Lens for a nikon d80?

I have a nikon d80 and am looking for a telephoto lens for it. But, I don't have much to spend. I have a quantaray 70-300 (not junk as people say it is) I use it for my son's rugby games and have gotten some great shots. But it just isn't enough zoom. I'm going on a tour to get photos of eagles this summer. Any suggestions?

A budget option would be a 500mm preset or mirror lens, but I don't know how they'd cope with your metering options (they're also MF only).

I do know that my 400mm preset (which I've had for 20-odd years, changing t-mounts as necessary) allows Aperture Priority and Manual exposure on my Canon EOS.

After 300mm it gets expensive really fast. There's some 400, 500 and even 600mm reflex lenses but they have a tendency towards low contrast and donut bokeh.() almost all of these would restrict you to M only since they're effectively Ai lenses.

Next up is old primes and a teleconverter. Nikon's 300mm and an 1.4tc is a popular combination. The old 80-400 VR is also popular.

The most realistic option is, I think, Sigma's 150-500. Comes with stabilisation and a motor for reasonably fast focussing.

Once you get much over 300mm zoom lens prices start to soar (with your eagles!)
Like this highly regarded 150-500mm Sigma
http://www.amazon.co.uk/...001542X64/

There are plenty of cheap mirror lenses on the market.
Here is an 800mm one
http://www.amazon.co.uk/...00281H62E/

Or for £80 here is a 500mm:
http://www.amazon.co.uk/...003XO3N7M/

As an alternative for a one-off project have you considered renting a lens?