Near Barrington, the warblers are flitting through Crabtree Nature Center a bit early this year. A few miles to the south at Morton Arboretum in Lisle, George Ware is noticing isolated splashes of yellow on maple trees.
Have flora, fauna and bugs been fooled by the first three weeks of an uncharacteristically cool August?
Not exactly.
These occurrences, experts say, are the final manifestations of a summer that has been as peculiar as cherry and magnolia blossoms in August, which, by the way, are sprouting at the Chicago Botanic Garden in Glencoe.
August, a month known for heat-distorted vision and pavement bucklings, has felt a lot like fall, especially during the past few chilly nights when the mercury slid into the 50s. The results have sprung up throughout the Chicago region.
For the record, August temperatures throughout the state are running 5 to 7 degrees below average for the month, according to Wayne Wendland, state climatologist with the Illinois State Water Survey. Rather than daily average temperatures of about 70 degrees in Chicago, the average is somewhere around 65 so far in August 1994, Wendland said.
While the extended forecast calls for a bit of a heat wave Thursday and Friday, nighttime temperatures will continue to be perfect, even a bit chilly, for lounging on the veranda. High temperatures may reach 90 before Sunday, but lows will dip into the 50s.
The recent temperatures may have shrunk insect populations early in Canada and in Minnesota and other northern states, encouraging the warblers, vireos and fly catchers to arrive about a week early at Crabtree Nature Center, said Kenneth Wilz, naturalist at the estimated 1,500-acre Cook County forest preserve.
Other animals have barely noticed the change, said Mike Johnson, wildlife biologist for the U.S. Fish and Wildlife Service. In fact, Johnson said, the animals probably are less stressed out this August than in typically muggy, tortuously hot predecessors.
But alas, the cooler weather has not been enough to stave off the annual scourge of avian botulism at area retention ponds.
Large numbers of duck deaths have been reported in Aurora and Arlington Heights and at a Mt. Prospect apartment complex, where at least 30 ducks have died in the last week, according to Johnson and other wildlife authorities.
As for bugs, they behave much like animals or trees in cool weather. They slow down a bit when it gets chilly-a phenomenon appreciated by many back-yard barbecue guests who have noticed fewer mosquitoes at dusk-but are soothed back to life once daytime temperatures reach the 80s, as they have registered throughout this moderate August.
That’s the observation of Phil Nixon, entomologist with the University of Illinois Cooperative Extension Service, who added that insects tend to be more influenced by the length of daylight rather than by cool temperatures.
Galen Gates, horticulture collections manager at the Botanic Garden, has the answer to why early spring blooming plants have displayed blossoms at this time of year.
It’s called remontant bloom, and it occurs when an extended period of hot temperatures somewhat suddenly turn to cooler temperatures. That shift activates flower buds, he said.
At Morton Arboretum, the cool temperatures that initiate the breakdown of chlorophyl in leaves and set off a weakening of leaves’ attachment to branches have brought “a modicum of indication” that the arboretum will be experiencing early colors, said Ware, a research fellow and former director of research at the living museum of woody plants. Yellow has risen from trees about a week early, Ware noted.
“We’re having September weather,” he said. “It is generally speeding up the changes in the trees toward autumn color and toward dormancy.”
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