Every spring and fall, something extraordinary happens in Utah’s skies. Millions of birds funnel into Great Salt Lake from places as distant as the Arctic tundra and the southern tip of South America. For these birds, the lake is a vital refueling stop on one of the longest journeys known to the animal kingdom. Each year, more than 12 million birds and over 330 species rely on Great Salt Lake. But, as the lake shrinks due to upstream water diversions, the food and habitat they depend on are steadily disappearing.
Why It Matters
Think of Great Salt Lake as a single stop in a chain of rest stops that stretches across the entire Great Basin. Birds that travel between South America and the Arctic depend on a network of freshwater and saline lakes to rest and refuel along the way. This network supports roughly 99% of North America’s eared grebes, 90% of Wilson’s phalaropes, and 50% American avocets. More than half of the region’s saline lakes have already reduced in size by 50% to 95% over the past 150 years, and shorebird populations across the area have decreased 70% since the 1970s.
This matters because, unlike freshwater lakes, the specialized habitats Great Salt Lake provides cannot easily be replaced. Great Salt Lake is by far the largest and most popular saline lake for birds in the West. If the lake follows the same path as Owens Lake, which was drained dry decades ago by the Los Angeles Aqueduct, migratory birds won’t have a place to rest. John Luft, the Great Salt Lake ecosystems program manager for the Utah Division of Wildlife Resources, compared this dilemma to driving from Salt Lake City to Wendover expecting to stop and refuel at the only gas station along the way, only to find it nearly empty.
The Food Web Crash
Birds don’t come to Great Salt Lake for the scenery. They come for the food. The lake’s entire avian food web relies on two small but mighty creatures: brine shrimp and brine flies. Eared grebes can eat up to 30,000 brine shrimp a day and effectively double their body weight at the lake before flying nonstop to the Salton Sea or the Gulf of California. Wilson’s phalaropes do the same and fly all the way to South America.
This food web depends on water. As lake levels decrease, salinity rises, and at a certain threshold, algae can no longer support healthy populations of brine shrimp and flies. The Utah DWR noted that brine shrimp typically require salinity around 18% or lower to successfully hatch each spring. Microbialite fields, similar to coral reefs, support brine flies and are breaking apart under wave action as water levels drop. In the lake’s north arm, microbialites are now encased in salt and have made that part of the lake essentially unusable as a food source for birds.
Without enough food, birds can’t replenish their fat reserves that they burn during their long migration. This likely won’t cause birds to die at the lake itself; rather, birds that can’t find food there will typically just keep flying. This means birds will be exhausted and underfed and will have to continue their migratory routes in worse conditions and will be more susceptible to disease, predation, and starvation somewhere else.
More Birds and Less Food
Bird counts at Great Salt Lake haven’t uniformly dropped. For some species, they’ve gone up. The Utah DWR explained why this isn’t actually reassuring. As smaller saline lakes in the Great Basin dry up entirely, displaced birds are forced to fly to Great Salt Lake because it’s one of the last saline lakes left standing. For example, eared grebe counts have roughly tripled over the past decade because they have nowhere else to go.
More birds competing for a shrinking food supply means more competition and a higher risk of disease spreading through dense flocks. In fact, thousands of eared grebes have died from avian botulism and avian flu in recent years. Additionally, raptors such as great horned owls have also experienced disease and died after eating other sick birds.
What Can Be Done?
Unlike other saline lakes, Great Salt Lake hasn’t crossed an irreversible threshold; but, the window to avoid ecological collapse is closing. Utah has taken real steps, such as a $40 million trust to improve wetland habitat and a state-federal effort to map out a water strategy. Congress has also funded a USGS Saline Lakes Program to better monitor saline lakes and the wildlife that depends on them.
However, monitoring and small trusts don’t deliver water to the lake. The biggest tool Utah has is reducing the amount of water diverted before it reaches Great Salt Lake. This can be done through water leasing, water conservation in urban yards, and improved water policy. Any water that makes it to the lake can help improve habitat for millions of birds that have nowhere else to go.
