A recent study reveals that birds, beyond their plumage and beaks, utilize their legs as a natural thermostat, adjusting blood flow to regulate body heat. Published in Biology Letters and based on thermal imaging of 14 bird species in Australia, the research suggests that birds may evolve longer legs as a response to global warming, enhancing their ability to cool down.
Monte Neate-Clegg, an ecologist at the University of California, Los Angeles, praises the "elegant" study and anticipates that further research will deepen our understanding of how birds worldwide will adapt to climate change.
Bird beaks and legs, filled with veins not insulated by feathers, serve as effective cooling mechanisms, enabling birds to manage their body temperature in varying climates. The study, led by evolutionary ecologist Alexandra McQueen at Deakin University, employed thermal imaging in public parks in Australia's Victoria state to observe birds in their natural habitat.
Despite challenges posed by the COVID-19 pandemic, the team successfully captured images of species such as the Australian wood duck, purple swamphen, and superb fairy-wren. By analyzing wind speed, temperature, humidity, and solar radiation, researchers estimated the birds' surface temperatures and observed their thermal adjustments.
On warmer days, with temperatures reaching up to 40°C, birds employed both their beaks and legs to dissipate excess heat. In contrast, during winter conditions as low as 2.5°C, the beaks continued to shed heat, while the legs retained cold temperatures. This suggests that birds strategically restrict blood flow to their legs on colder days, conserving heat in those areas.
Matthew Symonds, an evolutionary ecologist at Deakin and study co-author, explains that birds may have less control over blood vessels in their beaks due to their proximity to the brain, which requires constant blood flow. Biologist Raymond Danner at the University of North Carolina Wilmington, not involved in the study, suggests that these findings could elucidate why birds in cold climates tend to evolve smaller beaks.
As global temperatures rise, McQueen predicts that bird species experiencing diverse temperature ranges throughout the year might evolve larger legs. This adaptation would aid in managing heat in warmer settings without compromising heat retention in colder conditions, leading to potential "shapeshifting" in their legs relative to their beaks over time.
More: https://www.science.org/content/article/too-hot-too-cold-birds-use-their-legs-thermostat
