Thursday, May 3, 2012

Como Park Bluebird Trail Update: May 3rd, 2012

Post contributed by Sharon, volunteer Bluebird Trail monitor:

This is the bluebird nest with the cowbird eggs and
was taken on May 5, when two more bluebirds had hatched. 
You can see 4 bluebirds and the 2 unhatched cowbird eggs.

Some happy news on the trail this week.  The bluebird nest I thought had failed, had not!  Inside were at least four bluebird nestlings; the parent birds monitored me from nearby.  I am glad I was wrong, and very glad I was abundantly cautious and did not remove the nest last week.  It is unusual for a nest to contain five eggs for three weeks, as incubation usually lasts about 12-14 days, tops.  Incubation begins after the last egg is laid, and bluebirds generally lay 3-5 eggs, so it must be that incubation began right after I checked three weeks ago, and the eggs hatched right after I checked last week.  Two tiny pinkish bluebirds had just hatched in the other bluebird nest on the trail.  Two blue eggs, and two speckled cowbirds eggs remain.  A third new bluebird nest has been built in a box in an area with lots of tree swallow activity.
      Chickadees in two boxes have hatched and when I opened their boxes, they lifted their tiny heads and gaped, making soft, nearly inaudible peeping noises, as their parents scolded me from nearby branches.  The third chickadee nest is still totally covered in fur.
      A cowbird egg remains in an abandoned nest.  If it has not hatched in two weeks, I will remove both the nest and egg so another pair of birds can move in.  Two nestboxes contain small amounts of nesting materials.  From the last box I removed the beginnings of a house sparrow nest.  House sparrows often add non-organic materials like plastic wrappers and trash to their nests while other birds do not.  They are a non-native species and can be aggressively destructive to bluebirds and their eggs, so their nests are removed to discourage them from the trail and to prevent future problems.

This photo was taken in the woodland May 3,
it is of the parent great-horned owl (right) and a juvenile (left)

      While on the trail, I came across a family of great-horned owls in the woodland, a parent and two large fluffy owlets perched in an oak.