He told the operator the bird had attempted the lunch food heist in Bristol city centre and urged officers to check nearby CCTV for evidence.
In another call a woman reported the owner of a guest house where she was staying for refusing to cook breakfast.
Police are highlighting the number of calls they get in a day with 25 out of 1,000 on Wednesday "inappropriate".
Another 999 call to the Portishead HQ came from a woman who had locked herself out of her home.
"Not something that should be reported via 999 - you might be blocking an emergency call," the police tweeted.
Acting Deputy Chief Constable Gareth Morgan said he hoped a 24-hour "tweetathon" on Wednesday would give an insight into the works that goes on behind the scenes.
A man rang 999 to report a gull had ripped a sandwich out of his hands in a call branded a "misuse" of the number.