Small bird populations are declining. Here's what researchers on Cape Cod are doing.

WELLFLEET, Massachusetts — Audubon wildlife biologist James Junda cushioned a catbird’s head between his index and middle finger. He put a band on its leg, gently spread a wing to note its colors and condition, measured its length, then turned it over. He blew on its breast. The feathers parted to reveal a brood patch, a fluid-filled sack that breeding females develop to incubate their eggs. Had it been a breeding male, the bird’s cloaca, an external reproductive structure, would have been enlarged.  

“Now for the final humiliation,” Junda said. 

He put the bird headfirst into a black tube that sat on a tiny scale. He called out the weight (35.9 grams, or 1.2 ounces) to volunteer Peggy Sagan, who was writing information down on a chart. Junda slid the bird out of the tube and released it into the understory of Massachusetts Audubon’s Wellfleet Bay Wildlife Sanctuary. 

Junda is a master bander with Massachusetts Audubon. He and a team of staff and volunteers have been collecting data on the sanctuary’s birds since April 15. The work is timed to coincide with spring migration. They also do an 11-week study to capture fall migration data. 

Junda uses the information for an annual Audubon report, the Atlantic Flyway report done by the Eastern Bird Banding Association, which is sent to the Bird Banding Laboratory run by the U.S. Geological Service. Scientists analyze the data, along with data from every other banding station in North America.

The trends are disturbing, Junda said. 

Why are bird populations declining?  

Researchers are seeing overall declines in bird populations, Junda said. The latest State of the Birds for the U.S. report conducted by the North American Bird Conservation Initiative found that bird declines are continuing in almost every habitat, except wetlands. The report comes three years after an article published by the journal Science showed North America has lost 3 billion breeding birds since 1970.

Climate change, loss of food sources, more non-native plants and fewer insects are to blame, Junda said, adding that flying insects are declining in a major way. The birds that depend on them — swallows, swifts, and aerial insectivores — are mostly declining. 

There is greater variation in the times birds arrive for breeding. They are coming earlier and later than has been traditionally noted. That disruption has harmed birds. Birds are arriving with less body fat and muscle mass, more are dying on their way, and overall survival rates have declined. 

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How birds are banded

Twenty-four mist nets measuring 13 by 2.5 meters are set up in different habitats across the 1,100-acre sanctuary including old growth oak forest, field, marsh, black locust and cherry forest, and edge of marsh.  

The nets are set up at dawn and taken down five hours later. They are checked often. Any birds caught in the nets are gently and carefully removed, put in soft cotton bags with the location noted, and carried back to the banding station.  

Pliers with specially sized holes for specific species are used to attach aluminum bands to the bird’s leg. Those bands move up and down the leg and birds will wear them forever.

Parameters of the Mass Audubon bird study

The studies are held for six weeks in the spring (April 15 to June 3) and 11 weeks in the fall (Sept 1 to Nov. 15). 

Nets are put up in the same locations, year after year, and serve as a control in the experiment. 

Records are kept about bird species, feather condition, body mass, fat, cloaca and brood patch status and other factors using standardized codes and numbers. 

These are the bird species researchers have caught and banded in Wellfleet.

The sanctuary is home to 50 to 60 known species of birds, Junda said, including warblers, willets, great horned owls, osprey, forest- and plains-dwelling birds, and birds that tend to live high in the tree canopy and low in the understory. 

The species that have been banded include the American redstart, hooded warbler, magnolia warbler, grackle, robin, eastern kingbird, pine warbler, common yellowthroat, chickadee, titmouse, and catbird, among others. Pictures of the birds can be found on the Instagram account massaudubonwellfleetbay.

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What people can do to help save the birds

"Nobody should be spraying anymore,” Junda said. "The insects are struggling. We don’t need to spray our trees and further hurt them.” 

“A big thing people can do is to plant native plants,” Junda said.

Non-native plants like lilacs, have beautiful blooms, but bugs don’t eat them.

"They (insects) don’t eat lilacs. They can’t. You want bugs to eat your plants. You want them to feed on your flowers.” 

Bring youngsters to bird banding events held at Audubon sanctuaries. It gives children a chance to see birds in the hand. They are mesmerized by the birds, Junda said.

Denise Coffey writes about business and tourism. Contact her at dcoffey@capecodonline.com. Follow her on Twitter: @DeniseCoffeyCCT.