It's early summer, and a flame of yellow streaks through the trees at Davenport's Nahant Marsh.

A bird-watcher identifies the flame as a prothonotary warbler, a migratory songbird sometimes called a "poster child" for songbird decline.

The warblers' numbers have dropped 42 percent since 1966, according to surveys conducted under the auspices of the United States Geological Survey, a scientific agency of the United States government.

Because of these plummeting numbers, the prothonotary warbler is listed as a "species of continental concern" by Partners in Flight, an association supported by governmental and private groups.

But why the decline? Is it habitat loss at the birds' breeding grounds in eastern North America, problems during migration to Central and South America or troubles encountered once they get to their winter home? Or a combination of all three?

These are questions Brian Peer, a biological sciences professor at Western Illinois University-Quad-Cities, hopes to help answer with a research project he and colleague Rob Porter initiated at Davenport's Nahant Marsh, and adjoining Carp Lake.

This spring, Peer and Porter, of the university's recreation, parks and tourism administration department, and about eight students installed 80 nest boxes at the two locations.

Initially the boxes were part of a study on house wrens, but when Peer realized that the area also presented perfect habitat for prothonotary warblers, he finished his wren work within a week, then turned his total attention to the warblers.

The yellow birds normally nest in tree cavities, preferably under a leaf canopy and over water (to protect the nest from predators such as raccoons or snakes).

But such cavities can be difficult to find. Warblers cannot drill their own cavities as woodpeckers do, so they must rely on finding a cavity already-made. And they have to compete for these spots with other birds such as starlings, wrens and Eurasian tree swallows.

But it turns out that all the warblers need is a nest box — made of lumber, mounted on a 5-foot post of electrical conduit and stuck in the ground —  and they will come.

Peer and Porter weren't sure of this at the beginning, so they purchased a game caller, a portable speaker with downloaded recordings of bird calls, to attract the warblers to Nahant.

"It was totally unnecessary," Peer said of the caller. "That was the greatest thing, the day I saw a prothonotary warbler on one of our boxes. It was really great."

The area became saturated with warblers, with about 30 boxes providing homes for warblers that typically produce at least one clutch of four to six young.

The raising of dozens of prothonotaries in Davenport is a good thing in and of itself, and Peer said he expects to increase the habitat "for these magnificent birds" in 2017 with the installation of 250 to 300 boxes in other Mississippi River slough and backwater locations.

What Peer wants to study

Then he will conduct research, monitoring the birds' breeding behavior, studying their interactions with parasitic cowbirds (birds that lay their eggs in other birds' nests, often to the detriment of the nest bird's family), and tracking the warblers' movements during the breeding season in addition to their migration to and from Central and South America.

To do this he will band the birds and attach tiny transmitters to their feet to track their movement. If a transmitter stops working during flight, Peer will know that the bird encountered problems during migration, and if it stops in Central or South America, he will know the difficulty was at that location. Then he, or someone, could physically go to that location to "see what is going on, why the birds are dying," he said.

To help pay for the project, including equipment (transmitters are about $180 each) and mileage, Peer is writing grant applications. Work so far has been financed by small grants from the Iowa Ornithologists' Union and Western. 

Prothonotary warblers begin arriving in the Quad-City area in late April, with the first eggs hatching by mid-May. By around July 4, they often are on their way back South.

Their nesting range is listed as eastern North America, although the core of that range is in the southeastern United States. Nahant is near the northernmost portion of that range.

The Carp Lake area is ideal because it is practically inaccessible to people and it swarms with mosquitoes, providing food. "It's not beautiful or aesthetically pleasing, but the birds love it," Peer said.

In fact, the entire Quad-City area all up and down the Mississippi River is prime nesting habitat, and many people don't realize that, he said.

Why recreation administration is involved

Western's recreation, parks and tourism administration program is geared toward human use of natural areas, but for that to happen, the natural areas, or environment, have to be protected in the first place, Porter said.

The program is "about managing the land for the species that live there and for the people who use it," he said.

In that sense, people in recreation/parks/tourism administration are the link between biologists and the general public, he said.

Porter is personally very interested in birding, and his students helped with the hands-on work behind the research project, helping to build, erect and take down the nest boxes. They also are helping in the lab with research.

"The students are very excited," he said. "It isn't very often that you get students who want to do work outside the classroom."