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Eastern Kingbird, White-throated Sparrow, Passerine feet
  Order Passeriformes - Perching Birds
Wiki     ToL     EoL
  The Order Passeriformes contains 59% (5,712 species in 1,161 genera) of the 9,672 species of birds recognized by Sibley and Monroe (1990). Most passerines are small land-dwelling birds that feed on insects, seeds, fruit, or nectar. The largest passerines are the Australian lyrebirds (Menura) and the Raven, Corvus corax- 1.2 kg. The smallest passerines found in North America are the kinglets (Regulus) - 6g.
   Passerines are morphologically similar. They differ mainly in the structure of their syrinx, bill, and feet. Because of their similarities, classifications differ widely. This pages in this web follow the most widely accepted arrangement of taxa in North America (AOU Checklist). However, the Birds of the World arrangement follows Sibley and Ahlquist (1990). The two are cross-referenced.
   Sibley and Ahlquist (1990) divide the passerines into two suborders - the suboscines (eurylamidi and tyranni - sister groups) and oscines (song birds). There is general agreement that the New Zealand Wrens (Acanthisittidae), now restricted to New Zealand, represent an ancient and distinct group so we actually split the order into three suborders: Anthansitti, Tyranni, and Passeres. The first is an Old World group, the second is largely an Old World group but the tyrant flycatchers, cotingas, antbirds, ovenbirds, antbirds, and several other families radiated in the New World with their primary distribution in South America. The true song birds (Passeres) are widely distributed in all areas of the world.
   It is believed that passerines originated in Gondwana during the Paleogene - ~60 MYBP (million years before the present). The New Zealand Wrens appear to be a sister group to all other passerines. As Gondwana fragmented, ancestors of the oscines became isolated in Australia, the ancestors of the New World suboscines were found in South America, and the Old World suboscines in the connected Kerguelen - India - Madagascar plates. Oscines radiated in the Australo-Papuan region while the ancestors for the Passerida radiation expanded to contribute a third of modern species of passerines.
   Sibley and Ahlquist (1990) divide the song birds into two "parvorders" - the Corvida and the Passerida. Subsequent research suggests  that the Corvida actually include a paraphyletic assemblage of early and minor lineages of Old World birds, particularly from the Australo-Papuan region. The Current evidence suggests that the basal group includes the lyrebirds/scrub-birds. These are sister groups of other oscines so the "Corvida" is actually a paraphyletic group. The honeyaters and their relatives also appear to represent a distinct lineage. There are a number of groups whose status remains uncertain. However, most evidence suggests that the Passerida are monophyletic with the rockfowl and rock-jumpers the most basal groups of the clade. (Ericson, G P , M. Irestedt, and U. S. Johansson. 2003, J. Avian Biol. 34(1): 3-15).
   The classification scheme I have adopted attempts to blend that of Sibley and Ahlquist (1990) with subsequent reflection. However, the "Parorders" of Sibley and Ahlquist (1990) are probably better ranked as Infraorders or Superfamilies. There is not general a general agreement on classification of the Corvida.

Order Passeriformes
     Suborder Ananthisittidi - New Zealand Wrens
     Suborder Eurylaimidi - Old World (Broad-billed) Suboscines
     Suborder Tyrannidi - New World Suboscines
        Infraorder Tyrannides - New World Suboscines
           Superfamily Tyrannoidea - Bronchophones (birds with bronchial syringes)
           Superfamily Furnarioidea - Tracheophones (birds with a tracheal syrinx)
 Suborder Passeridi - Song Birds ("Oscines")
      Parvorder (Infraorder) Menuroida (Superfamily Menuroidea) - Lyrebirds and Scrub-birds
      Parvorder (Infraorder) Meliphagoida (Superfamily Meliphagoidea) - Honeyeaters
      Parvorder (Infraorder) Corvida (Superfamily Corvoidea) - Crows (and relatives) -
         clades of Australo-papuan origin
      Parvorder Incertae sedis - Picathartidae, Chaetopidae
      Parvorder (Infraorder) Passerida (Superfamily Passeridea) - a clade (line) including the
         Bombycilloidea?, Muscicapoidea, Sylviioidea, Certhoidea?, and Passeroidea
Eastern Kingbird

