So for some background on why birds are so beloved by fossil bird researchers (or palaeornithologists) in particular and are celebrities in their field:
Red-legged Seriema (Cariama cristata): Seriemas, like this fabulous individual, are the closest living relatives of the now extinct Phorusrhacids, which are better known as terror birds. They even have an enlarged claw in their inner toe that they hold upward and use for dispatching prey like Dromaeosaurs!
Nicobar Pigeon (Caloenas nicobarica): According to DNA analyses, this beautiful rainforest pigeon from the Andaman Archipelago is the closest living relative of the Dodo! Despite the fact that it lives on the other side of the Indian Ocean from Mauritius.
White-tailed Tropicbird (Phaethon lepturus): Back in the Paleogene, Tropicbirds like this one were kind of everywhere. They've been found from Aotearoa to Morocco and the UK from that time and were taking the ecological niches of gulls and terns, unlike the modern plunge-diving tropicbirds.
Blue-naped mousebird (Urocolius macrourus): Mousebirds are not only adorable, during the Paleogene they ruled the roost! A whole plethora of species dwelled in Eurasia and North America at that time, and occupied a wide variety of niches. They even include one of the earliest bird finds after the extinction of the other dinosaurs 66 million years ago.
Courol (Leptosomus discolor): Today, the Courol only lives in Madagascar. But back in the day, its relatives were spread far and wide in the tropical and subtropical forests of the Paleogene. Back then they lived all over Europe and North America.
South Island Wren (Xenicus gilviventris): New Zealand Wrens, like this one, are the most basal members of the Passeriform or songbird clade alive toda. Considering that Passeriformes represent more than half of known birds, it's quite humble to know where this monstrous radiation originated.
Southern Screamer (Chauna torquata): Screamers vaguely look like turkeys, but are actually very closely related to ducks. In fact, it appears that the ansestors of Screamers were much like ducks and had duck-like bills, which they later evolved into a more generalized beak like with Screamers today.
Puerto Rican Tody (Todus mexicanus): Todies are fun little blorpos that live mostly in the Caribbean. But during the latter parts of the Paleogene, they lived all over North America, and also in Europe, specifically France!
Little Eagle (Hieraeetus morphnoides): This guy is one of the smallest known eagles. Which is funny, because one of it's closest relatives is the extinct Haast Eagle, the biggest eagle known! The Haast Eagle is over 10 times the size of the Little Eagle, and attained that size in under 2 million years.
White-throted Rail (Dryolimnas cuvieri): Rails are surprisingly good flyers and easily spread to islands, where they often become flightless, and often go extinct after human contact. This rail is a special case, because most populations can fly, but a flightless subspecies evolved in Aldabra Atoll, twice.
White-spotted Flufftail (Sarothrura pulchra): Flufftails are adorable and fluffy, but also have a surprising history. According to DNA evidence, their closest relatives include the now extinct Caribbean Cave-rails of the genus Nesotrochis but also the mysterious and enormous Adzebills of Aotearoa!
Oilbird (Steatornis caripensis): Oilbirds are weird in so many ways. They eat fruit, echolocate, nest in caves and are quite greasy. And according to fossil evidence, they lived all over Europe and North America during the warm and tropical Paleogene, heavily contrasted by their modern range in tropical highlands of South America.
Egyptian Vulture (Neophron percnopterus): The Egyptian Vulture may be an "Old World Vulture" today, but it as well as the Bearded Vulture and Palm-Nut Vulture actually first evolve in North America and only cross the Atlantic 9 million years ago.
Marabou Stork (Leptoptilos crumenifer): Marabous are mighty impressive birds in their own right, but until relatively recently giant relatives of these as tall as humans lived across Africa, Mainland Asia, Java, and most famously Flores, where they lived with the dwarf human species Homo floresiensis
Subantarctic Snipe (Coenocorypha aucklandica): You may have heard of the Hokioi or Pouakai. These are Maori legends of an enormous predatory bird. You might think they were inspired by the Haast Eagle, but no. It was these small adorable snipes and their nightly display flights!