Greater Sage-Grouse (Centrocercus urophasianus; center, male; right, female). Males perform elaborate mating displays. (Credit: Museum of Comparative Zoology, Harvard University; Copyright © President and Fellows of Harvard College)
For the birds—and for the birders
The Harvard Museum of Natural History’s new exhibit, Birds of the World, is designed for you. Vying for attention with the impressive hanging whales in the gallery above the Great Hall of Mammals and showcasing the global diversity of modern birdlife, the new exhibit occupies the same space as the former North American bird display. Although the location is the same, both the birds and the balcony have undergone a dramatic renovation. In addition to being redesigned, with all cabinets repainted and relit to appeal to the general museum-going public, the exhibit is also organized to serve as a resource for birders and biologists curious about the evolutionary relationships that connect groups they know and love.
Global diversity in your own backyard
Birds are extremely diverse—over 10,000 species are alive today. In Birds of the World, nearly 750 specimens are on display; taxidermied mounts as well as 13 articulated skeletons were selected from the Ornithology Collection and from other public exhibits. These birds were chosen to represent as many different families as possible. Due to the Museum of Comparative Zoology’s extensive collection of mounts, members of 178 living bird families —roughly 80%—are now included. Many of the old Thayer Hall North American specimens are back in the cases, although some groups, such as ducks, had to be winnowed to a few key genera. Instead of being grouped by their biogeographic area—the common organization in most natural history museums—the birds are now organized according to their evolutionary history.
The modern study of bird relationships relies on research combining many different types of data, from comparative anatomy to paleontological studies on fossils to current cutting-edge work using genomic data. In December 2014, a new phylogeny, or tree of life of birds, was published, based on genome sequencing of 48 key lineages (Jarvis et al. 2014). This is an immense increase in information; 10 years ago, the only bird with a sequenced genome was the domestic chicken. Recent work has greatly improved our understanding of bird relationships, and these new results are reflected in the exhibit’s organization. A large panel with a phylogeny tree shows the current relationships of the major groups. Smaller trees will soon be added to the individual cases so that interested visitors will have access to the underlying organization at a more detailed level. The average museumgoer may not care that penguins are the closest living relatives, or sister group, to albatrosses and tube-nosed seabirds; or that toucans are nested within the colorful smaller-billed barbets; or that sunbirds and hummingbirds, although superficially similar, are extremely distant cousins-but these stories are there if your curiosity is piqued.
The exhibit is not only about the birds, but also about evolution. Convergent evolution can be seen everywhere you look. When habitats or other selective forces are similar, animals often evolve to look, act, or sound like other species despite being only distantly related. The small size, iridescent plumage, long bill, and modified tongue of nectar-feeding sunbirds and hummingbirds exemplify convergent evolution, along with many other instances on display. Fulmars look like gulls, but they aren’t close kin. The quail-like body shape is apparent in a number of different groups; “quail” themselves have independent origins in the Old and New Worlds. Buttonquail are not true quail at all, but in fact are more closely related to gulls and shorebirds. Common names are particularly misleading. Vultures in the Americas are not most closely related to vultures in the Old World, but rather, with condors form a separate family, renowned for their sense of smell. If you have ever pondered the similarities in terrestrial habits and plumage shared by Ovenbirds and waterthrushes (Lovette et al. 2010), or wondered if auks and penguins are close relatives or merely look alike due to the demands of polar life, you can find answers in the new display cases.
Studies on the evolutionary history of birds have produced a number of surprises over the recent years. Flamingos and grebes are each other’s closest relatives, a finding that is backed up solidly by molecular work (Van Tuinen et al. 2001), skeletal similarities, and the discovery of intermediary fossil forms (Mayr 2004, Mayr 2005). This took many people by surprise, reflected in the new name for the group: the Mirandornithes, or wonderful birds (Sangster 2005). Parrots turn out to be more closely allied with songbirds than previously suspected, and falcons are more closely related to parrots than to other extremely similar-looking accipiters—the raptorial appearance and predatory lifestyle may have arisen independently (Hackett et al. 2008).
Macaroni Penguin (Eudyptes chrysolophus), Atlantic Puffin (Fratercula arctica). Penguins
and puffins are distant relatives despite their similar outward appearance. (Credit: Museum
of Comparative Zoology, Harvard University; Copyright © President and Fellows of Harvard College )
New studies of tanagers, the second largest family of birds after tyrant flycatchers, reveal other surprises. For instance, many species formerly belonging to this group, e.g., Scarlet Tanagers, are actually more closely related to cardinals. Conversely, many tropical species called cardinals, such as the Red-crested Cardinal and the Yellow Cardinal, both with striking pointed crests, are now grouped in the tanager family (Burns et al. 2014). Other unlikely members of the tanagers include the finch-like saltators, the tiny conebills, and the hooked-billed group of flowerpiercers. Bananaquits are also tanagers, as are their close relatives, the Darwin's finches, famous for their radiation throughout the Galapagos Islands. All this you can now see for yourself.
