Kermit Love, the costume designer for some of ballet’s most renowned choreographers whose greatest fame came as a creator, with Jim Henson, of the beloved “Sesame Street” characters Big Bird and Mr. Snuffleupagus, died on Saturday in Poughkeepsie, N.Y. He was 91 and lived in Stanfordville, N.Y.

The cause was congestive heart failure, said Christopher Lyall, Mr. Love’s partner of 50 years.

Although Mr. Love collaborated with luminaries of dance like George Balanchine, Agnes de Mille, Robert Joffrey, Jerome Robbins and Twyla Tharp, it was the 8-foot-2, yellow-feathered Big Bird and his 7-foot, woolly mammoth-like friend Mr. Snuffleupagus  both perennially 6 years old  that brought him global attention.

“For Kermit, the costume was just the beginning,” said Kevin Clash, who is now senior puppet coordinator for “Sesame Street” and considers Mr. Love his mentor. “He taught how to create the character out of the costume.”

Caroll Spinney, 74, the man inside the bird since “Sesame Street” was first telecast in 1969, said, “We traveled the world doing shows for kids, sometimes with Big Bird conducting orchestras.”