“Birds surviving the heat” symposium was a great success

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

South Africa

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

North America

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!

Generating interest in your science and writing…

Scientists receive pressures from every angle to perform and justify their existence (parents, deans, students, bureaucrats, politicians, you name it..).  One reason for re-vamping my lab website was to keep a chronicle of lab activities as well as provide a more digestible version of our science to the public.  Since our work is sometimes highlighted by science writers and reporters, I had always assumed it was the scientists who had a tough time getting recognised.  Then I read the blog of a Science Writer, Diane Crow, who had contacted me a few months ago, interviewed me about our work on tegus.  She writes about how she tried to pitch her writing to news-outlets.  Sounds similar to a scientist’s challenge to get their work published.


For anyone interested in science writing and the challenges inherent to it, check out Diane’s blog:  http://dianacrowscience.com/543-2/

She gives an excellent and frank account of how a science writer has to make what scientists write interesting and friendly to readers.  Sadly, in the case of the tegu story,  this was a pitch that did not work, but that is one of the reasons why I wanted to post a link to her blog!  We appreciate your work!

Here’s to you Diane!   Keep up the good work and engagement on science!

Hibernation and Thermoregulation Research

I just came back from the International Hibernation Symposium (15th!) from Las Vegas and saw this article about one of our participants.  This is great to read, and helps explain why so many of us are passionate about understanding thermoregulation and hibernation.  Some work is biomedically inspired, some is evolutionarily inspired.  Anyhow, here is a nice article about Dr. Domenico Tupone, one of our colleagues and participants:


Thanks for Dr. Matteo Cerri for sharing this link.

Burning love for our science?

I just found out that an image from our published research has been selected by NSERC’s “Science Exposed” contest.  This photo is an actual research figure but also a captivating depiction of a novel discovery: namely endothermy in a lizard.


Here is the photo.

The link to vote is here:


We would all appreciate your vote.  I know some of the other pictures are stunning landscapes and digitally rendered fluorescent images, but our lizard image is the genuine article.

For more information on the science article, please see:


Tattersall, GJ, Leite, CAC, Sanders, CE, Cadena, V, Andrade, DV, Abe, AS, and Milsom WK. 2016. Seasonal reproductive endothermy in tegu lizards. Science Advances. 2: e1500951.


Hornbills and Toucans and Beaks…

Avian bills are fascinating structures, having evolved a 465px-birdbeaksa-svgmyriad of forms and functions, as depicted in the montage on the right from: https://en.wikipedia.org/wiki/Beak

Today a new publication on this subject has been published in PLoS One, highlighting the multi-tasking capacity of form and function.  You can find it here and blogged about here.

The authors make the major point that hornbills use their bills like toucans do (as radiators of body heat, showing evidence of greater relative blood flow recruitment at warmer temperatures), but that their calculations suggest that the per area rate of heat exchange in the hornbills is less than the toucans.

This is a nice addition to the recent work done by a number of us in the field (see references below, e.g. Symonds and Tattersall, 2010), emphasizing that bills are not the dead, static structures that many assume they are.

One main point the authors note (they base their comparison mainly vs. toucans from our 2009 paper) is that the bills of hornbills are not as effective as dissipators of heat compared to the toucan and quite likely for multiple reasons: 1) the hornbills’ bill is thicker, so is a heavier barrier to heat exchange, likely because the hornbills use their bills as digging implements and must be more robust, and 2) toucans “switch on” their blood flow at lower temperatures than hornbills, and the lower the air temperature, the greater the driving force for heat loss, and 3) the hornbill bill is relatively smaller than the toucans.  The reason for the hornbill vs. toucan comparison is because the two lineages have long been viewed as old world vs. new world convergences (although that is really an oversimplification).

One point I’d like to emphasize that is often missed in the popular press.  These large billed birds are not unique in their bills’ thermal radiator function, since many other birds exhibit similar capacities to modify blood flow to their bills (geese, ducks, sparrows to name a few).  They are, however, striking in how large their bills are, which is why they garner such attention.

Here is a photograph of a hornbill (what mother could not love that face?):

Glenn_pic 2.jpg

Photo: Courtesy Dr. Andrew McKechnie



Figure from van de Ven (2016), showing the obvious blood vessels under the surface of the bill.

Some technobabble about how the measurements are made:

Like myself, these researchers used thermal imaging to obtain their results (see their paper for images and thermal videos), which means that heat exchange is an estimation of events and is done under sampling assumptions.  I’ve been working on calculations to make things easier for myself and colleagues (see below for R package), and came across a couple of things.  Firstly, some of the assumptions van de Ven et al (2016) used are different than the ones we made (Tattersall et al 2009).  We assumed higher wind speeds (5 m/s) in our modelling, which I think are a little on the high side of reality.  van de Ven et al (2016) on the other hand, assumed a wind speed of zero and therefore incorporated only free convection estimates.  Gates (2003 – Biophysical Ecology) advises that forced convection is the more realistic scenario for heat exchange in animals since wind speeds are rarely exactly zero, and suggests values between 0.5 and 1 m/s.  This means that van de Ven’s estimates of convective heat will be underestimates, while our toucan data are over-estimates.   Anyhow, the good news is that van de Den realized this when making comparisons to our previous work and made comparisons using free convective heat exchange (while politely not criticizing us for our over-zealous wind speeds).  The take home message though is that their published values for both species are on the low side, while our published values are more for what a flying bird might experience.

For anyone interested in using their thermal images for similar analyses, I have create a package in R called “Thermimage” to help in the calculations.

See https://cran.r-project.org/web/packages/Thermimage/index.html for the package itself and https://github.com/gtatters/Thermimage/blob/master/heatcalc.R for some sample scripts.


Gates, DM 2003. Biophysical Ecology.  Dover Publications, Mineola, NY, 611 pp.

Symonds M.R.E., Tattersall G.J. 2010 Geographical variation in bill size across bird species provides evidence for Allen’s rule. American Naturalist 176, 188-197. (doi:10.1086/653666).

Tattersall G.J., Andrade D.V., Abe A.S. 2009 Heat exchange from the toucan bill reveals a controllable vascular thermal radiator. Science 325, 468-470. (doi:10.1126/science.1175553).

van de Ven T.M.F.N., Martin R.O., Vink T.J.F., McKechnie A.E., Cunningham S.J. 2016 Regulation of Heat Exchange across the Hornbill Beak: Functional Similarities with Toucans? Plos One 11, e0154768. (doi:10.1371/journal.pone.0154768).

Additional sources

Greenberg R., Danner R.M. 2012 The Influence of the California marine layer on bill size in a generalist songbird. Evolution 66, 3825-3835. (doi:Doi 10.1111/J.1558-5646.2012.01726.X).

Greenberg R., Danner R., Olsen B., Luther D. 2012 High summer temperature explains bill size variation in salt marsh sparrows. Ecography 35, 146-152. (doi:Doi 10.1111/J.1600-0587.2011.07002.X).

Greenberg R., Cadena V., Danner R.M., Tattersall G.J. 2012 Heat loss may explain bill size differences between birds occupying different habitats. Plos One 7. (doi:ARTN e40933 DOI 10.1371/journal.pone.0040933).

Hughes A.L. 2014 Evolution of bill size in relation to body size in toucans and hornbills (Aves: Piciformes and Bucerotiformes). Zoologia-Curitiba 31, 256-263.

McNab B.K. 2001 Energetics of toucans, a barbet, and a hornbill: Implications for avian frugivory. Auk 118, 916-933.

Seki Y., Bodde S.G., Meyers M.A. 2010 Toucan and hornbill beaks: A comparative study. Acta Biomater 6, 331-343.