A bird hitting a piece of equipment at Northpower's Maungatapere substation took out power to more than 4500 Whangarei properties.
Northpower spokesman Steve MacMillan said a bird strike caused a flash in a conductor on a 33,000 volt electricity cable about 11.30am yesterday.
The strike caused an "explosion" and cut power to more than 4500 homes and businesses.
Some of properties had power restored almost instantly, with power fully restored by 12.45pm.
Mr MacMillan said the areas affected included Maungatapere, Poroti, Kioreroa Rd and Whangarei South area, including part of the CBD.
He said bird strikes cutting power was a relatively common occurrence and the type of bird that caused yesterday's outage could not be identified as there was little of it left.