The wise and wary corvids

Many people have remarked on the story that appeared in a recent issue of The New York Times about a scientist’s discovering that crows can recognize individual human faces, but a perhaps more remarkable account of crow intelligence appears in the current issue of Bird Watcher’s Digest

It’s long been known that the corvids – crows, ravens, magpies, and jays – are quite smart, doing things like using tools and employing automobile traffic to break open nuts.

The Times story told of a wildlife biologist at the University of Washington who did an experiment in which crows on campus were trapped and banded by students wearing a “caveman” rubber mask. A Dick Cheney mask was used as a “neutral” mask by students not involved in the trapping.

In the weeks and months that followed, student volunteers who walked around campus with caveman masks were yelled at by the crows, which ignored the Cheney-masked students. Two years later, the number of crows recognizing the caveman mask as dangerous had spread to many birds that had never been trapped, indicating that parents and others in the community had taught offspring that this was a dangerous face.

In the current Bird Watcher’s Digest, columnist David Bird (yes, his real name – he’s a professor of wildlife biology at McGill University in Toronto) recounts an experience witnessed by ornithologist Russ Balda, which appeared recently in The Wilson Journal of Ornithology.

Mr. Balda was watching a crow eating seeds on a large platform feeder in Flagstaff, Ariz. Unlike other birds that came and went, the crow just stood there, hogging the feeder.

A Steller’s Jay landed on the edge of the platform and started scolding the crow for about 10 seconds. The crow ignored the pest, so the jay got closer and started making feinting movements at the crow. The crow then turned and faced the jay, which backed off.

The crow resumed eating, but the jay kept returning and repeating its harassment performance. Then the jay tried aerial techniques, swooping down on the crow a couple of times, without actual body contact.

After that didn’t work, the jay did something that astounded Mr. Balda. It flew to a mahogany tree and broke off a twig about four inches long. With the twig in its mouth and the narrow end pointed outward, the jay landed on the platform and lunged at the crow, narrowly missing it with the stick.

The crow jumped toward the jay, which dropped the twig and moved backward. The crow then picked up the twig and lunged at the jay!

The jay then took off, followed by the twig-wielding crow in hot pursuit.

In effect, and perhaps in fact, both the jay and the crow were employing a weapon – perhaps the first time this kind of “combat” has ever been observed, at least, by a scientist.

Weapon use of a different sort – bombing – has been observed in a couple of species. Professor Bird points out that Black Eagles have been recorded dropping sticks on the heads of intruders to their nests. “A female American Crow was observed dropping pine cones, not once but three times, onto the head of a human climber ascending to its nest,” he said.

Corvids’ using tools has been widely reported, and of course, a weapon can be considered a form of tool, but the Flagstaff indicate was different.

“Balda's observation may indeed be the first incident of a bird holding an object in a weapon-like fashion to undertake an aggressive action against another bird,” Professor Bird said.

He adds, “It was a pity that the crow did not have its own stick to duel with the jay.”

Two-ton snakes

What is it about snakes?

Is it that they are legless and armless, so much different from our well-appendaged selves? Is it because they slither so low and we walk so tall?

Or is it just that we fear some rattler or copperhead will sink its fangs into a leg and send us to the Great Beyond?

Prejudice, pure and simple. The snake is a wonderful creature that spends its days making our lives better by gobbling up rats, mice, shrews, voles, and other vermin.

Fear not our snakes. Fear, instead, a real killer: the shiny, glittering, ordinary, everyday automobile.

Over the past century, cars have killed scores of people in my own little town. Not one person has died of snakebite – or even snake-fright.

Mousetrap in a tree

If you were to go walking in the woods on a moonlit night, a dog in a tree might watch you.

More likely, though, the gray fox would have slipped far away before you were anywhere near being seen by him. He would not have been pressed to run up a tree – a feat he can easily accomplish, unique among North American canines.

No, the fox would have heard you coming from a long distance off. Sensitive ears, able to detect a mouse squeak at 300 feet, help make him a valuable pest-control device. Vermin like rats and mice are among its favorite foods and, as disease and tick carriers, one of our least favorite visitors.

Early in the morning, in the pre-dawn light, you may spot the long, low form of a gray fox winding around your lawn, ears up, nose down, a four-footed mousetrap.

