Sustainable Shetland is seeking judicial review of the decision of Scottish Ministers in April to grant consent for the Viking Energy wind farm on the Shetland mainland.
The original plan for 150 turbines was initially reduced to 127 after consultations and then the Scottish Government reduced the number further to 103 to resolve an issue regarding Scatsta airport.
The 850-strong campaign group says ministers could not reasonably have established the scientific facts over the protection of the Whimbrel bird without an inquiry.
According to RSPB Scotland the UK's breeding Whimbrel population, which is now found almost exclusively on Shetland, has declined rapidly in the last 20 years. The species is red-listed as a threatened species.
It is estimated the scheme will generate £566 million of capital expenditure and tens of millions of pounds in annual income for the island.
James Mackenzie, of Sustainable Shetland, said: "The EU Bird Directive affords the Whimbrel protection because it is a species in severe decline and the UK and the Scottish Government are bound by that and must take active measures to protect the Whimbrel.
"The Scottish Government's own advisers Scottish Natural Heritage (SNH), objected to the development because they thought the disturbance and mortality of whimbrel would be too much. SNH also had an objection on landscape grounds."