HOUGHTON - The trio of peregrine falcon chicks at the Houghton-Hancock Lift Bridge are starting to leave the nest.
The Michigan Department of Transportation (MDOT) installed two nest boxes - one each on the north and south bridge towers - in spring 2012 and a pair of peregrine falcons showed up the next spring. The falcons got a prime nesting spot and MDOT got a top-flight pigeon patrol.
According to head bridge operator Robert Paavola, the number of pigeons on the bridge has plummeted dramatically since the falcons took up residence and chased them away.
A father peregrine falcon stands watch atop a nest box occupied by three falcon chicks on July 15. The box is one of two attached to the Houghton-Hancock Lift Bridge in 2012. The young birds were too old to be safely banded.
"The pigeon population is down significantly," Paavola said. "Not necessarily because the falcons are killing them. They just don't even come around anymore."
The reduction in pigeon numbers from dozens down to a few may save the department some maintenance money down the line, he added. "Pigeon droppings can take paint right off metal bridge surfaces."
After failing to mate last year, the peregrines nested again this year and successfully hatched three eggs in mid-June. MDOT also has boxes with nesting falcon pairs on the International Bridge in Sault Ste. Marie and the Mackinac Bridge. Every nesting site is special - in 2013 there were just 47 nest sites in the entire state - and the Lift Bridge represents one of just a handful of successful nests in the Upper Peninsula.
"In the U.P., I know of only four successful nests this year, including Houghton and the Mackinac Bridge," said Michigan Department of Natural Resources (MDNR) Wildlife Biologist Brian Roell. "I am not sure if the birds at the Porcupine Mountains were successful, so it could be five."
Placing boxes on an accessible structure like the Lift Bridge helps the MDNR follow the raptor's comeback. Bands are attached to the legs of young birds so that scientists can track the dispersal, migration, life span, reproductive success, behavior and population growth of the falcons.
Adding to that data is what wildlife experts had in mind when they came to the bridge in mid-July to try to band the trio of chicks.
MDNR Wildlife Technician Brad Johnson said there's a narrow window of opportunity for banding the young birds. Once they're too old, they pose a flight risk - they might try to jump from their box and could kill or injure themselves in a fall.
"We try to get them before they're three to four weeks old," Johnson said. "At five weeks, it's too late. They're too old and if they're spooked they'll bail out of the nest."
Unfortunately, the Lift Bridge chicks appeared to be a little too advanced by the July 15 visit. Their size, coloration and feather development indicated they might try to bolt.
While Johnson and MDNR Wildlife Researcher Erin Largent peered at the nest box through a window in the bridge's machine room to evaluate the chicks, the wary father peregrine stood watch on the roof of the box. His mate, a larger bird, screeched and circled the Lift Bridge tower, clearly agitated by the presence of humans close to her hatchlings. Unlike the male, she carried a leg band.
MDNR wildlife experts plan to make a follow-up visit later this summer to try again to read the band on the elusive mother falcon. The codes on the band should tell them where and when that peregrine was hatched.
The peregrine has been removed from the federal endangered species list, but is listed as an endangered species in Michigan. The falcon family at the bridge is a great example of the species' comeback.
"It is simply amazing that, after just two years of placing the box, there is a pair raising three chicks," Roell said. "The chance of this occurring is very unlikely, but it sure worked in Houghton."