Mating matters

The season of nesting is a good time to take a look at the kinds of male-female relationships that exist in the bird world. Many birds form lifetime partnerships – though they may have quick “flings” on the side – while others mate for only short periods or have multiple mates.

Ornithologists describe three kinds of mating arrangements: monogamous, polygamous and promiscuous. In monogamous pair bonds, the birds mate for at least the breeding season, raising their young together. Ornithologist David Lack estimated that at least 90% of nest-raised birds come from monogamous pairs. So do 80% of precocial birds – those able to walk about and feed themselves shortly after birth.

In many, perhaps most cases, monogamous pairs remain mated until one of them dies. Canada Geese are among the most faithful birds, mating for as long as 20 years. Most gulls also pair for life. The Rose-breasted Grosbeaks at the left are monogamous. This system is the most efficient and effective, providing the best protection and service for the brood of nestlings.

Some birds, such as House Wrens, generally stay with one mate for only one brood. In fact, while the male is raising the first brood, the female may take off, find a new mate, and begin a second nest. Talk about energy!

In the case of polygamous pair bonds, one male or one female may have several mates. In the more common arrangement, like the harems of lore, one male has several females. This is called polygyny. Wild Turkeys, Ring-necked pheasants, grouse, Bobolinks, and Red-winged Blackbirds are polygynous. The male generally sticks with and protects his several wives and their offspring while each female takes care of raising the children. This system is more selective than one-on-one mating; The one male that is able to build a harem of several females will be stronger and perhaps healthier than the average male and will likely pass on these traits to offspring.

In a few species, the female makes use of several mates. The Spotted Sandpiper lays eggs in several nests and the males incubate them. This system, called polyandry, allows one female to produce many eggs and is useful in situations where the breeding season is short, such as in the Arctic.

Promiscuous mating occurs when two birds have sexual relations and part company. Typically, and perhaps not surprisingly, the male takes off, leaving it up to the female to raise the resulting family. The most famous practitioners of promiscuous mating are the hummingbirds and woodcocks. Dr. Steve Kress, a noted ornithologist with National Audubon, says that typically, either the brood is small, such as in hummingbirds, allowing the female to raise the chicks alone, or the offspring are precocial, as in woodcocks, able to walk and feed themselves soon after birth.

For a long time ornithologists thought that monogamous birds were totally faithful to one another. However, DNA testing and close observation have revealed that monogamous birds may have fleeting “affairs” with other partners.

Zoologist David Barash and Judith Eve Lipton reported in The Myth of Monogamy in 2001: “When it comes to actual reproduction, even bird species long considered the epitome of social monogamy, and thus previously known for their fidelity, are now being revealed as sexual adventurers. Or at least as sexually non-monogamous.” These include eagles and geese, long thought to be strictly monogamous.

Swans, doves, finches, hawks, wrens, flycatchers, thrushes, and warblers occasionally switch from monogamous to polygamous pair bonds.

What happens when a mate dies during the nesting season?

Birds that form monogamous pairs do so largely to share in the job of raising young. Nesting season is a dangerous time, full of threats to the parents as well as the eggs and nestlings. Predators, as well as disease and accidents, may kill birds, leaving a widow or widower to care for the nest. Among monogamous pairs, it’s difficult or impossible for one bird to find food and protect the nest.

Fortunately, there are what ornithologists Allan and Helen Cruickshank call “a floating population” of unmated birds that are available – even anxious – to jump in and replace missing mates.

Happy hummers

The Ruby-throated Hummingbirds are back and, from our own experience at least, there are plenty of them.

For years, Sally and I have had hummingbird feeders of various kinds, and always got a modest showing of Ruby-throats. Last year, because of some modifications to our house, we did not have our usual feeding station.

This year, we decided to try something new: Feeders hanging from windows, one in the kitchen (where we’ve never had one before) and one in the bedroom (which had been our traditional location).

While thumbing through a Kinsman Garden Company catalogue last winter, I noticed “super suction hangers.” “Bring your hummingbird feeders right up to your window glass and enjoy a super close-up view, with this high quality suction hanger,” Kinsman said.

Our previous feeders were hung from steel swing arms mounted solidly to the house. The catalogue said the suction hangers could safely handle feeders (or small plants) up to three pounds. They were only $6.95 so I ordered two.

