It’s early March, and that means spring is springing in the bird world. The red-tails were building nests when I was down in Panoche valley, the Mockingbirds have arrived here in the neighborhood as they do every spring, the oak titmice are singing their lungs out, and it looks like the Bald Eagle pair near Calaveras Reservoir is nesting again.
Okay, technically, they are way above Calaveras reservoir, in the top of a high tension power tower. I’ve been watching this pair when I can since 2008; I believe their first year nesting here was 2007. In 2008, the nesting failed as far as we can tell. In 2009, they fledged one chick, in 2010, they fledged 2. In 2011, they abandoned this nest and built a new one down in the treeline nearby; my life at HP was strange enough that I basically had no time to watch them, so I have no idea if they successfully fledged. and here in 2012, they’re back in their original nest and starting again.
Typically they’ll work on the nest in late January and early February. Egg laying seems to happen in late February or early March. There was a report by one birder that they were working on the nest earlier in the week; when I checked in on Friday, as you can see, she (assuming it’s the female, she spends ~80% of the time on the eggs, her mate covers the other 20% but does most of the hunting) is in it. In the 40 minutes or so I watched, she never left the nest. This isn’t absolute proof they’ve laid — I was talking to an expert today and eagles can have false incubations — but we believe, especially given their track record, that she’s laid and is sitting.
Incubation is about 35 days. If all goes well, at the end of March or (more likely) early April, they’ll hatch. Bald eagles can lay one to three eggs; they rarely fledge three chicks, typically, the weakest chick is ejected by the others at some point. If food is somewhat scarce, the strongest chick will prevail. The third egg is essentially an insurance policy in case something happens to one.
The parents will care for them; early on, dad is the primary hunter, as they mature, mom will be able to spend more time away from the nest and do more hunting. Bald eagles are typical fish hunters, but this pair is a pair that has adapted to the local area and hunt primarily ground squirrels, which number in the zillions in this area (the Benito County eagle pair does the same).
By mid-May, the chicks will be testing their wings. By early June, they’ll fledge and leave the nest, and the cycle will be done for another year. This pair is bonded, they will likely be together and nesting unless one of them dies. They’ll continue to breed throughout their lives, as long as 30 years if all goes well.
Here’s some video I shot of them in 2010 with the chicks close to ready to leave the nest.
My hope this year is to monitor them every couple of weeks until the chicks hatch and then every week or ten days or so through fledging. And get some much better video when I can. And probably borrow a bigger lens, since they’re far enough away that the 420mm setup I use just isn’t enough… The good news is the nest is nicely visible from the roadway for those that want to look, but visitors can’t really annoy or interact with the birds. the bad news is that you need good binoculars or preferably a scope to get good looks, and even my birding photo gear has trouble getting quality images at this distance against the wind and a common bit of heat shimmer that will show up when things warm up…
Doesn’t keep me from working at it, though…
You can see some of my photography of these birds from earlier years here.