Greetings from a very, very new birder!

Armed with my Stokes Talons (highly recommended for other newbies), I
spent this afternoon at Discovery Park. I saw a lot of birds that
probably wouldn't excite anyone except me (including an extraordinary
PILEATED WOODPECKER on the bluffs who decided to search for grubs a
few feet from where I stood, two PIGEON GUILLEMOTS, five RED NECKED
GREBES, several HORNED GREBES, and 18 BRANDT)...but I was curious
about two I noticed:

First, I saw a cluster of between 40 and 50 WESTERN GREBE off the
north end of the lighthouse. Is it typical for them to be in such big
groups? I've never seen more than a couple at a time. There may have
been some Clarke's in there, too, but it was difficult to tell without
a scope, which I probably need to purchase. The grebes floated in the
same spot for the entire afternoon. Second, I saw what I swear were
three RHINOCEROS AUKLET -- the size and markings make me think there's
nothing else they could be (orange bill, white plume behind eye, white
mustache, light underbellies). Do they usually get their breeding
plumage by now? Are they common around the park? Sorry if these are
really basic questions, but I'm eager to learn. Thanks!

Meg
gavigan(at)u(dot)washington(dot)edu