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Yellow Warblers Love the Boise River: A High School Student Investigates

For the past few months, Sage International School senior, Zoe Daly has been working on a project using Yellow Warbler data from the Intermountain Bird Observatory’s Boise River Research Station.

A Yellow Warbler is weighed at our Boise River Site, just before being released. Photo by Tom Carroll

A Yellow Warbler is weighed at our Boise River Site, just before being released. Photo by Tom Carroll

In the Fall of 2017 IBO ran nets daily during fall migration for the first time ever! This gave us an excellent, fine-scale picture of migration at the river station. We were also able to complete a full MAPS breeding season banding protocol this summer, sampling songbirds at the site once every 10 days. Simultaneously, we collected the same data at our long-standing Lucky Peak station.

This gave us the ability to compare between our Boise River and Lucky Peak stations like never before.

When we first started banding at the Boise River site, we knew that it was special for Yellow Warblers (we once caught more than 200 of them in a single day!) but we had never looked at the hard data or quantified exactly what was going on. So, when Zoe came along and told us she loved looking at data and graphs, we knew exactly what she should do.

The Cottonwood overstory and thick willow, currant, and rose shrub layer at our Boise River Site is ideal habitat for Yellow Warblers.

The cottonwood overstory and thick willow, currant, and rose shrub layer at our Boise River Site is ideal habitat for Yellow Warblers. Photo by Tom Carroll

Zoe took our banding data from Lucky Peak and the Boise River and compared Yellow Warblers at both sites. In particular, she looked at the fat levels of Yellow Warblers.

She found that Yellow Warblers were significantly fatter at our Boise River Station than at Lucky Peak.

This means that the habitat at the Boise River provides food that Yellow Warblers need during migration and stopover. They are able to spend time at the site, eat, and “fuel up” with fat for the next leg of their migration journey.

Zoe also found that Yellow Warblers at Lucky Peak tend to leave the area soon after their young fledge…they don’t stay at the site during late summer when migrants begin fattening up. Instead, they seem to travel to the river to finish molting and fattening up for migration.

This goes to show that the riparian habitat at the Boise River is a key resource for neotropical migrants like Yellow Warblers.

Congratulations to Zoe for completing this poster and finding such interesting results! Thanks also to Guy Falconer of Sage International School who connected Zoe with IBO to begin this internship.

Check out Zoe’s full poster to learn more:Poster showing graphs of Yellow Warbler fat levels. Yellow Warblers were fatter at the Boise River than at Lucky Peak

(full size poster PDF available here)

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