Not so common

 

Another highlight from the boat trip to Bodega Canyon and Cordell Bank yesterday was a group of Common Dolphins (Delphinus sp.).  Although I'm familiar with this species from the Atlantic Ocean, this is the first time I've seen this dolphin on a trip off Bodega Head.

In contrast to Pacific White-sided Dolphins, Common Dolphins have a more pronounced beak and a darker dorsal fin (see above) and a striking hourglass-like pattern on their sides.  The front portion of this hourglass is colored with a beautiful golden hue:

 

I'm tempted to call these Short-beaked Common Dolphins (Delphinus delphis), but I'm not 100% certain about the identification.  If you have more experience separating Short-beaked from Long-beaked Common Dolphins, please weigh in!  

Don Roberson does a great job at describing some of the differences on his web page about Monterey Bay dolphins and porpoises.  A Short-beaked Common Dolphin has (1) a shorter beak, (2) a brighter front panel (of the hourglass), especially between the pectoral fin and the eye, (3) a dark eyeline between the beak and the eye contrasting with the bright white front panel, and (4) a dark line extending from the pectoral fin to the vent.  

Short-beaked Common Dolphins are also known for spending time in deeper, offshore waters, whereas Long-beaked Common Dolphins are more often in shallow, coastal waters.

Here are more views of some of those characteristics: the dark dorsal fin, the golden color along the side, the bright area behind the eye, and the short beaks:

 

 

 

While the dolphins were bowriding, we noticed a smaller animal among them — a young calf!  This young dolphin was grayer than the adults.  In the pictures below, look for the calf swimming above the adults and note the much grayer coloration overall.

 

 

Although their range includes areas farther north, Short-beaked Common Dolphins are only seen occasionally north of Santa Cruz.  Their occurrence here this year may be associated with warmer ocean water.

 

Slow rollers

 

I joined a Redwood Region Ornithological Society pelagic trip to Bodega Canyon and Cordell Bank today (7 September 2014).  One of the highlights was an encounter with a few Orcas (Orcinus orca).  [In the photo above, there are two Black-footed Albatross in the foreground.]

The Orcas were slowly rolling at the surface.  Their enormous dorsal fins would emerge one after the other and then disappear below the surface.

 

Below are examples of at least two different individuals.  Note the size and shape of the dorsal fin and the gray blaze or saddle just behind it.

 

 

One more shot, with Pink-footed Shearwaters.  The shearwaters are ~19 inches long and have a wingspan of ~43 inches.  Using the shearwater length for scale, we estimated the height of this Orca's dorsal fin to be ~71 inches (nearly 6 feet)!

 

World Shorebirds Day!

September 6th is World Shorebirds Day, so it seems appropriate to post some images of one of my favorite shorebirds.

While doing a shorebird count in Bodega Harbor this afternoon, I noticed some movement in a shallow marsh pool: 

 

Several Red-necked Phalaropes (Phalaropus lobatus) were actively feeding in the pool.

I chose these pictures tonight because they also show some of the habitat the phalaropes were using.  Sometimes the birds would swim in open water.

 

Other times they would cruise up and down small creeks lined with Salicornia:

 

The phalaropes would occasionally pause to look for insects among the floating algal mats: 

 

I hope you get to enjoy or think about some of your favorite shorebirds this weekend!

 

Checking in

 

Adult Brush Rabbit (Sylvilagus bachmani) with young (on left), 24 August 2014

O Sole Mio

Are you ready for your next mystery close-up?  Can you guess what this is?

 

I'll zoom out a little more: 

 

Do you have an idea now?

How about if I zoom out even a little further?

 

Can you tell that this animal has two shells (or valves)?  And that it's just starting to open up and to extend its tentacles outward?

Warning: If you haven't guessed yet, the next photo might give the answer away.

 

Yes!  This is a scallop, specifically a juvenile Rock Scallop (Crassadoma gigantea).  And those small black dots lining the margins of the shells are its eyes — lots of them!

If you look at a cross-section of a scallop's eye, you'll find a cornea, a lens, a double retina, and a concave mirror that reflects light back to the retinas.  This illustration will help visualize those structures:

 

Modified from Speiser, D.I., E.R. Loew, and S. Johnsen.  2010.  Spectral sensitivity of the concave mirror eyes of scallops: potential influences of habitat, self-screening and longitudinal chromatic abberation.  J.  Exp.  Biol.  214: 422-431.  [This figure shows the eye of a Sea Scallop, Placopecten magellanicus.  The scale bar represents 0.1 mm.]

Some research has been done into scallop vision.  It's thought that scallop eyes can probably detect large moving objects (such as predators), and possibly nearby habitat characteristics as well as food particles moving by in the water.

The next image shows the entire animal.  It was only ~1 cm across.

 

This small scallop was the star of a recent music video produced by Eric during his Invertebrate Biology class.  I can't help but sing the praises of this wonderful footage of a scallop in action!

Walking a-long

 

This one's for Megan, and anyone trying to learn more about shorebirds.  Long-billed Curlew (Numenius americanus), Salmon Creek Beach, 2 September 2014.

Snowy in September

 

A Snowy Plover to start September — on Salmon Creek Beach, 1 September 2014.