Is the chickadee population in decline in Michigan?
Michigan Radio's MI Curious project is a news experiment where we investigate questions submitted by the public about our state and its people.
In December, longtime Ann Arbor resident Ellen Rusten asked this question:
"It seems to me that there are fewer chickadees in Ann Arbor than there were 40 years ago. Is that true and, if so, why?"
Rusten says she asked her question because her family likes the outdoors and "we always did casual bird watching from the kitchen windows in Chelsea and Ann Arbor."
She clarified that it is the Black-capped Chickadee that she was seeking information about.
"I remember them being almost as prevalent as sparrows back then. I liked the grey, almost silver feathers of their wings, and how they puffed up into rolly-pollies when the cold wind blew," she said. "I have been up here about eight years and I have seen only one."
A common query
Julie Craves is the supervisor of avian research at the River Rouge Bird Observatory at the University of Michigan-Dearborn. She also answers readers' questions for Birdwatching magazine. She says questions about the increase or decrease of a certain bird population are common.
"Most bird populations ebb and flow, from decade to decade and year to year," she said via e-mail.
To calculate the change, Craves looked at the Ann Arbor Christmas Bird Count data beginning in 1974 (the 40 years ago that Rusten mentioned in her question).
The data reflects the average number of chickadees "per party per hour." It's a measure that takes into consideration how many people were out counting and for how long.
"For 1974-1983, the average was 3.6. Now that the latest count numbers are out, I just looked at 2005-2014, and the average is 5.5," she said.
So based on this count, the numbers are up in Ann Arbor. See this chart:
You can look up more Christmas Bird Count data here.
Additional data decoded
However, the Christmas Bird Count only covers one day, so Craves decided to compare it to the observatory's Winter Bird Population Survey that covers the whole winter period.
The survey is modeled after the National Audubon Society’s Winter Bird Population Study and takes place at the same time each year — December 20 to February 20. Craves said that the survey shows a "long-term decrease over the last 22 years, but a slight increase over the last 10 years."
So her data show a modest upward trend in the chickadee population.
Crave says Ellen Rusten's observation of fewer chickadees is normal.
"When most people observe common backyard birds, they also see numbers vary from month to month, even day to day." She added that the numbers for frequent feeders, such as chickadees, can vary due to variations in natural food sources, the presence of predators and even the weather.
"As someone who has looked at birds for 30 years, [I] can look at weather fronts, and things move according to weather."
Migration patterns make counting a challenge for researchers
Craves' research at the observatory used to focus on banding and counting various bird species, including chickadees. She says winter counts are good sources of data for year-round species like chickadees. However, she notes that a portion of the northern chickadee population does move to southern Michigan each year, which can make the count challenging.
So what does Craves predict for the chickadee in this year's winter bird study (which concluded on February 20)?
"Nothing drastic, at least on a larger scale. Things can be super regional."
Due to funding cuts, Craves has not banded any chickadees for a few years, but she has observed that they appear to not be moving in large groups.
"I wouldn't be surprised if there was an increase in numbers."
— Chrissy Yates, Michigan Radio Newsroom