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The other day I was on a field trip with a couple of students in the Natural History Club, at Younger Lagoon. We had permission to go down into the lagoon itself, where we chased tiny red mites around rocks in the intertidal without getting caught by waves, observed a very interesting interaction between a coyote and assorted water fowl, and witnessed killdeer mating. Did you know that in killdeer the actual copulation is preceded by about half a minute of massage? Neither did we! The purpose of the field trip, other than merely to be outdoors looking at cool stuff, was to spend some time doing focused nature journaling. As a result I didn't have my big camera with me. But I did have the good binoculars, and got to watch all of the action closely.

Nature journaling should be part of any natural history club. Over the years I have seen an increase in the tendency to equate nature journaling with science illustration or other types of art. This conflation is what causes people to believe that they can't keep a nature journal because they don't produce museum-quality works of art. While I appreciate a beautiful science illustration as much as anybody else, a nature journal serves a completely different purpose. A nature journal's job isn't to be beautiful. Its job is to be informative.

If you were to compare my nature journal entry with a photograph of the site, you would see that my sketch is nowhere near realistic in the sense of looking exactly like the real thing. I've compressed the entire lagoon into a short stretch that I could fit in these two pages. But I think the sketches and notes do convey the fascinating things what we saw that day. And even if I were not familiar with Younger Lagoon, I would be able to look at these pages and remember them. That's the job of a nature journal.

Entry in my nature journal

I returned to Younger Lagoon two days later with the camera in tow, hoping that some of the birds we'd seen on Monday would still be there on Wednesday. In addition to the usual Canada geese and mallards, I hoped to shoot a couple of water birds that I didn't recognize.

Let's start with the obvious:

Three Canada geese in flight
Trio of Canada geese (Branta canadensis) coming in for a landing
2021-03-24
© Allison J. Gong

All told, there were a couple dozen Canada geese, in the water, in the air, and on the sand. They were a noisy bunch, as usual. Except for when the coyote showed up. Read that little story in my nature journal.

Now take a look at these geese:

Gaggle of 12 Canada geese and one greater white-fronted goose swimming in Younger Lagoon
Gaggle of geese
2021-03-24
© Allison J. Gong

See the one goose that doesn't belong? That was the mystery goose I saw on Monday, and was fortunate enough to see again on Wednesday. From the photos in my bird field guide—National Geographic Field Guide to the Birds of North America—I thought it might be a greater white-fronted goose (Anser albifrons), although I couldn't be entirely certain. I knew I hadn't seen one before, but a consultation with Cornell's All About Birds verified the ID. iNaturalist shows only a handful of observations of A. albifrons in the Monterey Bay region. The greater white-fronted goose is a long-distance migrator, breeding on the tundra of the high Arctic and overwintering in California's Sacramento and San Joaquin Valleys and the Gulf coast of Texas and Louisiana.

Canada goose in water, greater white-fronted goose on land with wings outspread
Greater white-fronted goose (Anser albifrons)
2021-03-24
© Allison J. Gong

A third goose, and another winter-only bird, is the snow goose. It is a little bigger than the greater white-fronted goose. While the word "snow" implies white plumage, snow geese also come in a blue form, which is a dark blueish gray with a white head. The blue coloration is due to a single gene, and the allele for blue is incompletely dominant over the allele for white. The blue and white morphs are the same species and interbreed freely. The offspring of a pure blue bird and a pure white bird will be dark, but may have a white belly. Goslings from pure white parents will be white, and those from pure dark parents will be mostly dark but may have some white.

Snow geese (Anser caerulescens)
2021-03-24
© Allison J. Gong

Of the two snow geese in the photo, the one in the front is all white except for the black wing tips of the species, while the one in the back has more dark coloration. In the photo the beak looks dark, but in better light it's as pink as on the bird in the front.

So that's three species of geese. Now whose butts are these?

Duck butts at Younger Lagoon
2021-03-24
© Allison J. Gong

These tails belong to American wigeons (Mareca americana), a male and female pair in the background and a lone male in the foreground. As you might guess from the behavior, wigeons are dabbling ducks, foraging on aquatic vegetation. Like the greater white-fronted goose and snow goose, these are also winter visitors to California's waterways, and will soon be headed north.

In their winter plumage, the wigeons are rather dull. The breeding male has a brilliant green patch extending backwards from his eye and a broad white streak from the top of the bill over his head. During the winter the green patch becomes is much less conspicuous, although the white streak remains.

Trio of wigeons, with their tails sticking up out of the water
American wigeon (Mareca americana)
2021-03-24
© Allison J. Gong

Three species of waterfowl. I couldn't get the snow geese to cooperate and make up the quartet.

