Birds of the World

COAST BIRDS
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WORLD BIRDS
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ANECDOTES

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TRAITS
 Ratites
 Tinamous
 Cracids/Galli
 Waterfowl
   Screamers
   Ducks

 Penguins
 Loons
 Grebes
 Procellarids
   Albatrosses
   Petrels
   Storm-Petrels

Totipalmate Swm

   Tropicbirds
   Gannets/Boobies
   Pelicans
   Cormorants
   Anhingas
   Frigatebirds

 
Waders
   Herons
   Ibises
   Storks  

 NW Vultures
 Flamingos
 Raptors
 Gruiformes
   Buttonquail
   Bustards
   Cranes
   Rails

 Shorebirds
   Sandgrouse
   Plovers
   Oystercatchers
   Stilts
   Sandpipers
   Gulls/Terns
   Auks

 Pigeons
 Parrots
 Turacos
 Cuckoos
 Owls
 Frogmouths
 Nightjars
 Swifts/Humbd
 Colies
 Coraciae

   Hornbills
   Hoopoes
   Trogons
   Rollers
   Kingfishers
   Bee-eaters
   Jacamars/Puffbd

 
Pici
   Honeyguides
   Woodpeckers
   Barbets/Toucans

PASSERINES
   NZ WRENS
   OW SUBOSC

      Broadbills
      Pittas

 NW SUBOSC
   NW Flycatchers

   Becards
   Cotingas
   Manakins
   Antbirds
   Ovenbirds
   Woodcreepers
   Antthrushes
   Tapaculos 

 OSCINES
 Lyre-/Scrub-birds
 Bowerbirds
 Aust. Wrens
 Honeyeaters
 Scrubwrens
 Aust. Robins
 Kinglets
 Shrikes
 Vireos
 Whistlers
 Corvids
 Birds-of-Paradse
 OW Orioles
 Cuckoo-shrikes
 Fantails
 Drongos
 Monarchs
 Bush-shrikes
 Wattle-eyes
 Vangas
 Waxwings
 Dippers
 Thrushes
 OW Flycatchers
 Starlings
 Mimids
 Nuthatches
 N Creepers
 Wrens
 Gnatcatchers
 Tits/Parids
 Larks
 Swallows
 Leaf-Warblers
 Bulbuls
 Cisticolas
 White-eyes
 Babblers
 OW Warblers
 Flowerpeckers
 Sunbirds
 OW Sparrows
 Accentors
 Pipits
 Estridids
 Weavers
 Whydahs
 9-prim. Oscines

   Fringillines
   Carduelines
   Hawaiian Honycrp
   NW Sparrows
   NW Warblers
   Tanagers
   Cardinals
   NW Blackbirds

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TRAITS
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Skeletal Features
  Palatal Structure
  External Nares
  Nasal Bones
  Columella
  Cervical Vertebrae
  Sternum

Legs and Feet
  Tarsometarsus
  Toes
  Feet
Development
Internal Features
  Supraorbital Gland
  Syrinx
  Intestinal Convolutions
  Intestinal Caeca
  Carotid Arteries
  Thigh Artery
Feathers and Skin
  Pterylosis
  Aftershaft
  Natal Down
  Number of Flight Feathers
  Wing Formula
  Fifth Secondary
  Powder Down
  Oil (Uropygial) Gland
  Rhamphotheca
Muscular Features
  Pelvic Musculature
  Deep Plantar Tendons
  Jaw Muscles
  Other Muscles
Other Features
   
 

Feathers and Skin

 
  Pterylosis
  In most birds, contour feathers occur in tracts (pterylae) with bare areas (apteria) between them. Ostriches, penguins, and screamers have no apteria - all areas of their skin are feathered. In most birds, the head and neck are covered with feathers with one tract running down the back to the base of the tail. Ventrally, there are usually two tracts, diverging at the neck and running along the flanks on each side.
   In some groups, down may occur in the apteria and persist into adulthood. In other groups it is restricted to the pterylae or replaced by contour feathers as the young grow.
    Variations in feather tracts are probably adaptive and their use in making taxonomic judgements is limited.   
 
