For some reason, many of the sunburst anemones (Anthopleura sola) in a certain area at Davenport Landing were geared up for a fight. I don't know what was going on before I got there yesterday morning, but something got these flowers all riled up. We think of them as being placid animals, but that's only because they operate at different time scales than we are used to. A paradox about cnidarians is that they don't do anything quickly except fire off their stinging cells; that, however, they do with the fastest known cellular mechanism in the animal kingdom. Go figure.
What looks like an anemone wearing a tutu is actually an anemone ready to fight. The normal filiform feeding tentacles are easily recognized. But those club-shaped white tentacles below the ring of feeding tentacles are called acrorhagi. They are all about fighting. The tips are loaded with potent cnidocytes that usually aren't used to catch food. They are used to fight off other anemones, and possibly predators.
Here's another shot of the same animal, which shows how the feeding tentacles and acrorhagi are arranged in concentric rings:
So who would this anemone be fighting? This individual was the only one of its kind in the pool where it lives. I don't know why its acrorhagi are inflated. I suppose they could be used to fend off a would-be predator, but I didn't see any other animal in the pool that seemed a likely candidate.
But look at this duo:
Now, clearly there is (or had been) something going on between these individuals. They both have their acrorhagi inflated. I've been looking at this photo for a while and can't decide which is the aggressor. At first I assumed that the anemone on the right had initiated an attack on the other. But now I wonder if that is a defensive posture rather than an offensive one. That animal does seem to be more bent out of shape than the one on the left.
I've seen anemone fights before, and I've also seen anemones living side by side, tentacles touching, in apparently perfect amity. It's very clear that they can coexist peacefully. Why, then, do they sometimes choose to fight? It's important to point out that Anthopleura sola is an aclonal species. Unlike its congener A. elegantissima, whose primary mode of growth is cloning, each A. sola represents a unique genotype. With these anemones, whether or not two individuals fight is not determined by relatedness.
In a different pool these two anemones are sharing the carcass of a rock crab.
Maybe that third anemone at the top had also taken part in the feast, but at this point it seemed to be minding its own business. Given the demonstrated aggression of some A. sola, it would be interesting to know whether or not this trio ever fight amongst themselves. When we 'ooh' and 'aah' over them in the tidepools they look like passive flowers, and we forget that they are active predators. But we humans have access to the anemones' home for only a few hours every month, and I have no doubt that they get up to all sorts of shenanigans when we're not looking.
This morning I went to Natural Bridges. The tide this morning was the lowest of the season, but early enough that for the most part I had the intertidal to myself for a couple of hours. I always like those mornings best.
I did meet a docent out there, and we chatted for a few minutes. Towards the end of the excursion, when the tide had turned and I realized I had to get to the marine lab for the usual Friday feeding chores, she pointed out something that didn't make sense to her. She described it as two anemones side-by-side, but one was really stretched out down towards the water. She wondered what could be going on, as the other anemone looked normal.
Looks strange, doesn't it? What this anemone is doing, I think, is disgorging the remains of its most recent meal. If you look at the oral end, which is indeed stretched down towards the sandy bottom of the pool, you can see two things sticking out. The whitish blob is the internal part of the anemone's pharynx. It is not at all uncommon for anemones to sort of prolapse the pharynx, especially after a big meal. Remember, anemones have a two way gut with a single opening for both food ingestion and waste expulsion. The other thing sticking out of the mouth is a clump of mussel shells thickly coated with slime.
Here's a close-up of what's going on at the mouth of this anemone:
It's hard to tell whether or not the mussels have been opened and digested by the anemone. It looks like at least some of the acorn barnacles attached to the mussel might still be alive, although smothered in slime. Nor can we see how many mussels are still inside the anemone's gut. In any case, the anemone is getting rid of this part of the mussel clump. However, this isn't a phenomenon that can really be watched, unless you can watch in time-lapse. The docent asked, "Doesn't it use peristalsis, or something like that?" The answer is that no, anemones don't use peristalsis. They don't have the type of muscles that can contract in that way. The anemone still has to somehow expel wastes and undigestible matter from its gut, through that single opening that we call a mouth but functions as both mouth and anus.
