The south west coast has been battered by storms since January with Goretti, Ingrid and Chandra all causing floods and devastation for both humans and wildlife.
Roland Gauvain, the chief executive of AWT, said the Channel Islands had “so far been reasonably lucky”.
He said there had been a major seabird wreck (the term for a mass-mortality event) in 2014 when 54,000 birds were recorded washed up, of which about 30,000 to 36,000 were puffins.
He added colleagues in France had also collected data for Spain and Portugal and found thousands of dead seabirds had been recorded.
“It seems the wreck has reached over 10,000 at this point, though there is a lot of proving figures to be done. That’s probably an underestimate of what has been found so we’re looking at a major seabird wreck,” he said.
Puffins rely on their eyesight to hunt and need clear water to find food but rough seas had made it difficult for them to feed, Gauvain explained.