Has a dry summer affected hummingbirds?

by Stephen Lyn Bales

Ounce for ounce - no, change that; too heavy - gram for gram - no, this is America: No one knows what a gram is - however you measure them, ruby-throated hummingbirds are remarkable creatures. In “The Sibley Guide to Birds” they weigh in at .11 ounces (3.5 grams for you enlightened metric users). If my math skills have not totally left me, it would take 145 ruby-throats to make a pound of hummingbird.
Take two dimes out of your pocket and hold them in your hand. That 20 cents weighs four grams, slightly more than a ruby-throated hummingbird. Not much, right? Whether you use the metric system or not, that is indescribably lightweight. A remarkable bird, in a tiny, tiny package. A male weighs about ten percent less than a female, so he’s a bantamweight powerhouse.
Here’s another equally astonishing factoid: Our hearts beat roughly 70 times per minute. A hummingbird’s heart beats about 500 times a minute at rest and revs up to more than a 1,000 beats per minute as the bird bobs and weaves around your backyard.
With all this high speed zipping around, ruby throats burn roughly 645 calories per hour. A typical Big Mac with cheese has about 700 calories and weighs roughly 7.6 ounces, or about 70 times more than a hummingbird, enough heft to effectively crash the diminutive bird, yet it burns an equivalent amount of calories in just over 60 minutes. If human metabolism was the same as theirs, we would need to eat 300 pounds of hamburger each and every day, or a Big Mac the size of a coffee table. Bon appétit.
Just about everything about hummingbirds is accelerated. They have the fastest wing beat of any bird, up to 90 beats per second during normal activity and as much as 200 flaps per second during courtship. Ahh, c’est amour. Perhaps that’s where they get their hum.
To power their dynamic lifestyles, they must eat constantly, visiting as many as 20 flowers per minute. Yet, even with all the copious intake, at any given moment a hummingbird is perhaps only a few hours away from starvation. A flowerless, feeder-less half-day could do one in.
There’s a general misconception that hummingbirds are powered by nectar and nectar alone. They do consume a full range of sucrose concentrations, as much and as often as they can find it, but according to foraging studies their major food source is insects. “It is accurate to think of ruby throats as miniature flycatchers,” writes hummingbird expert Bob Sargent. They need the sugary solutions to power their quick bursts of speed, but they need the fats, proteins and minerals from insects.
Hummingbirds migrate early
Ruby-throated hummingbirds spend their winters in Mexico, Central America and on Caribbean islands because flowers and insects are abundant there. A few remain in Gulf Coast states and the Outer Banks of North Carolina. Each year, they begin their migration north to nesting grounds in late February, many flying across the Gulf of Mexico. They really have to fatten up beforehand. The remarkable non-stop flight takes 18 to 20 hours. Recent studies indicate that they follow the blooming cycle of red buckeye northward. As trees bloom in a given area, hummingbirds arrive quickly thereafter. Hummers nest throughout the Eastern United States and up into Southern Canada.
Their return south begins early. Adult males are the first to go, departing in July, while adult females soon follow. That leaves the juveniles born that calendar year. Each female generally produces two clutches of two nestlings for a total of four young. Because they need to fatten up before they fly south, juveniles are the last to go and can be seen in our area through October.

Where are the hummingbirds?
I’ve had several phone calls the past few weeks with a similar query: “Where are the hummingbirds?” People who routinely have them in their yards are not seeing them. Personally, I’ve had hummers at my feeders all season. I also phoned Chris Mahoney in Chattanooga. She is a self-confessed humm-a-phile and has spoken several times at Ijams Nature Center about the petite sprites. Her yard is a ruby-throated Six Flags. “People should be seeing them,” said Chris. “I’ve had them all season and this is the height of migration season. The juveniles are passing through now.”
But this has been an unusual year. Drought has reduced the number of nectar-rich flowers, which attract protein-rich insects. Hummers need both. “Juvenile hummingbirds fatten up around their nesting grounds before they start to migrate south. If people are not seeing many, it may mean the birds migrated early or are delaying until better times,” said Chris. She also added that a lot of her jewelweed—a hummingbird favorite—has dried up.
We are not in a 100-years drought, but we are close. The first half of 2007 was the fourth driest since 1910. We received only 14.73 inches of rain. By comparison, the three driest years were: 1986 with 11.88 inches of rain, 1925 with 13.91 inches and 1988 with 14.49 inches. The National Climate Data Center reported in early July that our state’s dry spell is so severe it would take 15 to 30 inches of rain to end the drought. Dry conditions mean fewer flowers.

Keep your sugar-water feeders out
If flowers have been reduced by drought, hummingbird feeders are even more important than usual. Keep them out until the end of October, changing the sugar water solution often. It sours quickly in hot weather.
How the hummingbird population has been impacted by the drought can only be speculated from anecdotal observations. Getting an exact fix on their numbers would be like trying to count confetti swirling around a New Year’s Eve celebration. In a normal year, only about 20 percent of young survive migration and return the following year. That is just one in five. If this year’s crop survives in smaller numbers, we may never know. It is possible the females produced fewer young this year.
Nature has pulses. Environmental conditions drive evolution. In harsh years, fewer young are produced, so perhaps there are not as many hummingbirds in our backyards this year. Several harsh years in a row could severely impact the overall population. If this hot, dry summer is an indication of things to come, hummingbirds may adapt, moving their nesting territories to places that are wetter, with more flowers, or they may not. For a creature that must find massive amounts of succulent flowers and accompanying insects every hour, life is a frantic, swirling dervish, a mad race with the mantra “find food quickly or die.”

