More than 1000 newly-hatched chicks have been abandoned and left to fend for themselves in a field in the United Kingdom, sparking an investigation by the RSPCA.

The vulnerable birds were found huddling together to keep warm in the freezing temperatures, but it was too late for some. Many were found dead or dying.

"I have never seen anything like it - it was just a sea of yellow," RSPCA inspector Justin Stubbs said.

"Some, sadly, had to be humanely put to sleep. Thankfully, most of the chicks did not appear to be suffering."

The chicks were spotted by a passerby in a field in near Peterborough, in Cambridgeshire, on Friday.