The RSPCA has launched an investigation after around 1,000 day-old chicks were found abandoned in a field.
Some were dead or dying when inspectors arrived at the scene, but most survived after being put in cardboard boxes so they could huddle together to keep warm.
It is believed the birds were from a commercial chick producer nearby and may have been abandoned by a third party in the field in Crowland near Peterborough in Cambridgeshire.
The producer is fully cooperating and assisting the RSPCA with its investigations.
RSPCA inspector Justin Stubbs said: “I have never seen anything like it, it was just a sea of yellow. And the noise was unbelievable.
“The chicks are only about a day old and are really tiny and quite delicate. Some of the birds were dead or dying when we arrived so some, sadly, had to be humanely put to sleep.
“Thankfully, most of the chicks did not appear to be suffering.”
The breeder went to the scene to collect the surviving birds and took them back to their unit.
Mr Stubbs said: “These tiny birds wouldn’t have survived long out on their own at such a young age and in such unpredictable weather conditions.
“For someone to dump these vulnerable chicks is unbelievable.”