This Week’s Endangered Species in Focus: Least Bittern (Ixobrychus exilis)

This Week’s Endangered Species in Focus:

Least Bittern (Ixobrychus exilis)

  Least Bittern2 Least Bittern1 Least Bittern3



Status: Threatened Provincially and Nationally



The Least Bittern is one of the smallest and lightest herons in the world (no larger than an American Robin). It typically grows to only 13 inches in length, has a wingspan of 17 inches and an average weight of just 3 ounces. The crown and back of the males is black, but is lighter in the females and juveniles. The Least Bittern feeds on small fish, frogs and insects.

Important Dates:


June 30, 2008: Species Listed at Risk

June 30, 2013: Species Granted Habitat Protection



  • Widely found in North, Central and South America;
  • In Canada, the Least Bittern live in southern Manitoba, Ontario, Quebec and New Brunswick, but primarily breeds in southern Ontario;
  • Marsh bird monitoring programs estimate the decline in Ontario of over 30% between 1999 and 2009; and
  • In winter, the Least Bittern hibernates in the Southern United States, Mexico and Central America




  • The Least Bittern begins its nesting period in the prime marsh habitat of early spring. The presence of dense vegetation is essential for nesting because the nests sit on platforms of stiff stems – females lay approximately four or five eggs and can produce up to twice per season;
  • In Ontario, the Least Bittern can be found in a variety of wetland habitats, but strongly prefers cattail marshes with a mix of open pools and channels;






  • The main threat to Least Bitterns is draining of wetlands for conversion to farmland and urban development;
  • The Least Bittern does not tolerate human disturbance well and will leave marshes if human activity or habitat alteration becomes too great;
  • Least Bitterns generally fly fairly low and as a result are sometimes killed by cars, where roads pass through wetlands. They are susceptible to collisions with hydro lines, guy wires on towers, or hitting tall buildings that are illuminated at night (when they migrate);
  • Invasive species such as Purple Loosestrife, Reed Canary Grass, Common Reed, and Flowering Rush are outcompeting the cattails in which the Least Bittern breeds




  • The Least Bittern is protected under the Migratory Bird Treaty Act of 1918 – this statue makes it unlawful without a waiver to pursue, hunt, take, capture, kill or sell birds listed therein (“migratory birds”);
  • Also protected by Ontario’s Endangered Species Act, 2007 and the Species at Risk Act (SARA);
  • The Least Bittern and its Nest are protected under the Migratory Birds Convention Act; and
  • Birds that live in provincial parks and conservation areas also receive additional protection through their programs.



What YOU Can Do to Help the Least Bittern:

  • If you happen to see a Least Bittern and capture the sighting, contact the Ministry of Natural Resources to report your sighting and provide details of the location – learn about that process here (;
  • Bird Studies Canada is a not-for-profit organization working on the conservation of wild birds and their habitats – learn more about them here (;
  • Least Bitterns are quite shy and secretive, particularly during the breeding season (May to mid-July), and are easily scared away. If you know of a breeding zone, try to give them lots of room and distance;
  • Non-native plants create competition among the breeding ground for the Least Bittern. To learn what you can do to help eliminate these invasive species, visit Ontario Invasive Plant Council here (; and
  • As always, volunteer with your local Nature Club or Provincial Park to learn more about protecting our endangered species.




  • When alarmed, the Least Bittern freezes in place and sometimes sways to resemble wind-blown marsh vegetation;
  • Thanks to its habitat of straddling reeds, the Least Bittern can feed in water that would be too deep for other herons;
  • The nests of the Least Bittern are almost always within 10m of open water; and
  • 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 means “greedy eater of Mistletoe”!

One thought on “This Week’s Endangered Species in Focus: Least Bittern (Ixobrychus exilis)

  1. I have a juvenile Least Bittern on my property right now. I believe it was injured or stunned during a recent wind storm. LPBO of BSC have checked the situation and it remains here for now. Great opportunity to see this beautiful bird. I keep discreetly monitoring the situation. I did report the sighting.
    Julie Stone, Long Point

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s