Ducks keep nibbling my pants?

[Dux]

Mine love zippers too, also rivets on jeans and pockets, pockets, pockets to snuffle deep inside.

 

[Kp805]

Good afternoon,
So I have noticed a lot about ducklings nibbling, but my 4 are all 3 yrs old and adopted. We've bonded great and only one likes to be touched but the others all keep close to me. Lately though on the rare sunny days were it hits above 32 I'll go sit outside. 3 of them will run up and suddenly start nibbling on my pants and jacket and boots. It doesn't seem affectionate at all and even my drake who doesn't like me has hopped into my lap just to get a taste of my boots or pants.
Is there any reason why they would be doing this? Even my friendly one has been nibbling my jacket when she's sitting on my and has even sampled my nose (gently)!

I've read when ducks nibble on you it's a sign that they like you. The only duck that nibbles on me is the one I raised from a duckling. He gets so excited when he sees me. He's never afraid of me and he let's me pet him. He also tries to get in my house with his friends, cuz that's where he was raised. I LOVE MY DUCKS.