sniff the nest

A phrase describing when a guy is low-key hitting on a girl. Causally testing the waters to get a feel for the odds of him eventually getting some tail. In this context, 'nest' refers to the female crotch, around which he's sniffing.

Guy: 'Why is your phone buzzing today constantly? Who's texting you?'
Girl: 'This dude I met who offered to teach me how to weld.'
Guy: 'Weld? That's weird. He's probably also trying to sniff the nest'
Girl: 'Yeah, probs