Our human gut, of course, uses peristalsis to move food along from esophagus to rectum. And while for the most part we don't like to think about how that works, we have all experienced what happens when things don't go as planned. I doubt that anybody gets through life without vomiting, so it is probably safe to say we all know that it is a violent way to thoroughly expel food, toxins, and other noxious items from the stomach. Anemones, however, have no peristalsis and cannot vomit. How, then, does an anemone void its gut of something larger than the typical digestive waste?
This particular anemone is ideally situated to let gravity do the work. Hanging down like this and relaxing the simple sphincter muscle around the base of the tentacles will allow the mussel clump to eventually fall out. Without peristalsis to speed things along, it will probably take a while. Would it be finished by the time the tide comes back? I couldn't stick around to watch, so I can't say. But it was a very cool thing to see, even though it happens about as fast as paint drying.
In Morro Bay, CA, there is a stand of eucalyptus trees that has been designated a natural preserve. In 1973 the Heron Rookery Natural Preserve was established to protect great blue herons (Ardea herodias) as they nested. Since then other bird species have taken to nesting in these same trees. When we were there at the end of May we saw these species with nests in the eucalyptus trees:
Great blue heron (Ardea herodias)
Double-crested cormorant (Phalacrocorax auritus)
Great egret (Ardea alba)
Snowy egret (Egretta thula)
This particular rookery is not at all removed from human activity. It is right across the street from the municipal golf course and next to a hotel, and there is a walking/biking trail that runs directly under the trees. Signs advise people to keep their voices down, but pedestrians are walking under the trees all day, dodging the rainfall of guano from above. The birds don't seem to be bothered.
Unlike the Brandt's cormorants (Phalacrocorax penicillatus), which nest on cliffs and rocks, the double-crested cormorants nest in trees. Birds build nests with local materials, and there is a difference in what I could see making up the nests of these two species. The Brandt's cormorants at Natural Bridges in Santa Cruz were using seaweeds as the main building material; I could see birds flying back with algae in their beaks, and then either handing it off to a mate on the nest or tucking it into the existing structure itself. In some cases I could see the pieces of algae well enough to make a tentative ID.
Those are the Brandt's cormorants. The double-crested cormorants nest in the trees, as we saw at the heron rookery. Here's a pair that have a brood of three chicks:
At Morro Bay, which is an estuary rather than a rocky area, the double-crested cormorants use a lot of eelgrass (Zostera marina) in their nests. Eelgrass is very abundant in the Morro Bay harbor and Estero, whereas the birds would have to fly a bit farther to gather algae. Eelgrass, being a true plant, is less slimy than the algae are, and these cormorants' nests look much drier than the mounds of algae used by the Brandt's cormorants up in Santa Cruz.
A short distance up the coast at San Simeon the double-crested cormorants were nesting in a smaller rookery, also in eucalyptus trees. I liked the pattern of how these four nests were situated in three-dimensional space:
Returning to goings-on at the heron rookery in Morro Bay, the herons and egrets were also raising youngsters in that stand of eucalyptus trees. Remember, this rookery is very easily visited by humans. Here's a view of the trees, taken from the small parking area:
It's difficult to photograph the nests because of all the branches obscuring the view. We were also there near mid-day, with the overhead sun making lighting conditions less than favorable for good photography. I did find one comparatively visible heron nest, containing one parent and one sullen punk-ass teenager of a chick. The nestling had started growing feathers but was still almost half fluff, clearly not ready to fly yet.
Both great egrets (Ardea alba) and snowy egrets (Egretta thula) nest at the heron rookery. Here's a great egret nest with two chicks:
From what I could see, the herons and egrets don't use any marine material at all to build their nests. One factor that determines the suitability of a potential building material is proximity—even if a certain material is fantastic in other ways, birds may not use it (or may use less of it, compared to other materials) if it costs too much energy to fetch and bring back to the nesting site. For the herons at this site, sticks are easy to come by. Another thing to consider is that herons and egrets are not marine birds. Although some populations live and nest in coastal areas, most do not. Thus it is not surprising that their nests are built from materials that are terrestrial rather than marine.
