Fears have been voiced about disruption to breeding curlews if the A96 is rerouted away from Inverurie.
Concerns about the impact of proposals to upgrade the road between Aberdeen and Inverness on the “near threatened” wading birds with a distinctive song were expressed at Holyrood.
North East MSP Lewis Macdonald said the birds would be “disrupted and probably displaced” if the new road is diverted through farmland outside the town.
Locals are campaigning for the existing route to be upgraded, but that option has been dismissed by ministers.
The fate of the birds, classified as “near threatened” by conservationists, was raised during a Holyrood debate on “World Environment Day”.
Mr Macdonald, the Scottish Parliament’s curlew species champion, said: “Transport Scotland is considering rerouting the A96 away from Inverurie, and building a new dual carriageway through farmland and semi-natural habitat to the north and east of the town.
“That area contains what the RSPB describes as moderate clusters of breeding curlew, which would clearly be disrupted and probably displaced if that option is selected for the A96 project.
“If we are serious about tackling the crisis in biodiversity, breeding sites of endangered species need to be given the priority they deserve by transport and infrastructure as well as by environment ministers.”
A Transport Scotland spokesman said: “We value the environment we are working in and place particular emphasis on striking a balance between delivering the A96 dualling and respecting the sensitivities of the corridor.
“The in-depth planning and design work we are taking forward includes an environmental assessment of the options under consideration to ensure that we deliver the right scheme and keep impacts on the environment, communities, and businesses to the absolute minimum.”