In contrast to the healthy puffin chicks at Matinicus Rock, most Seal Island puffin chicks were underweight, and many were starving. Even worse, at Machias Seal Island on the U.S./Canadian border, researchers reported the worst-ever nesting season—only 12 percent of the 5,000 puffin pairs fledged a chick, and most of these were so underweight that they were likely to perish at sea.

White hake and Atlantic herring are usually the principal forage fish for puffins in the Gulf of Maine, but warmer-than-usual sea surface temperatures made it difficult to find sufficient supplies of these cold-water fish.