I am about to head down to Florida and hope to snap a few (thousand) bird photos with Mike (Busted Knuckles). I am kicking around the idea of renting a lens for the occasion. Typically I take my Sigma 150-600S and it does do a great job. But it is always fun to play and I "might" be able to afford a white lens with some girth in the next year. This has me thinking and looking at my usage of the Sigma 150-600S, I take a good amount of pictures with it (~30%) in remarkably few events that usually involve travel. Matter of fact, the only events that didn't involve travel where two trips to take pictures of loons over the summer. Everything else came from trips that required air travel.

So, the question is ---- What is the ultimate Supertelephoto lens for travel?