What bird sounds like a dinosaur?

A harsh, croaking kronk from a pond, river or marsh, especially from a big bird lifting off on slow wingbeats, is most likely a Great Blue Heron, whose call BirdNote compares to a pterodactyl. A loud, rolling, rattling trumpet from a flock overhead or a wet field is a Sandhill Crane, a sound one Montana naturalist found so ancient it made him think of dinosaurs. A single loud, barking kwok at dusk or after dark is often a Black-crowned Night-Heron.

Listen: the Great Blue Heron

BirdNote opens its episode on this bird with the call, written kronk-kronk, and asks whether it brings an ancient pterodactyl to mind. It is a fair question. The croak is harsh and low, nothing like a songbird, and it comes from the largest heron in North America, a tall blue-gray bird with a long neck and long legs that looks a little prehistoric even when silent.

Most of the time it is silent. A Great Blue Heron stands motionless in knee-deep water with its neck drawn back, waiting for a fish, then spears it with a sudden jab and swallows it whole. It saves the croak for when it is startled and flies off to safer water, so the usual way to hear it is to walk around a bend in a river and flush one you never saw. Look along riverbanks, lake shores, wet meadows, docks and even fields. They nest high in trees, often in colonies, and they fly with slow wingbeats that suit the sound.

The Sandhill Crane: the rattling trumpet

If the sound was less a croak and more a loud, rolling trumpet, think crane. Audubon writes the Sandhill Crane's call as a loud, rattling kar-r-r-r-o-o-o. Drew Lefebvre, writing for Montana Public Radio's Field Notes, describes his first crane call as something like an elephant crossed with machinery and a creaky hinge, so old-sounding that he thought of dinosaurs. Aldo Leopold called the crane the trumpet in the orchestra of evolution.

The prehistoric feeling has some basis. The oldest definite Sandhill Crane fossil, found in coastal Florida, is about 2.5 million years old, and the wider group cranes belong to goes back about 60 million years in the fossil record.

Sandhill Cranes nest around marshes and bogs, in open grassland or ringed by forest, and in migration and winter they spread into open prairie, farm fields and river valleys. Their numbers peak at migration stopovers on the Great Plains, and birds in Florida and Mississippi stay all year. In courtship they dance, spreading their wings and leaping into the air while calling; Lefebvre watched a pair do exactly that in a Montana meadow at dusk. Adults are gray with a red patch on the head and stand about three to four feet tall.

The croak in the dark: Black-crowned Night-Heron

If the noise came after dark, this stocky heron is a strong candidate. Its call is a loud, barking kwok! or quawk!, often heard at night or at dusk, and birds flying over at night give a shorter wok. Night-herons sit hunched in trees near water by day, fly out to feed at dusk and hunt mostly from late evening through the night, so they are calling right when your imagination is at its most helpful. In their nesting colonies they add a whole range of croaks, barks and other harsh calls. Look for them around marshes, rivers, ponds, tidal flats, canals and mangroves. Adults have a black cap and back and gray wings; young birds are brown with white spots.

How to tell which one you heard

• A deep croak or two as a big bird lifts off the water: Great Blue Heron, often just after you surprised it.
• A long, rolling, rattling trumpet, often from many birds: Sandhill Cranes, overhead or in open fields and marshes, especially at migration stopovers and during courtship dances.
• One sharp bark at dusk or overhead in the dark: Black-crowned Night-Heron.
• If you can see it: the heron is blue-gray with a long neck and a sharp bill; the crane is gray with a red cap, a shorter bill and a bushy tuft of feathers over the rump; the night-heron is stocky with a black cap.

If it keeps calling, hold up your phone. Warble can listen for the croak or the trumpet and name the bird, though a single far-off croak in the dark may leave it unsure.

Questions people ask

Warble is a game, not a field guide. Facts about birds on this page come from the sources above.