A plan to scrap a 20-year-long egg oiling program at a seagull colony next to a busy road is causing division amongst Tasmanian bird experts.
Since 1998, the Tasmanian Government's roads department has been oiling silver gull eggs to stop them hatching and flying onto the busy Tasman Highway, which passes water along the Sorell Causeway.
The oil suffocates the embryo and stops it from developing.
A spate of accidents was said to be caused by cars swerving to miss young birds learning to fly.
BirdLife Tasmania's Dr Eric Woehler is urging the department to stop oiling the eggs and instead repair fencing on the causeway to prevent birds from getting on the road.
"We don't believe the oiling is having an impact, certainly the survey suggests some of the eggs aren't oiled properly," Dr Woehler said.
"We're getting chicks hatching in the colony, so we question the efficacy of the whole process."
Ornithologist Els Wakefield has called for the program to continue, raising concerns with potential car accidents if the practice was stopped.
"If they do hatch they will probably get squashed on the road, so that's unethical as well for the birds," she said.
"The best thing is to stop them hatching before they even come out of the egg."
Silver gulls are known as seagulls and are the most common gull in Australia.
The Tasmanian Department of State Growth said it was "investigating alternatives" to egg oiling, which included upgrades to fencing.
It said there had been no reported crashes as a result of birds for the past five years.
Els Wakefield said the fence solution raised other potential complications.
"If they aren't oiling the eggs, that would be a very irresponsible thing to do because then the chicks wouldn't be able to escape from the road if they did get onto the road," she said.
But Dr Woehler said he believed the chicks would be able to fly back off the road.
"We believe that alternatives such as fixing up the fence to prevent the chicks walking up onto the road way is a much easier and cheaper solution," he said.
The area is part of an internationally significant wetlands.
Birds outsmarting barriers for decades
Between 1976 and 1978, four different methods were attempted to discourage gulls from breeding near the causeway, including netting over the nature strip, bitumen poured over the rocky embankment to render the surface smooth, and various netting installations.
"Wire netting was effective but two adults were caught underneath and perished. Hot bitumen was limited in extent and not feasible for both causeways but gull nesting was prevented where applied. Chicken wire had limited success and did not reduce the traffic hazard," a report found.
"Chicks that strayed onto the road usually ran the whole length of fence guarded by a parent that hovered overhead before going down the embankment. Chicks and adults became entangled in the net and died. Nylon netting prevented nesting for only one season."
The report noted in 1979 boulders were placed on the net at one area to stabilise the embankment against wave action, which then "provided an ideal nesting site for gulls".