Understanding Prairie Saline Lakes: A Quiet Guide for Birdwatchers

Prairie saline lakes are shallow lakes and wetlands on the northern Great Plains that become salty because water flows in but has no outlet. It leaves mainly through evaporation, and the dissolved minerals stay behind. Fish are scarce or absent in the saltier lakes, so small invertebrates such as brine shrimp, brine flies and midges can become very abundant. That food draws large numbers of shorebirds, waterfowl, grebes and gulls, especially during migration. For a birdwatcher, a saline lake is a place to read the shoreline, the water level and the season, and then wait patiently for the birds that follow them.

What are prairie saline lakes?

A prairie saline lake is a body of water whose dissolved salt content is noticeably higher than that of ordinary fresh water. Most lie within the glaciated prairies of southern Alberta, Saskatchewan and Manitoba and the northern plains of the United States, such as North Dakota and Montana. They range from small seasonal sloughs to large basins several kilometres across. Many are only a metre or two deep, or less.

Their saltiness comes from geography rather than from the sea. Each lake sits in a closed drainage basin, also called an endorheic basin. This is a low area where water collects from snowmelt, rain and groundwater but has no stream to carry it away. As the summer sun and steady prairie wind evaporate the water, the minerals it carried are left behind and become more concentrated year after year. Many Canadian prairie saline lakes are dominated by sulphate salts, such as sodium sulphate and magnesium sulphate, rather than the sodium chloride of seawater. That is one reason their shores can look chalky white instead of glittering like table salt.

How is salinity measured and described?

Salinity is the amount of dissolved salt in water, usually given in grams per litre (g/L) or parts per thousand (ppt), which are roughly equivalent. For comparison, seawater is about 35 g/L. Limnologists, the scientists who study inland waters, often group saline lakes into broad classes like these:

Category	Approximate salinity	What a birdwatcher might notice
Fresh	Below 0.5 g/L	Lush cattails and bulrushes, frogs, fish-eating birds such as grebes and terns
Subsaline	0.5–3 g/L	Still fairly lush margins, with plenty of dabbling ducks and diving ducks
Hyposaline	3–20 g/L	Thinner emergent plants, salt-tolerant grasses on the shore, abundant midges and amphipods
Mesosaline	20–50 g/L	Bare or crusted shorelines, few or no fish, brine flies and sometimes brine shrimp
Hypersaline	Above 50 g/L	Wide white flats and very simple food webs, sometimes dense brine shrimp

The same lake can move between categories. In a wet spring, fresh meltwater dilutes the salt. In a dry late summer, the shrinking water grows saltier. A lake's salinity therefore changes with the season, and over several years it can change a great deal.

What are alkali flats?

Alkali flats are the level, often white or grey-crusted expanses of mud and mineral deposits that lie around or within saline basins. The word alkali refers to the mineral salts that give the soil a high pH and a bitter crust. When water levels drop, alkali flats widen. Some shallow basins dry out completely and become nothing but flat for part of the year. For birds, the wet edge of an alkali flat is often the richest feeding zone, and the open, dry crust provides nesting ground for a few specialists.

Why do saline lake birds gather on prairie lakes?

Saline lake birds gather on prairie saline lakes mainly for food, open space and safety. Three conditions work together:

• Abundant aquatic invertebrates. Salt-tolerant insects and crustaceans, including midge larvae, brine fly larvae, water boatmen, amphipods (small shrimp-like crustaceans sometimes called scuds) and, in the saltiest lakes, brine shrimp, can reach high densities in summer. They are an energy-rich food for birds that must build fat reserves before long flights.
• Few competing fish. Most fish cannot tolerate high salinity. Where fish are absent, birds do not have to share the invertebrates with them.
• Open, shallow shorelines. Gently sloping, unvegetated margins let shorebirds probe and pick at the water's edge and let resting flocks see approaching predators from far away.

Because these lakes are scattered across a dry landscape, they act as migratory stopovers: places where migrating birds pause for days or weeks to rest and refuel between wintering and breeding grounds. Some prairie saline lakes host shorebird numbers large enough to be recognized as important sites within international shorebird conservation networks.