I did not see any snowy egret nests in areas where they could be photographed well. However, there were some adult snowies in their spectacular breeding plumage. There was enough of a breeze to ruffle up those long plumes that used to be harvested to decorate ladies' hats.
Look at these beautiful birds!
For several decades now, the cormorants, herons, and egrets have been nesting in these eucalyptus trees, which brings to mind the consideration of native versus non-native species. The trees themselves, blue gum eucalyptus (Eucalyptus globulus) are non-native, having been imported to California from Australia starting in the 1870s. This introduction was encouraged by calls to replace native trees that had been cleared for fuel and building material, both of which were desperately needed during and after the Gold Rush. Since ecologists began considering the effects of non-native species in the 1980s there has been a backlash against the blue gums. Given their large size, their having been planted in groups to serve as windbreaks, and their propensity for dropping a lot of debris, they are very conspicuous, and it is easy to get all hot and bothered at how in certain places they dominate the landscape.
At which point, however, does a species cease to be considered non-native? Having been established in California for 150 years, what is the role of E. globulus in the ecology of the Golden State? There are many people and organizations that would like to see the blue gums eradicated, or at least their populations greatly reduced. On the other side of the argument, groups such the San Francisco Forest Alliance posit that blue gums should be treasured as heritage trees.
At the Heron Rookery, some of the eucalyptus trees are dying. One reason is sheer old age. Another is the several decades' accumulation of bird wastes onto the soil, which is slowly killing the trees. As the blue gums die, the birds will have to find other places to nest. One of the pro-eucalyptus arguments is that many species of native birds—not just these here but other species such as red-tailed hawks, red-shouldered hawks, and a whole host of songbirds—nest in eucalyptus trees throughout the state. If the blue gums are removed, then where will these undoubtedly native birds nest? Especially if the native trees have long been gone?
Taking the long view, my guess is that the birds will figure it out. Ecological communities evolve over thousands of years. The 150 years of the eucalyptus trees' presence in California seems like a long time, but in terms of ecological time they are merely a blink of the eye. The herons, egrets, and cormorants have been nesting at the Heron Rookery for an even shorter period of time. When this stand of blue gums is gone, due to either natural attrition or removal by humans, the birds will find another place to nest. They might not choose a place that is so easily visited and observed by people, though.
Sometimes things just work out, through no fault of my own. In terms of good minus tides occurring in daylight hours, this weekend's tides are the best we will have all season. Today (Saturday 29 May) is the third of five intertidal excursions I have planned. This morning I went up to Pistachio Beach to collect some things for the Seymour Center. I always feel a teensy bit apprehensive agreeing to collect for anybody but myself, because it is quite likely that I will get skunked and not be able to bring back what is needed. So usually I just agree to keep my eyes open for things that are on the wish list and make no promises.
The current wish list for the Seymour Center includes fishes. I've already brought them some sculpins and a clingfish, but small pricklebacks are also welcome. Pistachio is a popular place for people who fish for large pricklebacks. Apparently they (the pricklebacks) put up a good fight and make tasty eating. The usual way of fishing for them is poke-poling. I am not entirely sure how that works, but it involves a long pole and baited hooks. I think the idea is to lure a prickleback out from its hiding place at low tide, when it is sort of stranded away from open water. Adults get up to 70-80 cm long, and are as big around as my forearm.
Unlike the fishermen, I was fishing for young pricklebacks, hoping to find some that were about the length of my hand. Possessing the ideal set of characteristics for avoiding capture—a long eel-like body, small head, slimy coating, and the ability to augur really quickly into even the tiniest crack amongst the cobbles—these small fish led me on a merry chase for quite a while. However, the advantages that I have over even a wily prickleback are an enlarged cerebral cortex, opposable thumbs, and the dexterity to use both a dip net and a zip-loc baggie. When all was said and done I had two appropriately sized pricklebacks in my baggie, and two others had gotten away from me. Oh, and I did also bag another clingfish!
