A few are treated paper, but most are midrange vinyl.

6" ruler on left for size reference. 

A few are 1.5", but most of these are between 2" and 6" in size. 
This is a nice collection, sent to me directly from the parks over the last two years. 

Some of the parks featured include:

Alaska Sealife Center

Bird Alliance of Oregon

Cascades Raptor Center

Charleston Marine Life Center

Dauphin Island Sea Lab

Flaming Geyser State Park

Fontenelle Forest

Fountain Rock Park

Georgia Aquarium

Granby Ranch Colorado

Hidden Valley Nature Center

Illinois Audubon Society

Masonville Cove

Mote Marine Lab

Sandy Creek Nature Center

Stainbrook Park

Sylvan Heights Bird park

Treehaven

Turkey Creek Sanctuary 

Tybee Island Marine Center (white one clear, it's a sticker NOT a window cling). 

Wild Basin... and more!!!

There are maybe 3 duplicates in the mix, but most of these are one from each place. 

FREE shipping to lower 48. 
Thanks for looking.