A bird walk through deep time
The colorful tanagers occupy the last case in the Birds of the World exhibit. To follow birds through time, save it for last and walk clockwise, starting with the large, flightless bird case to the left of the stairwell as you arrive on the balcony. These birds, called the ratites, are the most ‘basal’ group of birds, a term scientists use to indicate that this group split off from the rest of birds earliest in their evolutionary history. They are not technically older than other birds—a common misconception. All living birds today have been evolving for the same amount of time, but ratites —the group known as Palaeognathae-were the first to have branched off, or diverged, from the rest.
The ratites include many flightless birds: kiwis, rheas, ostrich, emus, and the impressive casqued cassowary, as well as the extinct moas and elephant birds. Many of these giants are too big to fit into the museum's cases. A chick and an egg represent the ostrich, and a cast of an elephant bird’s enormous egg gives visitors a sense of its former stature. Surprisingly, recent research shows that Palaeognathae also includes the smaller South American tinamous, which can fly, raising questions about how many times flight was lost (Harshman et al. 2008, Haddrath and Baker 2012, Mitchell et al. 2014).
Yet more surprising to some visitors—to children in their “T. rex” phase and to some adults as well—might be the fact that birds are indeed dinosaurs and that crocodiles are their sister group. A juvenile saltwater crocodile winds its way beneath the rhea’s feet, raising the question of origins and unexpected relatives. Skeletons of theropods, the agile, raptorial, meat-eating dinosaurs from which birds evolved, can be found together with a cast of the famous Archaeopteryx in the galleries on the museum's third floor.
After the ratites come the Galloanseres, the combined group of waterfowl—ducks and relatives—and landfowl or gamebirds, which include turkeys, pheasants, grouse, quail, and of course, chickens, as well as lesser known groups like the moundbuilders and curassows.
The remainder of birds—indeed, the majority of birds—are called Neoaves. Many of the major groups within Neoaves diverged from one another in a short window of time, making relationships difficult to determine. With the new bird genome project, scientists were finally able to unravel some of these events: pigeons, including the small ground-doves and the enormous crowned-pigeons, comprise an early-branching group and are related to the sandgrouse and to Madagascan mesites. Other relatives include the unlikely pair of flamingos and grebes. Cuckoos, bustards and turacos also belong to this early radiation, as do the Strisores, the group containing hummingbirds, swifts, and nightjars (Mayr 2010). The enigmatic foregut-fermenting hoatzin, a family of its own, has been traditionally difficult to place; it likely split off from other birds at roughly the same time in the distant past as these other early Neoaves.
Red-billed Streamertail (Trochilus polytmus). Over 330 species of hummingbirds exist today—all in the Western Hemisphere, with most of the diversity in Central and South America. The earliest hummingbird fossils, however, are from Europe, indicating a wider range in the past. (Credit: Museum of Comparative Zoology, Harvard University; Copyright © President and Fellows of Harvard College)
Other major divisions in the bird tree of life include a group of waterbirds and their relatives, and another group called landbirds. Within landbirds, the largest radiation
is that of the passerines, which includes over 5,000 species and is divided into the suboscines, or non-vocal-learning perching-birds, and the oscines, or songbirds, which likely arose in the Australasian region before spreading across the globe (Barker et al. 2004)
Songbirds are divided into a series of groups including crows and relatives, many of which are only found in Australia and Asia, such as birds-of-paradise, minivets, woodswallows, and the “true” orioles. North American orioles are in the icterid family, again misleadingly sharing a common name. Together, these are distinct from another songbird group, called the Passerida, which include the bulk of songbirds. Sister to the little-known rail-babbler (Eupetes), a specimen of which is on display, the Passerida include many of the songbirds familiar to North Americans: swallows, thrushes, wrens, tanagers, as well as the distinct groups of both warblers and sparrows from the New and Old Worlds.
Phylogenies are hard to describe in words; come to the museum to have them brought to life. In all of the display cases, recent research on each of the groups is surveyed so that closest relatives are placed close together. The exhibit is organized to be pleasing to the casual observer and informative to the bird sleuth. Other panels depict specializations of the bird body plan and maps of the radiation of passerines across the globe. New developments are in the works for the exhibit to become more multi-sensory in the future, maybe including bird songs and incorporating new interactive technology. As research continues and our knowledge about phylogenetic relationships changes, the exhibit will evolve as well.
Birds of the World exhibit information
The exhibit, made possible by a generous anonymous donation in memory of Melvin R. Seiden, Harvard AB 1952, LLB 1955, opened to the public on September 18, 2014. It is on permanent display at the Harvard Museum of Natural History, 26 Oxford Street, Cambridge, Massachusetts. Visiting hours are 9:00 am to 5:00 pm; Sunday mornings from 9:00 am to noon and Wednesday afternoons from 3:00–5:00 pm are free for Massachusetts residents.
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Maude Baldwin recently finished her PhD in Professor Scott Edwards lab in the Department of Organismic and Evolutionary Biology. She has been researching how hummingbirds, which lack the mammalian sweet receptor, instead use their savory receptor to taste nectar sugars. In 2014 she helped with the redesign of the exhibit, synthesizing new studies on bird phylogenetics to reorganize the bird balcony with Jennifer Berglund, Janis Sacco, and the exhibits staff at the Harvard Museum of Natural History, along with Jeremiah Trimble and Kate Eldridge in the Museum of Comparative Zoology’s Ornithology Department.