Loons are aquatic birds, recognized for their striking appearance and haunting calls across northern lakes. These birds spend most of their lives on water, establishing a reputation as exceptional divers. Their presence often symbolizes the wilderness of the northern hemisphere, prompting curiosity about their mysterious lives beneath the surface. Loons are built for aquatic existence, showcasing underwater abilities that allow them to thrive in watery habitats.
The Astonishing Dive Duration
Loons possess an impressive capacity for holding their breath, typically submerging for one to three minutes. Common Loons routinely stay underwater for 40 to 45 seconds during an average dive. However, under certain conditions, such as escaping predators or during intensive hunting, they can extend their breath-holding to five minutes. Dives lasting up to eight minutes have been noted, though longer durations like ten minutes are unverified. Loons can also reach significant depths, with common loons recorded diving up to 60 to 70 meters (200 to 230 feet) in search of prey.
How Loons Achieve Such Feats
Loons exhibit a suite of unique physiological and anatomical adaptations that facilitate their prolonged underwater excursions. Unlike most birds with hollow bones to aid flight, loons possess solid bones, which reduces their buoyancy and helps them submerge. They can further decrease buoyancy by compressing air from their lungs and feathers, sinking like a submarine to avoid danger. Their bodies are streamlined, resembling a torpedo shape, which minimizes drag and conserves energy during powerful underwater propulsion.
The muscles and blood of diving birds, including loons, contain high concentrations of oxygen-storing proteins like myoglobin and hemoglobin, allowing them to carry more oxygen into their tissues. During a dive, loons regulate their heart rate, a physiological response known as bradycardia, which conserves oxygen by reducing consumption. Blood flow is strategically redirected away from non-essential organs to prioritize oxygen delivery to the brain and heart. Their powerful, webbed feet, positioned far back on their bodies, act as efficient propellers, enabling agile and rapid movements through the water.
What Loons Do Underwater
The extensive dives undertaken by loons primarily serve the purpose of hunting and foraging. They are visual predators, relying on clear water to locate their prey, which predominantly consists of fish such as perch, minnows, trout, and smelt. Loons use their strong, pointed bills to spear or grab their catches, often consuming smaller prey underwater. Larger fish may be brought to the surface to be subdued before being swallowed whole.
Beyond fish, their diet includes various aquatic invertebrates like crayfish, shrimp, mollusks, and insects. Loons also utilize their diving prowess as a defense mechanism, submerging to escape aerial predators like eagles or other surface threats. Their ability to move swiftly and silently underwater allows them to evade danger. While less common, loons may also use underwater swimming for short-distance travel or navigation.