Which salt lake birds can you expect to see?

Salt lake birds on the prairies fall into a few familiar groups, each using a different part of the lake. Learning which group uses which zone makes a large, bright lake much easier to scan.

Group	Typical examples	Where to look	What to notice
Shorebirds	American Avocet, Wilson's Phalarope, Red-necked Phalarope, Sanderling, Baird's Sandpiper, Stilt Sandpiper, Piping Plover	Wet margins, shallow water, mudflats	Avocets sweep their upturned bills side to side. Phalaropes spin on the water to stir up prey. Small sandpipers run and pick along the edge.
Waterfowl	Northern Shoveler, Gadwall, Northern Pintail, Redhead, Lesser Scaup, Ruddy Duck	Open water and sheltered bays, especially in less salty basins	Shovelers filter the surface with broad bills. Diving ducks prefer deeper, slightly fresher lakes.
Grebes	Eared Grebe, Horned Grebe	Open water	Eared Grebes often gather in flocks on salty lakes and feed heavily on invertebrates.
Gulls and pelicans	Franklin's Gull, Ring-billed Gull, California Gull, American White Pelican	Islands, bars and open water	Gulls hawk flying insects over the water. Pelicans often loaf on bare points and islands.

The Piping Plover deserves special mention. This small, sand-coloured shorebird nests on bare gravel and alkali shorelines of some prairie saline lakes and is listed as threatened or endangered in parts of its range. If you see one, enjoy it from a distance and never approach a beach where it may be nesting.

How do seasonal water levels change prairie saline lakes?

Seasonal water levels shape almost everything a birdwatcher sees on a prairie saline lake. They decide how much shoreline is exposed, how salty the water is and which birds find it useful. The general pattern runs like this:

Spring

Snowmelt and spring rain raise water levels and dilute the salt. Ice often lingers on the lakes into April, and salty water can stay open a little longer in autumn because dissolved salt lowers its freezing point. Waterfowl arrive as soon as open water appears. Northbound shorebirds pass through in the greatest numbers from late April through May, often in waves that follow warm southerly winds.

Summer

Evaporation draws the water down through June, July and August, widening the mudflats and alkali flats. Avocets, Wilson's Phalaropes and Piping Plovers nest along suitable shores. Invertebrate numbers build as the water warms. By midsummer, the first southbound adult shorebirds may already be returning, sometimes in early July.

Late summer and autumn

Water is usually at its lowest and saltiest in late summer, and the exposed margins can be broad. This is often the best time for shorebird variety, as adults and then juveniles move south through August and September. Phalaropes and grebes may gather in large flocks to feed. Ducks and geese build in September and October, and the salt-tolerant vegetation around the shore turns rusty red and gold.

Winter

Most prairie saline lakes freeze. Bird activity shifts to the surrounding grasslands, and the basins rest until the next thaw.

Wet years and dry years

Beyond the annual cycle, prairie saline lakes rise and fall over runs of wet and dry years. A basin that was a wide lake one decade may be a cracked white flat the next. A lake that is poor for shorebirds when it is brim-full may become excellent once falling water exposes its shallows. Revisiting the same lake over several years is one of the most rewarding ways to understand it.

What can you notice on a saline lake shoreline?

A saline lake shoreline usually forms visible bands, or zones, from the water outward. Each zone tells you something about the lake and the birds likely to use it.

1. Open water. Look for floating grebes, ducks and spinning phalaropes. A pinkish or reddish tint in very salty water can come from brine shrimp or salt-loving microorganisms.
2. The wet edge. A strip of saturated mud and very shallow water is where most shorebirds feed. Clouds of brine flies or midges here are a good sign of food.
3. Mudflat and alkali flat. Bare mud or white crust is used for resting flocks and, by a few species, for nesting. Note how wide this band is. A widening band means the water is falling.
4. Salt-tolerant vegetation. A ring of low, tough plants lies between the flat and the grassland. Its plants show how salty the soil is.
5. Upland grassland. The surrounding prairie hosts sparrows, larks and raptors that hunt over the basin.

