An intriguing study recently made headlines with its findings that a certain gene loss in hummingbirds enhances their efficiency at breaking down sugar for energy. As fascinating members of the avian kingdom, hummingbirds are renowned for their seemingly effortless hovering flight – achieved by burning sugar in their flight muscles at exceptionally fast rates.
Understanding the Hummingbird
Native to the American continent, approximately 350 species of hummingbirds can be found, each more iridescent than the last. These small, lightweight birds, measuring barely 5cm long and weighing a mere 2 grams, draw comparisons with India’s sunbird species. The Aztecs historically referred to them as Huitzilin or ‘A ray of sun’.
Honouring their descriptive name, the signature ‘Hum’ of the hummingbird is created by wing beats at an astounding rate of up to 50 times per second. In addition to these impressive wing speeds, hummingbirds possess remarkable maneuverability. They can hover majestically to sip nectar from tubular flowers such as Lantana and rhododendron, and are even able to fly backward.
When it comes to metabolism, hummingbirds top the charts among vertebrates for the highest metabolic rate relative to body mass. Nectar serves as their primary source of energy, thanks to their digestive system’s rapid sugar uptake. This unique metabolic feature allows them to utilize energy from nectar ingested just moments ago.
Mimicry and Dance: Behaviours of the Hummingbird
Like parrots and songbirds, hummingbirds have shown capability in vocal mimicry. They also display rhythmic movements correlating with auditory sensations, adding a dance-like aspect to their behaviours.
The Indian Sunbird: A Lookalike Cousin
Indian Sunbirds, members of the Nectariniidae family, bear many similarities to hummingbirds despite being unrelated. The result of convergent evolution, these slightly larger birds can also hover temporarily and are attracted to bright, tubular flowers. As critical pollinators of the ‘Flame of the Forest’, sunbirds play a crucial role in their ecosystems. Given the high-energy demands of hovering, they adopt a perching tactic when feeding unlike hummingbirds. Their habitats span across tropical forests, inland wetlands, savannas, and scrubland in Africa, southern Asia, the Middle East, and northern Australia.
Insights from Recent Genome Studies on Hummingbirds
Genome studies on hummingbirds have recently unveiled a significant evolutionary change: the loss of the gene (FBP2) responsible for an enzyme crucial to gluconeogenesis coincided with the appearance of their hovering flight. Unlike in humans, where intense exercise can cause a spike in blood glucose levels due to gluconeogenesis, hummingbirds feature a unique metabolism that allows them to efficiently use energy from nectar. With this new understanding, we could unlock new insights into energy metabolism and its possible applications for human therapies.
Note: Gluconeogenesis refers to the process which converts non-carbohydrate substrates (such as lactate, amino acids, and glycerol) into glucose.
