The whooping crane is one of the tallest birds in North America and one of the rarest cranes in the world. Their diet consists primarily of blue crabs, clams, frogs, minnows, rodents, small birds, and berries. Whooping cranes are carnivorous and omnivorous birds that forage in wetlands.
Diet
Blue Crabs
Blue crabs make up the majority of a whooping crane’s diet during the winter months in coastal marshes. Blue crabs are abundant along the Gulf Coast where whooping cranes overwinter. An adult whooping crane requires around 400–500 blue crabs per day to meet its dietary needs. The birds wade through shallow water feeling for crabs with their feet. Once caught, the crane will shake, stomp, or stab the crab to break its shell before consuming it.
Clams
Clams are another important food source for whooping cranes in their wintering grounds. They use their long beaks to dig in the mudflats and extract clams buried a few inches below the surface. Clams provide protein, carbohydrates, and lipids which give cranes energy. Consuming clams helps supplement blue crabs in the whooping crane diet.
Frogs
Whooping cranes will opportunistically feed on frogs when the abundance of blue crabs and clams is lower. Most frogs are consumed during the spring and fall migrations when the cranes stop to rest and forage in wetlands. Capturing frogs requires speed and precision to grasp them before they jump away.
Minnows
Aquatic minnows are sometimes eaten by whooping cranes during migration or in summer nesting areas. These small fish are swallowed whole by the birds as they wade through shallow wetlands. Minnows provide an important source of protein for whooping cranes.
Rodents
Small rodents like mice, voles, rats, and muskrats may supplement the whooping crane diet occasionally. They use their powerful beaks to stab and kill rodents in wetland areas. Consuming rodents gives them added protein.
Birds
Whooping cranes have been observed preying on the young of other bird species that nest near their summer grounds. Examples include ducklings, goslings, and baby coots which are still flightless and vulnerable to predation. While not a primary food source, birds can provide extra nutrition for growing whooper chicks.
Berries
During summer nesting, whooping cranes will consume certain berries that grow near their wetland habitat. Berries supply important vitamins and carbohydrates. Some types eaten include blueberries, cranberries, currants, and grapes. Berries complement their diet of minnows, frogs, and rodents during the summer.
Foraging Habits
Whooping cranes employ various foraging techniques to capture prey depending on the food source. To find blue crabs, they will wade slowly through marshes probing their feet to feel for crabs hidden in vegetation or mud. For clams, the birds walk slowly and repeatedly insert their beak into the sediment to grab buried clams. For minnows, frogs, and rodents, the cranes stalk through shallow water before employing a rapid strike to grab prey. They may also dig in mud or turn over debris to uncover hiding prey.
Habitats
Whooping cranes forage in a variety of wetland habitats along their migratory route and summer nesting grounds. In winter, they feed almost exclusively in open saltwater marshes and lagoons along the Texas Gulf Coast. On migration and in summer, they stop to feed in freshwater wetlands including marshes, wet meadows, riverine habitats, and pond edges. Nesting birds forage in nearby wetlands.
Diet Changes
Chicks
Very young whooping crane chicks are fed by their parents, who regurgitate food into the beak of the chick. Chicks are fed a diet of mostly aquatic invertebrates like crustaceans, mollusks, and insects which are high in protein. As chicks grow older, parents will provide more vertebrate prey like fish, frogs, and rodents. By the end of summer, chicks forage independently and are eating mostly adult foods.
Migration
Whooping cranes must shift their diet during migrations in the spring and fall. While wintering on Gulf Coast marshes, blue crabs and clams make up 90% of their food intake. But during migration they no longer have access to abundant coastal prey. Instead, migrating cranes stop to forage in inland wetlands. They feed opportunistically on prey like aquatic plants, frogs, fish, seeds, berries, and agricultural grains found in temporary stopover habitats.
Wintering Grounds
The primary shift in whooping crane diet occurs when they arrive on their Texas wintering grounds in late fall. While summer diets are varied, the primary winter foods become blue crabs and clams from coastal marshes up to 95% of the time. These high-calorie prey allow the cranes to build energy reserves for the return migration in spring.
Threats to Food Supply
Loss of wetland stopover habitat along migration routes threatens the food supply of whooping cranes. Draining and development of wetlands reduces areas for cranes to forage. Chemical pollution from agricultural and industrial sources can reduce populations of crabs, clams, fish, and other prey. Climate change may also shift wetland hydrology and ecology, impacting food availability.
Wetland Loss
It’s estimated over 50% of natural wetland habitat in North America has been lost to agriculture and development over the past 200 years. This shrinks the amount of migration stopover areas available for whooping cranes to find food. Conservation programs that protect and restore wetlands are crucial for ensuring food supply during migration.
Pollution
Toxic chemical pollution like pesticide runoff accumulates in wetlands and harms many aquatic species like crabs, clams, and fish that whooping cranes rely on. Pollution can reduce prey availability or make certain foods dangerous to consume. Protecting water quality in crane habitats is key.
Climate Change
Rising sea levels may inundate and alter coastal marshes used for wintering. Drought can shrink inland wetlands, concentrating and reducing prey. Such habitat changes associated with climate change may impact populations of important whooping crane prey species.
Unique Adaptations for Feeding
Whooping cranes have evolved several specialized adaptations to help them find and capture food efficiently:
Long Beak
The beak of a whooping crane averages 8-10 inches long. This lengthy beak is used like a pair of tongs to grasp prey. Their beak allows them to probe into mud or vegetation to catch buried clams, crabs, and other food.
Long Legs
Whooping cranes have legs that can measure up to 4 feet long. Their long legs allow them to stride through deeper water to chase prey like fish, frogs, and crabs in wetlands. Long legs also enable them to walk over obstacles while searching for food.
Good Eyesight
Whooping cranes have excellent long-distance vision. Their eyes can detect subtle movements of prey while foraging, even when flying high above a marsh. This sharp vision guides them to productive feeding areas.
| Prey Item | Habitat | Foraging Method |
|---|---|---|
| Blue crab | Coastal marshes | Feeling in mud with feet |
| Clams | Mudflats | Probing beak in sediment |
| Frogs | Freshwater wetlands | Rapid strike |
| Minnows | Shallow water | Bill sweeping |
| Rodents | Marsh edges | Stabbing with beak |
| Berries | Bushes near wetlands | Plucking with beak |
Conclusion
Whooping cranes are specialized to feed on a variety of wetland prey including crabs, clams, aquatic insects, frogs, fish, rodents, and berries. Their long beak and legs adapted over time to capture food in diverse wet habitats. Conservation efforts focused on protecting wetlands are crucial to preserve food resources for the endangered whooping crane along its migratory flyway across North America.
