A pair of Bald Eagles have established a nest at Eagle Park in Maple Grove, MN, (I wonder if that’s how it got its name?) and it looks like they are incubating eggs. As I sat along the shore watching very shy and uncooperative Wood Ducks, one of the eagles flew into the nest and relieved the incubator of duties (temporarily). Here’s the sequence of events, along with a narrated commentary.
“You-hoo — I’m back!” It looks like the eagle is bringing a meal, but from what transpired next, I’m guessing it was nest material from the nearby marsh instead.
Eagle 1: “Wake up I’m landing now.” Eagle 2: “Yeah, yeah, I see you.”
Eagle 1: “Hey, look at this great fuzzy stuff I got to line the nest”. Eagle 2, not impressed, anxious to leave.
This nest is near the top of a large maple tree, about 60 feet up. As seen in these photos, eagle nests are constructed of stout sticks, but lined with softer material, like the marsh grass one eagle brought to the nest. According to the experts, Bald Eagles tend to nest far from human disturbance in a stand of mature trees near large bodies of water, but this pair’s nest is about 100 feet from an industrial complex across a small marsh from a golf course, and 100 yards from a busy road. They must be quite tolerant, or very experienced breeders.
Eagle 1: “Enough sitting, I’m outta’ here.” Both male and female incubate the eggs, but the female puts in the greatest proportion of incubation time. The male relieves her to go hunt for her own food, but she relies on her larger body size and fat reserves to make it through the month of incubation.
“Move this stick over here, and I’ll be more comfortable.” Eagles re-use nests over a period of four to five years, or until they blow down or fall out of the trees. They bring in new material each year, and keep adding structure to the nest where it seems too flimsy. Bald Eagle nests can be as much as 13 feet deep, 8 feet across and weigh more than a metric ton (1000 kg).
“Still two eggs there? Yup.”
“OK, roll them over and then I gotta’ sit down on these babies without breaking them…” All birds turn their eggs over every couple of hours to insure even incubation of the embryos and to prevent the blood vessels that cover the yolk from sticking to the egg’s inner shell surface.
“Incubation time — sooooo boring. 15 down, 20 days to go”. (A rough guess, but these birds have been incubating since I first saw them here on March 30)
I’ll be gone out of town for a while, but I’ll be back to check on the chicks in late April. They might have hatched by then.