A commuter tweeted that the front carriage of the 7:11am service between Leuchars and Edinburgh was out of use due to the bird being trapped overnight.
The train, which left originally set off from Aberdeen at 5.46am.
It has been reported that the bird “became trapped in the carriage and repeatedly crashed into the windows, leaving a trail of blood and debris”.
Baktosch Gillan tweeted: “Remarkable reason for the front coach of the 7.11 @ScotRail train from Leuchars to Edinburgh being out of use. “Overnight a bird, thought to be a seagull, became trapped in the carriage and repeatedly crashed into the windows, leaving a trail of blood and debris”
Replying to Baktosch Gillan’s tweet, a ScotRail social media manager said: “It’s one of the oddest events I’ve heard of in a while! Sorry for the reduced capacity on board”
A ScotRail spokesman said: “We’re very sorry for the lack of the capacity on this service.
“But we are pleased to confirm that the bird is alive and well.”