Having had that bit of success and not wanting to press my luck, I started poking around just for the hell of it, without any clear objective in mind. As I've said before, what we gain from a super low tide like this (-1.6 ft) is not only access to more real estate in the low intertidal, but more time to spend there before the tide returns. I took lots of photos, which I will present in chronological order. These will give you an idea of what it was like out there this morning.
Even the hike across the beach yielded something nice—this small stand of Postelsia palmaeformis, the sea palm. These poor junior kelps will be taking a beating with these spring tides rushing up and down. That's the price they pay for living out there on those exposed rocky points.
The leather star Dermasterias imbricata isn't one of the most common stars in the intertidal around here. It was one of the species that was hit pretty hard by the most recent outbreak of Sea Star Wasting Syndrome. We see one every so often, but they are nowhere as abundant as the ochre stars or bat stars.
Pistachio Beach isn't the best place for large anemones, but of course there are some. This is one of the few big Anthopleura anemones that I saw today. There are many of the small cloning anemones, A. elegantissima, in the high intertidal, as well as the moonglow anemones, A. artemisia, in the mid and low sandy areas.
I was so pleased to see my favorite red alga doing really well in the low zone! It is so pretty.
And at the same time I accidentally discovered a pretty big rock crab, which was tucked under a rock. For its species, this one was pretty calm and didn't come at me with big claws up. It could be that this crab is a male, and is clasping a female beneath him. I didn't check.
One of the things I found while turning over rocks to look for fish is this purple urchin:
And a bit later, a nice healthy group of Dictyoneurum californicum. As these thalli age, they will develop longitudinal splits at the base of the blades. Right now they are young and crispy.
And who can resist such an exuberantly decorated limpet? Certainly not I! Reminds me of the fancy hats that ladies used to wear for Easter. Or Beach Blanket Babylon.
Chitons, the overlooked molluscs that reach peak abundance and diversity in the intertidal, can be very common along the coast. Species composition varies from site to site, though. Here at Pistachio Beach, the two species of Tonicella are very common. I found several of them on the undersides of rocks. This one is T. lokii.
After two hours of catching fish and looking around, I was getting cold. Time to head back up and out. That took an additional half-hour or so, because I kept getting distracted by the algae. For example, look at how beautiful this Fucus is. And note the swollen tips, which mean this thallus is getting sexy. 'Tis the season, after all.
One of the other rockweeds, Pelvetiopsis limitata, was also very thick and abundant.
The rockweeds share the high intertidal with a few species of red algae. The most common reds in this zone are the two (or however many there are) species of Mastocarpus, and Endocladia muricata.
I always want to stop and look around in the high zone on my way down. Because when I walk past sights like this, it's hard not to stay and study more closely. Then I remember that I can take as much time as I want in the high zone on the way out. This morning I took lots of photos of these reds and rockweeds.
How many different types of seaweed can you see?
So there you have it, my morning summarized in about a dozen photos. I hope your Saturday was as enjoyable as mine was!
The rocky intertidal is coming into its full summer glory right now. The early morning low tides have been spectacular in May, and they'll get better for the remaining few days of the month. This morning I went out to Franklin Point to poke around. Low tide was -1.8 feet (yippee!) at 06:13. And for once the swell was also down, so the ocean seemed very far away from the mid-tidal zone. See?
One thing that's nice about Franklin Point is that despite its exposure, especially on the north side of the point, all those boulders provide a lot of protection from the incoming waves. It's amazing how they serve to dissipate the water's energy. Of course, that doesn't prevent the inevitable rise of water in the pools, but at least when it arrives it just floods boots instead of knocking down a distracted marine biologist.
Here's a 20-second video I shot from the same spot.
Just as in any terrestrial habitat, summer is when the photosynthetic organisms come to dominate the rocky intertidal. Even a cursory glance shows that every surface is covered with algae and/or surfgrass. So why not showcase some of these organisms when they look their best?
In terms of biomass, Egregia is by far the most abundant alga along our intertidal coast. Individual fronds can be 5+ meters long, and several fronds arise from each holdfast. Higher up in the mid tidal zone the Egregia was forming curtains hanging down along vertical faces.
