Species At Risk

Least Bittern

(Ixobrychus exilis)


Least Bittern
Least Bittern occurrences map


The Least Bittern is the smallest member of the heron family, reaching only 30 centimetres in length. It has brown and beige plumage with large chestnut patches on its wings. The crown and back of males is black, but is lighter in females and juveniles. The throat is light tan with whitish streaks and the belly is white. The legs and beak are bright yellow. Young birds look similar to females but the markings are not as bold.

Action we are taking:


In Ontario, the Least Bittern is mostly found south of the Canadian Shield, especially in the central and eastern part of the province. Small numbers also breed occasionally in northwest Ontario. This species has disappeared from much of its former range, especially in southwestern Ontario, where wetland loss has been most severe. In winter, Least Bitterns migrate to the southern United States, Mexico and Central America.


In Ontario, the Least Bittern is found in a variety of wetland habitats, but strongly prefers cattail marshes with a mix of open pools and channels. This bird builds its nest above the marsh water in stands of dense vegetation, hidden among the cattails. The nests are almost always built near open water, which is needed for foraging. This species eats mostly frogs, small fish, and aquatic insects.


The main threat to the Least Bittern is destruction of its wetland habitat. Shoreline development, wetland loss and drainage, and invasive species are all serious threats. This species does not generally tolerate human disturbance well (e.g. lighting from buildings, boat wakes in protected channels, loud noise etc.) and will leave marshes if human activity or habitat alteration becomes too great.


The Least Bittern is protected under Ontario’s Endangered Species Act. This species also receives protection under the federal Migratory Birds Convention Act.

What You Can Do to Help the Least Bittern

  • The Ministry of Natural Resources tracks species at risk such as the Least Bittern. You can use a handy online form to report your sightings to the Natural Heritage Information Centre. Photographs with specific locations or mapping coordinates are always helpful. nhic.mnr.gov.on.ca
  • Report any illegal activity related to plants and wildlife to 1-877-TIPS-MNR (847-7667).
  • Bird Studies Canada is working to advance the understanding, appreciation and conservation of wild birds and their habitat in Ontario and elsewhere. For more information on how you can help, visit: www.bsc-eoc.org.
  • Least Bitterns are quite shy and secretive, particularly during the breeding season (May to mid-July), and are easily scared away. Try to give them lots of room and distance.
  • Private land owners have a very important role to play in species recovery. If you find a Least Bittern on your property, you may be eligible for stewardship programs that support the protection and recovery of species at risk and their habitats.
  • Non-native plants that aggressively compete with Ontario’s plants for light, water and space are called “invasive species”. These invaders are considered a threat to the wetland habitat of Least Bittern. To learn what you can do to help combat invasive species, visit: www.ontarioinvasiveplants.ca.
  • Volunteer with your local nature club or provincial park to participate in surveys or stewardship work focused on species at risk.

Did you know?

The Least Bittern is more likely to be heard than seen in its dense marsh habitat. The typical call given by males is a hollow, quiet “coo-coo-coo”. When alarmed, they can give a harsh “kek-kek-kek” call. They are most vocal in early morning and evening, but could potentially call anytime during the day or night.

Did you know?

The scientific name for this heron, Ixobrychus, was incorrectly translated from Latin in 1828. It was intended to mean “reed boomer” - a reasonable name given the bird’s call, however if translated literally it really means “greedy eater of Mistletoe”!

Did you know?

Least Bitterns generally fly fairly low and as a result are sometimes killed by cars, where roads pass through wetlands. They are also susceptible to collisions with hydro lines, guy wires on towers, or hitting tall buildings that are illuminated at night (when they migrate).

Did you know?

There is a rare colour variation of this species that was once thought to be a separate species, the Cory’s Least Bittern. In the Cory’s, the rich beige areas are replaced by dark brown. While it was known from a number of areas within their range, this form was once regularly encountered in Ontario, especially in the marshes at Ashbridges Bay in east Toronto. Sadly, these marshes were destroyed decades ago, and this form is now rarely reported anywhere.

The Endangered Species Act

Contact your local ministry office

Often the best source of local information on species at risk is your nearest ministry office. Call with your questions or concerns.