Help hummingbirds avoid hypothermia

by Bob and Judy Hoy, Stevensville

Hummingbirds split from swifts and treeswifts around 42 million years ago, most likely in Eurasia, and made it to South America about 22 million years ago, eventually coming to North America. In all that time, hummingbirds have been co-evolving with native flowering plants, and had to fly from flower to flower and hover while feeding. Flying warms both the hummingbirds, and the small amount of nectar they drink from flowers while hovering.

Feeders were first made in the 1950s, and those feeders did not have perches, so the birds had to hover while feeding. To some, providing a perch seemed like a kindness to the birds and because of consumer  demand, feeder manufacturers added perches to most of their feeders beginning in the 1970s.

In 1983, Bob Hoy, a biologist, discovered what we called “perch  hypothermia” after he observed the hummingbirds being unable to fly normally, fluttering down to lie on the ground unresponsive and hypothermic after drinking cold sugar water from the feeder while sitting motionless on the perches. We attempted to bring this serious condition to the attention of bird lovers, the USFWS and ornithologists, but nothing official was done.

All hummingbird researchers contacted recently, including Dr. Sara   Hiebert, Professor Emerita of Mathematics and Natural Science, Swarthmore College, Swarthmore, PA, Dr. Brett Tobalske, UM, Professor, Director of the Field Research Station, UM, Missoula MT., and Dr. Jack Kirkley, Prof. Biology, Western Montana College, Dillon, MT say that what National Audubon Society calls cold-stun on their website https://www.audubon.org/news/hummingbird-feeding-faqs is definitely hypothermia. Both the website and the researchers say this condition is extremely dangerous to the affected hummingbird. Researchers also stated that hypothermic, unresponsive birds are close to death and can only recover if warmed. Hypothermic hummingbirds often flutter or fall to the ground where they are highly susceptible to being killed by predators, being injured or dying. A female hummingbird incapacitated by hypothermia can’t return to her nest to save her eggs or hatchlings from being killed by cold and/or starvation. This results in the loss of the entire family and is likely contributing to declines in hummingbird species.

Attracting hummingbirds by supplemental feeding can provide many hours of enjoyable hummingbird watching, and can be beneficial to the hummingbirds, if the welfare of the birds is always the primary consideration. Please use only perchless feeders in areas where the temperatures go below 55 degrees.