Overt aggression

Well, I can't help but post a few more Red Phalarope photos.  After having been blown close to shore during recent storms, there are still some individuals in Bodega Harbor and at Doran Beach.  Because Red Phalaropes are usually found much farther offshore, this has been an unusual opportunity to study this pelagic shorebird.

A few days ago I had noticed — first by sound, then by sight — some rather aggressive behavior.  One individual would posture towards or actively chase another, often while vocalizing loudly.  According to the Birds of North America account, more information is needed about Red Phalarope behavior and vocalizations outside of their breeding areas (in the Arctic).

Below is a series of images documenting this aggressive behavior.  I have lots of questions about it, but I'll let you review the pictures and wonder about what's going on, too:

 

 

 

 

 

 

Are both females and males aggressive?  What triggers the aggression?  Does it have to do with the availability of food?  The density of birds?  Their condition (e.g., hunger level)?  

Some individuals seemed more aggressive than others — why?  What distance triggers aggressive behavior?  Most of the time, it seemed like they had to be relatively close to each other (less than 2 feet).  

Do they defend certain feeding areas?  Sometimes it seemed like they were defending a particular site...but it also seemed as though that could be temporary, i.e., they eventually moved elsewhere.

What other questions do you have?

P.S.  I hope to post examples of vocalizations tomorrow.