A pair of loggerhead shrikes nested this year at Fermilab near Batavia in Kane County. Vicky Byre of the Chicago Academy of Sciences first saw them in early May. By May 18 there were eggs in their nest, and on June 8 five young birds were fledged.
This is good news, because the loggerhead shrike is in serious trouble in Illinois. Once a wide-spread and common species in the state, it is now on the endangered list. The pair that Byre found are the only known nesters in all of northeastern Illinois.
Shrikes--the name is cognate with "shriek" and refers to the shrill calls of many species in the family--are a group of songbirds, close relatives to thrushes, vireos, and starlings, that have evolved into predators. Most of the loggerhead shrike's diet is insects, with grasshoppers at the top of the list, but it also eats mice, small birds, and small snakes and lizards.
It takes a fierce songbird to capture such prey. Loggerhead shrikes are only eight to ten inches long, smaller than robins, yet they have been known to capture and kill bluebirds, creatures only slightly smaller than they are.
Their principal weapon is their beak, which is heavy and powerful and supported by large muscles that give loggerheads their big-headed, thick-necked look. They peck hard at anything they are trying to kill, but they kill prey mainly by biting. They have a toothlike structure on the upper beak that fits into a notch on the lower beak to produce an effective biting machine. They go for the back of the neck, biting rapidly until they snap the spines of their victims. Falcons have similar structures on their beaks and use them in much the same way.
Because they lack the powerful feet and curved talons of falcons, hawks, owls, and eagles, shrikes' hunting--and eating--strategies are much different from these other birds'. The other raptorial birds capture their prey with their feet and in many cases kill with their sharp talons. The shrike's weak feet aren't up to heavy work of that sort, though some loggerheads have been known to carry dead prey in their feet.
There are 74 species of shrikes worldwide, but only two in North America. The northern shrike-- which we see here in the winter-- is a circumpolar species found at high latitudes in both hemispheres. The loggerhead shrike is the only species in the family that is endemic to North America. It nests all across the continent, from Canada to the Mexican state of Oaxaca. In winter, northern loggerheads--such as those that nest in Illinois--fly to southern parts of the United States.
Loggerhead shrikes are garbed in gray, black, and white: a black mask covers the eyes; the crown and back are gray; the tail is black edged with white; the wings, black with a flash of white in the outer flight feathers.
They hunt by sitting on an elevated perch, scanning the land around them. Their vision is extraordinary, as good as that of hawks and eagles. They can see something as small as a grasshopper at distances in excess of 50 yards. Experiments have determined that they can identify one of their own species from 1,250 feet away, and see a mouse running on the ground 240 feet away. When they detect possible prey, they drop from their perch in a downward arc and then, beating their wings rapidly, fly low and straight directly toward the quarry.
Hawks and owls use their powerful feet to hold their prey while they tear off bite-size pieces with their beaks. The shrikes have developed another method. They either wedge their catch in the forks of tree branches or, more commonly, impale it on thorns and then pick at it. Where shrikes are living, you may come across a larder in a thorny bush: a collection of insects, birds, mice, and small reptiles, dead, impaled, and awaiting eating. As many as 15 small snakes--along with various insects--have been found in such larders. These larders give shrikes one of their widespread common names: butcher birds.
When a once-common bird declines as catastrophically as the loggerhead shrike has, we naturally want to know why. Habitat loss is the first explanation that comes to mind, given recent state history. In presettlement Illinois, the loggerhead would have been a bird of the savanna or of woodland-prairie borders, since it needs open country to hunt over and trees to nest in and perch on while it scans the countryside for prey.
In the early days, Illinois farmers--who lacked the abundant timber that eastern farmers used for rail fences--planted dense hedgerows around their fields. Osage orange, a shrub or small tree bearing long, sharp thorns, was a favorite hedge species, and loggerheads immediately exploited this new environment. In fact, they were probably among the species that actually benefited from settlement.
But as Illinois agriculture became more and more specialized, as corn and soybeans became almost the only crops and farmers wanted to plow every inch of land, the hedges were cut down. And of course the native prairie and savanna were almost eliminated from the state.
But loggerhead shrikes are not terribly fussy about their habitat. If the look of the place, the physiognomy, is right, they don't seem to care what species of plants grow there. An old field full of Eurasian weeds and dotted with European buckthorn shrubs looks just as good to them as virgin prairie bordered by native hawthorns. The multiflora rose is a nasty, invasive, and very troublesome alien, but the Fermilab shrikes made it their home anyway.
In the forest preserves of northeastern Illinois, there are thousands of acres of weedy old fields dotted with buckthorn bushes. So why don't we see shrikes nesting there?
Stanley Temple of the University of Wisconsin asked himself that question. To answer it, he surveyed shrike populations and habitats in southern Wisconsin and Minnesota. He found that loggerheads were reproducing quite successfully wherever they nested. (The Fermilab birds were quite successful, too. Birds that can fledge five young from a single nesting are doing very well indeed.) But most of the suitable habitat was empty of shrikes. The birds were not able to increase or even sustain their populations. If the problem was not a lack of nesting habitat, what was it?
Temple concluded that the difficulty lay not in the summer range but in the winter range. Most loggerheads nesting in the northeastern quarter of the United States winter in the coastal grasslands near the Gulf of Mexico. Over the past few decades, vast areas of these grasslands have been converted to cereal production, especially to rice fields. Migrant loggerheads find less and less good habitat, and they must compete with resident populations for the little that remains.
According to Temple, most migrant loggerheads end up hunting along roads from perches on telephone wires. This is a very dangerous place to live given the speed of auto and truck traffic, and most of the migrants simply don't make it through the winter. Illinois has lost almost all of its loggerhead shrikes not because of anything we are doing--or failing to do--but because of events taking place 1,000 miles away.
According to Greg Butcher of the Cornell University Laboratory of Ornithology, the loggerhead has been designated as a species of "management concern" by the U.S. Fish and Wildlife Service's office of migratory bird management. The species has vanished from New England, and its status in the rest of the midwest is as shaky as it is in Illinois. It may end up on the federal threatened or endangered list.
However, according to Dr. Temple, loggerheads are doing quite well from the Dakotas west to California. The birds in those populations winter in Texas, Oklahoma, New Mexico, and other inland locations that have not been as drastically altered as the Gulf Coast.
Temple also suggests--although he does not have the hard evidence to prove it--that the decline of the eastern bluebird is a direct result of the loss of those Gulf Coast grasslands. "We have put out thousands of bluebird houses," Temple told me, "and while we have seen some improvement, we have not seen the recovery we would have expected. It may be that for bluebirds, too, the trouble is not primarily on the nesting grounds but is instead in the wintering areas."
(Note: A Midwest Regional Birding Symposium jointly sponsored by the Chicago Academy of Sciences, the Chicago Audubon Society, and the DuPage Birding Club will be held September 15-17 at the College of DuPage. Featured speakers include Don and Lillian Stokes, coauthors of Stokes Nature Guides; Dr. Frances Hamerstrom, an esteemed wildlife biologist from Wisconsin; Pete Dunne, principal author of Hawks in Flight, and several other notables. The cost of the three-day symposium is $40. You can get registration forms by writing the Business and Professional Institute, College of DuPage, 22nd Street and Lambert Road, Glen Ellyn, Illinois 60137-6599. Or call 858-2800, extension 2770 or 2772.)