* London Array expansion scrapped due to bird study delays
* Other offshore wind projects have been scrapped or reduced
By Susanna Twidale
LONDON, Feb 19 (Reuters) - The need for a study into the potential threat to the red-throated diver, a type of waterfowl, has forced developers to scrap a project to expand the world's largest offshore wind farm, Britain's London Array.
The consortium of Denmark's Dong Energy, Germany's E.ON and Abu Dhabi state-owned energy investor Masdar joined a growing list of companies scaling back plans to build new offshore wind capacity in Britain.
An assessment of the potential impact to birdlife from construction of the project in the Thames Estuary would take at least three years, the group said on Wednesday, citing the delay, the cost and the added risk.
"There is no guarantee at the end of three years that we will be able to satisfy the authorities that any impact on the birds would be acceptable," Mike O'Hare, general manager of the London Array, said in a statement.
The Royal Society for the Protection of Birds (RSPB) said it had worked with London Array to ensure its initial development would not harm wildlife in the area but "raised concerns over the second phase of the London Array because of the displacement impact on the (bird breed) red-throated diver".
The project would have added 200 megawatts of capacity to the existing 630 MW wind farm.
It also would have affected 38 percent of the red-throated diver's UK wintering grounds, the RSPB said. The bird's UK wintering population totals 17,000 and is in decline, according to the RSPB website.
The decision to scrap it was due to "technical challenges and the environmental uncertainties surrounding the site", the group said.
The British government aims to install 8 to 15 gigawatts of offshore wind capacity by 2020 to help meet emissions reduction goals and European renewable energy targets.
But in the past few months, RWE and Iberdrola-owned Scottish Power have both scrapped or scaled back huge offshore wind farm projects, citing the costs involved in developing deepwater sites.
Last week, a consortium of RWE, SSE, Statkraft and Statoil reduced the number of offshore wind projects it plans to develop at the Dogger Bank Zone in the North Sea to six from eight, cutting total capacity to 7.2 GW from 9 GW.
"The overall project pipeline for UK offshore wind is still healthy, although obviously it's disappointing when projects don't go ahead or are scaled back," said Nick Medic, lobby group RenewableUK's director of offshore renewables.
"We're maintaining our global lead, with more capacity installed in UK waters than the rest of the world put together," he added.
Britain has 22 operational offshore wind farms with 3,653 MW of capacity and a further 1.4 GW under construction, according to the UK's Department of Energy and Climate Change (DECC).