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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Tuesday, July 24, 2007

An appreciation of wrens

Bewick's wren was the least expected and smallest of the tunnel's visitors. What poetic justice if it were only a member of the genus Troglodytes (the cave dweller). But that's not the case. Troglodytes is a scientific name reserved for the even smaller house wren and its Old and New World relatives.

I encountered the species last summer when a pair took up residence near the potting shed. The male was a respectable songster who crooned exuberantly from a Photinia hedge next to the garage. Believe it or not, I haven't found a recording on the web that can equal this particular bird's singing. Apparently, there's a lot of individual variation in song. Anyway, they hung around until late fall and then disappeared. It was disappointing they didn't show up this year, but it's good to know there are a few down in the ravine.

Howard Ensign Evan's book, "Pioneer Naturalists" tells us that Audubon named this wren after Thomas Bewick (1753-1828), an engraver who authored "A history of British Birds". It was a kind gesture, but I think the German name "Zaunkoenig", or "hedge king" is a far more appropriate moniker for wrens. Hedge Kings rule the thickets, and it's a treat to see one at close range. German appreciation of the wren's diminutive short-winged body plan inspired the naming of the LF-1 Zaunkoenig. It was a curiosity of aeronautical design -- a little, slow-flying barn stormer kind of plane capable of very short takeoffs and landings.

When it comes to defending territory wrens in general are "butt-kickers", and the house wren is a grim eviction agent. I'll never forget the Saturday afternoon I was "taking the airs" on the back porch in northern Virginia. I had been reading and watching dogfighting carpenter bees in front of the garage, when something fluttering in the martin house caught my eye. It was a house wren.

The martens had long since abandoned the metal contraption next to the vegetable garden, and house sparrows were the present occupants. The wren flapped its wings and struggled in the entrance of a nest chamber in an alarming way, making me think it had been snagged by a lurking blacknake. But then it popped out of the nest hole and "what the hell?!" -- it tried to fly off with a nestling hanging from its beak!

The nestling was nearly the size of the wren, and the flight trajectory portended a crash landing. Downward they went for a few feet, before the wren released the chick. I was agog. It was back at it in no time, and a few minutes later it had finished the job. There were three pin-feathered chicks on the ground. Horrors!

Now this, I thought, was an unusual observation, so I eagerly shared it with my National Zoo colleague, Gene Morton. Gene is a highly respected ornithologist and wren enthusiast, who periodically honored me by asking for a status report about the Carolina and house wrens that lived around our house.

Well, the observation didn't exactly get him hopping. He acknowledged that house wrens were famous for this kind of thing, and that they don't hesitate to evict nestling chickadees, titmice and tree swallows. They destroy their eggs too. It's not that they are vigilantes who systematically oust all cavity nesting dickeybirds, but they like to keep several potential nesting sites vacant. It's an inducement to hen wrens. Many of them are practicing polygamists.

We also had a resident population of Carolina wrens in northern Virginia. They often visited the windows of my home office and cocked their heads while searching the spider webs. In our 30 years of residence there were a few severe winters that starved out "the Carolinas". A year or two would pass before we would again hear their familiar song ("tea kettle tea kettle tea kettle").

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