On Saturday, EPIC volunteer Ronald Pieters hosted a bird walk at Salines d’Orient as part of International Migratory Bird Day. We are currently in the fall migration period when a number of birds are making stops in the Caribbean. On the walk we saw 34 species of bird, including migratory and resident species. Below are photographs of a few of the birds we saw.
The next bird walk is scheduled for December 10th, so get in touch with EPIC if you are interested in attending.
I have a couple follow-ups to previous posts. The first involves the ruddy turnstone with the banded leg. I heard back from bandedbirds.org, which is indeed still active and receives resightings pretty much daily. I also got a response from reportband.gov. This bird had hatched in 2007 or earlier, and was banded on May 14th, 2009 in Cape May County, NJ. Also, instead of just sending the info, they build it into a certificate of of appreciation awarded to the person who reported the sighting. If this isn’t a great way to encourage people to go out and check for banded birds, I don’t know what is.
My other follow-up concerns the very beautiful wolf spider I saw two days ago, which is in the last photo in this post. I was consulting Mark de Silva’s book on spiders of St. Vincent and the Grenadines and noticed that my spider was strikingly similar to Hogna sanctivincenti, which was thought to be endemic to (only found in) St. Vincent. I emailed Mark, and he agreed that it is probably the same spider, noting that so little is known about the spiders of the Caribbean we really don’t have a good idea of their ranges. In the case of this spider, the sighting here is probably a pretty strong indicator that this species may also live on many of the islands between here and St. Vincent. Think about how much there is to be learned about the creatures on this island and our neighbors in the Caribbean.
Even a short walk around the Grand Case area can be full of little mysteries. Or, at least, a few things that are interesting to ponder. Here are a few things I wondered about yesterday.
Étang de Cimetiere, at the southwest end of Grand Case, is a popular nesting area for many egrets. In particular, there is one mangrove surrounded entirely by water that is the most popular. (You can see it during nesting season here.) You can see a current photo below, and it is pretty amazing how defoliated this tree is in comparison to those on the shore. It’s easy to understand that a nest surrounded by water is going to be safer for eggs and chicks, but are nesting aggregations normally this extreme? Also, how long can the tree withstand this disturbance, and if it dies, where will the egrets nest? It is interesting to note that cattle egrets, which are now probably the most common egret on the island, are actually an old world species that came here on its own. They first became established in South America in the 1930s, and expanded from there. So, they’re actually fairly new here and perhaps it wouldn’t be that surprising if they’re more than a mangrove can handle.
I am also intrigued by Étang de Grand Case, which is somewhat different from most of the other ponds on the island. On the south side of the pond there’s a large grassy wetland area. It is pretty much like the typical temperate wetland one would find in the US, but unlike the mangrove wetlands that are the primary type seen in tropical areas. In this area, you can see various grasses and succulents that are adapted to wetland conditions. It makes me wonder if this is a naturally occurring habitat, or if it is there because mangroves were cleared from the area at some point. There are some similar areas surrounding the airport pond in Grand Case and near the lagoon, so it is also possible that this exists here naturally. Perhaps there were more areas like this that are gone now because they’re easier to clear and develop than mangroves.
Then, of course, there are the frogs. When walking around Étang de Grand Case, I found two dead frogs, both several times larger than any frog I’ve seen on the island. They have the toe-pads of a tree frog, so my best guess is that they are Cuban tree frogs, which are large and are on the island. If that’s true, then every other Cuban tree frog I’ve seen has been relatively small. Regardless of the species, though, why were they dead? It’s well known that amphibians are vulnerable to pollution because their skin is permeable, so perhaps that’s the case. I suppose they could have also been killed by a bird that was big enough to kill them but too small to swallow them. There are many possibilities, but for now it is a mystery.
The photos below include the things mentioned above, as well as immature common moorhens, an American coot with its chicks, a great blue heron, a Caribbean leatherleaf slug, a spitting spider with its egg sac and a really pretty wolf spider.
After figuring out how to find the critters hiding in the sargassum, I couldn’t help but do the same thing again the next day. I didn’t really change my technique, but I figured I would post Sargassum II: Crustacean Bugaloo anyways.
If you’re curious about the technique for photographing them, it was pretty simple. I used a coffee filter to strain the sea water so it was relatively clear and put it into a clear glass bowl with a little flash on each side, triggered by my camera. To get underwater, I just used the flat port from my camera housing, holding it in the water with one hand while I pointed the camera with the other. I think a better approach would be to use translucent container (like tupperware) that would act as a diffuser and put a matte-finish bottom inside the container maybe either black or white. Perhaps I can try this next time.
Below are a whole mess of photos of shrimp and crabs. One thing you might notice on many of the shrimp is a lump on one side of the thorax. These are isopods which parasitize the shrimp. Specifically, they are from suborder Epicaridae, which includes a variety of isopods that parasitize crustaceans (or actually, other crustaceans, because isopods themselves are also crustaceans). The females, which are much larger than the males, attach themselves to the gills of their shrimp hosts and feed on their blood. Often, and it looks to be that case in these photos, the shrimp actually grow their carapace over the isopod, creating the lumps you see in the photos (compared to the symothoid isopods you can see on fish, where the isopod itself is visible). Also, there was one free-swimming isopod that you can see below, it’s dark and curved.
