By Kate Crowley
Bird silhouettes swirl and swoop in graceful arcs and curves against the blue sky. In certain light their dark feathers have a purplish sheen, and so they are called purple martins (Progne subis). The largest member of the swallow family, they have a long history of entertaining us humans with their mesmerizing aerial ballet. Their vocalizations have been variously described as musical, buzzy, staccato, gurgling chatter, and guttural. I think their sounds are best replicated by pursing your lips and quickly whispering zhupe zhupe.
Unfortunately, all is not well for these delightful avian neighbors. According to Ron Windingstad, Audubon Minnesota's coordinator of the Audubon At Home program, martin populations have declined 78 percent nationwide in the past 40 years. In Minnesota, annual surveys show an average martin-population decline of 3.9 percent each year from 1966 to 2007, according to the North American Breeding Bird Survey.
Purple martin experts say the bird's decline is mainly due to two nonnative species that also flourish around humans—the house sparrow and the European starling. Both invade and destroy martin nests and eggs. And in recent decades, purple martins have found fewer of the martin houses that once graced nearly every farmstead.
Now a loosely affiliated, statewide organization called the Purple Martin Working Group is trying to aid the recovery of purple martins. About 50 purple martin landlords manage colonies on wildlife refuges and parks. These martin guardians try to educate and recruit others to join them in the effort to bring back martin colonies—birdhouse by birdhouse.
Humans' association with purple martins goes back a long way. American Indians hung large gourds to dry, some purposely hollowed out for purple martins to use as nests. European settlers put up wooden birdhouses, and martins took up residence.
Indians and European settlers alike realized many benefits of having the birds as neighbors. As insect eaters, purple martins provided pest control for crops. And because martins chased off crows and raptors, they also acted as guard birds for poultry flocks and drying meat hung near dwellings. Any winged predator that approached a colony was instantly faced with a mass attack.
Resident purple martins provided people with countless hours of entertainment as they performed aerial acrobatics and nonstop chittering. And the colony serves as a fine example of successful communal living. Historical records indicate purple martins were prevalent in prairie portions of our state. According to T.S. Roberts' classic Birds of Minnesota, martins in the early 20th century were nesting in abandoned woodpecker cavities, as well as among rock cliffs and outcrops. Along the shores of Mille Lacs Lake, they took up residence among piles of boulders. With expansion of human populations, people cut down many forests with nesting-cavity trees. Today, purple martins east of the Rocky Mountains depend almost entirely on human-made structures.
In 1886 large colonies of martins were nesting on Spirit and Hennepin islands in Mille Lacs among common tern colonies. They were still there in the 1930s. Mille Lacs Band of Ojibwe tribal wildlife biologist Kelly Applegate has spoken with Ojibwe elders who remember putting up martin houses. Applegate, who is also director of the Minnesota Purple Martin Working Group, has six colonies on tribal lands. "There's no shortage of insects around Mille Lacs," he says, "There are mayflies, midges, and smaller lake flies coming off on a weekly basis."
Another advocate and member of the working group is Daryl Lindstrom, Jr., who grew up on a farm near Rock Creek in east-central Minnesota. In 1993, for his eighth birthday, he asked for a purple martin house. His initial interest was sparked primarily by the size of the birdhouse.
"I was always interested in birds and made birdhouses using milk cartons or whatever I could find," he says. "And one day we were driving to my aunt's place along Cross Lake, and I saw these huge birdhouses up on poles and they seemed really cool." He got a field guide, read about purple martins, and put up an apartment-style nest box. Only house sparrows and starlings moved in.
Like many childhood pursuits, this one faded over time. Then, seven years later when Lindstrom was randomly searching the Web, he stumbled across the Web site of the Purple Martin Conservation Association. "I had always been blown away by how swallows fly, and when I found out the martin was the largest, like a super swallow, I wanted to learn more about them," he says.
The Web site introduced him to the use of plastic gourds for martin housing and how to build a gourd rack, which he did. Still no martins came, however.
