Birds of Seabrook Island

COAST BIRDS
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WORLD BIRDS
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ANECDOTES

  Brown Pelicans
 
 
 

Species Acct.
Loons
Grebes
Procellarids
Pelicans
Herons
Ibises
Storks
Vultures
Flamingos
Waterfowl
Raptors
Turkeys
Quail
Rails
Limpkin
Cranes
Shorebirds
Gulls
Terns
Auks
Doves
Parrots
Cuckoos
Owls
Goatsuckers
Swifts
Hummers
Kingfishers
Woodpckrs
Flycatchers
Shrikes
Vireos
Crows/Jays
Larks
Swallows
Tits
Nuthatches
Creepers
Wrens
Kinglets
Gnatcatchers
Thrushes
Mimids
Starlings
Pipits
Waxwings
NW Warblers
Tanagers
NWSparrows
Cardinalines
Icterids
Finches
OWSparrows

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Structure
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Feather Structure
  Contour Feathers
  Flight Feathers
  Color
  Molt
  Feather Care
Feather Function
  Flight
  Thermoregulation
Reproduction
Development
Brood Patch
The Skeleton
  Legs and the Ankle Joint
  Feet
  Bills and Nostrils
Muscles and Bones
Internal Structures and Systems
  Control Systems
  Digestive and Respiratory Systems -
     Circulation
  Urogenital System - Osmoregulation
 
 

Feathers - Function

  Having explored feather structure, replacement, and care, recall that feathers have two fundamental functions - flight and thermoregulation.
 
 

Flight

  The bird's wing forms an airfoil (broader at the leading edge, convex above, concave below). As air flows over the surface, it must travel a longer distance over the upper surface, decreasing the static pressure on that surface and producing lift. By altering the angle of the wing with the air flow, birds can vary the amount of life produced (up to a point). Slotting of the outer primaries increases the elements producing lift. The entire wing (and to an extent, the tail) contributes to lift.
   While lift keeps a bird airborne, thrust is necessary to move the bird through the air. This is provided by flapping flight, primarily by the hand and attached primaries. The overall pattern involves moving the wings down and forward on the downstroke, then up and backwards (with the wingtip forming a figure 8).
   Once underway, a variety of birds have adapted energy-saving techniques of soaring. Many raptors and other larger birds may ride thermals, rising cylinders of warmer air heated by the ground. Dynamic soarers (albatrosses and other sea birds) may use differential winds found over the surface of the ocean, flying in a series of zig-zags. Some seabirds also soar in the upward air currents along the face of waves (watch our pelicans flying low over the incoming waves before they break). Consult the web or one of the references for more information.
  Osprey Brown Pelican
White-rumped Sandpiper
White-rumped SandpiperCalidris fusciollis. Bear Island WMA
  Osprey, Pandion haliaetus. North Beach. Note alula at wrist.
Brown Pelican, Pelecanus occidentalis. Pitt St., Mt. Pleasant. Note elongate fore-wing.
     
 

Thermoregulation

  Birds (like mammals) loose heat by radiation, convection, conduction, and evaporation. Radiation may be affected by plumage - color is important but is not easily changed (that requires a molt). Many individuals have fewer feathers in summer, allowing the surface of their outer "shell" to warm (transfer heat to the surface) and facilitate radiation from a warmer surface. Some behaviors that disrupt the integrity of the feather coat may facilitate heat loss (but "sun-bathing" may have other roles as well). Conduction is generally insignificant - feet are already cooled and birds don't cuddle cold objects (but skimmers regularly press their body on cooler sand). The most important mechanism for heat loss at higher temperatures is by evaporation. Wet legs (below) help. Some birds carry water in their feathers to their nest and drip it on eggs/young to help them cool. Bathing may lead to temporary cooling if water is available. However, many birds rely on gular flutter to increase heat loss by evaporation from the wet surfaces of their mucous membranes in the throat. Rapid ventilation over the surface promotes heat loss independent of respiration and allows birds to survive otherwise lethal high temperatures
   Legs and feet are also be important in thermoregulation - remember that birds maintain a relatively constant body temperature. Vultures and storks may void their urine and feces on their legs ("urohydrosis") to aid them in cooling when it is hot (one of the earliest evidences linking them phylogenetically to each other). Birds that wade or swim have their feet and legs exposed to water that is almost always cooler than their body temperature. In all birds, the arterial blood heading toward the feet passes through a bed of smaller vessels in the thigh that is closely applied to a similar venous net containing blood returning from the feet. Thus, there is a counter-current exchange that conserves heat - arterial blood is cooled, venous blood is warmed. The gull standing in melt water on a cake of ice regulates blood flow to keep its foot above freezing - but not much. The American Tree Sparrow foraging in snow similarly regulates its heat loss. Heat is generally conserved in cold weather and can be dissipated in warmer times...
   
    Banner - Brown Pelican. North Beach.