Bluebirds in Minnesota are easy to love
The little shallow lake that borders my property, Assawa Lake, is quite low this summer. Rainfall has been sparse and the wetlands and waterways throughout this part of the state bears this out. As I stood in the tall grass adjacent to the lake on a spot that would normally be underwater, I noticed a bluebird perched high in a nearby tree at the tip of dead branch.
A moment later the bluebird left its perch and flew down toward the lake and, surprisingly, landed on a mat of vegetation that consisted of lily pads and watershield plants. Watching the bluebird and curious about what it was up to, I observed the bird peck at something with its beak. In the next instant the bluebird was aloft and flew to the exact perch it had just left, but this time with an insect meal held securely in its bill.
That a bluebird would land seemingly on the water was surprise enough, but what wasn't a surprise was the fact that these insectivorous birds are as adept and opportunistic as a bird can be. Eastern bluebirds, those avian darlings of open, rural areas, golf courses, and backyards are among the most beautiful of our songbirds.
Much has been written about eastern bluebirds, including by yours truly. Garnering much attention from people wherever the bird exists, bluebirds are one of those species of wild birds that are easy to fall in love with. Beautiful blue plumage, reddish breast, and docile disposition — not to mention that they take kindly to the many and varied artificial nest boxes we humans build for them — it's no wonder bluebirds are at the top of birders' lists of favorite birds.
Eastern bluebirds are the only of the three species of North American bluebirds that occur in Minnesota. The other two species, the mountain bluebird and the western bluebird, range throughout areas that their names suggest — within the mountains and western landscapes of the continent. Whereas the range of the eastern bluebird includes all of Minnesota and more than half of eastern United States and southern tips of most Canadian provinces, the mountain bluebird occurs as far north as Alaska.
Here in northern Minnesota, migrating eastern bluebirds begin showing up in late March-early April. Males arrive before females and soon after arrival they begin establishing breeding territories. When female bluebirds filter back into the state, male bluebirds are waiting and soon begin showing receptive females potential nesting locations that he's already scouted for and located. If any given male suitor impresses a possible mate, she will not only pair-bond with the male, but eventually select one of his nesting cavities for which to lay eggs inside of.
As just mentioned, bluebirds are obligate cavity nesters. Choosing from a wide variety of tree cavities such as naturally occurring cavities or those created by woodpeckers, eastern bluebirds will also readily nest inside of artificial nest structures, aka birdhouses. Many other birds are obligate cavity nesters, too, including tree swallows, purple martins, and house wrens. In fact, tree swallows and house wrens often compete with eastern bluebirds for both tree cavities and artificial nest boxes.
It is for this reason — competition for nest space — that it is recommended when erecting bluebird houses where tree swallows are also found, to erect the birdhouses in pairs, side-by-side. A bluebird pair sometimes is outcompeted by the more aggressive tree swallow, and so will often give up the nest-box and leave. On the other hand, pairs of birdhouses will sometimes be occupied by the tree swallow in one house and the bluebird in the other house. It doesn't always work, but it's worth trying if you experience tree swallows bullying your bluebirds.
After courtship, during which the male bluebird frequently brings food to his mate, the pair begins nest-building chores. Both birds assist each other in material collection, but it's usually the female that constructs the actual nest-bowl. Fine grasses and stems are normal nest materials, but so are white pine needles if readily available. Feathers are rarely used, if at all.
Following a weeklong nest construction project, the female lays four to five blue to whitish eggs. She alone incubates the eggs for about two weeks until the eggs hatch. But because the nestlings are born without feathers, the female continues to brood, keeping her nestlings warm and safe while the male brings much needed food for his brooding mate and newly hatched offspring.
Soon afterwards when the nestlings are a little larger and are growing feathers, the female begins to join her mate for the relentless two to three-week feeding routine of stuffing healthy supplies of insects into the gaping mouths of their always hungry young.
In all, it takes up to a month, maybe a little longer, from incubation to their offspring fledgling. And chances are good that after the pair of bluebirds have ensured their nestlings can fend for themselves, they might just do it all over again and raise a second brood! Often is the case that the juvenile bluebirds join their parents in the rearing of the second bluebird brood.
Though our summer is now waning, eastern bluebirds are still here and no doubt raising their second broods. And soon you will begin noticing groups of bluebirds as they prepare themselves for the long migration to southern states and Central America. In the meantime, until they leave us behind for a few months, let's take heart of observing our beloved bluebirds as we get out and enjoy the great outdoors.