7/2/2023 0 Comments Hummingbird migration 2021During the mid-summer, birds entered torpor at consistently low fat stores (~5% of body mass), and torpor duration was negatively related to evening fat load. We tracked torpor use and body composition in ruby-throated hummingbirds ( Archilochus colubris), a long-distance migrant, throughout the summer using respirometry and quantitative magnetic resonance. However, the physiological ‘rules’ that govern torpor use are unclear. Bob has served as a managing editor and author for publications such as “The Illinois Steward” magazine and the “Illinois Master Naturalist Curriculum Guide.Many small endotherms use torpor to reduce metabolic rate and manage daily energy balance. He has been a lifelong student of many aspects of the Natural World, including archaeology. Reber is an emeritus faculty member in the Department of Food Science and Human Nutrition of the University of Illinois at Urbana–Champaign. Your supply of food energy may be just what they need! There is always a chance that migrating ruby-throats from the north, northeast or east will be passing through. It is tempting to take in hummingbird feeders soon after you know that the birds you have fed all summer have taken off southward. Will a similar scenario come into play for the fall migrating ruby-throated hummingbird that needs a continuous food supply over the land it navigates during migration? Will current and future land development and destruction of native food-bearing habitats impact the ruby-throats? Time will tell. Granted, these birds could stop even further inland to eat, but that makes the trek even longer. ![]() Commercial interests rule and natural areas are destroyed, robbing neotropical migrants of their essential “fuel stops” they depend on. Many of these lands close to the Gulf are high economic value areas and are being developed. Their last stops were traditionally made on land within a few miles of Gulf waters to eat native foods and replenish their fat storage. Neotropical migrants, including warblers and thrushes, make stops to “tank-up” on native berries and such before embarking on the long non-stop flight over Gulf waters. The potential of land development and destruction of native habitats along the Gulf Coast and in Central America impacting migrating bird species has been raised. Read more at “Estimating apparent survival of songbirds crossing the Gulf of Mexico during autumn migration” or “Stopover biology of ruby-throated hummingbirds (Archilochus colubris) during autumn migration.” While ruby-throats can theoretically store up enough energy, it is more risky than it is for other neotropical migrants such as warblers and thrushes that can make the trans-Gulf flight in approximately 22 hours. Crossing the 1,000 kilometer (621 miles) Gulf of Mexico is just too risky. Thus, ruby-throats typically stay over land to supply calories during the entire migration. ![]() While it is theoretically possible for some ruby-throats to store up enough fat to power a trans-Gulf of Mexico water crossing, all factors such as weather conditions must be tilted in their favor. Fall migratory destinations for ruby-throats include areas as far north as extreme southern Texas, down through Mexico, and as far south as Costa Rica. Hummingbirds caught by an unanticipated cold snap during migration, or even a hard frost in fall, often die.Ī successful migration south not only requires leaving early enough-usually starting in late August or September in Illinois-but also an ample supply of calories along the entire migratory route to replenish burned-up calories on a daily basis. Eating and maintaining body temperature means survival. Given a diet of nectar, small insects and spiders, staying in temperate weather conditions is a must. During aerial acrobatics, the rate soars above 1,200 beats a minute. At rest, a ruby-throat’s heart beats about 250 times a minute. The bundle of energy we call a ruby-throated hummingbird has an extremely high metabolic rate.
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