A man jumped on a sleeping swan and throttled it because he thought it was a goose and wanted to eat it, Aberdeen Sheriff Court has heard.
Monteiro said he thought the swan was a goose
Luis Monteiro, of St Machar Court, Aberdeen, pounced on the mute swan on the banks of the River Don.
The attack happened on 4 June in front of shocked witnesses.
Monteiro, 34, admitted intentionally killing the bird and was warned he could face jail. Sentence was deferred for background reports.
The offence is punishable by a six-month prison term and/or a fine up to £5,000.
Monteiro also admitted being on bail at the time of the offence, which was a contravention of The Wildlife and Countryside Act.
Depute fiscal Heather Carmichael told the court Monteiro and a neighbour went to the riverbank for a picnic after shopping at a nearby supermarket.
"There was a swan sitting by the riverbank, apparently sleeping," she said. "The accused jumped on top of the swan and put his hands around its neck."
The incident was witnessed by Monteiro's female companion and a young man who was with friends.
"They all saw the accused sitting on top of the swan, and after a short time its neck went limp and fell towards the ground," Ms Carmichael said.
The witnesses saw Monteiro wrap a jacket around the bird and leave the scene, walking "briskly away".
Police officers caught up a short time later and found he had left the bird's body a short distance away.
Defence agent Patrick O'Dea said: "He accepts he carried out this offence. His explanation was he was originally going to eat the animal, thinking it was a goose.
"But he dumped the bird when he saw police and became scared.
"He is apologetic for his actions."
A post-mortem examination showed the swan's injuries - a broken neck and internal bleeding - were consistent with someone holding it between their knees and breaking its neck with their hands.
After the case, Grampian Police wildlife officer George Sangster said: "There's a big difference between a goose and a mute swan. It's one of our largest birds and is easily recognisable.
"Essentially all wild birds are protected by the law in this country.
"It wouldn't matter whether it was a goose or not - he has no right to kill either bird.
"We are pleased at the outcome of this case and we hope this sends out a clear signal that Grampian Police and police forces in general take wildlife crime very seriously and offenders will be prosecuted.
"Thankfully, the persecution of swans is quite rare."
At one time, swans were a popular delicacy and some of the animals - particularly on stretches of the River Thames - belong to the Queen.