Least Bittern

Ixobrychus exilis

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Photo of a least bittern male walking.
The least bittern is about as big as a pigeon. Most people see it only in flight, over cattail marshes.
Jim Rathert
Family

Ardeidae (herons) in the order Pelecaniformes

Description

The pigeon-sized least bittern is usually seen in flight over a cattail marsh. Adult males have buff and chestnut inner wing patches that contrast sharply with the black of the outer half of the wings. Females and immatures are brown instead of black. Song is a rapid, soft series of notes, coo-coo-coo-COO-COO-Coo-coo-coo, usually sung in the predawn and dusk. It is similar to the song of the black-billed cuckoo, and it might be mistaken for the chuckling sounds made by some frogs. Calls are varied, including a startled qua, and a series of keks that sound like those of rails.

Similar species: The American bittern is more than twice as large. The green heron is also much larger. Rails are also found in marshy areas, but their necks are short and they lack the sharp-contrasting wing patches described above.

Size

Length: 13 inches (tip of bill to tip of tail); about the size of a pigeon.

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Photo of a least bittern male in flight.
Least Bittern Male In Flight
Least bitterns have a distinctive wing pattern with buff and chestnut inner patches that contrast with a dark outer half.

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Photo of a least bittern female over nest and eggs, feathers ruffled.
Least Bittern Female and Nest
Note the distinctive wing coloration on this female least bittern as she ruffles her feathers.

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Photo of a least bittern hiding in cattails with bill-up pose.
Least Bittern
Least bitterns straddle plant stems just over the water. They freeze instantly, bill pointed up, if alarmed.

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Photo of two least bittern chicks, three days old.
Least Bittern Chicks
These three-day-old least bittern chicks were down-covered and fairly helpless upon hatching.

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Photo of a least bittern chick among cattails.
Least Bittern Chick
Immature least bitterns, like the young of animals everywhere, are particularly vulnerable to predators.

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Photo of a least bittern chick in bill-up posture.
Least Bittern Chick
Even at a very young age, least bittern chicks instinctively freeze in a “bill-up” posture when alarmed.

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Photo of a least bittern female over nest and eggs.
Least Bittern Female and Nest
In Missouri, the least bittern is present statewide as an uncommon, local summer resident — they breed here.

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Photo of a least bittern female over nest and eggs.
Least Bittern Female and Nest
Least bitterns build platform nests above the water in cattails and other emergent marsh plants.

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Photo of a least bittern male straddling cattails in a marsh.
Least Bittern Male
The least bittern sings a rapid, soft series of notes, "coo-coo-coo-COO-COO-Coo-coo-coo," in the predawn and dusk.

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Photo of a least bittern male among cattails in a marsh.
Least Bittern Male
It is likely that loss of wetlands is causing declines of least bitterns, but this secretive bird is difficult to study.

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Photo of a least bittern male with outstretched neck.
Least Bittern Male
The least bittern is pigeon-sized, with a longer neck than green herons and our rails. This is only apparent when the neck is outstretched, however.
Habitat and conservation

In summer, least bitterns frequent cattail and river bulrush marshes, shrub swamps, and sometimes cattail-choked farm ponds. Listen at dawn and dusk for their soft calls. They straddle plant stems just over the water, and they freeze instantly, bill pointed up, if alarmed. Seeing them requires patience, unless you canoe or wade through the wetlands where you heard them. Try waiting quietly, scanning above the cattails of a marsh; you may see one fly low and disappear into the vegetation again.

Foods

Like other herons, the least bittern forages around shallow water, stalking prey slowly, then quickly jabbing with its bill. Being a small heron, this species eats relatively small fish, plus insects and other small animals it can capture and swallow.

Distribution in Missouri

Statewide.

Status

Uncommon, local summer resident.

Life cycle

Platform nests are frequently constructed 1–4 feet above water in cattails, river bulrushes, nutsedges, and buttonbushes in deepwater sites. A roof of bent-over stems is often constructed over the nest. A clutch comprises 2–7 eggs. Upon hatching, the down-covered young are fairly helpless. Least bitterns arrive in Missouri in May and fly south by the beginning of October. Their year-round and winter range extends from southern Florida and Mexico clear down to southern Brazil.

Human connections

These secretive birds are difficult to study, and researchers do not have much information about population trends. It is likely that loss of wetlands has affected, and is affecting, this species, causing declines. For the sake of this and many other species, we must preserve wetland habitats!

Ecosystem connections

The behavior of camouflaged animals goes far to making their cryptic coloration successful. When a least bitterns freezes with outstretched neck and up-pointed bill, swaying gently with the breeze, it blends perfectly with the surrounding grasses. Many camouflaged insects have similar behaviors.