Widely publicized heat waves have led to mortality and breeding failure of birds, and mortality of other taxa, including many humans, across the globe. Climate models predict further increased temperatures in addition to altered drought and other severe weather patterns, all of which can exacerbate thermal challenges. With a changing global climate, a major challenge facing scientists is to predict if and how species will survive rising temperatures.
Predicting these events requires models and an understanding of underlying thermal biology. Mechanistic, process-based models allow us to predict how higher air temperatures and heat waves impact avifauna. Building these models relies on a detailed theoretical understanding of processes related to thermal stress, as well as parameterization with data from varied sources. Birds of arid habitats provide an ideal model system for developing mechanistic models because they face a number of physiological and behavioral constraints related to the avoidance of lethal hyperthermia and maintenance of water balance. These constraints are often manifested as consequential trade-offs affecting survival and reproduction. Recent catastrophic mortality events, most notably in the Australian arid zone, highlight the direct impacts that periods of extremely hot weather can have on desert birds. In addition, recent research has also revealed various more subtle impacts that only become apparent from detailed, species-specific studies, and/or consideration of the chronic effects of hotter daily conditions in addition to more extreme events.
It was for the above reasons that a team of concerned Physiologists assembled at the North American Ornithology Conference this past week (Aug 18, 2016) to participate in the following symposium topic:
“Surviving the heat: integrating physiology, behavior, and morphology to predict population responses to climate change”
Here were the broad topics covered:
Physiological tolerance limits. Predicting climate change impacts on endotherms using physiological tolerance limits is much more complex than it is for ectotherms. This aspect surveyed recent work aimed at quantifying avian heat tolerance and evaporative cooling capacity in a manner that allows for comparative analyses, and examined how these factors vary among biomes at a global scale.
Behavioral trade-offs and constraints as revealed by intensive, species-specific studies. This section focussed on recent work documenting consequential trade-offs between heat dissipation behaviors and foraging / provisioning nestlings, biologically relevant time scales of high temperatures, and the ways in which high temperatures affects social systems, with a focus on cooperative breeders. It also included work aimed at identifying behavioral indices of sensitivity to heat tolerance that can provide the basis for rapid assessments of species’ relative vulnerabilities to thermal stress.
Morphological responses to past and future climatic changes. Morphological adjustments to climate that facilitate thermoregulation are widespread among birds, though little is known about the capacity for further adaptation in response to ongoing climate change. This aspect surveyed morphological adaptations to climate and discussed the potential for further change, including probable constraints, and consideration of how to incorporate this knowledge into process-based predictive models.
Spatial models. A key aspect of this symposium concerned ways in which species-specific physiological, behavioural, and morphological data could be incorporated into spatial models to predict responses to climate change, with a focus on the probability of extirpation. In addition to the presentations devoted to this topic, there were excellent talks on modeling avian distribution in the context of climate change to provide a backdrop against which to consider ideas from the empirical and theoretical presentations.
The symposium concluded with a 45 minute discussion session, during which future integrative directions were discussed, and short-comings of various approaches identified. The symposium was well attended and we received excellent feedback from speakers and attendees. Moreover, the participation of speakers from North America, southern Africa and Australia reflected the global focus of this symposium. Participants and attendees were exposed to novel techniques and analytical approaches presented by some of the world’s authorities.
I tried to get photos over everyone’s title slide (but not posting data or non-twitterable material), but missed a few (including my own!) due to my involvement in introducing speakers.
Names, affiliations, and titles of the speakers’ talks
Susie Cunningham, University of Cape Town – Fitness costs of behavioral thermoregulation and threshold temperatures revealed by behavioral data sets
Michelle Thompson, University of Pretoria – Can heat dissipation behaviour be used as an indicator of underlying physiological stress?
Margaux Rat, University of Cape Town – The impact of elevated temperatures on social networks of a communal passerine, the Sociable Weaver Philetairus socius
Krista Oswald – Threats of climate change to a Fynbos-endemic bird: physiological responses show low heat tolerance thresholds irrespective of season in the Cape rockjumper (Chaetops frenatus)
Andrew McKechnie, University of Pretoria – Phylogenetic variation in heat tolerance and evaporative cooling capacity among Kalahari Desert birds
Alex Gerson – Differential use of hyperthermia as a thermoregulatory strategy in birds exposed to high temperature.
Blair Wolf, University of New Mexico – Physiological challenges for desert bird communities in a rapidly warming world
David Luther – Males with larger bills sing at higher rates in a hot and dry environment
Bill Talbot – Surviving the heat: Nocturnal Sonoran Desert birds
Thomas Albright – Mapping lethal dehydration risk in desert birds of the Southwest USA under current and future climates: integrating physiology and microclimate
Ray Danner – Heat limits behavioral performance
Glenn Tattersall – Bills as radiators of body heat
Sekercioglu, Cagan – The effects of climate change on tropical birds
Janet Gardener – Temporal changes in avian body size over the last 50 years are associated with heat dissipation in Australian passerines
Many thanks to the NAOC organisers for allowing us to host this symposium!