The so-called penguin jumpers are meant to keep birds covered with oil from a recent shipwreck warm while awaiting cleanup.
"When you get even a drop of oil on these birds, it opens up a channel (in their coats) so water can penetrate," Cornell University ornithologist Kevin McGowan told ABCNews.com "It's like a hole in their wetsuit."
The Napier yarn shop Skeinz posted a notice on their Web site with a pattern for the sweaters. The result, the owners said in a recent blog, has been a "deluge" of ready-to-wear jumpers.
The posting called the response "really precious and overwhelming."
ABC said an estimated 1,000 penguins have died as a result of the Oct. 5 grounding of the container ship Rena, which spilled about 350 tons of fuel into the sea.