I have posted several times this fall about our visit in the Rocky Mountains. I still have images that haven't been shown in either of my galleries. Can't resist to show you the American Pika again today because I just watched a documentary about the effects the warming of the earth has on this little critter. It is not easy to get really close to the pika but this photo shows their natural habitat, the boulder-covered hillsides above 8,000 feet altitude.
The other animal is a Golden-mantled Ground Squirrel. It was on the watch, not far from the trail on a grassy hillside. It almost seemed to pose for us... ;-)
The background in the pika picture has natural lens blur that separates the animal from the background nicely. Not as good as with a fast and much more expensive f/2.8 or f/4 lens, but the Sigma 50-500 f/4-6.3 still delivers a decent result here. The grassy background in the squirrel picture was much more distracting and so I used a blur filter in Photoshop to improve the result in the upper part of the photo. Still not perfect but I believe it is a feasible solution to work around the limitations of this lens.