I wanted some equally affordable feeders, and checked the master maker of hummingbird feeders: Perky-Pet (an odd name for a company specializing in wild bird feeders). There, among more than 50 (!) hummingbird feeders, I found Model 211, a plastic unit holding eight ounces and costing a mere $6.99. (Model 201 costs only $5.99, but it holds 18 ounces, which, in our territory is too much – more on that below).

So in April, I hung both feeders, one on a kitchen window 10 feet from the ground – it’s raised and lowered with a line – and one on the bedroom bay window, which can be reached by a crank-open side window. We waited a couple weeks, sighting only a couple of male hummers stopping on their way north. Then suddenly last week, the females arrived.

Now from before dawn till dusk, we have hummingbirds visiting both feeders. Often two show up at once and one winds up chasing the other away – typical territorial behavior. Having two feeders at different sides of the house may allow two females to set up nearby nesting territories and each to have the convenient food source.

The window mounts let us to observe all this activity as close as a foot or two away. The small expense – about $30 for two feeders and mounts – is well worth the entertainment these birds provide.

Don’t waste your money on special hummingbird mixes or nectars. Many commercial products use red dye – mostly as a sales gimmick. A red feeder, often with yellow around its openings, is all that is needed to attract hummingbirds; red fluid is unnecessary.

To make your own effective, inexpensive nectar, mix a quarter cup of white sugar with a cup of water. (Do not use brown sugar, honey or other sweeteners.)

Some people recommend boiling the water from public supplies to reduce the amount of chlorine – not a problem if you’re on a well.

Change the nectar every few days; in hot weather, even sooner. Potentially harmful bacteria can grow in the solution if left to “ferment” in the sun.

In the East, where there is only one species of hummingbird, feeders holding a small volume of nectar are more practical than big ones. Two or three hummers won’t consume 18 ounces in three or four days, the safe life of the nectar. They probably can’t even handle eight ounces. Out West, where there are many species that are probably not fighting each other for territories, feeders can serve many birds at a time and tend to empty more quickly.

Perky-Pet has a little three-ounce feeder that I will also try. Model 215P costs only $5.99 and is designed to be hung in planters.

Bird Watcher’s Digest has an excellent online guide to hummingbirds, including an extensive collection of “frequently asked questions.” Visit birdwatchersdigest.com, look for “Backyard birds” on the green menu bar, and select “hummingbirds.”

Ash yellows

For folks with White Ash trees, early May can be a nail-biting time as they wait and wait for the leaves to appear.

Ashes are one of the last native trees to leaf out in the spring. Many are still not out yet.

But ash owners aware of the “ash yellows” are particularly anxious to see leaves in the hopes that this deadly disease has not struck their tree. The result could be a hulk costing many hundreds of dollars to remove.

Ash yellows is a protoplasma, a kind of parasitic bacteria possibly transmitted by beetles, that attacks ashes and can kill them as in as quickly as one year – an amazing feat, considering White Ash may be anywhere from 50 to 100 feet tall, with up to a five foot diameter trunk.

One sign of a diseased tree are “witches’ brooms,” spindly clusters of leaves amid limbs that are otherwise leafless (see picture)

No one knows for sure how it spreads or exactly how it works, and no one has a way of preventing ashes from catching it.

But by now, if your ash has avoided infection, at least leaf buds should be appearing. If not, better plan on calling a tree crew.

Save the wood, though – ash is great in the fireplace.

Treetop visitors

Spring’s leafless trees are a far cry from Shakespeare's bare ruined choirs of winter. Where late the sweet birds sang is springing to life with song. Those branches are the hotels and summer homes of countless migrants.

The earliest of the tree flowers are blooming. Where there are flowers, there are usually insects. And where “bugs” are, birds are sure to follow. In fact, insects drawn to the early-flowering trees are important food for warblers, tanagers and other small migrants heading north in the weeks to come. Some will stop here to nest for the summer while many others eat and run, heading farther north.

For bird watchers the leafless limbs of early spring are a blessing. The scores of colorful arrivals are much easier to spot without lots of green blocking the view.

So instead of watching spring arrive on the thermometer, dust off the binoculars and point them to the passing parade of treetop visitors.