Where have all the bison gone?

By Stephen Lyn Bales

Cowbirds!
The word alone can send bird lovers into a tizzy. They’ll cuss. They’ll scream. They’ll get red-faced and spit. Even genteel Sunday schoolteachers have been known to swear and toss brand new copies of Better Homes & Gardens at the sight of a cowbird on one of their bird feeders. How dare they show themselves in our yards during nesting season? We know what they do. Bad birds, bad!
If you have ever been a parent, you know it is not easy raising a child. And if you have more than one – say, two, three or four – your job is even harder. Suppose someone slipped another baby into your nursery. Instead of twins, you had triplets, instead of quadruplets, quintuplets. You would probably accept the extra youngster as your own and work hard to care for it. But what if over time the stowaway outgrew its crib mates, becoming bigger and more demanding? And what if over time it outgrew even you, but still begged for food?
What an outrageous notion! Is this even possible?
Yes. Brown-headed cowbirds are resourceful. When it comes to parenting, they are no-shows. No cowbird ever builds a nest or raises its own babies. They do not even know how; they let some other bird do the incubating and nurturing. Each spring, mated female cowbirds slip around the neighborhood laying eggs in other bird’s nests.
Omelet of impact
Because they do no work, a female cowbird may lay up to 40 eggs over several weeks. The sneaky mother may also remove an egg from the nest so the host mother does not notice the subterfuge. Over 100 different species of birds are known to raise cowbird babies. In many cases, the foster parents are smaller and probably exhausted by the time nesting season is over.
How can mother birds be so fooled? Why do so many kinds of birds put up with such shenanigans? Mother birds are not dumb. They are highly protective of their clutches. Somewhere along the line, surely the host parents notice the difference between their own eggs and the larger cowbird eggs.
For a long time, ornithologists believed evicting the egg was too dangerous. If the surrogate parent tried to push the unwanted egg out of the nest, it might accidentally toss or break one of its own. From a safety point of view, it was more practical to raise the odd chick than risk harming the natural clutch. A recent study indicates the danger to the host nest is even greater than ornithologists realized.
Cowbird retribution
Jeffery Hoover of the Illinois Natural History Survey and Scott Robinson of the Florida Museum of Natural History conducted a four-year study of prothonotary warblers. The bright yellow songbird nests in hollow trees and stumps on the shorelines of swamps and lakes and rivers. Cowbirds often utilize their nests.
Researchers allowed cowbirds to lay eggs in some nests but prevented it in others. The warblers rarely rejected the parasite eggs, so researchers removed them by hand. In 56 percent of the nests that had been purged of the introduced egg, cowbirds discovered the eviction and sought revenge. If their egg had been destroyed, they in turn destroyed the host eggs or nestlings. It is simply more prudent for host species to accept the extra mouth to feed than to risk losing the entire brood.
How did such a parasitic relationship ever begin? Ornithologists believe in colonial America, cowbirds – then known as buffalo birds – followed herds of bison around. They ate insects kicked up and attracted to the large grazing beasts. Because bison were always on the move, cowbirds could not settle down long enough to build nests. They learned to slip their eggs into other cribs along the way.
When our ancestors killed most of the buffaloes, cowbirds started hanging around cattle instead. Even though cows do not go anywhere, cowbirds are clueless parents, so they continue to do what comes naturally. They evolved to follow migrating buffaloes and provide insect control. That was their role. Since one female could produce as many as 40 young in a season, it is an evolutionary success.

Be fruitful and multiply
The mandate for every species is to reproduce itself. Nature rewards resourcefulness. Cowbirds are not devious, but practical. When we wiped out the buffalo and replaced them with cattle, cowbirds did what they had to do to survive: settle down on the farm. Consequently, they have been able to expand from their original range into developed land coast-to-coast.
Who is to blame here: the resourceful cowbird or the buffalo killers? And why did we almost drive the American bison to extinction? Who initiated such a thing? It was the U.S. government, which in the mid-1800s wanted to reduce the population of the Plains Indians by eliminating their main source of food. Railroads were also being built across the country’s heartland, and herds of buffaloes could slow and even stop a train.
Some estimates report that as many as 100,000 bison were killed per day during the height of the slaughter. Buffalo Bill Cody become a hero, in part, because he boasted he could kill more than a hundred bison at a single stand, firing his gun so often it became too hot to hold.
Sir Isaac Newton postulated, “For every action there is an opposite and equal reaction.” More concisely, actions have consequences. The brown-headed cowbird had to adapt to survive. Would you have rolled over and played extinct? The next time you want to hurl a copy of Better Homes & Gardens at a cowbird, try a symbolic toss at the grave of Buffalo Bill Cody instead. He is buried on Lookout Mountain above Denver, Colo., and I suspect there is a cowbird egg being incubated by another bird nearby.