  Aftershaft
  The presence, relative development in relation to the shaft, or the absence of an aftershaft is often mentioned when related groups are compared. (The aftershaft is a second feather growing from a single follicle - see Structure for a discussion.)
 
  Natal Down
  The presence of one or two coats of natal down, appearing before the juvenile feathers, and their color and growth patterns have also been used to infer relatedness.
 
  Number of Flight Feathers
  The number of remiges (primaries and secondaries) and rectrices (tail feathers) may help define a given taxa.
   Birds typically have 9-12 primaries with the most common number being 10. If the number is reduced, it is the outermost primary that is lost.
   They have 8 or more secondaries (depending largely on the length of the forewing). Hummingbirds have only 6-7 secondaries but pelicans have 29. There is, therefore, much variation in this number of feathers.
   Birds usually have 8-12 rectrices (tail feathers) but some that use the tail in display may have many more (up to 32 or so). Scansorial (climbing) birds such as woodpeckers and creepers may strengthen the innermost rectrices to act as a prop against the trunk while they forage. Other scansorial birds such as nuthatches and the Black-and-white Warbler do not use their tails which are often relatively short.
 
  Wing Formula
  Relative lengths of the primary feathers are usually constant any may be used to construct a wing formula. In some taxa, this may help in the identification of birds from similar species.
 
  Fifth Secondary
  Normally, in the forearm of the wing, each secondary is matched by a corresponding greater covert (a contour feather). In a number of taxa, however, there is an extra covert between the fourth and sixth secondary with no corresponding secondary (the fifth is missing). This is believed to be a developmental anomaly - as the skin develops, torsion realigns the follicles to provide this gap. Species missing the fifth secondary are termed aquintocubital or diastataxic. Those with the feather are quintocubital or eutaxic.
   Loons, grebes, penguins, procellariids, pelicans, cormorants, herons, storks, waterfowl, diurnal raptors, cranes, shorebirds, parrots, owls, and goatsuckers are mostly diastataxic.
   Galli, cuckoos, colies, trogons, coraciiformes, piciformes, and passerines are mostly eutaxic.
   Other groups including pigeons, rails, swifts, and hummingbirds are variable.
  Fifth Secondary Development of the 5th secondary. Left - the eutaxic condition in a pheasant. Right - the diastaxic condition in a Golden Eagle. Note that the 5th covert is present but there is a gap in the secondary sequence - the firth secondary is matched with the 6th covert. 


© University of Michigan, Museum of Zoology.
 
  Powder Down
  Waders, some parrots, and other birds have patches of downy feathers that grow continuously but the barbs fracture and ablate from the base as they emerge from the follicle. These keratinaceous shards may be used in preening and, like the secretions of the uropygial gland, have a role in maintaining functional feathers. The downy secretions feel oily on your fingers.
   Many birds with well-developed powder down have reduced uropygial glands but not all birds lacking oil glands produce powder down.
   The number and location of powder-down patches is part of the characterization of taxa that possess them but has not proven to be particularly helpful in making taxonomic inferences.
 
  Oil (Uropygial) Gland
  The oil gland is located on the surface of the pygostyle at the base of the tail feathers. Its secretions are preened into all of the feathers of the individual and are essential for maintaining feather structure. It is sometimes called the preen gland.
   The oil gland often has an oval of feathers around the orifice forming a tuft (producing a tufted oil gland). When these feathers are missing, the gland is said to be a nude oil gland. The shape of the gland may be oval or bilobed.
   The gland is missing in several ratites, bustards, frogmouths, some parrots, some pigeons, and some woodpeckers. Its function may be supplemented by powder-down in some taxa.
 
  Rhamphotheca
  The horny scales that cover the maxilla and mandibles are known collectively as the rhamphotheca. A median ridge and lateral ridges on the palatal surface form the horny palate.
   The rhamphotheca is usually simple - one scale each on the maxilla and mandible (most birds). The presence of two or more scales (on the maxilla) form a compound rhamphotheca. In procellariids, the rhamphotheca contains 7 - 9 plates.
   In most birds, the rhamphotheca grows continuously to balance mechanical wear. In a few, it is shed or molted (and is said to be deciduous).
   
Nazca Booby
Nazca Booby, Sula granti. Note at least two scales in the upper mandible.