from the Tribune-Review, Mary Ann Thomas, Sept 11, 2020, W PA

Their bags are packed for a 1,000-plus mile flight to Mexico and South America. The essential luggage for a ruby-throated hummingbird? Up to an extra gram of fat.

Yes, fat on the smallest breeding bird in the eastern United States is discernible, desirable for migration and definitely measured at the banding station at Powdermill Nature Reserve of the Carnegie Museum of Natural History in Cook, Westmoreland County.

Pennsylvania’s only breeding hummingbird species, the ruby-throated leaves heavier in fall migration than when they arrived in mid-April.

The region is in peak hummingbird fall migration, which is between Aug. 20 and Sept. 20, said Annie Lindsay, bird banding program manager at Powdermill’s environmental research station. Powdermill has operated the banding station since 1961, making it the longest running, year-round station in the country.

Last week, the station netted 25 hummers in a single day, which is a lot but doesn’t break the birding station’s single day high of 39. On Wednesday, banders caught 14.

“Once they’re done breeding, their next job is to eat and migrate,” Lindsay said.

With the smallest bands imaginable, much smaller than a pea, maybe the size of that tiny screw that holds the joint together on a pair of eyeglasses, Powdermill banders and volunteers are getting the job done.

They notice and record the larger size of the hummers heading south.

“We assume a bird that is really fat is ready to leave,” Lindsay said.

Normally, the 3-inch ruby-throated hummingbird weights 3 to 3.5 grams — about the weight of several paper clips. They can gain 0.2 grams to a whole gram of fat before migration, according to Powdermill records.

“One of the misconceptions is hummingbirds won’t migrate if feeders are up but that is not true,” she said. The changing amount of daylight is one of the drivers prodding them to move on, Lindsay said.

In fact, regional and state experts advise keeping hummingbird feeders up until late October and changing the sugar water every three days.

The hummingbirds undeniably love the feeders.

The birds are widely distributed throughout Pennsylvania and is a “species good at taking advantage of suburban habitat,” said Sean Murphy, the state ornithologist with the Pennsylvania Game Commission.

“They are a natural phenomenon that hits you in the face on how wonderful nature can be,” he said.

They are peculiar in how small and fast they are, but there are other interesting qualities such as the fact that, unlike a number of other bird species who also migrate south, hummers migrate alone and during the day, he noted.

“They rise in the morning, fuel up on flowers nearby and spend the day migrating and at the end of the day and they will stop and fuel up before night.”

It’s all the more important to keep up feeders to help the late migrants, which are usually females and juveniles, he said.

“If they are lucky to find your feeder and fuel for the night, that will benefit them for the rest of their trek,” he said.