"Loon Lessons"

So much to learn.  So little time.  Herewith some gleanings from what I thought was a very interesting book.

"Their legs are so specialized for diving and positioned so far aft that standing, let along walking, is nearly impossible; hence, the adoption of the Scandinavian word for "clumsy," lom or lumme, which stuck as their common name."

"Loons differ from other similar diving birds... they are unique, or monophyletic, in that they have been on their own evolutionary trajectory for more than 50 million years..."

"Have you ever noticed that the great majority of white birds have black wing tips?... Now, have you pondered that essentially all diving birds are black?.. What is the connection between the two?  Melanin does more than color the feather; it makes the feather stronger and more resistant to wear..."

"The skull of a loon is unusually thick and heavy for a bird; this allows it to descend with less effort.  Also, many of a loon's bones are solid rather than mostly hollow, or pneumatic, as found in most birds... a Bald Eagle is 20-25% larger than a loon yet weighs about the same (8 to 11 pounds)."

Marine birds (puffins, albatrosses) have a salt-excreting gland above each eye that produces a solution 1.5x as salty as seawater (to aid the kidneys).  Loons share this adaptation (because they winter in the oceans).  These glands are deactivated by ocean oil spills, which thus devastate marine birds.  Here is a map of the summer (dark) and winter coastal (cross-hatched) ranges for loons:

It was a sobering realization for me, after seven decades summering with loons, to learn at my age for the first time that these birds overwinter swimming in the ocean.  

"Loons are very comfortable in the open ocean... researchers have reported them 50-60 miles from shore." (depends on how far out the continental shelf extends - typically a couple hundred feet below the surface)

"There have been reports of loons caught in commercial fish nets set at 180-230 feet, which would take just over two minutes of dive time... their upper limit is likely closer to 5-6 minutes, with a maximum dive depth of 300 feet or more."

"Some chicks are born naked and helpless, a condition known as altricial, while others are born fully feathered and capable of feeding themselves, precocial (or superprecocial).  Loon chicks fall somewhere near or just above the middle of this range (subprecocial)... Loon parents have to be attentive to their young, especially during the first two weeks of their life..."

Loons lay two eggs  "A one-egg clutch is rare in the bird world, observed in only one group of birds, the tubenosed seabirds such as albatrosses and petrels."

"Botulism type E has caused periodic outbreaks of fish-eating bird mortality in the Great Lakes since the 1960s, but since the turn of the century, outbreaks have occurred more frequently... In a span of ten years, from 2000 to 2009, more than 20,000 loons died from type E botulism."

During migration, loons fly between 2,700 and 6,200 feet above ground level. Rapidly beating wings generate lots of heat, so it is advantageous to fly where the air is several degrees cooler.  With their narrow wings and heavy bodies, they lose elevation on the recovery stroke if they fly too slowly.  "To prevent this, loons beat their wings rapidly (more than 200 beats/minute), which increases flight speed.  Consequently, the optimal flight speed for loons is a fast 70-75 miles per hour, compares to 40-45 for smaller, aerodynamic ducks."

"If loons, like pigeons, can detect air pressure changes, then they may be able to move before a major storm hits, but they cannot fly during winter.  Loons undergo a winter wing molt that renders them flightless.  In all my work, I have never seen an adult Common Loon in flight during the months of December through February."

The author spent his entire professional life researching loons, so this book reads a bit like a graduate-level textbook, with lots of data and detail.  In addition to the excerpted topics above, there are chapters on anatomy, diet, social behavior, migration techniques, and of course the wails/yodels/tremolos.  It is effectively a "bible" of all one would want to know about loons, and thus perhaps TMI for the casual reader.  Conversely, it will be a treasured resource for serious "birders," and also for people who spend their summer afternoons relaxing at a lake "up north."

So, thank you Noel and Gregg for inviting me to your lake home this summer, and for the dinners of freshly-caught bass, sunnies, and walleye...