His international success has much increased since acceptance at Birds in Art in 1992. His work was selected for this exhibition at the Leigh Yawkey Woodson Art Museum several times more, and were also acquired by the museum. He was accepted by the Society of Animal Artists in 1993, and received an Award of Excellence in 1995.

His paintings have been published in three American books so far: The Best of Wildlife Art, part 1 and part 2, from North Light Books, and Wildlife Art from Rockport Press. For a Dutch book on rare birds he painted more than 50 detailed gouaches. He also participated in a book on the raptors of Georgia (Baltic) with four well known Dutch bird painters.

Ulco also works in the old European tradition of magical realism. These contemplative, mysterious works are well received by art critics on his side of the ocean.