I recently finished watching the lectures from Sean Anderson’s Conservation Biology class on iTunes U. Compared to the last course I watched, Principles of Evolution, Ecology and Behavior, Conservation Biology is less revelatory and perhaps less interesting for a layperson, but that’s not a criticism of the course itself. Conservation Biology has a much narrower focus, which inevitably means it will have a narrower audience.
What you do get is pretty great for anyone interested in the subject. On the scientific side, concepts like island biogeography and metapopulations are covered in detail. There are also many discussions of conservation history and policy, so you end up with a good understanding of topics like the history of protected areas and the Endangered Species Act. This history helps put the current conservation thought and policy in context. There are also a number of lectures which illustrate conservation principles by focusing on a single species, which are quite excellent.
Overall, I really enjoyed this course. I would highly recommend it to anyone interested in the topic. Anyone more interested in an introduction to big ideas in science would probably find this class a little too detailed. On a practical note, the lectures aren’t numbered in iTunes and there are lectures from multiple years available. I watched the 2011 series, and a few of them appear out of sequence in iTunes, but this wasn’t an obstacle to understanding or enjoying the lectures.
By now St. Martiners are plenty familiar with the huge influx of sargassum that has washed up on our eastern shores. You may have also noticed how abundant shorebirds and other birds are on those same beaches right now. Is there a connection and perhaps a silver lining to this smelly nuisance?
The starting point for a possible connection is the impact of the sargassum on invertebrates that scavenge vegetation on our beaches. Although I can’t be sure, it seems highly likely that isopods, insects and other small, coastal detritivores are experiencing a population explosion due to the large increase in available food and shelter. Shorebirds are obviously foraging on these mounds of rotting algae, and other birds like the barn swallow are feasting on flying insects in these areas. But are we seeing more birds right now? If so, how could that be?
Probably the total bird population has not increased. After all, unlike insects, most of these birds only breed once a year, so it is too early to see much of an impact in overall bird numbers. It’s possible that some birds that might have starved in a normal year would have survived with this extra food available, but that’s probably a relatively small number.
On the other hand, we are in the middle of a pretty busy time for migration, with many species either arriving to or leaving the island between August and October. Perhaps it is possible that some birds would stay here a little longer than they otherwise would, increasing the local population. Presumably the extra food wouldn’t encourage birds to fly here earlier than usual, because they would have no idea that the extra food is here. I think it is possible that if some birds delay their annual departure and others take longer visits as they fly over, this could be noticeable, particularly when combined with the normal seasonal arrival of other species.
Another possibility, which seems pretty likely and may be happening at the same time, is that bird populations on the island have gravitated towards the impacted eastern beaches to take advantage of the resources there. In this case, people (like me) may be more apt to notice the large numbers of birds on some beaches while not noticing that other areas have fewer birds than normal.
Of course, maybe nothing special is happening at all. Shorebirds arrive on the island at this time of year every year, and unless you’re counting, it’s hard to tell if there’s really any difference this year. Unless someone is actually studying this on one of the affected islands, we probably won’t know. It’s too bad school is out for the summer, because this would be a pretty great science fair project.
Below are some photos from Baie de l’Embouchure. Right now you can go there and see a lot of sargassum and lots of shorebirds.
Above is a photo of a ruddy turnstone (Arenaria interpres) that I took yesterday at Salines d’Orient. When reviewing my photos in the evening, I noticed it has a flag on its left leg that says PU6. Although it hadn’t occurred to me before, in retrospect it seems obvious that there is at least the potential to see banded birds on St. Martin.
If you live on the island or have visited at different times of year, you’ve probably noticed there are a number of birds that are only here part of the time. The laughing gull is probably one of the most noticeable, but maybe you’ve also noticed that the population of barn swallows on the island has gone from none to roughly a bajillion in the last week or so. St. Martin is a temporary home for many migrating birds that spend the rest of their time in North or South America. I would go so far as to guess that the majority of species that can be seen on the island are migrants.
This turnstone was banded in the US, probably on the Delaware Bay, which is a major stopover point for this species. Adam from EPIC says that he sees banded birds here, particularly ruddy turnstones, on a regular basis. I found a couple places to report banded bird resightings: bandedbirds.org and reportband.gov.
Reporting banded birds is an easy way to get involved in research and protection efforts, and adds some extra excitement to birdwatching. On bandedbirds.org, you can find information about what species are banded and what information to record when you see a banded bird. Obviously, the bands and rings used to identify the bird are important, but it is also valuable to record information about things like the number of birds in the flock and the ratio of banded to unbanded birds.
Saint Martin is just one small island, but seeing banded birds is a reminder that the fate of ponds, wetlands and coastlines here has an impact on animals that live as far away as Canada and Brazil. Good luck spotting some banded birds!
