A 50-year-old parrot was among four birds stolen from their aviary in south Norfolk.
Thieves struck at Swallow Aquatics at East Harling, near Attleborough, overnight.
Staff arrived at the business, on the B1111 Harling Road, to find the birds had been taken.
Livestock supervisor Branden Darlison-Hoskin said: "There were two blue and gold macaws, Albert and Lily and the other two were African greys, Burt and Daisy.
"Our manager has had Burt for more than 30 years and he was given to him by someone who'd had him for 20 so he is more than 50 years old.
"With all the stress I'd be surprised if he makes it to be honest.
"We came in this morning and both aviary doors were open and the padlocks had been cut with bolt croppers. I believe whoever has taken them knows what they're doing."
Mr Darlison-Hoskin said the birds would normally sell for £1,000, while African greys require paperwork to show that they are captive bred and have not been taken from the wild.
Police have been informed of the theft.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here