In summer 2001, he went with his family to Memory Lake Park in Grantsburg, Wis., and noticed, "These beautiful swallows slicing through the skies. I knew they had to be martins ? just as the books I had been reading for years had described. However, the books never could quite capture the magical sight and sound of these beautiful creatures."
Then he noticed six dilapidated martin houses situated around Memory Lake with only two resident martins. "There were huge entrance holes, leaning poles, roofs peeling back, and paint chipping," he says. "All I could think was, 'Why would they want to be here instead of my new gourds at home?'"
The next summer, growing increasingly frustrated with his martin-less gourds, Lindstrom sent a letter to the Grantsburg Board of Trustees about the status of purple martins in general and of martin colonies in Grantsburg. At the board's invitation, Lindstrom attended a board meeting and impressed the members with his ardor and commitment. They provided him with $150 to build a new martin house.
The next spring the martins returned and took up residence in the new house, and Lindstrom officially became a purple martin landlord. From 2004 to 2009, his East Central Purple Martin Recovery Project has raised more than $10,000 in donations for martin houses and now provides shelter for 125 nesting pairs.
I joined Lindstrom on one of his weekly rounds to the six colonies he manages. All are on property belonging to businesses or municipalities in east-central Minnesota, except for the original one in Grantsburg.
On a sunny day this past June, we visited a colony on the shore of the Snake River in Pine City. Hanging from two crossbars on a 16-foot-tall pole were 24 white plastic pods (the modern-day equivalent of the gourds hung by Indians). Lindstrom slowly cranked a boat winch to lower the nests. The winch has an automatic brake—a good thing because altogether the houses weigh about 125 pounds.
Each nest was a perfect cup of green leaves, aspen mostly, cradling five to seven creamy white eggs. The nests were lined with a layer of pine needles, which Lindstrom put in last spring. The female martin does most of the nest building. She might add straw, leaves, twigs, feathers, rags, paper, string, and shreds of bark. If she leaves the nest before she starts incubating, she covers the eggs with some green leaves. Only the female incubates the eggs, for 15 to 18 days. The summer of 2009 started off beautifully for Lindstrom's colonies, with lots of new nests and lots of eggs. But disaster struck at the end of the month.
On July 1, Lindstrom sent me an e-mail: "The last several days have been very cool and windy, with downright cold nighttime temperatures in the 40s. Before this cold snap, it has been in the mid 90s. The martins have had a very tough time dealing with these weather extremes. I decided to head to the Rush Lake colony to see how it was doing. Not good. I didn't even count the number of dead. Somewhere around 25-30 chicks! I was carrying dead young out of the compartments by the handfuls." The result for the purple martins of east-central Minnesota was basically a lost nesting season.
While the vagaries of weather are uncontrollable, starlings and sparrows can be managed. Starlings can be kept out by using the proper size entrance hole.
House sparrows can't be so easily deterred. When sparrows get inside, they poke holes in martin eggs or break and throw them out. When Lindstrom finds eggshells scattered on the ground beneath the poles, he knows what has happened. The sparrows also attack and kill adult martins.
"[Martins] didn't evolve with [house sparrows]," Lindstrom explains, "so they don't know what's going on or what to do when a sparrow starts pecking it as it stands at the entrance with its head poking out of the door." To trap sparrows, Lindstrom places a small aluminum box inside the nest entrance. Birds can get in, but not out. If a purple martin or tree swallow enters, Lindstrom releases them unharmed. Killing sparrows can be hard for purple martin landlords to accept, but it was the same dilemma for people who restored eastern bluebird populations.
Despite the lost nesting season of 2009, Applegate is optimistic about the outlook for purple martins.
"This is the first time since I began working with them that we're in a position to bring them back," he says. "If we keep up all of the hard work that all the agencies and all of the different levels of citizens are putting in, we'll be able to stabilize first of all, then reverse the trend, and make them popular again."
Applegate hopes to see a revival of the 1960s trend of adorning lawns and gardens with purple martin houses. Back then, he says, "You put up a flag and martin house too."