Habitat loss causes decrease in Minnesota bird species
I recently received a letter from Mr. Darrel Lillquist of Guthrie. Living on the Century Farm his grandfather homesteaded in 1898, Mr. Lillquist wrote about the bird life he enjoys around his home. At the time of his writing to me he had counted nine species of birds at his feeders, including crossbills. He also reported observing from time to time less common species such as northern cardinals and black backed woodpeckers visiting his bird feeders.
Mr. Lillquist has observed plenty of wildlife over the past 60 years that he has spent living on his farm. He's also noticed changes - some good, some not so good. Observing a bald eagle, for instance, used to be a rarity, though he recalled watching a pair nesting near Hart Lake as a child. Today he reports seeing at least one bald eagle nearly every day. Trumpeter swans, too, have increased in abundance to where he now observes the birds nesting and raising their families.
But it's what Mr. Lillquist is not seeing, or at least not as many in recent years, that has him wondering why. He mentions specifically five species of birds: evening grosbeak, killdeer, great blue heron, meadowlark and bobolink. Well, Mr. Lillquist, regarding at least a couple of your birds of concern, you are not alone in wondering where they have gone.
Two of those birds that Mr. Lillquist mentions are among my favorite grassland nesting passerines: the bobolink and meadowlark. Both are members of the blackbird family (Icteridae) and I've always had a special connection with them.
I first became acquainted with both these birds on the farm when I was just a boy. Our alfalfa fields teemed with large flocks of bobolinks, while meadowlarks sang from adjacent fence posts and power lines. Recalling my many walks along our hayfields, the sweet music of singing male bobolinks and meadowlarks were everywhere.
In subsequent summers, however, our hayfields held fewer and fewer bobolinks and meadowlarks. One of the reasons, and I suspect similar circumstances were occurring in the Guthrie area, farm hayfields and grasslands were disappearing. And what hayfields did exist were typically mowed too early destroying not only nesting habitat, but nests as well. Additionally, row crops, trees, brush and developments began to replace traditional bobolink and meadowlark habitat.
It wasn't until years later as a graduate student studying birds in the Prairie Pothole Region of North Dakota, did I become reacquainted with the bobolink and meadowlark. Despite the fact that western and northwestern Minnesota provides suitable breeding habitat for the birds, and still does to some extent, the greater concentration of breeding bobolinks and western meadowlarks occurs in North Dakota and, especially for the western meadowlark, throughout the Great Plains where grasslands and rangelands are much more extensive than what is found in Minnesota.
That said, Breeding Bird Survey data have shown a steady decline in bobolink and meadowlark populations across their breeding range. Regarding bobolinks, the literature states that, "In addition to habitat loss, the factor most frequently cited for declines in bobolink populations is the more frequent mowing of hayfields (Brauning 1992, Brewer et al. 1991)."
Furthermore, research points out that "The bobolink is one of very few North American passerines whose entire winter range is south of the equator in South America. Its winter biology is poorly known, and factors on its South American winter range could also be contributing to the recent population declines."
Similar things can be stated about the status of western and eastern meadowlark populations. Occurring in similar grassy and open habitats as their bobolink relative, the melodious, yellow-breasted meadowlarks - both the western and eastern species - are also experiencing population declines. Whereas western meadowlarks primarily breed throughout the Great Plains, eastern meadowlarks occur mostly east of the Great Plains. Even so, both species can be found in Minnesota.
Of the eastern meadowlark, Audubon Minnesota reports a 71 percent statewide population decline. "Like many grassland birds," Audubon states, "meadowlarks are threatened by agricultural production that uses monoculture row cropping and early season mowing. Suburban development of open fields (also) contributes to their habitat loss."
BBC data indicates similar trends for western meadowlarks, though this species of meadowlark is more abundant than its eastern relative. According to BBC, it's not entirely understood why populations are in decline. However, research suggests that loss of habitat, drought and winter severity are partly to blame for population declines for both species of meadowlark.
Even brood parasitism by brown-headed cowbirds is believed to be a contributing factor to not only eastern meadowlark population declines, but, to some degree, the declines of western meadowlark and bobolink populations as well.
And so it is, that although bobolinks and meadowlarks have not disappeared from Minnesota's prairie grasslands, local populations will continue to decline, if not entirely disappear, when suitable breeding and nesting habitat is lost.
Be that as it may, appropriate and abundant habitat exists in the Red River Valley and otherwise open landscapes throughout northwestern Minnesota. One noteworthy place to observe singing and nesting meadowlarks and bobolinks in the northwest is Glacial Ridge National Wildlife Refuge located east of Crookston.
Though perhaps not as plentiful as they once were, these wonderful birds continue to breed and nest here in Minnesota, just not in numbers they once enjoyed. Undeniably, the sweet and jangling warbles of bobolinks, as well as the melodies of meadowlarks, are songs and birds to treasure as we get out and enjoy the great outdoors.
In the coming weeks I'll write about other birds of concern.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife.