If you spend a lot of time outdoors this summer, you might run across a bird that had an unfortunate fall from the sky. Some birds – especially American crows – are especially vulnerable to West Nile virus and can die from the disease within five days.

That makes the crow an excellent sentinel bird for the mosquito-control districts mapping the spread of West Nile virus. Because an infected crow does not have time to wander far from home once it gets sick, the place it was discovered is considered a place where West Nile virus has already dug in.

Beware the mosquitoes cruising the area. They may have bitten this bird. Wear long-sleeve shirts and pants, and apply mosquito repellent. Be safe and stay indoors around dawn and dusk, when the female mosquitoes that go after humans buzz about.

How do you tell if the bird you came across was infected with West Nile virus?

Go to www.fightthebite.net, the Sacramento-Yolo Mosquito & Vector Control District website, and click on "Report a Dead Bird." Fill out the form with your contact information, and the location and description of the avian specimen.

If the district has staff members available, one may come to pick it up that day. Or they may ask you to store the bird in a plastic bag for retrieval the following day.

We did exactly this when, during a recent lunch-hour walk, we found an American crow belly-up at 23rd and Q streets in midtown Sacramento. After reporting the bird's location to www.fightthebite.net, we received a prompt jingle back from a state tech eager for us to gather the bird for next-day pickup.

You cannot catch the virus from the bird, the tech told us, so go get a shovel and put the bird in a trash bag. Tie it up and put it in a safe and secure location.

We made do with three plastic grocery bags – one to protect each hand and the third as a depository for the bird.

Turns out, we learned the next day, the Sacramento-Yolo Mosquito and Vector Control District can't simply come around and pick up every single dead bird. Its staff already knew the neighborhood harbored West Nile virus and was busy sampling mosquitoes in the area.

It would, however, be keen to come out to pick up dead birds in places where the West Nile virus was not previously detected.

As for this crow, go ahead and chuck it, district officials said.

But having completed three-fourths of the job – finding, reporting and gathering – we decided it was our civic duty to go the extra distance to find out if our bird had West Nile virus. We hopped in the car and drove the bird down to district headquarters in Elk Grove. There, we dropped it into a small picnic cooler with a masking-tape label that said "dead birds."

Thanks to some quick work by lab biologist Stan Wright, we heard within days that our bird did indeed die from West Nile virus. Be cautious outdoors, Wright said, reciting the "four D's": Drain standing water; use repellent with Deet; leave dawn and dusk to the mosquitoes.

Wright was enthusiastic about the notion of citizen participation. In the fight against the bite, he said, it can make a big difference.

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