Thursday, July 27, 2017

Cute Phenology: Return of the House Wrens

Yesterday's phenology post was true, but it wasn't cute.

I was sitting here writing it, in the last hour of my online day, and thinking "Can't this story at least be made cute?" And actually caterpillars that aren't inchworms, but try to move like them, are sort of cute...if the story hadn't been about how they need killing anyway. (Hibiscus leaf caterpillars. Hah. They ate the flower petals too!) But I went home, and was at once reminded that I'd left out a part of the story that is cute.

Namely: why did I see only six caterpillars, only in the final stage before they molt? Moths don't lay one egg per host plant, the way some butterflies do. Noctuid moths lay eggs by hundreds. Most of the caterpillars that hatch are too small to be seen or identified by humans, and never grow bigger, because they are eaten by smaller animals. Those animals include microscopic parasites, other insects, frogs and toads, mice and rats, and also songbirds. They definitely include cardinals, although in summer my cardinals stuff themselves on seeds and fruits and don't eat a great number of insects. They also include House Wrens.

House Wrens, Troglodytes aedon, are found all over North and South America. They don't depend on human houses to live in, or live near--but they are attracted to human houses, and like to nest as close to their human family as they dare, because they can eat the insects that annoy humans. Here's Audubon's famous painting of House Wrens, showing an unusual but typical choice of nest site.

Now in the public domain, this painting by John James Audubon shows House Wrens nesting in a man's worn-out hat (nineteenth century style). Troglodytes means "cave dwellers," but House Wrens may choose to nest in almost any hollow object humans leave in a yard or on a porch.

Here's a closer looks a bit more gray than my wrens, but that may be a browser effect. Then again, this one was photographed in New Mexico, and different local populations of T. aedon vary slightly in color.

Troglodytes aedon NPS.jpg
Donated by S. King to

Though tiny (adult birds are usually less than five inches long, counting tail feathers, and weigh less than an ounce; you could gather a whole family up in your hands), House Wrens have a bold, cheerful species "personality" that makes them especially amusing for their humans to watch. They use a variety of sounds, including cheeps, chirps, warbles, and a raspy scolding noise, and positively gesticulate with their heads and tails, to communicate with each other. (They will also make the raspy scolding noise at humans, at cats and other possible dangers to their nest. In what wrens have in the way of minds, this probably seems to be warning all right-minded living creatures off their territory...rather than calling predators to their nest, which, in the case of cats, possums, rats, and some squirrels, is what the wrens are doing.) They will fly toward larger animals, either to swoop in and grab a fly or mosquito, or in hopes of discouraging the larger animals from raiding their nests.

Are wrens matriarchal? They can look that way in spring, when males try to impress females with their nest-building skills. A male wren may build five or six possible nests, or may merely propose even more nests that he probably knows he'll be told not to bother finishing, and invite a female to choose one. When the female chooses a nest, she is also choosing its builder. She may remove some of the sticks the male wren used to build the nest and will probably choose the inner lining on which she will incubate her own eggs, relying on the male to deliver food for about two weeks before the eggs hatch. Once baby wrens hatch, both parents keep busy feeding them--mostly on nuisance insects--for another three weeks. After that, the young wrens start to fly and hunt insects for themselves, and the parents may enjoy a bit of a rest or may, in some places, start another family.

Then again, in another sense wrens have more gender parity than many songbirds enjoy. For many songbird species the rule is "Males are disposable." Males have colorful coats and spend lots of time flitting and singing, while females quietly mind the nest, have coats that fade into a background of tree bark, and may outlive two or three male nesting partners in a season. Among wrens, males and females are equally well camouflaged, and equally noisy. Females may even be more aggressive; female wrens have been known to crack neighbors' eggs, following the universal rule that birth control is something the neighbors need more than you do, and are thought to sing to warn neighbors when they're at their nests.

In England the similar species sometimes called the Winter Wren, Troglodytes troglodytes, featured in a considerable range of folklore, apparently because they are so little yet so loud. "The Wren, the King of All Birds" was supposed to be protected from hunters except for a special ritual hunt in midwinter, which in recent years seems to have been more of a joke than an actual raid. Female wrens were sometimes used as symbols of "liberated," aggressive, or overtly sexy women; when the Women's Royal Naval Service was formed jokes about those women being "Wrens" were inevitable.

