Temporal tolerance extremes in passerine birds

Anthropogenic climate change has increasing effects on our natural world, with rising temperatures, loss of habitat, and displacement of many species. Some species may be more heavily affected than others, and some may be able to withstand the rise in temperature in their habitat (Latimer and Zuckerberg, 2020). For birds inhabiting areas where the ambient temperature (Ta) surpasses normothermic body temperature (Tb), there are physiological and behavioural issues surrounding water balance maintenance and hyperthermia. More research is required to understand how heat tolerance differs amongst avian species, as many previous studies focus on resting metabolic rate compared to the extremes which are becoming more relevant as global temperature rises (Noakes, Wolf and McKechnie, 2016). This study has compiled data from the literature on passerine birds around the world and aims to compare maximum Tb amongst a range of species. Body mass and maximum Ta has been measured too, as Pollock, Brawn and Cheviron (2020; McKechnie, et al., 2017; Whitfield et al., 2015) found that heat tolerance increases with body size of desert birds. This study will aid the knowledge of extreme temperatures which a range of passerine birds can sustain and can be used to compare with other bird species around the world.

To create the database for review, we researched the literature for relevant papers using Google Scholar and Science Direct from the 1st to 6th of February 2024. Keywords used in the search process were “temporal”, “tolerance”, “birds” and “passerine”. Each paper was evaluated for relatedness to the topic, mainly assessed by readiness of data on maximum Tb and Ta (measured in degrees Celsius), species weight (measured in grams) and if the data was collected in the regions summer or winter period. The latitude and longitude of the study sites were converted to decimal degrees, and papers which did not give exact locations had estimated coordinates mapped.

References:

Latimer, C.E. and Zuckerberg, B. (2020). Habitat loss and thermal tolerances influence the sensitivity of resident bird populations to winter weather at regional scales. Journal of Animal Ecology, 90(2), pp.317–329. doi:https://doi.org/10.1111/1365-2656.13332.

McKechnie, A. E., Gerson, A. R., McWhorter, T. J., Smith, E. K., Talbot, W. A., & Wolf, B. O. (2017). Avian thermoregulation in the heat: Evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance. Journal of Experimental Biology, 220, 2436–2444. https://doi.org/10.1242/jeb.155507

Noakes, M.J., Wolf, B.O. and McKechnie, A.E. (2016). Seasonal and geographical variation in heat tolerance and evaporative cooling capacity in a passerine bird. The Journal of Experimental Biology, 219(6), pp.859–869. doi:https://doi.org/10.1242/jeb.132001.

Pollock, H.S., Brawn, J.D. and Cheviron, Z.A. (2020). Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming. Functional Ecology, 35(1), pp.93–104. doi:https://doi.org/10.1111/1365-2435.13693.

Whitfield, M. C., Smit, B., McKechnie, A. E., & Wolf, B. O. (2015). Avian thermoregulation in the heat: Scaling of heat tolerance and evaporative cooling capacity in three southern African arid-zone passerines. Journal of Experimental Biology, 218, 1705–1714. https://doi.org/10.1242/jeb.121749