Time to be social

I went out for a quick peak at Bodega Harbor at the end of the day and noticed this flock of birds near Porto Bodega.  How many do you count?  Can you tell what they are?

 

I'll zoom in a little closer.  Even though these are silhouettes, I think you'll be able to see enough characteristics to help you with the identification:

 

Did you notice the relatively short tail (or what sometimes looks like a lack of a tail), the rounded head, and the stout bill?

Here's one individual in slightly better light:

 

I counted thirteen individuals in this flock of Pied-billed Grebes (Podilymbus podiceps) — see first photo.  

I decided to write about Pied-billed Grebes tonight because I don't often see larger flocks of this species, and I thought it would be fun to ask if you've seen large gatherings of Pied-billed Grebes and if so, what's the largest number of individuals you've recorded?

A few fun facts about Pied-billed Grebes:

Males are generally larger than females, and have heavier bills.  If you've noticed subtle size variation among individuals, it could be a difference between males and females.

 

Their stout bills are somewhat unusual for grebes.  The shape is helpful for handling crustaceans (such as crayfish).

Although highly territorial during the breeding season, Pied-billed Grebes are apparently more social during the non-breeding season.

 

Facts above from The Birds of North America account by Muller and Storer (1999).