A sandpiper weighing less than two ounces has just flown 2,000 miles without stopping. It drops into a shallow marsh at the edge of a field, legs barely steadying beneath it.

Everything depends on what it finds here — invertebrates in the mud, shallow water, and cover from predators.

If the marsh was drained for development last season, the sandpiper has nowhere to land.

Migration Is the Most Dangerous Thing a Bird Does

Birds experience their highest mortality rates during migration. The journey between winter and summer ranges is not one continuous flight — it happens in stages, over weeks, with stops along the way where birds rest, recover, and refuel. These stopover sites are not optional extras. They're survival infrastructure.

Wetlands are the most important of these sites. They provide the specific combination of shallow water, exposed mudflats, invertebrate food sources, and protective cover that migrating birds need to rebuild energy reserves before the next leg of their journey. Without them, birds arrive at breeding grounds depleted, or don't arrive at all.

Different Birds, Different Needs

The specifics matter. Dabbling ducks like Mallards, Teal, and American Wigeon rely on shallow emergent marshes less than 1.6 feet deep with adjacent mudflat areas. Increase the depth slightly and the plant community shifts — diving ducks, geese, and swans favor that zone instead. Wild rice stands at the right depth serve as stopover habitat for Wood Ducks, Canvasback, and Redhead.

Shorebirds — sandpipers, plovers, dowitchers — need different conditions again: water only one to eight inches deep, sparsely vegetated mudflat areas, clear sightlines to spot approaching predators like falcons. They use natural mudflats but also seasonally flooded agricultural fields when those conditions line up.

Songbirds migrate too, and they're drawn to structurally dense shrub-dominated wetlands — alder thickets and shrub-carr — more than other forest types. Studies in northern Wisconsin found that these wooded wetlands had greater species diversity and higher numbers of migrants than adjacent upland forests during the same migration window.

What Happens When Wetlands Disappear

Migration is a chain. Each link depends on the next. When a key stopover wetland is drained, developed, or degraded, the birds that depended on it don't simply find another spot — they arrive at the next site underweight and energy-depleted, with less capacity to survive. Population declines accumulate across generations, slowly and without an obvious single cause.

Over 600 migratory bird species depend on wetlands as stopover sites across North America alone. The loss of wetland area — through drainage, development, and altered hydrology — breaks the chain at multiple points simultaneously.

What Protection Looks Like

Protecting individual wetlands matters, but protecting connected networks matters more. A chain of wetland stopover sites along a flyway functions as a whole system — each site supporting the next. Large marshes over 50 acres within wetland complexes that include sedge meadows, lowland hardwoods, and open water provide the highest conservation value for the most species.

The birds don't know which side of a property line they're on. They just know whether the mud is there when they land.