|
by Cameron Smith What I like about nature are its stories. Everything, no matter how microscopic or how big, has a fistful of stories to tell. Some are about roles being played, for everything has a place and a function. Some are about friends and enemies. And some are about secrets waiting to be told. Since we are well into spring, and bluebirds and black flies are back, there are a couple of new stories to tell.
First about bluebirds. They are so pretty, with their marmalade-orange breasts and blue bodies, that it’s no wonder people build bird houses to attract them.
Where I live, a neighbouring couple has erected bluebird houses at the edges of open fields for about four kilometres along our local gravel road. They’ve been most careful to follow instructions in bird books about how to build and maintain the houses, including suggestions to clean them after hatchlings have left the nest.
What no one realized until recently is that cleaning the nests may endanger baby birds. When I told our neighbours, they were dismayed. They had been so careful to do what they thought was right.
It’s a classic case of writers of bird books failing to recognize that nature is a system of intricate checks and balances. If you tip the scales, things can get seriously out of whack.
It was Christopher Darling of the Royal Ontario Museum (ROM), who discovered that throwing out the casings also means throwing out the enemies of the blowflies -- tiny parasitic wasps called jewel wasps. Darling is the ROM’s chief curator of entomology (the study of insects).
The wasps kill blowflies by drilling holes in the pupal casing and laying eggs. When the eggs hatch, they feed on the blowfly pupa. Darling learned that wasp larvae spend the winter in the blowfly pupal casings, and in the spring resume their development and emerge as adult jewel wasps.
Clean the nests of blowfly casings and, come springtime, there will be no jewel wasps immediately on hand to kill the next generation of blowflies.
And black flies? A description offered 375 years ago by a missionary, Brother Gabriel Sagard, still resonates. They were ``pestiferous and poisonous … little demons,’’ he said. ``They make one look like a leper, hideous to the sight. I confess that this is the worst martyrdom I suffered in this country.”
Yes, but as Douglas Currie points out, when they are in water in their larval stage, they are a huge link in the aquatic food chain. ``If we didn’t have them, things would be very, very different.’’ Currie is a curator of entomology at the ROM.
As larvae they cluster in their millions in running water -- up to 1.2 million per square metre -- filtering out minute debris (bits of carbon) and living organisms such as algae and plankton. They, in turn, are food for a wide array of other living creatures.
``There’s nothing else as prolific until you get down to protozoa and bacteria.’’ says Currie. ``And because they are filter feeders, they’re very sensitive to what’s put into the waters.’’ So they’re also valuable as an environmental early warning system that can indicate deteriorating water quality.
The fact that black flies are returning to the lower Mississippi River basin, speaks volumes about the recovery of the surrounding landscape, he says. They had been wiped out by pollution and flood control measures.
World wide, there are 1,600 species of black flies. Of them, 265 are in Canada, and 65 in Ontario. And of those in Ontario, only five bother humans, and only two are serious pests. Now that, says Currie, ``is a small price to pay for having a healthy environment to live in.’’
Or, as Darling says of his bluebirds, blowflies and wasps, ``Biodiversity is crucial for sustaining life.’’
|
