It only takes starlings 17 minutes to build a nest in a tractor, which can result in a costly fire.
Principal Rural Fire Officer Phill Wishnowsky says there were two bird nest related fires in farm machinery last week in the Martinborough area.
Both were extinguished before major damage was done, but the potential for damage and cost to the farmer is high, he said.
Spring and early summer brings a jump in tractor fires because of bird's nests.
"If a tractor does catch fire, not only can it mean the loss of the machine, but also the ability to carry out the work it is used for."