​Rebecca E. Koch
Assistant Professor
University of Wisconsin-Stevens Point
UWSP House Finch Project
Note: As with any project involving wild birds, all methods described here have been approved by local (UWSP IACUC), state (DNR), and federal (USGS) agencies.
The goals of this project are to perform long-term observations of the behavior and nesting success of house finches in Portage County, Wisconsin. By marking the majority of individuals in our local population of house finches with unique identifiers and performing observations of pairing, male feather coloration, paternity, and nest success across years, my students and I can answer questions about how and why songbirds like house finches have colorful feathers.
For questions or comments, please email me!
TELLING WHO'S WHO: Colored leg bands
Even to ornithologists, individual birds of the same species and sex are generally indistinguishable from each other! A bird's perspective will capture all kinds of tiny individual differences in feathers, colors, sounds, and even scents, but to our eyes, a female house finch is... a female house finch.
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So, in order to be able to see a bird in a tree and who know it is, we have to give each bird individual markers. For small songbirds like house finches, the simplest and safest way to do this is to put colorful little "bracelets" on each bird's legs! These are known as "color bands," and each bird has his or her own unique combination of colors. Here, you can see a female house finch held securely in what is called a "bander's grip," which gently cups the bird against the palm of the hand. This house finch is sporting four new bands: pink, gray, green, and aluminum! We can call her "PYGA" for short.
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Every bird also gets an aluminum band with a unique numbered identifier printed on it, courtesy of the U.S. Geological Survey (USGS) Bird Banding Lab. While this number is too small to be read from a distance--that's where the color combinations come in handy--the number provides a long-term individual identifier that enters an online database accessible by anyone handling birds within North America. That means if any of our little house finches flies its way up to a bird banding station in Canada, experts will know that this bird came from Stevens Point! When other songbirds accidentally find their way into the nets and cages designed for house finches, I also give them a unique aluminum USGS band to contribute to this (inter)national database. You can see a picture of a beautiful male American goldfinch with his shiny new USGS aluminum band here.
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CATCHING A FLYING OBJECT: Capturing songbirds
While this project relies primarily on observations of banded birds, birds must be caught at least once in order to give them these unique identifiers. I also collect basic measurements like the bird's body size and weight, take pictures of colored feathers, and sometimes collect a tiny blood sample for DNA analysis (using about the same technique as we use a finger prick for a drop of blood).
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I use two methods to capture house finches:
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1. Mist nets! These are the most widespread tools used to catch birds. Mist nets are made of a fine mesh of webbing arranged into rows of loose pockets, held spread between two poles. The nets are of such fine material that they can be difficult to perceive, and birds gently impact the net while in flight, becoming wrapped up in the loose pockets of material. I keep an eye on mist nets at all times so that when a bird becomes caught, I can quickly untangle it and prepare it for measurement and release within minutes. The risk of injury to birds during mist netting is vanishingly small, and it is a technique used worldwide for both birds and bats.
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While birds caught in mist nets can look hopelessly tangled, the nets are well designed to hold birds just long enough for careful extraction. The American goldfinch pictured here was out of the net in less than 30 seconds, despite his best efforts to grab on to the net with his feet!
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2. Birdfeeder traps. These ingenious cages were designed decades ago by scientists hoping to take advantage of house finches' love of sunflower seeds. Essentially, this trap is built out of a cylinder of hardware cloth, closed at the top and bottom, with short narrow "tunnel" entrances near the base of the cylinder. These tunnels have perches facing outside of the trap, enticing birds to land and take a look. Then, finches creep through the tunnels to reach a birdfeeder placed in the center of the trap. The inward-facing tunnel shape without an inside perch makes it difficult for many birds to orient and navigate their way back out of the trap from the birdfeeder. When a bird is inside the cage of the trap, I can simply reach in a trap door on the top and pull out the bird!