"Others flew away. It appeared to me the driver, just the way he did it, had done this sort of thing before. It could well have been a lot worse.
"I was horrified. I am guessing it's something he does for fun. I wish I had the opportunity to get the vehicle's number plate."
The Department of Conservation in Whangārei has not been informed about the incident but has urged anyone with information to call its 24-hour number 0800 DOC HOT / 0800 36 24 68.
Spokeswoman Abi Monteith said as red-billed seagulls were commonly seen in coastal areas, many people didn't realise their numbers were declining nationally.
She said the species has a conservation status of "at-risk: declining", which meant it was unacceptable to kill or harm protected seagulls.
Nationally, there are now fewer than 100,000 red-billed gulls left, and over the next 30 years, their numbers are expected to fall by between 50 to 70 per cent.
Robert Webb from the Whangārei Native Bird Recovery Centre said people did not realise seagulls were a protected species and that there was a hefty maximum penalty for injuring or killing them.
"There's no excuse to run them over. Either go around them or slow down and allow them to move. People should also think before throwing food at them on the side of the road. If you have to feed them, get out on to the beach."