My only concern with not wearing underwear is -- what if the bike shorts get torn? I have Shebeest Shindiggers for summer and they are lightweight. Which I love.

But when I'm birding, I worry about sitting on a rock or tree trunk. That lightweight fabric could snag. I doubt it would tear very much, but it's something to think about.

Speaking of wearing underwear while biking, I once went biking with a pair of panties stuck to the Velcro on my parka. I snatched it out of the dryer in a hurry and didn't notice. It was dark, so I doubt anyone saw, except maybe my doorman who helps me get the bike outside. Luckily he is very discreet.