Forest pigeon with Sigmonster + 2x TC

Haven't done a "shoot out" per se,.
But IMHO strenghts and weaknesses of the two break down pretty much as expected,..

500mm with IS means a peice of ordinance that can brought into action much quicker,. can be used on the fly and or hand held in a pinch with excellent results. Is readily at home on a monopod for long hikes,. and of course still offers excellent flexibility with it's love affair for Canon T-Cons.

Sigmonster best used with rock solid support, MLU and cable release.
Added length and zoom flexibility make it the perfect tripod mounted perching bird lens.

Based on your love of super long range shots,. You'll keep the Sigmonster,
Based on your amazing use of lower shutter speeds,. You'll LOVE the Canon's IS in those situations.

That's my expectation of what the 500 can bring to the table, CDS. The weak points in my system now are:

1. Long distance fliers. The Sigmonster is slowish at this because of its lack of focus limiter, and of course shooting fliers hand held is still the best way to catch them. The 500 can be hand held, the Sigmonster can be too, but only if I'm Big Show...

2. Shots when I'm using the vehicle as a blind - the 500 is perfect for this application.

For close or large fliers, the 400 5.6L is better suited. For light, mobile birding or if I can get very close to the bird, the 100-400 L IS is the tool. For long distance perchers or waders, or for blind work, the Sigmonster rules.

Romy

Yeah,. I can't wait to get that beast on the shore for waders when it gets the right season