Passeriformes – Perching Birds – The Largest Bird Order
According to Suzanne Alexander, Representatives of the Passeriformes (perching birds) — the world’s largest bird order, containing some 60% of all species.
The class Aves (birds)/ sometimes reduced to the rank of subclass of the class Reptilia (reptiles)/ has a varying number of orders (groupings of families with common characteristics) according to the system of classification adopted. The popular method adopted by Ernst Mayr, and leading to what has become known as the Basel Sequence, recognizes 27 orders containing 159 families. Of these, by far the largest, and also the most advanced, is the order Passeriformes, containing some 5, 100 species — almost 60% of the world list!
Characteristics of the Perching Birds
The ‘perching birds‘ always have four toes with the irreversible hallux (‘first’ toe) directed backward to form a foot which is well adapted to gripping a slender perch such as a branch, twig, reed or grass-stem. Toes are never webbed. The song is another feature of the Passeriformes and, though the quality varies, the order certainly contains the world’s best songsters and mimics.
These landbirds frequent a wide variety of habitats, hatch blind, naked and helpless young, and their parental care is mostly well developed. The order is cosmopolitan, absent only from polar latitudes and some inhospitable islands.
Current research into DNA-hybridization (a method which assesses the similarity between the chromosomes of different species) should help to settle many of the disagreements over classification which still occur.