The New Zealand penguin pages explain in detail how humans have significantly altered the threats to these harmless birds:

Before the arrival of man, marine mammals were the only mammalian predators of penguins in New Zealand. Rats were the first mammalian predators introduced, albeit accidentally, but several more were deliberately introduced. Cats were the first, in an effort to control rats and mice. There is now a large population of wild cats in New Zealand, which is continually added to by the dumping of unwanted kittens by irresponsible pet owners

Beyond the new predators introduced by humans, there are also pages on oil (humans), climate (humans), fishing (humans), and habitat (humans). And after all that, if you can imagine, they have a page on the threat from humans. Unfortunately, the amazing (under water) flying ability of penguins is only adapted to reduce their vulnerability to non-human related threats. Time will run out before they develop another countermeasure, so some self-regulation by humans is in order…