Although their name comes from their natural tendency to nest in small cavities in cliffs, both Troglodytes aedon and T. troglodytes are familiar enough with humans to have traditional pet names. Males are traditionally called "Johnny Wren" and females are "Jenny Wren." TV's Fred Rogers called a wren puppet character on his show "Trog," just to be different.

When I was growing up at the house I now call the Cat Sanctuary, a wren family was part of the household. It used to be possible to hang laundry out to dry in the open air (now, due to more trees pumping more moisture into the air, a dry towel hung outdoors in the morning will be a wet towel by sundown), and we used to save all the laundry for a sunny day and dry it on wires strung all across the yard. Laundry would be anchored to the wires by "clothes pins," actually little spring-bound wooden clamps, which we kept in a couple of hanging baskets on the porch. One year our Jenny Wren chose to rear her brood in a tiny nest in one of those baskets. Nobody wanted to move or disturb her nest--we just limited ourselves to half the "clothes pins" for six weeks. Just in case anyone might have forgotten, Jenny would squawk and rasp when we took "clothes pins" out of the basket she wasn't using. She made sure we knew where she was!

Our dominant bird family are cardinals--bold, bright, cheery songbirds, substantially bigger than wrens. Cardinals are territorial. They have thick, strong little beaks that can grip about as hard as those spring-clamp "clothes pins"; males use those beaks to tear out feathers or eve n grab the throats of neighboring birds of other species that try foraging in "their" territory. Many other North American songbirds are bigger than cardinals, but birds generally respect each other's territory, such that most birdwatchers have seen a little songbird chasing a much larger, predatory bird. If you have resident cardinals you seldom get a close look at other songbirds. But we did have wrens, because the sassy little wrens were willing to define "their" territory in space that was too close to humans to interest the cardinals.

The wrens continued to live at the house after I moved to the city...until 2006, when a particularly regrettable in-law of mine went to help with a maintenance job and, without asking, just assumed it was acceptable to spray poison at the paper wasps. Apart from the fact that anyone who behaves civilly toward Polistes fuscatus can carry these little animals around in his hands if he so chooses, and anyone my wasps sting probably deserved worse...I'll stop even more disastrous effect of this lout's stupidity was that it killed the wren family. They had been nesting in a door wreath, which I'd been planning to burn the minute they moved out, and I found dead baby wrens below the wreath. And spent the rest of the summer swatting mosquitoes the wasps and wrens would so gladly have prevented from bothering us...the native mosquito species avoid biting me, but swarm around Mother. We try not to make this lot of Nephews feel too badly ashamed of their paternal-line relatives, but they do need to know why all of those relatives are now legally banned from the Cat Sanctuary. Because those wrens were more useful than that whole wretched tribe of in-laws ever made themselves, that's why.

The cardinals are permanent residents (unlike many cardinals, who go to South America and continue eating mostly fruit all winter) but they don't do much to earn their keep in summer, so they survived the poisoning of the wrens. So did enough of the paper wasps that they came back and cleaned up the mosquitoes in 2007. But the Cat Sanctuary was wrenless until 2017. It was early July, during my ten-day vacation from cyberspace, when I heard that once-familiar scolding rasp from the hedge. Many birds make the rasp noise (pet parakeets do, and I once witnessed a mockingbird doing it to imitate a cicada)...I looked, and there, making no effort to hide its well camouflaged self, in the privet hedge was a wren.

Sigh. I didn't properly prune the privet last summer because of the weird weather. It really needed pruning this year; instead of spreading and maintaining a nice dense soil-holding hedge, unpruned privet grows tall and unwieldy. But I don't want to disturb the wrens' nest. I'm delighted that another wren family has moved in.

The Rose of Sharon bushes are directly below the privet bushes in which the wrens are nesting...and that is undoubtedly why I found only the six hibiscus leaf caterpillars eating the Rose of Sharon bushes yesterday morning. (I looked again, this morning. I didn't see any more.) In nesting season wrens, like most birds, will eat almost anything, but their primary protein source is thought to be small, well camouflaged caterpillars. They are one reason why so many insects that can eat the plants in your garden so seldom do eat enough of them to affect the plants' output of fruit or flowers.

The cats...due to their recent life changes, the cats would have been spending more time indoors in any case. Wrens need protection from other pets only while helpless babies are flopping about in nests, and they deserve that much protection. The cats complain bitterly about being left indoors all day while I'm in town, but when I'm at home, and they go in and out with me, they seem to enjoy all the extra attention and grooming and food treats they get, so it's a trade-off for them too.