The ibis was chosen as Miami's unofficial mascot by Nathan Duncan in 1926 when the school's yearbook chose its name to be "The Ibis."
"Miami adopted a native marsh bird called the Ibis as the official mascot in 1926. The Ibis is known for its bravery as a hurricane approaches. Folklore maintains that other birds look to the Ibis for leadership. The Ibis uses its instinct to detect danger. It is the last sign of wildlife to take shelter before a hurricane hits, giving warning that danger is imminent. As the storm passes the Ibis is the first to reappear, a sign that clear skies are approaching."
The first official mascot for the Miami Hurricanes was a 65-pound brown and white bulldog named Hurricane I. Chosen in 1950, the canine wore a ceremonial orange and green blanket with his name lettered in white.
Sebastian was created in August 1957 by Norman A. Whitten, Director of the Student Union at UM, and was used as a homecoming competition entry. The next year, student John Stormont performed at Hurricanes football games dressed up in a makeshift ibis costume. The current costume dates from the 1980s.
The mascot was named after the San Sebastian building, which became a University dormitory in 1939. The building, now an apartment building, still stands at the intersection of LeJeune Road and University Drive in Coral Gables.
During the first national championship season for the Miami Hurricanes football team, including their 31-30 victory over #1 Nebraska in the Orange Bowl, the Ibis was portrayed by Bill Mooney, a senior at the university, from Orangeburg, NY. 
From 1984 through 1992, Sebastian was portrayed by John Routh, who also portrayed The Miami Maniac at baseball games, and later Billy the Marlin for the Florida Marlins. Routh created what is now Sebastian's signature: the C-A-N-E-S cheer, where Sebastian forms the letters with his body.
Sebastian was tackled by a group of policemen in 1989 for attempting to put out the Seminole's Chief Osceola's flaming spear. At the time he was wearing a fireman’s helmet and yellow raincoat and holding a fire extinguisher. When a police officer tried to grab the fire extinguisher he was sprayed in the chest. Sebastian was handcuffed by the other four officers but released when they realised how ridiculous it looked for them to be arresting a bird.
Sebastian typically leads the University of Miami football team as it enters the field through the smoke.