I am far of an expert, but I think that at least two of these Coastal Birds are Water Birds, today's theme in Sunday Stamps - II. They were issued on June 1st, 2015. The birds represented are: the roseate spoonbill (Platalea ajaja), king eider (Somateria spectabilis), magnificent frigatebird (Fregata magnificens), and red knot (Calidris canutus).
These stamps (designed by Tyler Lang) remind me the work of Charley Harper. And I am not the only (see comments!). Harper is well-known, but I have just recently discovered this artist, thanks to FinnBadger. I am sure you can spot some more water birds on the postcard he sent to me: Mystery of the Missing Migrants (1990).