1/27/2024 0 Comments Hummingbird migration 2021However, it remained unclear whether hummingbirds switched from using torpor strictly in energy emergencies, to using it as strategy to prepare for migration. It is thought that this bird may use torpor as a way to accelerate fat build up before its annual migration. Like most long-distance migrants, ruby-throated hummingbirds increase their fat stores before departing, using these stores to fuel their journey. The ruby-throated hummingbird ( Archilochus colubris), for example, travels over 5,000 kilometers in its fall migration. Many hummingbirds migrate to areas with warmer weather, where food remains available, for the winter months. If they go to sleep with too little fat, they can descend into torpor to stretch out that limited energy supply and survive until morning. Hummingbirds, for example, eat nectar all day long to meet their high energy needs, but must build fat reserves to see them through their overnight fast. Some animals use torpor to survive times when food is not readily available. Similar to hibernation, although shorter in duration, torpor is a state of minimal activity, low body temperatures and reduced metabolism that helps animals conserve energy in unfavorable conditions. Torpor is an energy-saving strategy used by warm-blooded animals, including birds and small mammals. Moreover, this study highlights the underappreciated importance of facultative heterothermy in migratory ecology. These findings demonstrate the versatility of torpor throughout the annual cycle and suggest a fundamental change in physiological feedback between adiposity and torpor during migration. During the migration period, birds were more likely to enter torpor on nights when they had higher fat stores, and fat gain was positively correlated with the amount of torpor used. Remarkably, this energy emergency strategy was abandoned in the late summer when birds accumulated fat for migration. During 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. Human disturbance to habitat and climate change are the two greatest threats to biodiversity of our time 2, 3.Many small endotherms use torpor to reduce metabolic rate and manage daily energy balance. We have reached a turning point in the modern era for biodiversity loss 1. Our analyses and geographic modelling highlight the urgent need of regulatory action to conserve hummingbirds uniquely capable of filling their niche in North America. We found no evidence for such an effect, thus supporting the hypothesis that trends reflect true demographic change. We also tested whether apparent declines might be due to a growing mismatch between the timing of breeding and the timing of BBS surveys. In contrast, Anna’s hummingbird populations have increased dramatically since 1970 in their range in western North America. Contrasting the trends from the past half-century, ruby-throated hummingbirds of Eastern North America have declined since approximately 2004 throughout most of the species’ breeding range. Among the Selasphorus genus, Allen’s, rufous, and broad-tailed hummingbirds have declined since 1970, and the rate of decline increased from 2009 to 2019. To examine the conservation status of North American hummingbirds, we analyzed Breeding Bird Survey data for 8 species and 3 genera from 1970 to 2019 (long-term) and from 2009 to 2019 (short-term, approximately three generations). As pollinators, hummingbirds play a critical role for both the function of ecological communities and in providing ecosystem services for people.
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