Why do birds migrate to the Great Salt Lake?

The Great Salt Lake in Utah is a major stopover point for migratory birds traveling along the Pacific and Central Flyways. Over 200 species of birds visit the Great Salt Lake each year, with millions of individual birds stopping to rest and feed during their long migrations. But why do so many birds go out of their way to visit this salty lake in the middle of the desert? There are several key reasons why birds are drawn to the Great Salt Lake during migration:

Abundant food sources

The Great Salt Lake provides plentiful food resources for migrating birds. The high salinity of the lake makes it inhospitable for fish, allowing brine shrimp and brine flies to thrive. These small invertebrates occur in densities of up to 6,000 per liter of water, providing an incredibly abundant food source for birds. Birds like phalaropes, avocets, stilts, and grebes rely heavily on brine shrimp and flies to fuel up for their onward journeys. The lake also supports extensive wetland habitats along its shores, offering seeds, aquatic plants, and insects for species like ducks, swans, and sandpipers.

Ideal stopover habitat

In addition to food, migratory birds require safe places to rest and roost during their migrations. The wetlands surrounding the Great Salt Lake provide ideal stopover habitat, with shallow, protected waters for wading and roosting. Islands in the lake offer refuge from predators and disturbance. The remote location means birds face relatively low pressure from human disturbance. The lake’s position along major migratory flyways also makes it a strategic stopping point for refueling. Birds traveling along the Pacific Flyway or Central Flyway can stop at the lake to take a break from their marathon flights.

Critical breeding grounds

Some migratory birds do more than just stop over at the Great Salt Lake – they come to nest and breed. The lake supports over 250 bird species annually, with approximately 150 species nesting around its shores. In particular, it provides vital breeding habitat for species like American avocets, black-necked stilts, snowy plovers, white-faced ibis, Caspian terns, and Forster’s terns. These species rely on the Great Salt Lake’s wetlands to raise their chicks, taking advantage of the abundant food resources. Up to two million waterbirds nest at the Great Salt Lake each year, taking advantage of this unique inland habitat.

Detailed Reasons Why Birds Migrate To the Great Salt Lake

Here is a more in-depth look at why birds are so reliant on the Great Salt Lake during migration:

Food abundance

As mentioned, the Great Salt Lake supports incredibly high densities of brine shrimp and brine flies that migrating birds prey upon. Salinity levels in the lake can exceed 20%, much saltier than ocean water. These hypersaline conditions inhibit predators like fish, allowing invertebrates like brine shrimp and flies to thrive without risk of predation. Brine shrimp densities in the Great Salt Lake can exceed 6,000 shrimp per liter during peak seasons. That’s over twice the density found in tropical seas! Brine flies occur in even higher concentrations, with up to 800,000 larvae per square meter of shoreline. This superabundant food provides the high-energy resources migrating birds require to fuel their long journeys. Species like phalaropes, grebes, terns, and sandpipers all feast on brine shrimp and flies at the lake.

Roosting and nesting sites

In addition to food, migrating birds require safe places to rest and roost during their travels. The Great Salt Lake provides habitat for roosting and nesting across its 750+ square miles of surface area. Islands like Hat, Gunnison, and Cub provide isolation from predators. Extensive wetlands along the eastern shores also give birds shallow, protected waters to roost. Marshes, mudflats, and beaches around the lake provide shelter. Birds can conserve their energy reserves by resting and roosting at the lake before resuming their strenuous migrations. For nesting birds, the Great Salt Lake wetlands offer ideal protected areas to rear chicks, with wet meadows, salt flats, and ponds suited to different species’ needs.

Strategic location

The Great Salt Lake lies directly along the Pacific and Central migratory flyways, two major bird migration corridors in North America. Each spring and fall, birds traveling these routes can conveniently stop to rest and refuel at the lake’s habitats. Species migrating along the coast or through the interior of the continent all pass near the Great Salt Lake’s position in Utah. The lake’s remote desert location means fewer urban hazards and human disturbances for weary migrating birds. Its inland position also makes it a safe shelter from ocean storms. Birds times their migrations to take advantage of this strategically located stopover site along their routes.

Range of saline habitats

While extremely saline overall, the Great Salt Lake does contain some gradient of salinity levels ranging from freshwater inflows to hyper saline concentrations exceeding that of ocean water. This range of salinity across marshes, ponds, and open waters allows diverse bird species with different salt tolerances to find suitable habitat. Salt-loving species like Wilson’s phalaropes and American avocets frequent the hypersaline waters where food is most abundant. More freshwater-dependent birds like gadwalls and cinnamon teal can utilize the less saline wetlands and ponds. The diversity of salinities across the lake’s habitats support more species of migratory birds.

