The whole idea is to get the biggest bang for your buck!
So I'll propose a formula to minimize the miles driven (and the exhaust pipe pollution) to see a bird.
The Formula:
miles driven per birder divided by species seen
leads to
drive alone to Bonny and see 50 species and drive back = 300 miles divided by 50 species = 6.0 - a high number - not good
But make the same trip with 4 birders in a car : 300 miles driven divided by 50 species, DIVIDED by 4 birders, so a score of 1.5 per birder - much better.
The idea is to have the lowest number, so driving 2 miles alone to see 50 species would be 2/50 = .04 a low number -very good
Seeing 10 species at a feeder, zero miles, would be ZERO miles, zero pollution, which is the lowest score possible.
A Big Year in Denver County by bicycle:
zero miles of tailpipe pollution for 150 species. Again ZERO
Or do what I do - take a nap. Zero miles, zero birds. Wow! ZERO.
The main point is to get a buddy or three to join you for longer trips.
"Let's Go Birding!"
Joe Roller, Denver