More than 100 racing pigeons with a value of more than £20,000 were destroyed in a fire at an allotment in Manor Street, Nelson, on Thursday night.
The birds belonged to a pigeon fancier who had birds of a similar value stolen from the plot in February.
Fire and Rescue Service Watch Manager Tom Simpson said the fire is believed to have been started deliberately.
The blaze also destroyed a shed on a neighbouring allotment, killing three ducks, three hens and a cockerel.