Birding on Port Island: The occupation (2012.2.2[Thu.])

 

Post Island has more “nature” than you might at first expect, given that it is a manmade construct. But its origins are not so interesting to me, or, I'm sure to the flora and fauna that make this their home.

    My wife, a woman who knows her birds, has observed little terns (Sterna albifrons) and even more surprisingly, the common kestrel (Falco tinnunculus), a smallish raptor, related to the falcon. No doubt they predate the kits of pigeons fluttering about the housing complexes by day. With a little luck, you might catch a glimpse of them readying to swoop down on their prey. Black kites (Milvus migran) are not the only masters of the sky here.

    The grey herons of Minami Koen are well-known denizens of the island and, seemingly unaware of the threat of their own extinction, their sedge has been expanding in recent years. What they are eating, I can't say - it can't just be fish from the little artificial stream that flows through the park - but whatever it is, their numbers have definitely grown. Out for a walk one day with Raj and Doug, we counted a total of 11 perched in the trees near the construction zone that separates the front and back zones of the island. I suspect that they use this as a base and sortie out to feed in coastal areas nearby.

    The grey herons have rivals in their striated kin(Butorides striatus) and the great cormorants (Phalacrocorax carbo) who also makes their nests here. My wife first spotted the striated heron, after finding a pale blue eggshell on a walking path outside our apartment. Several days later, she spotted a white spattering, resembling paint; unmistakably guano. Looking up, she saw a nest in one of the trees lining the walk, and squinting harder, made out the chick within. The eggshell was from its hatching. I suppose it has fledged and flown by now - at least our pathway shows no signs of it remaining.

    For insects, I have already written of the min-min zemi and Lesser Emperor dragonflies, but there are so many more! Among the coleopterans, we can find the white pointed flower chafer (Protaetia orientalis submarumorea), and its smaller green cousin (Oxycetonia jucunda), as well as the famous kanabun, or drone beetle (Pseudotorynorrhina japonica), the humble green chafer beetle (Anomala albopilosa), and the duskier Maladera japonica. We have our lepidopterans as well, with common straight swifts (Parnara guttata), hummingbird hawk moths (Macroglossum pyrrhosticta), and their pellucid brethren (Cephonodes hyla). That each keeps to its season makes their observation endlessly enjoyable.

    The pellucid hawk moths clearly prefer gardenias (Gardenia jasminoides); these sphingids reveal themselves in their pale beauty just as the flowers become fragrant in autumn. Mimics of bees, these have lost the scales from their wings and assumed a spindle-shaped form, in tawny hues, or dark green (which in fact is the color of a bird known as the Japanese white eye, Zosterops japonicas). Watching them flit among the flowers or lay their eggs among the gardenia is a refreshing sight. We can also find other common butterflies such as Asian swallowtails (Papilio xuthus), painted ladies (Vanessa cardui), and large grass yellows by the score. This in itself can be pleasing, since few expect the island to offer anything in the way of a natural setting to begin with.

    My rarest insect discovery to date was a green drab moth (Ophiusa tirhaca), which I have labeled in my collection as discovered on October 29, 2003. I was still a Team Leader at the time, and had been walking to have lunch with former TL Shigeru Kondo at a restaurant near Shimin Hiroba. I spotted the specimen in a clutter of dried leaves and caught it with my bare hand - it appeared to have recently emerged from its cocoon. These moths are exceedingly rare on Honshu, and are endangered even in the more forested areas of Kouchi on Shikoku. It is hard to imagine capturing one on this little artificial isle. And indeed I have never encountered this famed beauty since, so I cannot say whether they have established a habitat; it may have been carried here on a seedling or some such. Its larvae feed on poison oak (Toxicodendron vernicifluum) and Rhus javanica, known as nurude in Japanese.

    The forest near Minami Koen has many sawtooth oaks and other members of the beech family, making it a great spotto collect acorns with children. My son is a dedicated collector, but one day as he was examining his treasures he suddenly screamed. For there among the acorns was a grub that had just chewed its way out of a shell.

    A quick examination revealed it to be a relative of the acorn weevil (Curculio sp.), armed with a long, thin rostrum (named for its resemblance to a bird's beak) that it uses to bore holes in acorns to deposit its eggs. The larvae grow inside the nut of the acorn, and emerge later to pupate underground. I seem to recall this being a defense against being carried off by squirrels; in any case, my son found himself confronted by a larva in its last instar.

    My wife has since tried to teach him about the natural history of curculids, but he seems to have been scarred by the experience and wants nothing to do with larvae of any description, or even cooked shrimp for that matter (something about the fleshiness and segmentation). I can't really argue with that, as he is only recognizing the common body plan - insects are an ingroup of the crustaceans, after all, and share arthropod features. So take care when gathering acorns - there are often wriggling surprises within.

    So although we find ourselves conducting biological research every day on an artificial landform with an extremely young ecology. It is no accident that we find here species immune to the threat of extinction. Rats and cockroaches are not the only creatures who thrive in manmade habitats. Just thinking of it recalls to me the fragrance of the oaks...