Why are there no penguins in the Northern Hemisphere?

That’s an interesting question. The oldest known penguin species were not refrigeration specialists, but at home in the then warm New Zealand. The northernmost, most discreet penguin species are also able to deal with warm weather at times. There is no obvious reason why they cannot cross the equator. As efficient, fast floats, they are also not caught in certain flow systems.

Probably a suitable niche was never free further north. If the habitat is already occupied by other species, a newcomer is hard to settle. Unless, in any way, he is clearly superior and thus can spread invasively. However, penguins do not have much invasive potential. They increase rather slowly and they depend on breeding areas with little feasts.

The northern hemisphere has been full of a wide variety of sea birds for millions of years. Many of them are only on the northern hemisphere, but not on the southern hemisphere. Among them were also flight-incapable species such as the plotopterides addressed by Gregor, or the first in the 19th century. Century extinct giant alk. In general, however, the northern hemisphere has not been particularly well suited for flightless and slow-running birds for many million years, because there have always been mammals to the high north, which eats everything that cannot escape. Only remote islands that are inaccessible to mammals, but which have a sufficiently flat, easily climbable coast, are suitable as brooding for unfit sea birds.