But Egregia does know how to share the spotlight. Here it is posing with a couple of other low tidal denizens:
That's Egregia on the left, of course. One of the laminarian kelps, Laminaria setchellii, is taking center stage in this shot. When it lives in the subtidal Laminaria setchellii is an understory kelp; it gets to about 1.5 meters tall and can form dense stands. In this species each holdfast gives rise to a single stipe that in turn opens into a wide blade that is deeply divided, as you can see. The surfgrass Phyllospadix torreyi is on the right. There is a lot of surfgrass in the rocky intertidal these days. It's pretty treacherous stuff, too. It's very slippery and likes to cover pools that are deeper than you'd expect. I've learned the hard way that it cannot be trusted at all.
My favorite seaweeds are always the reds. And my favorite of the reds is Erythrophyllum delesserioides, looking so lush and pretty this time of year. It is a low intertidal species, and can be locally abundant. Some years it seems to get beat up and look ratty, but this year it looks great. Here it is, surrounding a couple of Laminaria setchellii.
Here's a grouping of Erythrophyllum and some other reds. I can see two species of Mazzaella, and of course there are Egregia and Phyllospadix mingled together on the right. So pretty!
When the tide is as low as it was this morning, a marine biologist has a lot of time to explore. I had just about exhausted the batteries in both my camera and my phone and was getting uncomfortably cold when I decided to head in. On the way back I stopped to take a look at the rockweeds, which live in the high intertidal. Franklin Point isn't a hotspot for rockweed abundance or diversity, but I did see this nice thallus of Fucus.
Fucus is the seaweed with the bifurcated branch tips. The tips are starting to swell up, which means this thallus is getting ready to spawn. Of all the algae, rockweeds are unusual in that they have what phycologists call an "animal-like" life cycle. They don't have sporophytes or gametophytes. They just have bodies, or thalli. Some thalli are female and some are male. Instead of releasing multiple kinds of spores and whatnot, they release eggs and sperm. The resulting zygote develops as you would expect, only instead of forming a young animal it grows into a baby seaweed.
I do love that olive green color of the rockweeds, which belong to the phylum of brown algae (Ochrophyta). Notice that there's a bit of similarly colored sheetlike seaweed right below the Fucus. That seaweed has the same color, but is in the red algae (Phylum Rhodophyta). Once again, we are reminded that the algae cannot be reliably sorted into phyla based solely on color. Mother Nature can be very tricksy!
So there you have it, my trip report for this morning's excursion to Franklin Point. The tides are excellent for the next several days, and I will be out there for most of them. This is my favorite time of the year.
A week ago I snagged a stint with a traveling nature journal that is making the rounds. It's a nature journal that is being sent to whoever wants to take it. Each user keeps the journal for five days or until five pages are filled, then sends it on to the next person. I was lucky enough to be the first person to respond when it became available, and the journal arrived chez moi this past Monday.
I gotta say, thumbing through the journal and looking at the work of the folks who had it before me was both thrilling and a little intimidating. But it was so exciting to get to study other people's nature journal pages. Just seeing the different styles and focuses was a fantastic learning experience for me. At first I wondered how the heck I would find five pages' worth of stuff to write/draw about in five days. However, something about having the book in hand released the mental block and stuff just flowed onto the pages. Oh, there was a lot of erasing and a little trepidation the first time I put pen to paper, but overall it was a lot of fun.
Anyway, here are my pages.
Monday 2021-05-17 I found the not-so-secret nesting spot for the Brandt's cormorants. This is apparently a new site for them. I had a lot of fun with the cormorants on the rock—all those postures to study and draw! And I'm very pleased with the larger pair in the corner. They actually look like cormorants!
Tuesday 2021-05-18 The journal has both white paper and tan toned paper. Nobody had used any of the toned pages yet. I decided to use it for these sketches of blooming sand plants. My favorite sketch on this page is the California poppies.
Wednesday 2021-05-19 While flipping through the photos I had taken at Asilomar over the weekend, I decided to draw some of the molluscs. My favorite on this page is the turban snail. And octopuses are really hard to draw!
