In the cool of the air conditioning

Phoenix, Arizona, the hottest city in the United States. Three months of the year, the daytime temperature exceeds 40°C. Since the invention of air conditioning a century ago, wealthy humans have lived in a cool bubble. Around them, animals are increasingly roasting in the Arizona sun as urban activity creates a deadly heat island; even rattlesnakes are fleeing.

More than 100 bird species are threatened by climate change in Arizona, but rosy-faced lovebirds found a trick. These small, colourful parrots have come a long way; their ancestors were captured in southern Africa, and shipped to American pet shops. Some escaped and, from the 1980s, an urban population settled in Phoenix. Several thousand now live in the metropolis, colonising the palm trees and cacti of the most wooded gardens, in place of the dry forests and savannahs of their origins. For the past decade, researchers at Arizona State University have seen them indulge in a strange activity. On the hottest afternoons between June and October, the lovebirds perch on the air vents of some buildings. At first sight, this does not seem to be a good idea, as one can imagine these ducts pulsating with the overheated air of air-conditioning units. Perching on these giant hairdryers would therefore be appropriate in winter, as European magpies do on some chimneys, but not during a heat wave. The puzzled researchers turned to the university’s technical services and solved the puzzle: the system in question dates back to the 1960s, when oil orgies made it possible to spend lavishly, including on artificially cooled air. Thus, the air vents frequented by the cute parrots are used to ventilate rooms cooled by air conditioners, evacuating deliciously cool air. The lovebirds literally queue up to swoon, as we open a fridge in the middle of a heatwave to catch a bit of freshness.

Why only these birds from elsewhere have figured out the trick? It is surprising not to see local creatures, such as mockingbirds and hummingbirds, also visiting the cooling vents. Of course, the manoeuvre is very technical as they have to perch on particularly slippery metal slats, with all the skill and intelligence of a parrot to stay on them. But there is more: the immigrants are intrepid and inventive. Where local species are content to endure the relentless heat, newcomers adapt and persist.

Reference: Mills, R., & McGraw, K. J. (2021). Cool birds: facultative use by an introduced species of mechanical air conditioning systems during extremely hot outdoor conditions. Biology Letters, 17(3), 20200813.

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