Loons primarily eat fish during the winter, relying on small to medium-sized species that remain available in their coastal and open water habitats. Their diet shifts from freshwater to more marine-based fish and invertebrates as they migrate to wintering grounds.
Background on Loons and Their Seasonal Habits
Common loons (Gavia immer) are well-known freshwater diving birds that breed in northern lakes during the summer. In colder months, they migrate to coastal marine environments, often along the Atlantic and Pacific coasts of North America. Their winter habitats differ significantly from breeding grounds, influencing the types of prey they can access and consume.
Unlike many birds that switch to seeds or plant matter in winter, loons remain primarily piscivorous year-round. Their specialized diving ability allows them to catch fish underwater, which remains their main food source even in winter.
Winter Diet: Fish and Marine Prey
During winter, loons feed mostly on fish species found in coastal waters where they spend the colder months. These fish tend to be small to medium in size, allowing loons to catch and swallow them underwater. Common prey includes:
- Herring
- Sand lance
- Smelt
- Small cod and pollock
- Mummichogs and other small forage fish
In addition to fish, loons occasionally consume marine invertebrates such as crustaceans and mollusks, although these are a smaller part of their diet compared to fish.
How Loons Catch Their Food in Winter
Loons are expert divers, capable of plunging up to 200 feet deep to pursue prey. Their streamlined bodies, powerful legs positioned far back on their bodies, and sharp, pointed bills make them efficient underwater hunters. In winter, when fish may be more dispersed or less abundant than in summer lakes, loons rely on their agility and keen eyesight to locate schooling fish near the surface or at moderate depths.
They often hunt in coastal bays, estuaries, and shallow marine waters where prey is accessible. Loons may also follow tidal movements to areas where fish concentrate, such as near underwater structures or kelp beds.
Winter Habitat and Its Impact on Diet
Loons’ winter habitats include saltwater bays, coastal inlets, and oceanic shorelines rather than the freshwater lakes they inhabit during breeding season. This change in environment means their prey base shifts accordingly:
- Temperate Atlantic and Pacific coasts: Loons eat marine fish like herring, sand lance, and smelt, which are abundant in cold coastal waters.
- Gulf of Mexico and southern US coasts: Loons may consume a variety of small fish adapted to warmer coastal waters.
These coastal areas provide relatively stable food supplies throughout winter, although loons still face challenges from weather and ice conditions.
Comparison of Summer and Winter Diets
During summer, loons primarily feed on freshwater fish such as perch, sunfish, trout, and bass found in northern lakes. In winter, their diet shifts to marine fish species, reflecting the change in habitat. Key differences include:
- Fish species: Freshwater versus marine species.
- Prey size: Winter fish tend to be smaller schooling fish compared to some larger freshwater fish caught in summer.
- Additional prey: Marine invertebrates may supplement the diet in winter, unlike summer when fish dominate almost exclusively.
This dietary flexibility allows loons to survive year-round in very different ecological niches.
Energy Needs and Feeding Behavior in Winter
Loons have high energy demands due to their active diving lifestyle and the cold environments they inhabit in winter. To meet these needs, they consume a significant amount of fish daily—often 20–30% of their body weight. Their feeding behavior adapts to winter conditions:
- Loons spend more time foraging during daylight hours when prey is easier to detect.
- They may feed in groups or alone, depending on prey availability.
- Loons rest and conserve energy between feeding bouts to cope with cold water temperatures.
Maintaining a fish-rich diet helps loons sustain their body heat and energy reserves during harsh winters.
Common Misconceptions About Loons’ Winter Diet
There are some misconceptions about what loons eat in winter, including:
- Loons eat plants or seeds in winter: Loons are almost exclusively carnivorous and do not eat plant matter.
- Loons stop feeding during migration: Loons continuously feed during migration and winter to maintain energy.
- Loons eat large fish year-round: While they can catch large fish, winter diets are dominated by smaller, schooling species more abundant in coastal waters.
Understanding these facts helps clarify loon ecology and the importance of preserving their winter habitats.
Frequently Asked Questions
Do loons eat the same fish in winter as in summer?
No, loons’ diets shift seasonally. In summer, they mostly eat freshwater fish like perch and trout, while in winter, they consume marine fish such as herring, sand lance, and smelt found in coastal waters.
Can loons survive on invertebrates during winter?
While loons may occasionally eat crustaceans or mollusks in winter, fish remain their primary and preferred food source. Invertebrates are more of a supplement than a staple.
How deep can loons dive to catch fish in winter?
Loons can dive up to 200 feet, though most winter feeding occurs in shallower coastal waters where prey is accessible. Their diving ability allows them to catch fish at various depths depending on conditions.
Do loons eat during migration or stop to rest?
Loons continue to feed during migration stops to replenish energy. They do not fast but instead rely on available fish in stopover habitats along their migratory routes.
Are loons’ winter feeding grounds threatened?
Yes, coastal development, pollution, and climate change can impact fish populations and water quality in wintering areas, potentially threatening loons’ food supply and survival.
How do loons find food in icy or cold winter waters?
Loons rely on their excellent eyesight and knowledge of local fish habitats. They often feed in open water areas free of ice, such as bays and estuaries, where fish remain accessible despite cold temperatures.
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