Thursday 2021-05-20 I used my last two pages to diagram sea urchin larval development. The difficult thing about this page was getting the layout to flow the way I wanted. I used about half an eraser, trying different arrangements of text and drawings! The sketches themselves were not that difficult, as I've drawn these larvae many times before.
So there you have it—a week's worth of nature journaling. It was an immense honor and pleasure to participate in this living document of nature observations. I've sent the traveling journal up to Anchorage, Alaska, and am excited to see what the next person does with it.
As we speed towards the summer solstice the days continue to get longer. The early morning low tides are much easier to get up for, as the sky is lightening by 05:30. Even so, when traveling an hour to get to the site, it's nice when the low is later than that. This past Saturday the low wasn't until 08:00. My parents were in Monterey for the weekend, so I decided it would be a good day to work the tide at the southern end of Monterey Bay, and then visit my parents. The Monterey Peninsula has some of the most spectacular tidepooling terrain in the region, and if I lived closer you can bet I'd know those sites better. Not that there is anything at all wrong with the sites on my end of the Bay and up the coast. But sometimes it's good to get out of one's comfort zone and explore the less well known.
So explore we did. It was cold and windy. The tide wasn't all that low and the swell was up, so we didn't get beyond the mid-tidal zone. My hip boots have deteriorated to the point that I have pinprick leaks at the seam where the boot part meets the leg part. Usually the tiny leaks don't bother me, but when the water is cold I definitely feel the trickles. What all this means is that I didn't get down into the low zone, which is fine. Biodiversity is highest in the mid zone anyway. The mediocrity of the low tide meant that I had to keep an eye out for sneaker swells, so less heads-down poking around and more scanning from above and then zooming in on individual items of interest.
One thing we noticed right away is that groups of Tegula funebralis, the black turban snail, were clumped together above the waterline of the high pools.
I'm trying to decide whether or not this is noteworthy. The pattern did catch my eye, but that might be only because it's unusual (although not particularly interesting). It was a cold and drizzly morning, so the snails didn't have to worry about desiccation. Was the clumping together benefiting the snails in any significant way? Hard to say.
The T. funebralis were also clumping together in the water! Here's a large clump of Tegula shells in a pool.
Almost all of these are snails, but can you see the one that is a hermit crab?
Poor Tegula funebralis. It is so common that it is invisible and vastly underappreciated. I find them quite charming, though. There's something about a grazing snail's slow way of life that is very soothing. Not that you might not fall asleep waiting for them to do something interesting, but it is good to slow down to the pace of nature. Anyway, Tegula is one of my favorite animals, precisely because it is so unassuming and ignored. One of delightful things about Tegula funebralis is when it plays host to Crepidula adunca. I've written about the biology of C. aduncabefore and don't want to rehash that here. I just wanted to show off my favorite photo of this trip to Asilomar:
I don't know why I like this photo so much. It certainly isn't the best shot I've ever taken. There isn't any vibrant color at all. The subjects are the same color as the background. But it works for me.
When it comes to a snail's pace, you can't find anything slower than Thylacodes. That's because Thylacodes squamigerus is the snail that lives in a calcareous tube. Much like a barnacle, or the serpulid worms that have similar tubes, Thylacodes makes one decision about where to live and lives there for the rest of its life. I see Thylacodes at places like Pigeon Point up north, but they are much more abundant on the Monterey Peninsula.
And the snail winners in the Most Likely to be Overlooked have got to be the littorines. These little snails (most of which are smaller than 15 mm) live in the highest intertidal, where they get splashed by the ocean just often enough to keep their gill sufficiently moist. They are never entirely submerged, but they do tend to gather in cracks, even the tiniest of which will hold water longer than a flat rock surface.
If you look closely at the photo above, you might see pairs of mating snails. Given where they live, high up in the intertidal where they are rarely covered by water, broadcast spawning isn't a viable option for the littorines. They have to copulate. There are, I think, eight copulating pairs in this group of ~30 snails.
