[KevinR]

I find the 55-300mm useful for some birds, but slightly lacking in reach. Also use a Sigma 170-500mm, and the 500mm end is about where I would like to be most of the time if I cannot stalk up close. Best with monopod to carry the weight. Spot AF. Spot AE or manual E and always in RAW so I can adjust afterward. Cheers Kevin

Sometimes they come to you, I got lucky here and had to use the 170mm end:

[KevinR]

These are hand held. Using a Tamron 70-300 Di on a K10D spot focus.

I have tried to use this Tamron 70-300 Di for birds, but always seem to get too much purple fringe against the bright sky or with high contrast. Still have the Tamron, but now much happier with Pentax 55-300

[KevinR]

First I think is with Pentax 55-300 at 300mm, but got in fairly close from a small boat.

Second is Sigma 170-500 at 500mm but bird up a high tree.

[Ahab]

I have tried to use this Tamron 70-300 Di for birds, but always seem to get too much purple fringe against the bright sky or with high contrast. Still have the Tamron, but now much happier with Pentax 55-300

Interesting, the only time I get PF is low light, low contrast. See my bright sky, high contrast images at post #2.