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Gaviiformes
 
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Loons
 
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All Loons
 
Images:   
Common Loon
 
 
Order Gaviiformes - Divers, Loons
Wiki     ToL     EoL
 
  Family Gaviidae - Loons
Wiki     ToL     EoL
EXAMPLE
  5 species, 1 genus (Gavia). Northern parts of the Northern Hemisphere (Holarctic). The Red-throated Loon (Diver) is circumpolar in distribution. Loons (New World) or Divers (Old World) breed on fresh water lakes and ponds but winter on salt water estuaries and along our coasts and on some large inland bodies of water.
   Loons are probably closely related to frigatebirds, penguins, and the tube-nosed swimmers (petrels, shearwaters, albatrosses) (Sibley and Ahlquist, 1990). However, Clements (2007) retains their traditional position with penguins at the bottom of the Neoaves. Loons and Grebes have been regarded as closely related. Although there are superficial similarities, the two groups are not now believed to belong close to one another - recent studies cluster grebes with or near flamingos. The Encyclopedia of Life places them in the Ciconiiformes - a largely paraphyletic group. Early penguins had skulls similar to those found in the Gaviiformes. There is some suggestion that they might be linked to the clade "Mirandornithes" which unites grebes with flamingoes.
   Loons are relatively large (21-36") aquatic birds (about the size of a large duck or small goose) with their legs set far back on their bodies. The femur is directed posteriorly and is tightly bound to the body by ligaments. Their patella is fused to the tibia and serves as an attachment for muscles used in swimming. This gives the leg and foot considerable mechanical advantage in the water. The tarsi are laterally compressed to streamline the leg in water. Their forward three toes are webbed or "palmate." They use their feet for propulsion on and under water but may use their wings when turning or to get a burst of speed. Dives last less than a minute and seldom go below 30' from the surface but dives to more than 200 feet have been reported.
   Because of these adaptations for swimming, loons are unable to stand upright on land - they come to land only to nest (and most are unable to take off from land). Their large feet are visible beyond the tail in flight. They patter along the surface of open water when taking off and all (except the Red-throated Loon?) require water for taking to the air.
   Their flight is strong and direct with steady, measured wing-beats. Their wings and tail are relatively short. They fly with the neck outstretched, slightly below the body.
   They have straight, sharp bills (dagger-shaped) and their tongue is small with a patch of spines at its base.
   They have large supra-orbital glands (involved in osmoregulation).
   Their breeding plumage is patterned (black, white, and gray) with contrasting spotting and barring. Winter plumages are dull gray and white. Males and females are alike but males may be up to 10% larger than females.
    Loons are territorial and monogamous - sometimes forming pair bonds for life. They first breed at 2 to 3 years of age. Loons defend their territories mainly by voice. Their loud, haunting calls evoke the north woods. Unfortunately, Hollywood feels that these calls provide an eerie but suitable background for many environments, including tropical rain forests... Some loons perform display flights. Adults become aggressive against intruders. Courtship involves bill-dipping movements. They also dive and swim past each other under water.
   Their nest is placed next to water on open land or in shallow water. All nest around lakes in the far north. The nest site is chosen by the male. The nest is usually a low mound of plant material with a shallow depression - sometimes little material is used in its construction. It is almost always less than 1 m from water. It is built by a sitting bird pulling plant material toward the nest and forming it into a mound around the body. Nest sites may be reused. Loons usually lay 2 (3) olivaceous eggs with darker markings over an interval of 1-3 days. Both sexes incubate - they have a single median brood patch. Incubation begins when the first egg is laid so the eggs hatch asynchronously. Incubation lasts 24 - 30 days. The downy hatchlings immediately enter the water but are brooded ashore for a few nights and then ride on the adult's back or are warmed under the wing. They are subprecocial and nidifugous. Both parents feed the young. Parental care lasts 55-75 days.  
   Loons spend most of their time on water. They dive frequently when feeding, usually up to 6 m, and remain submerged for up to 2 min. They are also able to vary their density so they can swim with just the head and neck above water. They eat fish which they pursue underwater by sight. Their eyes have adaptations facilitating vision both under water and in the air. They dive and pursue prey actively. They may form cooperative flocks for feeding in winter. They also feed on crustaceans, aquatic insects and larvae, frogs, and some plant material. Mollusks may also be eaten during the winter in marine habitats. Most loons feed near the nest but the Red-throated Loon may fly to the ocean or a nearby river. Fish are carried crosswise in the bill to feed the young for several weeks.
   Loons have a long hind process on the mandible. Both carotids are present. They have 14 or 15 cervical vertebrae. The sternum is compressed - it is twice as long as it is wide and the posterior border is notched. They have 11 primaries, 22-23 secondaries, and 16-18 tail feathers. Contour feathers have aftershafts. They have a dorsal apterium (unfeathered area) only on the neck. They have a double nestling down (the first set is pushed out as the second grows in) before attaining their juvenile plumage. This trait is shared with the tube-nosed swimmers (Procellariformes) and penguins (Sphenisciformes)
   All flight feathers are lost simultaneously in the post-nuptial molt leaving adults flightless until new feathers are grown (this shortens the time of molt considerably). Note that ducks also have a simultaneous molt.
   Loons may live as long as 30 years.
 
 
All Loons:

  Basal lineage:

     Red-throated Loon (Diver), Gavia stellata. Northern Eurasia and North America. Winters to
         the Caspian and Mediterranean.
     Arctic Loon (Black-thrroated Diver), Gavia arctica. Arctic Eurasia and western Alaska.
         Winters to southern Palearactic region.

  Black-throated lineage:
     Pacific Loon (Diver). Gavia pacifica. Coastal eastern Siberia and northern North America.
         Winters to Japan, southern Baja.
     Common Loon (Great Northern Loon (Diver)). Gavia immer. Western Palearctic and North
         America. Winters to southern US and southern Palearctic.
     Yellow-billed Loon (White-billed Diver). Gavia adamsii. Norhtern Eurasia and northern North
         America. Winters to northern Baja California.
Common Loon

Common Loon, Gavia immer. Seabrook.
Photo by Ed Konrad
                                                         SI Web

       
       
   
   
     
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
 

   
     
  Banner - Huntington Beach, looking north toward the Murrells Inlet breakwater.