Loons, iconic aquatic birds, are recognized for their distinctive calls and remarkable diving capabilities. These birds spend most of their lives on water, where their diet and hunting strategies are closely tied to their aquatic environment.
Main Aquatic Prey
Fish constitute approximately 80% of a loon’s diet. They primarily target smaller, non-spiny species. Common freshwater fish include yellow perch, minnows, suckers, sunfish, and small trout. In saltwater environments, such as during winter, loons eat fish like flounder and herring.
Loons prefer fish weighing between 10 and 70 grams, but can swallow larger fish up to 300 grams. Most prey is swallowed underwater immediately after capture, but larger items may be brought to the surface first to be subdued.
Supplemental Food Sources
While fish are the primary food source, loons also consume other aquatic organisms opportunistically. These include crustaceans like crayfish, aquatic insects such as dragonfly larvae and caddisflies, mollusks, leeches, and frogs.
Loons also consume small amounts of aquatic plant matter. They ingest small pebbles, which aid digestion by grinding down hard parts of their prey within their gizzard.
Expert Hunters
Loons are adapted for underwater hunting, with strong diving abilities. They can dive to depths of 60 meters, with some recorded dives reaching up to 70 meters. Their powerful legs, positioned far back on their bodies, act as efficient propellers, driving them at high speeds through the water. This rearward leg placement, however, makes them clumsy on land.
Their streamlined bodies reduce drag, allowing for agile pursuit of prey. Loons possess sharp, pointed bills, which they use to stab or snap up fish. Excellent underwater vision helps them locate prey. They can hold their breath for up to five minutes during dives.
Preferred Foraging Habitats
Loons forage in clear freshwater lakes and ponds with abundant fish populations. Water clarity is important for these visual hunters, as it allows them to spot and pursue prey. Lakes with sufficient depth are also important for deep diving.
During the breeding season, loons choose large lakes that offer space for flight and a consistent small fish supply. Lakes featuring islands and coves are favored for cover and security. During migration and winter, loons may also forage in coastal marine waters and large, ice-free inland reservoirs.
Environmental Influences on Diet
Loon diet and foraging success are influenced by environmental conditions and human activities. Water quality degradation from pollution and runoff can reduce water clarity, making it difficult for loons to find prey. For example, heavy rainfall can introduce dissolved organic matter, nutrients, and other materials into lakes, decreasing visibility. This reduced clarity impacts their ability to feed.
Climate change contributes to these issues, with warmer, rainier summers leading to more turbid waters and potentially altered fish habitats. Human disturbances, such as excessive boating and shoreline development, can also disrupt loon foraging areas by eroding shorelines and stirring up sediment. Lead poisoning from ingested fishing tackle and entanglement in fishing lines threaten loons.