LANGLEY — Imagine sipping nearly 100 to 200 pounds of sugar water through a narrow straw every day. Now imagine flapping your arms more than 50 times per second and flying a distance of 300 to 500 miles.

This is the daily existence of the Rufous hummingbird, a red-throated bird that migrates from northern Mexico generally up the West Coast, into British Columbia and the southern areas of Alaska.

But the numbers of Rufous hummingbirds are declining, which has caused the National Audubon Society to place them on a list of “common birds in decline.” Biologists are now scrambling to find out why the high-octane birds are disappearing.

Tom and Ann Campbell of Langley, members of the Whidbey Audubon Society, own a patch of land that could truly be called a birds’ paradise. With forest lands, pastures and a shallow pond, the two have created a habitat that many birds call home, including many Rufous hummingbirds.

Twice a year for the past six years, the two have hosted biologist Dan Harville, a hobbyist hummingbird bander. Harville’s mission is to gather data for a scientist in Victoria, B.C. as part of the Hummingbird Monitoring Network.

Harville visited the Campbells’ property near Langley this week to collect data on the birds, which requires a complex catch-and-release process. Capturing a bird that flies 25 miles per hour is no easy task, the Edmonds man said.

“We tried using other types of nets, but the birds are too fast and avoid our nets,” Harville said.

Harville relies on a high-tech system to capture the birds.

Like many birds, hummingbirds are wary of humans but their need for fuel can often outweigh their instincts and Harville uses their hunger to catch them.

Seated at his side Wednesday was Ruth Milner of the state Department of Fish and Wildlife. Armed with a radio transmitter, she sat near a weighted circular net that hovered above a hummingbird feeder filled with sugar water.

When a bird flew in, Milner moved a stick on the radio transmitter that triggered a net that fell in a flash.

“I’ve captured as many as 12 hummingbirds at once,” Harville said of the system.

Harville was hoping to net nearly 100 birds during his visit to Whidbey Island.

However, on this day, the rain and possibly the gathering of other guests of the Campbells kept many of the Rufous hummingbirds away.

But birds did come. And after one was captured, Milner reached in and plucked the bird from the net and carefully placed it inside a cloth bag and handed it over to Harville.

Harville, largely protected from the pelting drops under a covered porch, sat at a table with the tools of his trade; a micrometer to measure wing and bill length, a banding crimper and a short straw — which he uses to determine body fat mass and whether a female hummingbird is carrying an egg.

He took the diminutive bird from the bag and carefully pushed its head through a slot in a piece of white cloth, wrapping it up and clipping the fabric closed. He then placed the neat package onto a digital scale; and the bird in hand tipped the scale at 4.6 grams.

At that weight, it would take nearly 50 birds to equal the weight of a cup of water.

Then Harville proceeded with other data measurements.

“We determine age and sex. We look for an egg. If it’s a female, we’re looking to see if it is gravid (pregnant),” he said. “We’re looking to see if there is a lot of fat.”

Fat is good for a hummingbird because it’s stored energy, he said. But it also means the bird is also still migrating.

“The fat gets them from place to place. Most of these birds will feed every day while migrating.”

“They do run through a huge amount of fuel,” he added. “People say they eat anywhere from half to their full body weight every day.”

In addition to eating nectar or sugar water, Rufous hummingbirds eat insects and spiders to gather trace minerals and proteins for healthy bones and feathers.

Harville started banding hummingbirds in 2000 after Cam Finlay, a biologist in Victoria, asked him to help out with hummingbird monitoring in Washington state.

Studying the Rufous is vital to figuring out why their numbers are dropping, Finlay said.

“Rufous numbers have been falling for 10 years. We cannot prove it is habitat loss,” he said.

The birds winter in the highlands of Mexico, but as fewer and fewer hummingbirds make it to nesting grounds in British Columbia, Finlay said the trend of clearcutting forests from Mexico up through the West Coast and into Canada is potentially detrimental to hummingbird habitat.

“People are clearing land in Mexico to get grass for cattle. People in California, Oregon, Washington and British Columbia are clearing land to put houses in,” he said.

“When people clear land, they remove the brush and shrubbery that hummingbirds forage and nest in.”

After flying 300 to 500 miles, a Rufous hummingbird needs to eat to survive. If it cannot find food, it will die, Finlay said.

People like Harville are crucial because they help develop a picture of the birds’ population and migrating habits, Finlay said.

“We don’t have enough raw data to determine the entire population numbers,” he said.

“There is not a lot known about Rufous hummingbirds, about migration, about specific routes they may be taking to go back south,” Harville explained.

“The general feeling has always been the birds here essentially head east and go down the eastern side of the Rockies and back down into Mexico to winter,” he said, adding that banding helps researchers follow the birds over the rest of their lives.

In addition to learning more about population numbers and migration routes, Harville is curious about other details, too.

“There are also smaller things you can learn, like how they interrelate, how young birds disperse from the nest they were born in and what small area they move out into to feed,” he said.

Because of the risky sort of life these hummingbirds lead, Harville has seen that few young birds make it to adulthood.

“Eighty-five percent of the young die within the first year because it’s hard learning how to be an adult,” he said. “Like how to feed, how to avoid predators and not running into windows.”

“Once they get to adulthood, they live an average of three to four years with the oldest living as long as eight to 10 years.”

In all, Harville captured 31 hummingbirds at the Campbell home.

Of those, he banded a total of 28 birds — five males and 22 females — that had been out of the nest for more than a year and one female that had hatched this year. Two of the

31 birds had been captured and banded previously by Harville.

The Campbells were impressed.

“I had no idea I had so many birds,” Ann Campbell said. “Fifty birds can consume a cup of sugar water a day. Some days, we go through a gallon of sugar water a day.”

That equates to 800 birds enjoying Campbell’s bird paradise in Langley.

“It’s a good feeling,” she said.