Thursday, May 4, 2017

Great Horned Owl Fledglings

It's spring, and the marshes, grasslands and woodlands of California are brimming with life as young birds of all description hatch, grow and begin to fledge.  I've mentioned before that when I can't get out into a proper patch of wilderness, I enjoy birding at CSU Stanislaus.  This year, there is something particularly exciting on the college campus: a family of Great Horned Owls (Bubo virginianus).

Great Horned Owls begin breeding very early (or late) in the year, with courtship beginning in the late fall and early winter.  While out for a walk last December, Eric and I heard a pair of Great Horned Owls on campus.  Noting the presence of tall pine trees (potential nesting habitat) and an abundance of prey (gophers and waterfowl), I dared to hope they might choose to stay.  And it turns out, they did!

Great Horned Owls lay their eggs as early as January or February in California.  Eggs are incubated by the female for about four weeks, while the male keeps her supplied with food.  Baby owls are called owlets.  Great Horned Owl owlets are nearly naked, and their eyes are closed at the time of hatching.  At about one week of age, the owlets' fluffy white down is replaced by grayish down; at ten days old, their eyes open.  The female continues to brood the young owlets for a couple of weeks.

Three-week old owlets begin to practice hunting skills by pouncing on sticks in the nest.  At about six weeks of age, they become "branchers," venturing out of the nest onto surrounding tree branches.  Their main mode of transport at this time is climbing, using their talons to grip tree trunks and branches, as their wings have not yet fully developed.  Awkward test flights begin at seven weeks.

The owl couple at CSU Stanislaus has produced two owlets, which is typical for Great Horned Owls.  These fledglings most likely hatched around the beginning of March, and are probably around eight weeks old.  They already have some of their primary wing feathers as well as tail feathers (called rectrices) and are flying short distances between trees (which is fun to watch in the evenings!)

The young owls will stay together through the summer, fed sporadically by their parents as they learn to hunt.  As the juvenile owls grow larger, the parents will begin to roost separately from their offspring.  In the fall, the young will likely disperse to either find their own territory, or become "nonnesting floaters" until suitable territories become available. 

Testing his wings (just after sundown, hence the blurry photo)

Great Horned Owls are fairly common and abundant around the Great Valley, and I see them fairly often.  (I wrote more about their breeding habits earlier this year.)  But it is still a special experience every time I see a Great Horned Owl.  They are adaptable and can be found in a wide variety of habitats, from deserts to mountains, provided there is an availability of ample cover, nesting sites and prey.  In a world of rampant habitat destruction, it's comforting to know that a few stalwart species are still able to carve out a place for themselves in the midst of our human habitat.

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