Lack of Competition

The harsh salinity excludes fish that would otherwise compete with birds for food resources and be predators. Fish are a dominant group in most aquatic ecosystems, but they cannot survive in the Great Salt Lake’s extremely salty waters. This allows birds to exploit the brine shrimp and flies without facing competition or predation pressure from fish. The invertebrates have thrived in the fish-free waters, providing an unlimited buffet for migrating shorebirds, seabirds, and waterfowl stopping through the region.

Threats Facing Birds at the Great Salt Lake

While it provides critical migratory bird habitat, the Great Salt Lake faces an array of environmental threats:

Water Diversions

The lake’s water levels are sensitive to diversions of its freshwater tributaries for urban and agricultural use. Upstream water diversions have caused the lake to drop to record low levels in recent decades. If less fresh water enters the lake, salinity levels can increase to extremes that reduce food supplies and habitat for birds. Maintaining adequate water inflows is crucial for the health of the lake ecosystem.

Pollution

Agricultural runoff, mercury from mining, and wastewater discharge into the lake all pose pollution threats. Excess nutrients and contamination can degrade water quality, impacting the lake’s brine shrimp and flies and accumulating in birds that eat them. Keeping pollution out of the lake’s tributaries is key.

Wetland Loss

Over half the Great Salt Lake’s historical wetlands have already been lost to diking, draining, and development. Further wetland losses around the lake’s shores would degrade roosting and nesting habitat for migratory birds. Protection of remaining wetlands from additional development is important.

Climate Change

Changing precipitation patterns, hotter temperatures, and lower streamflows associated with climate change may alter the lake’s hydrology and salinity in ways that affect brine shrimp populations and wetland habitats. Monitoring and research are needed to understand climate impacts.

Human Disturbance

Recreation, industry, and urban growth around the lake can disturb roosting and nesting birds. Managing human activities to minimize habitat disruptions will be an increasing challenge with population growth.

Unique Adaptations of Birds at the Great Salt Lake

To thrive in the Great Salt Lake’s extreme environment, birds have evolved fascinating physiological and behavioral adaptations:

Salt Excretion

Birds have specialized glands above their eyes that filter excess salt from the bloodstream and excrete it in a concentrated brine solution from their nostrils. This allows them to drink the hypersaline water and still maintain proper salt balances in the body.

Buoyancy Control

Diving birds increase their blood volume and reduce air in their feathers to control their buoyancy and dive more easily in the dense, salty waters. This allows birds like eared grebes to efficiently hunt brine shrimp in the lake.

Heat Tolerance

Desert-adapted birds have strategies like hyperventilating to shed excess body heat and light-colored plumage to reflect sunlight, allowing them to withstand the hot temperatures around the lake.

Nest Site Selection

Nesting birds choose sites with freshwater springs or vegetation that block the salty soil and dust that could irritate nestlings. Parent birds may soak food items in fresh water before feeding chicks.

Early Migration

Some birds anticipate optimal brine shrimp availability by migrating early to the lake in February and March, before peak food abundance in April-June. This ensures they are in position to take advantage of the bounty.

Research and Conservation Efforts

Many researchers and conservation groups are working to study and protect the Great Salt Lake’s habitats:

Monitoring Programs

Ongoing monitoring tracks water levels, salinity, brine shrimp populations, migratory bird numbers, and contaminants to assess the lake’s ecological health. This data informs management decisions.

Wetland Restoration

Partners like The Nature Conservancy are restoring drained wetlands to provide additional habitat for roosting and nesting birds around the lake.

Education

Programs aim to teach local communities and industries about protecting water quality and reducing disturbance to important lake habitats used by migratory birds.

Advocacy

Groups like Utah Rivers Council and National Audubon Society advocate for policies and water management practices that sustain adequate flows into the lake for birds and other wildlife.

Sanctuaries

Designated wildlife sanctuaries and shoreline reserves around the lake provide protected habitats free of human disturbance for migrating and nesting birds.

Conclusion

In summary, the Great Salt Lake’s abundant brine shrimp and fly populations offer migrating birds a reliable food source to refuel during their arduous journeys along the Pacific and Central flyways. Its islands and wetlands provide safe roosting and nesting sites for millions of birds each year. Diverse saline habitats across the lake support shorebirds, waterfowl, and seabirds with a range of salt tolerances. Unique adaptations allow birds to thrive in the harsh desert environment. Continued research and conservation efforts are needed to safeguard the lake against threats from water diversions, pollution, climate change, and human disturbance. When properly protected, this unique lake ecosystem will continue fulfilling its critical role as a migratory bird oasis.