The RSPCA said it had rescued more than 100 birds, which had been taken to the West Hatch Animal Centre in Taunton.
Earlier reports suggested the white substance was palm oil, but scientists were unable to confirm this, though they believe it is vegetable-based.
Many birds were found at Chesil Cove near Weymouth but others are appearing up to 200 miles away in Cornwall.
There are also reports of some washing up in Hampshire and Sussex.
At least two of the rescued birds, which are mainly guillemots, have died but rescuers are trying to save others.
Martin Cade, warden of Portland Bird Observatory, said it looked like "hundreds of birds" were being washed up, covered in a "PVA glue-type" substance, while even more could be seen out at sea.
He said: "Most of them aren't dead, and if they get cleaned up by the RSPCA, they have a have a chance of survival."
Steve Trewhella, a naturalist based in Dorset, spent much of Thursday at Chesil beach.
Read on: http://www.bbc.co.uk/news/uk-england-dorset-21275648
As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.