URBAN YARDS CAN BE WILDLIFE FRIENDLY

During their first lab, I used to take the students in my vertebrate zoology class at the University of Puget Sound on a walk in the urban wilds. After we had walked a few blocks, I asked them to tell me why we weren't seeing any wildlife. When someone pointed out that we just saw a squirrel, I tell them that, sadly enough, this most obvious “wild” mammal isn’t native, nor are some of the “wild” birds we had seen.

But the answer is so obvious that eventually I always got the response I wanted:  “The habitat is so different from what it was.” They didn’t know the half of it! Not only do we cut down the trees, leaving a few token conifers, but we also wipe out the shrubs and herbs that make up the diverse understory of our forests. Each of those plant species has insects living on it, and all those insects disappear with their host plants. Guess the most important prey for our small wildlife species (amphibians, lizards, many birds and small mammals). That’s right, insects.

Don’t the cultivated plants we plant in the place of those we eliminate attract their own insects? Some of them do, but most aren’t native, and the insects that eat their leaves or pollinate their flowers may not occur here. And if they do appear, the typical response to them is a liberal application of pesticides. But it’s worse—most people favor evergreen plants such as rhododendrons and junipers that produce insect-deterring chemicals in their leaves and are thus relatively pest-free. Most evergreens fall in this category. And yes, I know honey bees aren't native, but they seem important in the pollination of many flowers, as our native bees have declined.

And the final habitat constraint most of us apply is instead of letting a great variety of (admittedly weedy) herbaceous plants become established in our yards, we literally mow ‘em down. If you watch your yard, you’ll see that the rare dandelions that go to seed are immediately attractive to any seed-eating birds in the neighborhood. But how many of us sanction this sacrilegious seed set? However we view them, seeds are the primary diet for many small birds and mammals.

So my answer is “Don’t do as your neighbors do.” If you’re like most of us and don’t live on a ten-acre lot with real habitat, do your best to simulate it. Remember two important food groups, seeds and insects. Plant native trees and shrubs, especially deciduous ones, which are more attractive to insects. Plant native flowers attractive to pollinating butterflies, bees and hummingbirds. Fruits are also important foods for many birds and mammals; plant plenty of fruiting trees and shrubs.

Don’t put any kind of biocides in your yard; save the aphids!

Leave a swatch of lawn unmown. Don’t rake up all the leaves and throw them away each fall; let them stay on at least part of your yard. Several of our wintering birds forage by turning over dead leaves, which shelter seeds from the summer before as well as a multitude of small arthropods and worms. Make a brush pile in one corner of the yard; songbirds love to shelter in it. Add a pond or fountain. You’ll be amazed at the wildlife habitat you’ve made.

Dennis Paulson

KINGS OF THE INSECT JUNGLE

Many insects are predators on other insects. Dragonflies and damselflies (order Odonata) come to mind immediately, as all of them eat smaller insects and spiders. But put them up against robber flies (order Diptera, family Asilidae), and they have not only met their match but been bested with ease.

Robber flies eat dragonflies and damselflies regularly, but there are almost no records of odonates turning the tables. One type of predator is clearly superior to the other. I have seen robber flies take insects from most orders, including their own. Size is no limit, as an inch-long robber fly can latch onto a flying dragonfly three times its size and bring it down to the ground instantly with a paralyzing bite. Presumably if the fly was captured, it could do the same thing to its captor.

The two wings of a robber fly are narrow but strong, and they propel their owner through the air with an audible—sometimes impressively loud—buzz. Their flights are usually short, and when you hear that buzz you can often find its source resting on a branch, rock or the ground. They usually perch right out in the open, again like a dragonfly, where they can see potential prey. They have relatively large, forward-pointing eyes as befits a predator.

The thick, tubular proboscis injects venom that is both proteolytic and neurotoxic. The neurotoxin paralyzes the prey almost immediately, and the proteolytic enzymes digest the innards into a liquid soup that the fly sucks out. The proboscis is strong and sharp enough to penetrate the hard cuticle of a beetle.

Many insects are poisonous and distasteful and brightly colored to advertise their unpalatibility. This adaptation must be against birds, because robber flies freely feed on such insects, as do dragonflies.

Robber flies are very bristly. The legs have long, sharp spines to hold onto the prey, much as in dragonflies. The face has a dense coat of bristles, called the mystax, presumably to protect it from the legs and mandibles of struggling prey (but it’s a sure thing that they don’t struggle for long).

Many robber flies are sleek and pointed at the rear, the jet fighters of the insect world. Others are fat and fuzzy, very effective mimics of bumble bees but just as effective as predators. They have been called aggressive mimics, mimicking their favored prey species to get close enough to make a kill.

Fly larvae are legless and look like maggots, and robber flies are no exception. Slim and pointed at both ends, at least some of them feed on the larvae of other insects, usually in rotting organic material such as logs and dead trees or in the soil. Surprisingly little is known about the larval life of this group, however.

With over 7000 species in the world, robber flies are diverse on all the continents. They are relatively uncommon in the wet western lowlands of the Pacific Northwest, just as many groups of insects are less common in our cool, cloudy summer climate. Head across the Cascades to see a lot more of them in the dry, open areas that they prefer.

Robber flies are easily observable, as they are fairly tame, but capturing one in an insect net and looking at it closely allows you to appreciate its adaptations even more. Be cautious, however, as their bite can be painful. I know enough about their adaptations that I have never allowed one to bite me!

Dennis Paulson

WAXWINGS, THE SMOOTHEST BIRDS

Anyone who looks closely at a waxwing usually exclaims "how smooth it is!" What is there about waxwing feathers that gives this impression? They really do seem smooth, perhaps in part because the body is uniformly colored and the individual feathers thus difficult to make out. Maybe that's all we need to know. Their jaunty crests, black face masks, and yellow tail tips make waxwings unmistakable birds.

Cedar Waxwings (Bombycilla cedrorum) are very common in the Pacific Northwest. Small numbers of them spend the winter, especially in the interior, but many more arrive in spring to breed throughout our deciduous and mixed woodlands. Because they are confirmed fruit-eaters, they breed later than many other migrants, so the young when just off the nest can find plenty of fruit. Many native trees and shrubs flower in early summer and have mature fruit in late summer, if you didn't know.

Waxwings are really tied to fruit and can survive on a fruit-only diet longer than other temperate zone songbirds. Males offer berries to females for courtship feeding, and the young are fed fruit more than is the case in most of our birds. Of course this diet is augmented with insects, which are better sources of some nutrients. Waxwings spend much time around water looking for emerging aquatic insects such as dragonflies, which they often catch in the air.

You can see waxwings hawking for insects above the treetops in late summer, but they are still seeking fruit at that time, and any plant fruiting in September may harbor small flocks of waxwings. In October, most of them take off for lower latitudes.

The "waxy" tips on wing feathers in waxwings are merely modifications of the feathers. Imagine the individual feather barbs becoming thicker and thicker, fusing, and becoming bright red. As a waxwing matures, it develops more of these tips, and their size and number are a sign of maturity. Birds with more red tips tend to breed together and breed more successfully, so more "wax" may be a sign of a bird with higher fitness.

Bohemian Waxwings (Bombycilla garrulus), bigger and more colorful, visit the Northwest only in winter from their breeding grounds in the boreal forest. They are more common on the east side of the Cascades, where flocks may be encountered in fruiting trees, many of them non-natives and often in cities and towns.

There is only one additional waxwing, the Japanese species (Bombycilla japonica). It looks much like the other two but has red tail tips; I wish I had a photo to share, but I've never seen one.

Dennis Paulson