Abstract
Most species-climate models relate range margins to long-term mean climate but lack mechanistic understanding of the ecological or demographic processes underlying the climate response. We examined the case of a climatically limited edge-of-range population of a medium-sized grassland bird, for which climate responses may involve a behavioural trade-off between temperature stress and reproduction. We hypothesised that temperature will be a limiting factor for the conspicuous, male snort-call display behaviour, and high temperatures would reduce the display activity of male birds.Using remote tracking technology with tri-axial accelerometers we classified and studied the display behaviour of 17 free-ranging male little bustards, Tetrax tetrax, at 5 sites in the Iberian Peninsula. Display behaviour was related to temperature using two classes of Generalized Additive Mixed Models (GAMMs) at different temporal resolutions. GAMMs showed that temperature, time of the day and Julian date explained variation in display behaviour within the day, with birds snort-calling significantly less during higher temperatures. We also showed that variation in daily snort-call activity was related to average daytime temperatures, with our model predicting an average decrease in daytime snort-call display activity of up to 10.4% for the temperature increases projected by 2100 in this region due to global warming. For lekking birds and mammals undertaking energetically-costly displays in a warming climate, reduced display behaviour could impact inter- and intra-sex mating behaviour interactions through sexual selection and mate choice mechanisms, with possible consequences on mating and reproductive success. The study provides a reproducible example for how accelerometer data can be used to answer research questions with important conservation inferences related to the impacts of climate change on a range of taxonomic groups.
Highlights
Climate change is a major and increasing global threat to biodiversity [1,2], a better understanding of species responses to climate change is important to inform and prepare policy makers and conservationists [3,4,5]
We investigated how elevated temperatures affected snort-calling of little bustard males, by remotely tracking seventeen free-ranging male birds during the mating season and classifying individual behaviour from fine-scale movement data collected using tri-axial accelerometers
The 17 male little bustards were tracked for a mean of 12.8 days during their display season, providing 8308 daylight acceleration sequences (5:00 to 21:00 hours), of which 41.5% were classified as snort-call display behaviour
Summary
Climate change is a major and increasing global threat to biodiversity [1,2], a better understanding of species responses to climate change is important to inform and prepare policy makers and conservationists [3,4,5]. Most climate-species models relate range margins to long-term mean climate variables on assumed equilibrium, and do not adequately capture responses to increasing climatic extremes and stochasticity [6,7] Such models lack a mechanistic understanding of the ecological, behavioural and demographic processes that currently limit range distributions and how these processes may respond to future climates. We examine how global warming responses may involve a behavioural trade-off between avoiding temperature stress and carrying out breeding displays, for a climatically limited, edge-of-range population of a medium-sized grassland bird. For some ectotherms such as reptiles and amphibians, the impacts of elevated temperatures on species’ behaviour patterns are well evidenced, and local population expiration can occur when temperature increases restrict key activities to a limited daily interlude [3]. Species restricted to open grassland, semi-arid and desert habitats may be vulnerable to global warming, as they are highly exposed to insolation, with limited ability to perform behavioural thermoregulation due to the open nature of the landscape that they depend on
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