How do salt-tolerant plants help you read a lake?

Salt-tolerant vegetation, also called halophytic vegetation, consists of plants adapted to soils where most prairie plants cannot grow. Common examples around prairie saline lakes include red samphire (also called glasswort), a fleshy, jointed plant that turns vivid red in late summer and autumn; Nuttall's alkali grass; saltgrass; sea-blite; and foxtail barley, whose silky purplish heads mark slightly less salty, often disturbed ground. A broad belt of red samphire hugging the flats usually signals strongly saline soil. Where the shore quickly gives way to cattails and bulrushes, the lake is likely fresher, and diving ducks become more likely than large shorebird flocks.

How should you prepare for a visit to prairie saline lakes?

Preparing for a prairie saline lake means planning for openness: strong sun, steady wind, few landmarks and ground that is softer than it looks. These steps help a visit go smoothly:

1. Check access first. Many prairie lakes are bordered by private land or community pasture. Use public viewpoints, road allowances and designated areas, and ask permission before crossing fields.
2. Bring a spotting scope. Birds on wide flats are often far away. A scope on a sturdy tripod turns distant specks into identifiable avocets and sandpipers.
3. Plan around the light. Glare off water and white crust can be intense. Morning or evening light, with the sun behind you, makes colours easier to see.
4. Dress for wind and sun. Bring a brimmed hat, sunglasses, sunscreen, layers and plenty of drinking water. Shade is rare.
5. Respect the mud. A dry-looking alkali crust can cover deep, sticky mud. Do not drive onto flats, and test the ground carefully on foot. Often it is better to stay on firm ground at the edge.
6. Protect your eyes and gear. Wind-blown alkaline dust can sting the eyes and coat optics. A lens cloth and a bag for your gear are useful.
7. Expect insects. Fresher margins and sheltered evenings can bring mosquitoes. Repellent and a light long-sleeved layer help.

What should go into your field notes?

Good field notes for prairie saline lakes record both the birds and the conditions, because conditions explain why birds were present. A simple, repeatable entry might include:

• Date, time, weather, wind direction and approximate temperature
• Water level compared with earlier visits, such as high, normal or low, or a rough estimate of how wide the exposed shoreline is
• Shoreline appearance: wet mud, white crust, colour of the water, colour of the samphire
• Species seen, with counts or careful estimates and the zone each was using
• Behaviour: feeding, resting, courtship, alarm calls, flocks arriving or leaving
• Visible food: brine fly swarms, midges, floating insect husks, shrimp
• Disturbance, such as vehicles, dogs or raptors, and how the birds reacted

Over a season, these notes begin to tell a story. You may see when falling water opened the flats, when the first southbound sandpipers arrived and which bay the phalaropes favoured. Sharing careful counts with local or regional bird-monitoring programs can also help others understand how these lakes are changing.

How can you watch saline lake birds with care?

Watching saline lake birds respectfully means letting them feed and rest without interruption. Migrating shorebirds may need every hour of feeding to build reserves for the next long flight, and each time a flock is flushed it spends energy it cannot easily spare.

• Stay well back from resting or feeding flocks. If birds stop feeding, raise their heads or start walking away, you are too close.
• Use your vehicle as a blind where roads allow. Birds often tolerate a stopped car better than a person on foot.
• Avoid nesting shorelines from late spring through midsummer. Eggs and chicks of plovers and avocets are camouflaged and easily stepped on. Respect any posted closures.
• Keep dogs leashed or at home near shorelines.
• Leave plants, crusts and mud undisturbed. Tire ruts in alkali flats can last for years.
• Take everything out with you, including fishing line and food scraps that attract predators.

Bringing it to your next outing

On your next visit to a prairie saline lake, start by standing still for a few minutes. Notice how far the water has pulled back, how white the flats are and whether the samphire has started to redden. Then scan zone by zone, from the open water to the wet edge to the flats, and let the birds show you where the food is. Write down what you see, and come back in a few weeks. These lakes change with every season and every dry or wet year. A patient observer who returns often will come to know them as quiet, shifting places where the salt, the water and the birds are closely linked.