Wednesday, April 6, 2011

Common Loon

Thanks to Penelopedia for blogging about this loon in a pond in residential Northfield.  I photographed it on 4 April 2011.  A less wild habitat is hard to imagine.  Large, closely knit, recently built houses surround the lake.  Half submerged, and making lengthy dives, the loon repeatedly swam around the lake.  Loons control their buoyancy by filling or partially emptying their air sacs.  These sacs are part of a bird's respiratory system.  Air sacs also allow an efficient, one-way flow of air across bird lungs.  
Various hypotheses exist for why loon's eyes are red. Perhaps the sexes are attracted to red eyes. Alternatively, below 15 feet of water, red is no longer visible.  Perhaps if the eyes are not visible, prey  have trouble recognizing predators.  Several sources claim the eye color allows for better vision under water.  Some other diving birds also have red eyes.  Loon eyes, however, are not red in winter.  The question "why do loons have red eyes?" does not seem to have a definitive answer.

1 comment:

  1. Glad you were able to see it. Interesting to learn about the air sac -- I could certainly tell it seemed to sit higher or lower in the water at various times.