One of my regular locations is Phinizy Swamp near the Savannah River in Augusta - a large water treatment project that has manmade wetlands. It's typical for me to walk on wide paths for 4-5 miles as I circle the manmade ponds looking for birds and other wildlife. This is the location I am most likely to carry two long lenses since it has songbirds and wading birds. I also test lenses here. The terrain is flat with grassed or dirt paths wide enough for a vehicle (private vehicles are prohibited), but it can be quite warm and the distances are all relatively long. The shortest loop is 3 miles - the longest more than 8 miles.
Another recent location was Linville Falls (NC) during peak of the spring migration. It is both a terrific birding location and a landscape location - with a short but strenuous hike to the bottom of the falls. This location calls for everything from 15mm to 800mm depending on your preferred subject matter. The bird activity was so good a landscape outing turned into birding and bird photography.
The third regular location is at Jekyll Island (GA) where the best shorebird location requires a 1 mile hike along the beach. This is where I may carry the 600 f/4 in a backpack - because I don't want to leave gear on the sand unprotected. In the morning I typically start with landscapes for sunrise, then switch to a long lens once it's light enough for birds in flight. The 800mm, 500mm PF, or 400 f/4.5 (one only) are carried on a Black Rapid strap.
There are other locations that can come up for songbirds or in large parks and wildlife refuges. My Christmas Bird Count route covers three nearby parks and about a 5 mile walk on hilly trails.
The common thread with all these locations is that I have specific subject matter that calls for a long or very long lens, as well as other opportunities.
