Forest Professionals Listen to the Birds

Gathering bird information Monitoring bird populations in any given area is usually started around 5 a.m., when the birds begin their morning calls. The bird researchers must be able to identify the sounds of over 100 different bird species. From their pre-assigned points in the woods, the researchers listen for all the different species they can hear from the point. Because the forest professionals were out midday when birds are typically quiet, Peterson demonstrated a technique for bringing birds in—chickadee mobbing. She set out an IPod with speakers on a stump in the woods that played the sounds of angry chickadees. These common birds often gang up on larger birds and when they do, it’s like a playground fight. Other birds come in to see what’s going on. Using the chickadee mobbing sounds, Peterson brought in the Ovenbird, the black and white warbler, and other chickadees. She looked for signs that they might be nesting and breeding, such as carrying nesting materials or food in their beaks.

Bird Watching in the Forest Riparian Zone:
How Logging Affects Habitat

“Teacher! Teacher! Teacher!” came the shrill cry from the woods.

“The birds talk to me,” said Anna Peterson with a big grin. “That’s an Ovenbird. Oh! And do you hear the squeaky wheel? That’s a black and white warbler. Cool!”

Her enthusiasm was catching for the audience of about 10 forest professionals, who gathered around her to learn about breeding birds’ response to forest harvesting in tree buffer zones near streams. Peterson is a University of Minnesota biology doctorate candidate finishing up a long-term NRRI research project on birds in forest riparian zones.

Loggers leave a buffer of trees near streams to protect the water quality, but sometimes those buffers hold valuable timber. NRRI wants to find out if harvesting of some trees can take place in those riparian zones without degrading water quality or negatively impacting wildlife. NRRI has been taking part in an 11-year-study on Pokegama Creek near Grand Rapids to understand the effect of two harvesting methods on bird populations—especially those considered “priority” species.

Two harvesting techniques are being studied: tree length cuts where the whole tree is taken from the site, branches and all, and cut-to-length harvesting where the branches are cut off at the site and only the log is taken.

What they’ve learned is that any harvesting of trees affects the bird community for as much as nine years after the harvest when the more particular birds start moving back into the harvested riparian zones.

“After a harvest, birds that migrate long distances come back to find their nests sites but if they’re gone they move on,” said Peterson. “But some birds do very well in early successional forests, like the Chestnut-sided Warbler.”

A separate but similar study at eight sites in northern Minnesota is also underway with funding from the Legislative-Citizen Commission on Minnesota’s Resources (LCCMR). This study began in 2001 to understand the effects of new riparian zone guidelines that allow some harvesting of timber in these buffer zones.

In particular, the study focused on how differences in tree density (residual basal area) would affect populations of birds. By harvesting riparian zones at different tree densities they could determine which bird species were associated with the different basal areas. They learned that with increasing tree densities, short-distance migrant species (like the American Robin) decreased and birds that prefer early successional forests like Mourning Warblers also decreased.

The May workshop, “At Water’s Edge: Current state of riparian forest management research in Minnesota” was well attended by over 100 natural resources professionals and loggers over the course of three days. UPM/Kymmene paper company allowed researchers the use of 144 acres for the Pokagama Creek studies. The company’s foresters took part in the workshop to continue to improve their management strategies.


The conference was sponsored by the Legislative-Citizen Commission on Minnesota Resources, Minnesota Logger Education Program, Minnesota Forest Resources Council, Society of American Foresters, University of Minnesota: Department of Fisheries, Wildlife and Conservation Biology, Department of Forest Resources, Extension-Itasca County, Natural Resources Research Institute, Sustainable Forests Education Cooperative, the USFS Northern Research Station, and the U.S. Geological Survey.

NRRI: Minnesota Birds

Posted Aug 8, 2008

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