Because Littorina's habitat makes broadcast spawning an unfeasible option, the snails must lay eggs. But the splash zone isn't a very friendly place for the eggs of marine animals. The littorines lay eggs in gelatinous masses in crevices or depressions where water will remain. After a week or so of development, the egg mass dissolves as it gets splashed, and veliger larvae emerge. They recruit back to the intertidal after spending some period of time in the plankton.
When all is said and done it's difficult to make the claim that snails live exciting lives. Nonetheless, they are interesting animals. The diversity of morphology and lifestyle we see in the intertidal snails makes them eminently worthy of study and appreciation. I like to think that, as biologists once again "discover" the usefulness of natural history, students will be encouraged to fill in some of the gaps in our understanding of these and other abundant animals.
It never really feels like springtime until the swallows have returned to the marine lab. This year the barn swallows (Hirundo rustica) came back right on schedule in the last week of March. They have been flying around ever since. I've seen them gathering mud on the banks of Younger Lagoon, but they haven't been very serious about nest building. The cliff swallows (Petrochelidon pyrrhonota), on the other hand, were late arrivals, and I was beginning to worry about them. I didn't see the first cliff swallow until the 1st of May.
Unlike the barn swallows, the cliff swallows immediately started spackling mud on the buildings. There have been a few aborted attempts, but overall they have been very busy little birds. I've been keeping an eye on one nest in particular, as it seems to be the one progressing most rapidly. This nest is located on a building that has been used every year, by both barn swallows and cliff swallows. In previous years I've seen and photographed the nests side-by-side. There isn't any reason to expect them not to nest together again.
So here's what has been going on so far.
The first stage is a simple shelf of mud. The birds are building on vertical walls, but corners where they can use two walls are prime locations. Even a tiny ledge can be used to support those first splats of mud, and once the mud dries it becomes foundation for additional layers. See the mud in the swallow's beak?
Sometimes the birds get this far and then decide to abandon the nest. And sometimes they keep going. Here's what's going on less than a meter away from this nest.
Notice how the birds use their tails as braces so they can cling onto vertical walls. Woodpeckers do the same thing. Of the four birds in the photo above, the two outer ones look like they're just starting to build. I've seen two birds flying in and out of that larger nest, but have no idea whether or not they're the same two birds every time. I suspect they are a mated pair.
The cliff swallow's nest is the gourd-shaped one, with a body that narrows to a much smaller opening just big enough for one bird to pass through. When the nest I was watching got to the stage in the photo above, I thought the opening would be on the left, since there's already a nice curve along that side of the front edge.
I might be kind of right. Today the opening is much narrower, and located off-center towards the left.
This nest may be finished tomorrow or the next day. It will have taken the birds about a week from start to finish.
Why are there no birds near the nest, you may ask? Well, when I walked out of the building I noticed that all of the swallows were in the air, and nobody was at the nest site. The birds were making alarm calls and flying around, but it didn't look like they were feeding, and none were returning to the nests even for short visits. I looked around and up and found the reason for the swallows' unrest.
The hawk was perched directly across from the swallows' nest site, and the swallows were not happy about it.
(For some reason the embedded video isn't working right now. You can watch it from YouTube directly by clicking on that link in the lower left corner.)
Some of the swallows flying around the hawk were barn swallows. I think they are nesting in the breezeway of the building under the hawk. Anyway, the hawk's presence was obviously upsetting to all of the swallows. It hung out for about 10 minutes and then flew away over the field. And immediately, the cliff swallows got right back down to the important business of building a home for the next generation.
A few weeks ago I went out to Franklin Point and saw that the sea lettuces (Ulva sp.) were spawning in the high pools. I revisited the site today, with a lower tide to work with, and spent a considerable amount of time looking for and photographing the staurozoans. I did find some, too! But they are not the focus of this post.
As the tide came back in, I spent more time working my way through the higher pools. At Franklin Point there are very few places where the water is still. Even in the high regions the intertidal terrain is more surge channels than pools. But if you go high enough up the beach there are some quiet areas where the water, if it moves, does so very slowly. It is in these areas where the algal spawn forms those beautiful patterns that I photographed at the beginning of the month. Today there was much less algal spawn accumulating in the calm areas. It was also windy (and cold) this morning, so the patterns were not as crisp as they had been in early April. Still pretty, though!
