Heron (bok) a diverse group of long-legged, long-billed and long-necked marsh loving birds belonging to the family Ardeidae of order Ciconiiformes. This family also includes the bitterns, ibises, spoonbills and storks. All egrets, Green Heron, herons and night herons are considered as 'herons'. These are wading birds, capable of walking in thigh-deep water; their size ranges from 45 cm (Pond Heron) to 150 cm (Goliath Heron); their feet are bare, their toes are unwebbed but fairly longish. Bills are long with pointed tips; necks are unusually long and S-shaped which are kept cocked when resting and retracted during flight and kept either erect or semi-crouched when active. Tails are generally short with 12 tail-feathers; long, broad wings have 10 primary feathers. Often male herons have filamentous decorating courtship plumage over head, neck and breast. Herons live close to water; roost in colonies; roosting trees may also be used for nesting. Such roosting and nesting places are called heronry. Sometimes they live close to cormorants and other ciconiiforms, spoonbills, and ibises.
Herons are carnivorous and largely eat fishes and frogs. Usually the birds stand still in or near the water or on some objects floating or emergent in the water, and suddenly strike at the passing prey either impaling or killing it instantly. Cattle Egrets often follow grazing cattle and catch insects, frogs and small reptiles disturbed by them.
Common Bangladeshi herons are Pond Heron or Paddybird (Kani or Kana Bok), Ardeola grayii; Cattle Egret (Go-bok), Bubulcus ibis; Little Egret (Choto Sada Bok), Egretta garzetta; Median/Intermediate Egret (Majhari Sada Bok), Egretta intermedia (new name: Mesophyox); Large Egret (Bora or Jathua Bok), Egretta alba (new name: Casmerodius albus); Grey Heron (Dhushar Bok), Ardea cinerea; Purple Heron (Beguni Bok), Ardea purpurea; Giant or Goliath Heron (Brihat or Mohakai Bok), Ardea goliath; Black-crowned Night Heron (Wak or Nishi Bok), Nycticorax nycticorax and Tiger Bittern (Bagha Bok), Gorsachius melanolopus. All but the night and tiger herons are diurnal while these two species are nocturnal or crepuscular. Goliath Heron is either migratory or vagrant in the country and there have been only a few records of sightings during past few decades. Pond Heron, Little Egret and Cattle Egret are the most common and widespread herons in the country. Tiger Bittern is less common and secretive than the Night Heron. [Ali Reza Khan]