock. We hypothesized that carcasses of wild animals, a natural food resource that can be essential for avian scavengers, could be more abundant in periods of weather instability but depleted when high livestock numbers lead to over-grazing. In addition, increasing vulture population numbers also negatively affect body mass suggesting density-dependent competition for food. Interestingly, the relative strength of individual, population and resource availability factors on body mass changed with age and territorial status, a pattern presumably shaped by differences in competitive abilities and/or age-dependent environmental knowledge and foraging skills. Our study supports that individual plastic traits may be extremely reliable tools to better understand the response of secondary consumers to current and future natural and human-induced environmental changes.

Methods

Variables obtained during field work 1999-2017  and additional variables used in modeling procedures . Additional information is shown in the main manuscript.

Unpublished data

Funding

Severo Ochoa Excellence Award from the Ministerio de Economía y Competitividad, Award: SEV-2012-0262

Spanish Ministry of Economy and Competitiveness and EU/FEDER, Award: REN 2000-1556 GLO

Spanish Ministry of Economy and Competitiveness and EU/FEDER, Award: CGL2004-00270

Spanish Ministry of Economy and Competitiveness and EU/FEDER, Award: CGL2012-40013-C02-01

Spanish Ministry of Economy and Competitiveness and EU/FEDER, Award: CGL2015-66966-C2-1-2-R

Spanish Ministry of Economy and Competitiveness and EU/FEDER, Award: RTI2018-099609-B-C21

Severo Ochoa Excellence Award from the Ministerio de Economía y Competitividad, Award: SEV-2012-0262