On my way back up the beach I saw something that looked like an iceberg viewed from the air.
This is an accumulation of foam being pushed ashore. I didn't have any way to collect a sample to bring back to the lab for closer observation, but foams like this are usually due to algal particulates. Surface agitation whips up the organic matter, which act as surfactants and produce tiny bubbles. I'd be willing to bet that the Ulva spawn is at least partly responsible for this foam.
I watched the foam for several minutes, and was rewarded for my vigilance. I found an area where the highest reach of the incoming tide was gently washing back and forth.
I found the slow swirling to be rather mesmerizing. Maybe that was due to the early morning, the brisk sea air, or hunger pangs. But when I saw this I thought to myself, "I've seen that somewhere before." You might be able to guess where.
To validate my intuition, when I got home I looked up some images and found that I was sort of right after all.
Okay, so maybe the resemblance isn't as strong as all that. But I can still imagine the streams in van Gogh's painting swirling and flowing the way the algal foam does. What do you think?
For animals that do essentially nothing when you see them where they live, chitons have a lot of charm. They are the kind of animal that, once you develop the search image for them, you start seeing everywhere. It helps that they are easily recognized as being chitons because of their eight dorsal shell plates—nothing else looks like them. Depending on species, those shell plates can be smooth or sculpted, and pigmented or not. Patterns of sculpting and pigmentation (or lack thereof) are diagnostic features used to distinguish different species. Some species are reliably consistent in appearance and look the same wherever you happen to see them. Other species show a lot of phenotypic variation, often even at a single site.
One of my favorite chitons is Mopalia muscosa, the mossy chiton. It's one of the easiest of our chitons to identify, because its girdle (the layer of tough tissue in which the shell plates are embedded) is densely covered by long, curved spines. They're called spines, but they're quite soft and flexible. Your basic Mopalia muscosa looks like this:
Mopalia muscosa is one of the species whose appearance is quite variable. Many of them wear algae, usually reds but occasionally greens or browns, on their shell plates. Not all species of chiton do this. I've often wondered why some chiton species wear algae and others do not. This individual is probably fairly old, judging by the worn condition of the shell plates. The plates show signs of erosion, but are not decorated. There are some small pieces of coralline algae amongst the spines of the girdle, though, which I always associate with age. Smaller, and presumably younger, M. muscosa tend not to have algae on the girdle even if they are wearing some on the shell plates.
The degree of shell decoration in M. muscosa varies from none, as above, to heavy encrustation. This individual below has been colonized by only a small bit of coralline algae and perhaps some brown diatom-ish film on the edges of the shell plates:
This next one has only a small bit of coralline alga, but sports a jaunty sprig of something quite a bit larger.
This season's fashionable chiton will go all out with the coralline algae, wearing both encrusting and upright branching forms. Look at this:
Sometimes the chitons wear the larger leafy red algae, in addition to or in place of the coralline algae. I always think that these individuals must be very old, by chiton standards.
And sometimes the chitons are so covered with algae that they blend in perfectly with the surrounding environment.
These chitons can get very heavily fouled by algae. Is there any benefit to the chiton, to carry around a load of red algae? And if wearing algae is for some reason advantageous, is there a way for a chiton to attract algae to settle on their shell plates? Well, let's think about that. Chitons' main predators would be sea stars, crabs, and birds. Sea stars do not locate prey visually, so camouflage would not be very helpful in avoiding them. Birds such as oystercatchers and surfbirds certainly do pry up chitons and limpets, and blending in with the background just might help a chiton go unnoticed by an avian hunter.
Regarding the matter of how the algae end up living on chitons' bodies, I want to start with the question of how prevalent algal fouling is on Mopalia muscosa, and the extent of fouling on the chitons that are wearing algae. A little research study might be a fun way to spend my time in the intertidal. Pigeon Point is a lovely site on a foggy summer morning, and many of the most heavily decorated M. muscosa in my photo library are from there. Yes, I can foresee several visits up the coast over the next few months. Laissez les bons temps rouler!