Thursday, May 22, 2008
Falcons band together under I-5 Bridge
Under the watchful eye of the mother bird, WSDOT biologist, Michael MacDonald and Martin Muller from the Falcon Research Group successfully banded three 3-week-old peregrine falcon chicks on the I-5 Ship Canal Bridge – and I was there.
I must admit, I was a little afraid to tag along. It wasn’t the fear of heights that got me nervous; it was the fear of momma bird defending her young. Last year she was pretty aggressive towards our falcon banding crew. At one point she even sunk her talons through three layers of Michael’s clothing in attempt to ward him off her nest.
This year, much to Michael’s surprise, momma bird yelled at him, but didn’t strike. In fact, she didn’t try to take a whack at any of us. What’s more, when Michael and Martin were banding the chicks, momma bird had laid down in the nesting box! A most unusual posture for an adult peregrine that’s not incubating eggs. (photo by Martin Muller, above)
It makes for nice calm working conditions though (photo, right).
Another oddity about this year’s banding was that there were only three chicks in the nest instead of four. Martin tells me that female falcons usually reproduce four chicks a year for an average of six years. “Because this is her sixth year laying eggs,” said Martin, “laying only three eggs could indicate her energy level is down. In theory this could be her last nesting season, but we won’t know for sure until next year.”
It takes a lot of energy and persistence to be a fledgling peregrine falcon (photo by Martin Muller, right). Only half of all chicks survive their first winter, they usually don’t breed until they are two years old and they only live an average of eight years in the wild.
These bird-eating raptors help out the WSDOT bridge maintenance crew by hunting starlings and pigeons, the main source of bird droppings which corrode the bridge paint. The faster the bridge paint corrodes, the more often bridge maintenance crews must work on the bridge. I guess you could say that providing a nesting box for the peregrine falcons helps save taxpayer dollars.
But we didn’t always have their winged help.
In the 1970s, the chemical dichlorodiphenyltrichloroethane (DDT) nearly drove Washington state’s peregrine falcon population to extinction. DDT found its way up the food chain and accumulated in the peregrines, causing their eggs to become too weak to even support the weight of the mother incubating her eggs. The eggs shattered before fledglings could hatch. DDT was finally banned in 1972.
Ten years later the population started showing signs of a comeback and the Falcon Research Group began banding and tracking peregrine falcons to see where they go and what they do in the wild. Today, there are over 120 documented nesting pairs in Washington.
This is me, (photo, below right) Broch Bender, holding a peregrine chick.