Avian Weather Perceptions

"We don't know how [birds are able to detect when a cold front is approaching]. There are a number of hypotheses but we don't know for sure yet."
"We know that birds and other animals can detect subtle changes in air temperature. Many birds somehow sense that very minute drop in air pressure that typically signals low pressure coming [accompanying a storm]. [Birds have several options] That depends on the bird. They either want to get out of there, or they want to hunker down."
"We've done a lot of work on various sparrow species that forage on the ground. If you're a sparrow in winter and a storm is coming, that probably means there is going to be snow. Sparrows need to eat while they can. When we expose these sparrows to a drop in air pressure they start eating more [to store energy]."
"A large number of animals are probably detecting these subtle changes in barometric pressure. How sharks are sensing that under water is a total mystery. I'm interested in understanding in what situations they can cope, and in what situations they will not be able to cope."
"If these extreme events [in weather] become more common, I think it's useful to understand how animals predict and cope with them. Birds are important, not only for the ecosystem but they are culturally important to us. Really, I'm just motivated in trying to understand how they are coping with the changing environment."
Scott MacDougall-Shackleton, Advanced Facility for Avian Research, University of Western Ontario

Sparrows are      known to eat more when they sense a drop in air pressure signalling he arrival of a winter storm. Photo:  Judith Gustafsson

It remains a speculative mystery to scientists how it is that birds have foreknowledge of a winter storm's arrival. With that knowledge they make decisions that are vital to their survival; whether to fly away to safety or to choose to hide until the storm passes. Whichever decision they make is invariably integrated with their feeding requirements. Sensing changes in air pressure, however slight, they are also able to detect when temperature drops, linked to a cold front incoming.

At the University of Western Ontario where Dr. MacDougall-Shackleton, a behavioral psychologist, has his laboratory, the facility is home to the world's first hypobaric climate wind tunnel for bird flight. Research into the physiology and aerodynamics of bird flight at different altitudes is enabled when researchers turn air pressure up and down to study their effect on birds. When high pressure is simulated in the lab along with cold weather linked to winds out of the north in spring, birds decrease their northbound migratory flight behaviour.

Birds in southeastern states in the U.S. managed to develop through an evolutionary track, a measure to dodge storms approaching from the west. They enact a formula whereby they fly south to avoid the path of the storm, then turn west and finally return flying back up behind the storm. Infrasound --  sound at a frequency too low for human hearing -- may cause birds to react. One current theory is that because low-frequency sound travels a long way, birds can hear the sounds of distant rumbles from thunder "probably many hours in advance" of its actual appearance.

"We have now clearly demonstrated that birds, both when wintering and migrating, have their own internal barometer, which helps them make decisions about everything from flight to feeding,"
"This has been hypothesized for a long time and there is a large body of evidence that animals in the wild behave differently when weather changes but we now have an experimental demonstration where we held everything else constant except for barometric pressure proving definitively this long-held belief."

According to climate theory, a warming world will result in more frequent and more violent storms. Dr. MacDougall-Shackleton would like to find out how this, should it occur, will affect bids and other wildlife. There is the issue to be studied whether too frequent and too violent storms may overwhelm the capacity of birds to persevere.

One of Dr. MacDougall-Shackleton's doctoral students is conducting research on whether a bird may become too physically stressed to survive a frequent succession of such storms. If a laboratory bird is exposed to a simulated storm approaching once weekly, the birds appear capable of handling the situation. Should the lab simulate two storms weekly "they would start losing some weight.So they weren't able to keep up with their energy balance."

"Birds have evolved to cope with bad weather. They have experienced it all through evolution. But it's possible that some species may be in trouble", should increasingly violent weather eventuate in the future over what is being experienced at the present time.