Hummingbirds Found with Unique Strategy to Overcome Conditions During Migration

A collaborative study was recently presented regarding a species of hummingbirds that thrive in between countries. These hummingbirds are quite different among the avian creatures, as they can significantly drop their body temperatures to match their anatomical conditions during the night and travel fast between their breeding grounds and winter shelters.

The thermoregulation found from the hummingbird species adds contributing aspects to the biology of avians and other non-hibernating animals that live in higher mountains. According to the authors, the best exhibitor of torpor is the ruby-throated hummingbirds.

Thermoregulation in Ruby-Throated Birds During Migration

Previous research showed that many animals could undergo hibernation during colder seasons. During this process, the animals rest their bodies and skip food consumption for longer days. Hibernation lets them survive the harsh conditions of winter while being warm with the calories they acquired prior to the season.

Alongside hibernation, scientists defined another process that other animals chose to go through. This periodic state is called torpor, in which the animals perform similar steps to survive the winter's extremities. During torpor, the metabolism in specific creatures slows down gradually down to 95 percent. The unique feature allows them to express particular thermoregulation, which helps them maintain the right amount of temperature of their bodies while conserving their energy at the same time.

University of Toronto's Department of Biological Sciences expert and author Erich Eberts said in a FloridaNewsTimes report that their team wants to dive into the complex aspects of torpor in hummingbirds they can exert energies that are unattainable by other birds. The expert said there seems to be a mystery behind their energy-saving movements and an outstanding skill to travel 3,000 kilometers between their breeding areas in North America and their winter shelters in Central America.

The study on the hummingbird's energy-saving strategy consisted of measurements in data collected from 16 ruby-throated hummingbirds in 3 separate periods. The scales included body size, fat, and lean masses. The oxygen circulation in the avians was also measured through an approach known as respirometry, which gives the biggest indication once they undergo torpor.

According to the study, the birds maintained their lean body masses, and upon reaching 5 percent of fat below their body mass, the ruby-throated hummingbirds began entering torpor. This is opposed to the common usage of body fat during summer migration when it exceeds up to 20 percent more. By this strategy, the hummingbirds will budget their stored fat effectively even if they travel fast and the nights are longer than usual.

Nightly Torpor of Hummingbirds

A previous study was also conducted to distinguish the missing aspects that mobilize the torpor process. The examination was made possible through the help of a hummingbird species that reside in the mountainous regions of South America known as the Andes. The environment that sits at the heart of the Andes mountains is still untapped, enabling the highest peaks of the towering landscapes to stay cold at night, even in the summer season.

The hummingbirds of the Andes could live on top of the mountains that measure 3,800 meters of height above sea level. The analysis of the thermoregulation in the avians was collected through the observation of 6 species. Overnight, the study was met with extremely low temperatures, which scaled down to 2.4 degrees Celsius.

Across the subjects, 24 of the birds were able to undergo torpor. Each of the species that were observed had at least one member that went into torpor, which means that all of the selected species could perform the periodic thermoregulation state. The readings from the birds also varied depending on each individual and between distinct species. In addition, the time spent for torpor on each of the birds who were able to do it jumped between 5 to 10 hours.

According to a report by PhysOrg, the loss of mass in birds lowered gradually as their torpor process took long hours. During the thermoregulation, the birds were also recorded to have fed on their stored fat to keep their bodies on contrasting the external temperatures and dodge from freezing. A hummingbird species called black metal tail was the group with a body temperature closest to the environment's, scaling on just 3.3 degrees Celsius. This study was published in the journal Biology Letters, titled "Extreme and variable torpor among high-elevation Andean hummingbird species."

Co-author Henneth Welch said that their study on hummingbirds aims to determine the reaction of hummingbirds and other migratory birds that do not undergo torpor to the temperature and food availability under the changing climate of the planet. The study was published in the journal Ecology, Evolutionary Biology, titled "Reversal of the adipostat control of torpor during migration in hummingbirds."

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