Careful there little guy...it's a long way down. These 3 eaglets are a month old, about the size of a chicken, still downy but starting to grow their flight feathers. (Large view best)
Although photographing nesting birds can unduly stress them, if reasonable precautions are taken, it's usually not a problem. I checked some of the major bird organizations' ethical guidelines and came up with the following that work for me:
1) maintain a respectful distance from the nest and use a super telephoto lens. Ideally, the birds won't even notice your presence, especially if you're partially hidden or camouflaged.
2) keep your visit brief, a few minutes at most.
3) no flash or artificial light
4) Don't visit a nest more than once a week.
5) If the adults are trying to feed nestlings and are avoiding it, leave immediately.
6) Never remove branches or vegetation to get a clearer view, as they can provide predator protection