This spring, especially since early to mid-May, has been particularly active with birdlife in my neck of the woods. And now, avian offspring, too.
Why in just the past week here at Assawa Lake, I’ve observed four newly hatched cygnets hatch and swimming with their doting trumpeter swan parents, as well as seen a pair of tiny sandhill crane colts feeding in the sedge meadow with their watchful parents. I’ve also seen numerous broods of ring-necked ducks and blue-winged teal, nesting red-winged blackbirds and scores of other observations.
The forests and fields are alive with birdsong and birdlife. Earlier this week upon my daily wood duck nest-box check, I was delighted to discover that the wood duck hen’s patient work of incubating a nest full of eggs for an entire month was a success. Peering into the box from on top of a ladder one afternoon were 10 or so duckling puffballs huddled together for warmth and safety, some still wet from having just hatched.
Closer examination of the nestlings revealed a surprise. The tiny duckling nest-mates, all hatched at roughly the same time, were comprised of two different species! I expected wood ducks of course, which there were, but about half of the ducklings were hooded mergansers.
“I’ll be darned,” I thought. “A hooded merganser laid eggs in the wood duck’s nest.”
Called brood parasitism, or dump nesting, it’s actually quite common with some ducks, especially with cavity-nesting ducks like wood ducks, hooded mergansers, common goldeneyes, buffleheads and others (the brown-headed cowbird is also a brood parasite). Why brood parasitism occurs in waterfowl is not entirely understood, but competition for available cavity nest sites is likely a primary factor.
What the practice of dump nesting effectively accomplishes, however, is known. That is, the bird that lays eggs in another bird’s nest — whether the same species or a different species — avoid the high energetic costs and risks of not only incubating eggs but in raising the offspring as well. In the case of the wood duck hen that I was monitoring her nesting progress, she successfully hatched her brood, which included both her own offspring and her foster merganser ducklings, too. A mixed family, as they say.
Switching gears here, I took a drive one evening a short time ago to do some bird watching on Upper Rice Lake in Clearwater County. This large shallow lake, the largest lake in the county, is replete with wetland-dependent species of birds and Minnesota’s state grain: wild rice.
Managed for wild rice production, the lake is vital to migrating waterfowl and a host of other species of birds for the rich source of protein-rich food that wild rice and other aquatic plants provide, but also for the abundance of cover these same plants and others also provide.
On my recent journey to the north end of the lake where a 300-foot boardwalk was built and installed by DNR wildlife biologists a year ago for wild rice harvesters, waterfowl hunters, and wildlife enthusiasts to use and enjoy, I was pleased to see and listen to a sizable population of yellow-headed blackbirds.
Breeding male yellow-headed blackbirds are charismatic looking and behaving birds. With his golden-yellow head and yellow throat including part of his breast, along with white wing patches, large body size, and loud, raucous calls, there’s simply no mistaking a yellow-headed blackbird for any other species of wild bird. Females sport partly yellow heads, too, although mostly just on their throats.
These beautiful blackbirds are a rare sight in northern Minnesota, yet a few populations do exist here and there. When I conducted my graduate research in the Prairie Pothole Region of North Dakota, the larger prairie wetlands were always filled with yellow-headed blackbirds.
Indeed, my favorite season and time of the year, springtime, is drawing to a fast close already. As birds galore are singing and nesting nearly everywhere, now is the time to take it all in as we get out and enjoy the great outdoors.
Blane Klemek is a Minnesota DNR wildlife manager. He can be reached at firstname.lastname@example.org.