I've recently learned of a local eagle cam and have been enjoying watching a pair of bald eagles and their three chicks. While I don't have access to many days of video to check (the site buffers 12 hours), I have noticed a pattern the past few nights that I'm curious about.
Throughout the night (or spot-checks, anyway; it's not like I'm watching all of it in real time), I've noticed that one of the adults is almost always present, but not both. Usually it seems to be "standing guard" just outside the nest, like this:
The preferred position seems to be facing away from the camera, so even if the night-time video weren't low-res I can't tell if the bird seems alert or is sleeping.
Occasionally the adult is instead in the nest with the chicks:
But it's always just one adult when I've checked, though if the other were nearby and just out of camera range, I wouldn't be able to tell. During the daytime the adults don't seem to be reluctant to share the nest.
If it's not nearby, where does the other adult go? Bald eagles are, I understand, diurnal, so I wouldn't expect it to be that active at night. But when it's not active, wouldn't it "go home" to its nest?