Black Oystercatcher Monitoring

The Black Oystercatcher is considered an indicator species for intertidal health.  They live, feed and breed on rocky, intertidal shorelines that are vulnerable to rising sea levels, human interference, and predators.  Last year, at Montaña de Oro State Park Ca (MdO), only one of nine recorded nesting attempts produced a nestling that grew to maturity.

The Juvenile that grew to maturity is on the left, to the right, the proud parents of Site 7.  Note the two tone bill of the juvenile. (above photo by Gary O'Neill.)

Conservation efforts for Oystercatchers was limited by lack of baseline information.  A study was needed.  MdO nest monitoring began in 2007.  I am familiar with the MdO Oystercatcher population, having learned details on nesting habits from Sara Kelly, an experienced Oystercatcher (bloy) monitor.  I volunteered to be a nest monitor at Site 7. 

During nesting season Bloys are highly territorial, often nesting in the same location as the year before.  The nest may be in a slight depression or in a space between shale layers.  They share all nesting duties including chasing off interlopers.

9:08 am, Thursday May 21 -  My first monitoring experience began at site 7 aka "Danger Sign," on the north side of Quarry Cove.  The sign has been there as long as I have been volunteering at MdO, and that is over two decades.  I greatly doubt anyone has ever heeded the warning.

Monitoring should be done far enough away from the nest site so as not to cause the Bloy to alert.  They may abandon the nest.  Last year symbolic fencing was installed to keep people from disturbing the Bloys.  Do people climb over it?  YES!!

As soon as I arrived I took out my binocs and began monitoring.  I knew the approximate nest location (center of red circle), but only saw slabs of uplifted shale.  I assumed that hidden from view was a Bloy incubating two to three eggs.  While watching what I thought was the nest site, I took quick looks around for the mate.  About 10 minutes into monitoring a Bloy flew to a nearby
rock and began preening.

Since male and female Bloys look alike, I have named them Babbs and Bob.  Babbs was on a rock preening, Bob was hopefully on the nest.  After a few more minutes Bob rose up from a crack to the right of where I had been focused.  Babbs move in and settled down.  Through a crack in the shale I could see a tiny sliver of a bright red bill.  Now I knew where to look.!!  I had just experienced my first nest exchange. ( At the end of the blog is a youtube video of the exchange.)

The morning was beautiful, sunny, no wind.  Now, Bob was preening and Babbs was sitting on the nest.  All of a sudden chaos reigned.  Three raucous Bloy were flying over the next site.  Bob joined them and a moment later Babbs deserted the nest and flew off with the group.  I was in shock.  No one was sitting on the nest.  I felt helpless.  Fortunately, five minutes later Babbs returned to the nest.  Bob was across the cove feeding.  Later I learned this type of behavior is not unusual. 


My first monitoring experience was very interesting.  I do hope that this pair is successful.  At the present time it is the only nesting pair at MdO.
 

You may have to watch the video more than once, but you can see Babbs settle into the nest site.  From now on I will bring a real camera.

https://youtu.be/srqqWdMBgZw