RSPB Scotland has objected to proposals for an offshore wind farm near Aberdeen.
A planning application for an 11-turbine wind farm off Aberdeen Bay was submitted to Marine Scotland in August.
US billionaire Donald Trump has already complained about the wind farm plans affecting his golf resort north of Aberdeen.
RSPB Scotland said the area was home to seabirds and rarer species, and more research was needed.
Ian Francis, RSPB Scotland area manager for north east Scotland, said: "From an early stage, we have held many discussions with the developers, and we acknowledge the efforts they have made to reduce its scale and change the layout of the turbines, which has helped.
"However, more planning, research and monitoring is needed to ensure we truly understand the impact this site may have on local birds.
"The bay is an important area of many species. Since this is a European funded test centre, it is crucial that a thorough research programme is developed to help understand how this and the many forthcoming offshore wind farms can reduce their impacts on birds and other marine wildlife."
The European Offshore Wind Deployment Centre is a £150m joint venture by utility company Vattenfall, engineering firm Technip and Aberdeen Renewable Energy Group.
David Rodger, spokesman for the joint venture partners behind the EOWDC, said: "We welcome RSPB Scotland's input and its constructive comments.
"We have throughout the development of this project worked with RSPB Scotland and other environmental stakeholders.
"It has been acknowledged by all that additional monitoring and data would be required to have a better understanding of the potential impacts of the scheme.
"We look forward to working with Marine Scotland and RSPB Scotland to discuss the concerns and to share with them the emerging data we have on the proposed site."
The Trump Organisation said: "There are serious issues with this wind centre - it's badly sited and will have a detrimental impact on tourism and other important businesses operating in the area."
It is six years since the idea of a wind farm in the waters off Aberdeen was first mooted.
The marine consortium applying to build the wind farm has said the 11, next-generation wind turbines would be constructed as a testing ground for future developments.
It is expected it would create jobs and economic benefit by attracting scientists, researchers, engineers, offshore wind supply chain companies.