Greater white-fronted goose, American wigeon, and Canada goose
Left to right: greater white-fronted goose (Anser albifrons), American wigeon (Mareca americana), and a pair of Canada geese (Branta canadensis)
2021-03-24
© Allison J. Gong

Living as we do along the Pacific flyway, we find that spring and autumn are great times for watching birds as they migrate between summer breeding grounds and wherever they overwinter. Sometimes I think it's rather unfortunate that I don't get to see these birds in the glory of their breeding plumage, but that's okay because I get to see them in the winter. And the birds that left here for the winter are returning: I saw the first barn swallow of the season right after the vernal equinox! Soon they and the cliff swallows will be building their nests on the buildings at the marine lab. At home, the first of the season's hooded orioles flew past the back deck. He may have been on his way to a nesting site in a palm tree down the street. There is so much going on right now. I do love the spring!

A utility pole across the street and one house down has, for years, been an object of interest for a variety of birds. The hairy and downy woodpeckers drum on it in the spring, and various songbirds hang out and rest on the top. About a month ago now I saw a raptor up there, eating something. It was a female merlin (Falco columbarius). According to Cornell's All About Birds, merlins are in our area during the nonbreeding season, but I've never been certain about having seen one.

On the morning of Saturday 13 March I went outside to look around, and saw a bird on the pole. It appeared to be either eating or cleaning its beak. I ran inside to grab the camera, which fortunately had my longest lens and the 1.4x teleconverter attached, and snapped off a bunch of shots. The sun was rising, but I was able to get some decent photos of the bird even though from the best vantage point it was backlit.

Clearly, he's eating something:

Male merlin (Falco columbarius)
2021-03-13
© Allison J. Gong

But what is it eating? Rodent bits?

Male merlin (Falco columbarius)
2021-03-13
© Allison J. Gong

No, look at that foot. It's a bird!

Male merlin (Falco columbarius)
2021-03-13
© Allison J. Gong

Yep. Definitely a bird.

Male merlin (Falco columbarius)
2021-03-13
© Allison J. Gong

And here he is, taking a break between courses:

Male merlin (Falco columbarius)
2021-03-13
© Allison J. Gong

Merlins are members of the falcon family. Smaller birds make up the majority of a merlin's prey, but they also eat large insects such as grasshoppers. As with peregrine falcons, merlin populations were severely reduced in the years when DDT was widely used to keep insect populations down, but they have since recovered. Truly, the recovery of birds of prey after DDT was banned is one of the great successes of conservation biology.

There were feathers in the street below the pole. I assume they are from the merlin's prey, as when I looked at the top of the pole through binoculars I could see the same sort of feathers up there. I compared the feathers with photos on a few ID sites, but it's no easy identifying feathers without any additional context. Someone suggested that they might be from a male house finch. We have lots of those around all the time, so that's probably the best guess possible.

Feathers from prey of a merlin (Falco columbarius)
2021-03-13
© Allison J. Gong

So there you have it: Saturday brunch with songbird on the menu!

It has taken me months to gather all the photos and videos I needed for this post. I could blame it on the stress of teaching online for the first time, the COVID-19 pandemic itself, or residual malaise from the dumpster fire that was 2020. But really, it's the animal's fault.

In this case the animal is the orange cup coral, Balanophyllia elegans. I've written about this beast before, and lately I've been paying more attention to the corals that we have in the lab. In many ways it is the typical anthozoan—its life cycle consists of only a polyp stage (i.e., no medusa), it is benthic, and its body is vaguely anemone-like. Like the reef-building corals of the tropics, Balanophyllia is a scleractinian coral. This means that it secretes a calcareous base, or exoskeleton, upon which sits the living tissue of the polyp. But unlike the reef-building corals of the tropics, Balanophyllia is solitary, which means that it does not clone or form colonies. Nor does it contain photosynthetic zooxanthellae in its cells, as the reef-builders do. This means that Balanophyllia is a strict carnivore: unable to rely on photosynthetic symbionts to do the hard work of fixing carbon, Balanophyllia has to catch its own prey.

Balanophyllia has separate sexes and reproduces sexually. Males release sperm that are ingested by the female, and she then broods larvae for several months. What is strange about this is that, when you consider the anatomy of Balanophyllia (or any cnidarian polyp, for that matter) the question that comes to mind is, "Where are the larvae brooded?" So let's take a look at the basic cnidarian body plan.

Adult cup coral (Balanophyllia elegans)
© Allison J. Gong

The professor who taught my undergraduate course in invertebrate zoology described a cnidarian's body as a baggie inside a baggie, with a layer of jelly between the two baggies. The inner and outer baggies represent the tissue layers that developmental biologists refer to as endoderm and ectoderm, respectively. The jelly between the two tissue layers is called mesoglea. For the sake of this discussion, it's the endoderm that interests us. In a cnidarian, the endoderm is also called gastrodermis, because it is, literally, the skin of the digestive system. The cnidarian gut is a cavity that opens to the outside via a single opening. We could call that opening either a mouth or an anus, since both food and wastes pass through it, but for politeness' sake we call it a mouth. The gut itself does double duty as both the digestive system and the circulatory system, so its formal name is gastrovascular cavity (GVC).

