Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae, with 64 recognised species (some are called "egrets" or "bitterns" instead of "heron"). Within Ardeidae, all members of the genera Botaurus and Ixobrychus are referred to as "bitterns", and — including the Zigzag Heron or Zigzag Bittern — are a monophyletic group within the Ardeidae. However, egrets are not a biologically distinct group from the herons, and tend to be named differently because they are mainly white or have decorative plumes. Although egrets have the same build as herons, they tend to be smaller.
The classification of the individual heron/egret species is fraught with difficulty, and there is still no clear consensus about the correct placement of many species into either of the two major genera, Ardea and Egretta. Similarly, the relationship of the genera in the family is not completely resolved. However, one species formerly considered to constitute a separate monotypic family Cochlearidae, the Boat-billed Heron, is now regarded as a member of the Ardeidae.
Although herons resemble birds in some other families, such as the storks, ibises, spoonbills and cranes, they differ from these in flying with their necks retracted, not outstretched. They are also one of the bird groups that have powder down. Some members of this group nest colonially in trees, while others, notably the bitterns, use reedbeds
The herons are medium to large sized birds with long legs and necks. They exhibit very little sexual dimorphism in size. The smallest species is usually considered the Little Bittern, which can measure under 30 cm (12 in) in length, although all the species in the Ixobrychus genus are small and many broadly overlap in size. The largest species of heron is the Goliath Heron, which stand up to 152 cm (60 in) tall. The necks are able to kink in an s-shape, due to the modified shape of the sixth vertebrae. The neck is able to retract and extend, and is retracted during flight, unlike most other long-necked birds. The neck is longer in the day herons than the night herons and bitterns. The legs are long and strong and in almost every species are unfeathered from the lower part of the tibia (the exception is the Zigzag Heron). In flight the legs and feet are held backward. The feet of herons have long thin toes, with three forward pointing ones and one going backward.
The nests of herons are usually found near or above water. They are typically placed in vegetation, although the nests of a few species have been found on the ground where suitable trees of shrubs are unavailable. Trees are used by many species, and here they may be placed high up from the ground, whereas species living in reedbeds may nest very close to the ground.
Generally herons lay between three to seven eggs. Larger clutches are reported in the smaller bitterns and more rarely some of the larger day-herons, and single egg clutches are reported for some of the tiger-herons. Clutch size varies by latitude within species, with individuals in temperate climates laying more eggs than tropical ones. On the whole the eggs are glossy blue or white, with the exception being the large bitterns which lay olive-brown eggs.