Looking west, 2 December 2016
Friday, December 2, 2016
Thursday, December 1, 2016
Wednesday, November 30, 2016
Monday, November 28, 2016
I'm excited to share an update about the identity of last night's mystery object! Here's a reminder of the object that I wasn't sure about:
I had wondered about a bivalve periostracum (the outermost layer)...and also about a snail's operculum (the "trap door"), as had a few other folks. But I wasn't satisfied with either possibility.
For example, after checking various books, I couldn't find any clam with this shape. And, although I started looking at snail opercula, and some of them were closer in shape, the material (very thin and flexible), the chalky layer, and an odd twist along one side of the shell, didn't match with any operculum I was familiar with. Here's a picture of the twist that puzzled me:
However, a breakthrough came today via a Twitter exchange! Annaliese (at Oregon State University) sent out a request for assistance and Rebecca (at the California Academy of Sciences) responded with an identification, including a photo!
Here's the photo of a dried specimen from the California Academy of Sciences:
Compare that with my mystery specimen from Dillon Beach (now dried out, see below):
You can see how similar the shape and texture are.
I agree with Rebecca that this is a good match with her sample which is the *internal* shell of a California Sea Hare (Aplysia californica)! I'll admit that I hadn't known (or had forgotten) that Aplysia had an internal shell, and I've certainly never seen hide nor hare of such a shell. ;)
I know that this phenomenon might be confusing at first, but there are some snail relatives (like sea hares) that have internal shells that aren't visible from the outside. Here's a link to a diagram showing the development of a California Sea Hare (see Research study 2). Note that they have an external shell when very young, but the shell becomes internal in the adults.
Many thanks to Rebecca and Annaliese for solving the mystery!
P.S. Adult California Sea Hares were observed in Sonoma and Marin counties in 2015 and 2016. To review what the adults look like, see the posts from 28 September 2016 and 23 May 2015.
Sunday, November 27, 2016
Okay, this one is a true mystery. We found this object while walking Dillon Beach on 25 November 2016:
Our best guess right now is that it's the periostracum (outer covering) from a large bivalve. (It measured ~6.5 cm long by ~5 cm wide.)
However, the material and its transparency seem different than other bivalve coverings that we've seen, so we're open to any other thoughts or suggestions. The inner surface appeared to have a chalky white residue (perhaps from the middle shell layer of a clam?).
And even if it is the outer covering of a clam, we are uncertain about which species it's from.
Here's another view, this time from the side:
Let me know if you have any ideas about its identity. I'm still working on it, but it would great to solve this mystery!
ADDENDUM (28 November 2016): Several people have suggested this could be the operculum ("trap-door") of a large snail, e.g., a whelk. That's a strong possibility, and at this time I think I'm leaning that way.
ADDENDUM (1 December 2016): For the identity of this mystery object, see the post on 28 November 2016.
Saturday, November 26, 2016
Friday, November 25, 2016
We walked at North Beach on the outer coast of Point Reyes this afternoon (25 November 2016). We'd been walking for a while, watching the waves, and then noticed this bird on the beach up ahead:
A beautiful adult Peregrine Falcon...with prey! Can you see the feathers strewn out behind the falcon? [Click on the image for a larger version.]
It was tough to guess the identity of the prey from a distance, so after the falcon had flown to a higher perch with its prey, we went up to get a closer look at the feathers that had been plucked off. Here are two close-ups of the feathers (see below).
Do you have any guesses about which species of bird the falcon had caught?
The reddish color along the feather shafts is the best clue.
The falcon was eating a Northern Flicker!
(For pictures of a Northern Flicker taken last year, click here.)
When the falcon flew off, it landed on a piece of driftwood further south and continued to remove feathers:
We didn't want to disturb its meal. Then at the same time, Eric and I realized a beach feature could help us get a better look.
The beach had prominent, deep cusps today — high berms alternating with low valleys. Although it's hard to capture in a picture, here's one attempt to show the berms along the shore:
So the three of us (Eric, my mother, and I) belly-crawled from the bottom of a valley to the top of a berm and barely peaked over the top:
It worked! Our low-profile positioning provided amazing views of this falcon eating its prey without interrupting its meal.
As always, lots to be thankful for!