In the last column I wrote about the history of the Breeding Bird Survey on the occasion of its 60th year. The BBS has been a treasure trove of information for ecologists, ornithologists, conservation biologists and environmental managers interested in the changing populations of birds.

I recently did a search for “Breeding Bird Survey” using a database of scientific articles. The search yielded 523 papers.

Analyzing BBS data poses challenges because of the nature of the data collection. The surveys are done by thousands of observers with different degrees of skill in identifying birds by sight and sound.

Ideally, a particular BBS route is conducted by the same observer for decades. But a recent journal article describes a bias that may occur even in these ideal situations. Robert Farmer and colleagues analyzed BBS data as well as data from the Ontario Breeding Bird Atlas project and showed that older birders detected fewer birds by ear than younger birds. The effect was greatest for bird sounds with high-pitched frequencies but other species with lower-pitched calls and songs were also missed more frequently by older observers.

You can see the potential bias for a route that has been conducted by the same individual for 30 years. A decrease in bird abundance in later years may indicate poor detection by the aging birder rather than a real decline in abundance.

I have done nearly 100 BBS counts over the past 25 years. This year I have noticed decreased ability to hear cedar waxwings and other high-pitched species. Reluctantly but rightly, I will give up my BBS routes.

In Maine, 70 BBS routes have been established and only 36 are active. In contrast, all of the 23 BBS routes in New Hampshire are claimed and all but four of the 23 routes in Vermont are claimed.

We need better coverage of the Maine BBS routes. Some are in the northwestern part of the state, requiring considerable travel to be at the starting point before sunrise. But there are many vacant routes in southern and eastern Maine that may be convenient to your home.

You can see a map of the vacant routes at: www.pwrc.usgs.gov/bbs/RouteMap. If you feel confident identifying Maine birds by sound and sight, I hope you will consider adopting a BBS route. For more information, please contact Maurry Mills at Maurice_Mills@fws.gov.

Maurry is based at the Moosehorn National Wildlife Refuge in Baileyville and is the Maine BBS coordinator.

Merlin

The Cornell Institute of Ornithology is developing software called Merlin that identifies birds based on a digital photograph. The software is in beta testing and the developers are enlisting the help of birders. Go to merlin.allaboutbirds.org/photo-id and upload a photograph of a bird. You will be asked to provide the location where the bird was photographed as well as the date. Then you draw a box around the bird and indicate the bill tip, eye and tail tip with a mouse click. Hit “Next” and Merlin will provide possible matches.

I uploaded a photograph of a greater yellowlegs and Merlin nailed the identification. Currently, Merlin gives the correct identification in its three top suggestions 90 percent of the time. Uploading photographs trains Merlin to be even better. Eventually the software will be available for tablets and smartphones but is currently only available through a browser.

Oldest Bald Eagle

In June, a banded bald eagle was killed in upstate New York by an automobile. The bird was banded in 1977 in Minnesota. The bird was translocated to New York state in 1981 as part of New York’s bald eagle restoration program.

This male bird nested around Hemlock Lake and fathered many eaglets over the years. Even though it died prematurely from the collision, the bird’s 38 years of age shattered the longevity record for bald eagles by five years.

Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at:

whwilson@colby.edu