In earlier days,sailors would kill penguins that were not able to fly, now one of the main threats to penguins id the oil and petroleum being shipped by ships over the oceans, this is a hazard because there are ship wreck which drop all of the oil/petroleum and it can posion or harm the penguins and other animals.
Some other threats to penguins were that fishermen would kill them for bait or other reason like that.
Another main threat to penguins is the fisherman will catch them and kill them right were they caught them and they do not evene give notice to people, this is now illegal, but it is still being done.
Some other main threats to penguins are there food supply is running low, also that the global warming is starting to melt most of the ice and penguins have a really hard time living without it.
Some main predators which are a very big threat to the penguins are leaopord seal,which are only a threat when the penguins are in the water,stoat which are the size of a weasel also are a threat to the penguins when they are on the land, and medium sized shark will kill penguins occasionally.
This is the ice that they live on and the global warming is starting to melt it away very slowly.