World Penguin Day takes place on 25 April during the annual northern migration of Adelie penguins, a species of penguin that is native to Antarctica. The Adelie penguins individually migrate north to have better access to food during the winter months and then during the summer, return to the coastal beaches on Antarctica to build their nests. The holiday was created at McMurdo Station, an American research center on Ross Island. Researchers noticed that the Adelie penguins began this migration specifically on this day, and they created this holiday as a way to pass the time and give social awareness to these creatures.
Penguins are a group of aquatic flightless birds belonging to the order Sphenisciformes, family Spheniscidae. They live almost exclusively in the Southern Hemisphere, with only one species, the Galapagos penguin, found north of the equator. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have evolved into flippers. Most penguins feed on krill, fish, squid and other forms of sea life which they catch while swimming underwater. They spend roughly half of their lives on land and the other half in the sea. Almost all penguin species are native to the Southern Hemisphere, however they are not found only in cold climates, such as Antarctica. In fact, only a few species of penguin live so far south. Several species are found in the temperate zone, and one species, the Galápagos penguin, lives near the equator.
The evolutionary history of penguins is well-researched and represents a showcase of evolutionary biogeography. Although penguin bones of any one species vary much in size and few good specimens are known, the alpha taxonomy of many prehistoric forms still leaves much to be desired. Some seminal articles about penguin prehistory have been published since 2005. The basal penguins lived around the time of the Cretaceous–Paleogene extinction event somewhere in the general area of (southern) New Zealand and Byrd Land, Antarctica. Due to plate tectonics, these areas were at that time less than 1,500 kilometres (930 mi) apart rather than the 4,000 kilometres (2,500 mi) of today. The most recent common ancestor of penguins and their sister clade can be roughly dated to the Campanian–Maastrichtian boundary, around 70–68 mya and It is thought that the Penguin Ancestors were not yet entirely flightless during the Cretaceous Era.
The oldest known fossil penguin species is Waimanu manneringi, which lived in the early Paleocene epoch of New Zealand, or about 62 mya. While they were not as well-adapted to aquatic life as modern penguins, Waimanu were generally diver/loon-like birds but already flightless, with short wings adapted for deep diving. They swam on the surface using mainly their feet, but the wings were – as opposed to most other diving birds (both living and extinct) – already adapting to underwater locomotion. Perudyptes from northern Peru was dated to 42 mya. An unnamed fossil from Argentina proves that, by the Bartonian (Middle Eocene), some 39–38 mya, primitive penguins had spread to South America and were expanding into Atlantic waters. During the Late Eocene and the Early Oligocene (40–30 million years ago, some lineages of gigantic penguins existed. Nordenskjoeld’s giant penguin was the tallest, growing nearly 1.80 meters (5.9 feet) tall. The New Zealand giant penguin was probably the heaviest, weighing 80 kg or more. Both were found on New Zealand, the former also in the Antarctic farther eastwards.
Traditionally, most extinct species of penguins, giant or small, had been placed in the paraphyletic subfamily called Palaeeudyptinae. However there were at least two major extinct lineages. One or two closely related ones occurred in Patagonia, and at least one other—which is or includes the paleeudyptines as recognized today – occurred on most Antarctic and Subantarctic coasts. on Seymour Island, Antarctica, for example, around 10 known species of penguins ranging in size from medium to huge apparently coexisted some 35 mya during the Priabonian (Late Eocene).The oldest well-described giant penguin, the 5-foot (1.5 m)-tall Icadyptes salasi, actually occurred as far north as northern Peru about 36 mya. However The gigantic penguins became extinct by the end of the Paleogene, around 25 mya. Their decline and disappearance coincided with the spread of the Squalodontoidea and other primitive, fish-eating toothed whales, Although A new lineage, the Paraptenodytes, which includes smaller but decidedly stout-legged forms, had already arisen in southernmost South America. During the early Neogene saw another morphotype emerge the similarly sized Palaeospheniscinae.
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