I've recently gotten my hands on a cheap Maginon 500mm F/8 Super-Tele - a steal at 30€. Today I sat on a bench in a park nearby, next to a lake, and got plenty of opportunity to try to photograph different birds.
A fair amount of sunlight thankfully allowed me to shoot free-hand, at F/11-F/16, and even catch a few birds in flight, moderately sharp. Quick manual focussing is something I still need to learn....
Getting a sharp picture was far more difficult than on any other lens I own, and I also had serious chromatic aberration.
Now I realize why you pay 1000+ for a "good" super-tele
but I still feel like I got my money's worth.
First a picture from my new favourite go-to lens: One of the legendary SMC 50mm F/1.7. Go outside, people, and enjoy the springtime!
And one of the decently sharp images from the 500mm. There are plenty more on my Flickr, I don't want to flood the forum