Lately it seems like there is always another tropical storm just over the horizon, threatening us with death and destruction. Setting aside for a moment the impact on people and property, let’s consider the impact on wildlife on the island.
It’s been over fifteen years since the last major hurricane hit St. Martin, and according to many folks who have been around here since then there is a lot more wildlife on the island now. The bananaquit (Coereba flaveola, also known as the sugarbird or sucrière), which is extremely common on the island today, was rarely seen in the years after Hurricane Luis. Surely the same is true for many other species that are not as noticeable or well-known.
Even though hurricanes are a natural phenomenon that has impacted the Lesser Antilles since long before the arrival of people, habitat destruction has increased their impact on wildlife. Species that may already be struggling to survive in limited, degraded habitats may by wiped out entirely by a hurricane or take much more time to recover. Differing rates of recovery between species could alter the balance of our island’s ecosystem either temporarily or permanently.
A major hurricane is, in some ways, a big biological experiment. It has the potential to reveal a lot about how island ecosystems are impacted by a natural disaster and how they recover. Of course, much of what we could potentially learn is limited by what we already know about the island in its pre-hurricane state. In many ways, we don’t know that much. For example, there are several species of dove (zenaida, Eurasian collared and white-winged) that are similar in size and preferred habitat and probably compete with each other. If we don’t have a good idea of their relative populations today, we won’t really be able to tell if that changes after a hurricane.
On the other hand, even without a great deal of systematically-collected data, we would probably learn more about the impact of a major hurricane than we did last time around. In addition to data collected by the Réserve Naturelle, the Nature Foundation and groups like Environmental Protection in the Caribbean, there are plenty of less formal sources of data. Digital photography and online photo sharing, for example, will give us a much clearer visual picture of the impact of a hurricane next time around. With more dive centers on the island, there are more people familiar with the local marine environment than ever before. Hiking clubs, like St. Martin Trails, not only increase the number of people with firsthand knowledge of the island, but also make it easier to contact those people to collect personal observations.
Overall, the next big hurricane will be something of a missed opportunity to seriously study the biological impact of such a disaster. On the other hand, we’ll surely learn a lot more than we have in the past, so at least that’s a start.
After being away for a couple weeks, I returned to find the sargassum that had been washing up on the beaches of St. Martin has accumulated to a surprising degree. Sargassum is seaweed, and typically refers to a couple species in the genus Sargassum that live in the open ocean. This is unlike many macroalgae, which are attached to the bottom in shallow waters.
The Sargasso Sea in the North Atlantic Ocean is, of course, named after this alga. For the most part, currents surrounding the Sargasso Sea keep the sargassum in that area. The seaweed provides food and cover for certain marine animals, such as the loggerhead sea turtle.
At this point, I don’t know that there is a definitive answer about why such a large amount of sargassum is showing up in the Caribbean this summer. Some have noted that there are higher than average temperatures in the North Atlantic, which may have increased the amount of sargassum.
On St. Martin, primarily the Atlantic-facing eastern beaches have been impacted. In Grand Case, for example, one would have no idea that anything unusual was going on. Below are some photos from the beach at Grandes Cayes, where there are some pretty significant accumulations. When decomposing, the hydrogen sulfate that is released smells unpleasant and may pose some threat to those with asthma or other respiratory conditions.
What’s next? It’s tough to say. Removal from the beach is difficult without also removing sand, and heavy equipment would likely destroy sea turtle nests. As long as it stops accumulating, which seems likely, then it should biodegrade naturally over time. In the meantime, it’s a boon to isopods and other beach denizens that can eat it.
Underwood’s spectacled tegu (Gymnophthalmus underwoodi) is a small lizard that seems to be a recent arrival on St. Martin, probably within the last ten to fifteen years. It is named after the influential herpetologist Garth Leon Underwood. Amongst other things, Underwood revised the classification of Anolis lizards in the Lesser Antilles in the late 1950s. Originally just collecting a few specimens for a colleague, he undertook the revision when it became clear that many of the classifications, most dating back to the 1800s required an update. This was in part facilitated by the collection of live specimens, whose distinguishing features were much easier to discern than those of the stuffed museum specimens used in earlier taxonomic efforts.
Underwood’s spectacled tegu is probably originally from South America and likely brought to the Lesser Antilles inadvertently. It is parthenogenic, so all individuals are female and can lay eggs without being fertilized. This, along with its small size, probably contributes to its ability to spread to new islands. This family of lizards is referred to as “spectacled” because they have a transparent lower eyelid, allowing them to see through it even when it is shut.
On St. Martin, this lizard is closest in size to the dwarf geckos and closest in habit to the ground lizard. I have seen them most frequently in grassy lowland areas and rocky beaches (the dwarf geckos generally prefer forest floor leaf litter). The impact of this lizard on native species remains to be seen. In its current habitat, it probably competes primarily with juvenile Ameiva plei for food, while its presence in the forest would put it in competition with the two species of dwarf gecko.