Eastern Kingbird,
Tyrannus tyrannus
a suboscine
                  SI Web

White-throated Sparrow,
Zonotrichia albicollis,
an oscine
SI Web

White-throated Sparrow
     Passerines have an aegithognathous palate (except Conopophagidae). The bill and feet of passerines tend to be morphologically similar. Pelvic muscles are AXY (AX in Dicrurus). The ambiens is absent and the iliofemoralis externus is usually absent. The hallux is incumbent (level with the other toes) and directed backward to oppose toes 2, 3, and 4 which are directed forward (anisodactyl). Toes are not webbed or fused to any extent. The digital formula is 2-3-4-5. Flexor tendons are Type 7 (with exceptions). Two intrinsic muscles are present in the hallux but intrinsic muscles of other digits are missing. There is a full set of 8 extrinsic digital muscles.  When flexed, tendons in the hind limb "lock" to allow the bird to rest without expending energy to grasp the branch (hence the appellation "perching birds").
Ruby-crowned Kinglet

Passerine Anisocactyl Feet

Ruby-crowned Kinglet,
Regulus calendula

American Crow,
Corvis brachyrhynchos

American Crow
  Caeca are short and non-functional. The oil gland is naked and (indistinctly)  bilobed. Nasal glands are minute. They have only the left carotid. They usually have 14 cervical vertebrae (mammals have 7). The atlas is perforated. The metasternum is usually two-notched. The biceps slip is absent and the expansor secundariorum is often present. The tensor propatagialis brevis tendon is present. Most have a hypocleideum. They usually  have 10 primaries with the outermost feather often being reduced or vestigial, 9 secondaries (most species), and usually 12 tail feathers. They are eutaxic. The wing coverts are in three series and the aftershaft (a second partial feather shaft growing from one follicle) is absent in most (except New Zealand wrens).
   The molt of primaries is from the most proximal to the outermost feather (from feather #1 to #9 or 10). Secondaries are replaced from each end toward the 5th feather (i.e. from the elbow and wrist toward the middle feather). The tail feathers are replaced from the center to the outside it is said to be centripetal (the creeper, a tree climber that uses the tail as a prop, retains the central pair of tail feathers until the others are replaced).
   The structure of their spermatozoa is also distinctive - they have a spiral membrane around a darkly pigmented capital portion and a large acrosome.
   The structure of the syrinx (voice box) is used to characterize suborders. The syrinx may be located in the trachea, in the bronchi, or at the junction of the trachea and bronchi. The number of intrinsic muscles and their insertion on bronchial half rings are considered to be important as are the number of intrinsic muscle pairs (Menurae - lyre birds - have 2 or 3 pairs, Passeres have 4 or 5 pairs).
   All passerines scratch by bringing the foot over the lowered collateral wing ("scratching behind the wing").
   Most passerines lay colored eggs. Incubation periods range from 11 - 21 days for most (35-40 days in Menura). The young are hatched blind and helpless with sparse dorsal down ("altricial") - contrasted with the "precocial" young of many non-passerines in which the young hatch fully feathered and are able to forage immediately (e.g., quail). The development of passerines after hatching is also rapid - from a blind, helpless chick with only a tuft or two of down to an independent, fully grown (adult body mass), free-flying bird in 14 days or so  Note that parental care is important in almost all birds regardless of the young's stage of development at hatching and the "fledged" chick still has much to learn. Most passerines breed at 1 or 2 years of age. Their longevity varies but averages 2-3 years in smaller species and more than 3 years in larger passerines (up to ~18 years).
   Raikow (1982) analyzed 18 morhphological characters of passerines as a test of monophyly. Five corroborate monophyly: 1) aegithognathous palate, 2) "passerine" tensor propatagialis brevis, 3) bundled sperm with coiled head and large acrosome, 4) the enlarged hallux, and 5) the Type 7 deep plantar tendons. The division of M. pubo-ischio-femoralis into two parts and the loss of intrinsic muscles in the forward digits add support to the assumption of descent from a common ancestor.



  Banner - House Sparrow. Marken, Netherlands.