It's easy to imagine the GVC as being essentially a tubular vase, but it's more complex than that. The GVC extends into each of the tentacles, so the tentacles are actually hollow. The main cavity of the GVC, in the stalk of the polyp, is partitioned by thin layers of endoderm. The partitions are called septa, and serve to increase the surface area of the endoderm for digestion. Think of a large office building, divided into small cubicles by movable partial walls—there's much more total wall space for hanging things such as calendars than there would be in the big room with only four walls. In anthozoans, gonad tissue is associated with the septa.

Now back to how Balanophyllia broods its larvae. As we've seen before, Balanophyllia's planula larva is an orange-reddish wormlike blob about 2 mm long, which is ciliated all over. It doesn't feed, but survives on energy reserves supplied by the mother in the egg; it may also be able to take up dissolved organic material directly from the seawater. After brooding larvae for some period of time in their GVC, Balanophyllia females release larvae. Or rather, the larvae ooze out of their mother's mouth and crawl around to settle and metamorphose nearby.

The planulation season, when larvae show up amongst the corals we keep in the lab, begins in the fall and runs through winter into the spring. Sometimes the larvae metamorphose right away—one day there are no larvae and the next day there are baby corals. Other larvae squirm around for days or weeks, not getting any smaller but not metamorphosing, either. This past season (Fall 2020-Spring 2021) we saw both extremes: planulae that settled and metamorphosed right away, and others that I collected weeks ago and are still worming around.

Orange cup coral (Balanophyllia elegans) with a planula larva
2020-12-12
© Allison J. Gong

I peered into a bunch of corals, hoping to see what the larvae are doing inside the GVC, with no luck. Then I decided to try some time-lapse video under the dissecting scope, and had a bit of success with that. In the video below you'll see about two hours of action compressed into about 1 minute. Watch for a small red ball squirming around inside the GVC. And remember that the GVC extends into the tentacles, so the larva can wiggle its way in there, too.

All of which makes me wonder if the pathway from mother's GVC to the scary world outside travels in only one direction, or if the larvae can retreat back into the safety of the mom's digestive system. How strange is it, that the safer location might be inside the mother's gut!

Eventually, whether it be a matter of hours or weeks, the planula larva settles (i.e., sticks to a surface and stops crawling) and metamorphoses (i.e., makes the anatomical and physiological changes into the juvenile body). There doesn't seem to be a clear connection between surface characteristics and whether or not larvae will settle there. You might think that they'd choose to settle nearby or maybe actually on the parent, but that's not always the case. At some point, however, the larva will have to either settle and metamorphose, or die. When they metamorphose into juveniles, they reveal other aspects of their nature as scleractinian corals.

From what I've seen, the larva begins the settlement process by sticking to a chosen spot and becoming a more circular (i.e., less elongated) blob. On the other hand, I've seen perfectly round red blobs that look for all the world as though they might be pushing out tentacles, change their minds and go vermiform again. But once they stick permanently and begin to metamorphose by forming the polyp's body, they have to continue.

Newly settled orange cup coral (Balanophyllia elegans)
2021-01-29
© Allison J. Gong

The juvenile in the photo above has not yet pushed out any tentacles, but it does show signs of its scleractinian ancestry. The Scleractinia (stony corals) and Actiniaria (sea anemones) are both members of a group called the Hexacorallia. The Hexacorallia and Octocorallia are in turn grouped together as members of the class Anthozoa. As you might infer from the name 'Hexacorallia', animals in this group of a body symmetry based on the number six. And you can see in the photo above that the juvenile coral's body is divided into 12 wedges. When the juvenile begins growing tentacles and a more polyp-like body, the hexamerous symmetry becomes even more evident:

Young orange cup coral (Balanophyllia elegans)
2021-02-22
© Allison J. Gong

The young coral begins by forming six primary tentacles, which establishes the visible hexamerous symmetry. Then it grows the six shorter secondary tentacles. The bumps on the tentacles are cnidocyte batteries, clusters of stinging cells, indicating that the animal can already capture and kill prey. Good thing, too, because if it hasn't already then it soon will deplete the energy stores its mother partitioned into its egg.

By this stage in its development the coral will remain where it is for the rest of its life. As it grows it will deposit CaCO3 and grow taller, but the living tissue will always be restricted to a layer sitting on top of the calcareous base. Once the base grows more than a few millimeters tall, there is no living tissue in contact with the surface. Thus there is no mechanism for the animal to move to another location, or even to re-attach itself if it gets broken off its surface. There are many animals that are likewise unable to move once their larvae have attached and metamorphosed. The decision of where to put down roots becomes quite stark for them, as a bad one can result in a very short life indeed. The selective pressures that enforce a good decision are quite clear, and are important factors in the distribution patterns we observe in the intertidal.

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