John Hagan walks out of a stand of softwood trees, dominated by tall black spruce, along the Golden Road in Maine’s North Woods on July 20, 2021. Thirty years after leading a landmark study of how forestry in northern Maine impacts migrating birds in North America, Hagan and researchers returned in 2021 to examine how changes in land ownership and forestry practices impact bird populations. Gregory Rec/Staff Photographer

The northern half of Maine contains 10 million acres of forest with no paved roads, towns, or other significant development. These unorganized territories represent a huge amount of habitat for the Maine plant and animal life.

Most of this land is commercial forest. The owners regularly harvest trees to provide the timber and paper we all depend on. The timber harvesting provides a significant number of jobs in northern Maine.

An alarm was sounded in 1989 when John Terborgh published his book, “Where Have All the Birds Gone.” The Breeding Bird Survey, begun in 1966, was showing declines in many neotropical migrant birds. John Hagan, a research biologist at the Manomet Bird Observatory in Massachusetts, was one of the organizers of an international symposium in 1989 to examine the decline of the neotropical migrants. Hagan was inspired to undertake a study in the North Maine Woods to examine the impact of forestry on bird diversity and abundance.

Despite an overall decline in bird populations since the 1990s, John Hagan and his fellow researchers discovered some good news in their most recent northern Maine census – 42 bird species are more abundant now, while only 19 species have shown a decline. Gregory Rec/Staff Photographer

Hagan established collaborations with forest ecologists for the largest forest companies in the Moosehead Lake region. These partnerships were cooperative as all stakeholders were interested in the impacts of current logging practices on birds. The forest owners provided significant funding for the project and granted Hagan’s team access to these privately owned lands.

Field work was done in the summer from 1992 through 1994. The field team used the point-count method for their censuses. A point-count is conducted by standing at a fixed point and then counting all birds heard and seen within 10 minutes in a 50-meter radius. A detailed vegetation survey was done at each sampling point. Hagan’s team did point-counts at 387 points.

Stands of different ages support a characteristic suite of birds. For instance, newly clear-cut areas support some species like Lincoln’s sparrow and white-throated sparrows, followed a few years later by mourning warblers and chestnut-sided warblers.

The major advance of the study is the measurement of actual density of those species. Since the timber companies maintain a detailed map of the age of all the stands on their property, estimating the total number of a particular bird species is facilitated.

Impelled in part by a 2019 paper that reported that 30% of North American birds have perished since 1970, Hagan decided that repeating the earlier study 30 years later would have value.

Hagan procured funding and field work was done in 2021 and 2022, again with the cooperation of the timber companies. Field technicians did point-counts at 422 points in the Moosehead region over those two summers. The preliminary report of the project has just been released.

The ownership of most of the forests changed between the early 1990s and 2021. Logging practices changed as well. Clear-cutting has been nearly abandoned in favor of shelterwood cutting. In this technique, about two-thirds of a stand is cut, and then the remaining third is cut 10 years later when new trees have begun to grow in the understory.

With all the bad news about declining bird populations, the 2021-22 data provided some positive news. Forest management practices have improved the population trajectory of many birds. Forty-two species are more abundant now than they were in 1992-94 and only 19 species show a decline. American redstarts increased in density three-fold and black-and-white warblers doubled. Magnolia warblers showed the sharpest decline, about a 33% loss.

Some species, including the Lincoln’s sparrow, can be attracted to newly clear-cut areas. Google Lynda M. Gonzalez/Dallas Morning News/TNS

Hagan takes a holistic view of the North Woods. Rather than focusing on a single clear-cut or shelterwood cut, he envisions the industrial forest as a shifting mosaic. Older forests are always present, but as they are cut, other areas harvested earlier grow to replace the habitat. The one forest type that is underrepresented is the 100- to 200-year-old mature forest. Timber companies maximize their profits by harvesting 50- to 70-year-old tracts of forest.

The nine field technicians, mostly in their 20s, have pledged to repeat the study again in 2052. Great news!

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu.