Since its doors first opened in 1910, the National Museum of Natural History has inspired curiosity and learning about the natural world and our place in it. Building upon the strong foundation of our extensive collections, the staff of the museum have been at the forefront of essential scientific exploration and research, and groundbreaking public exhibition and education. This slideshow and the website (www.mnh.si.edu/onehundredyears/) is a living documentary of the Museum’s 100-year history.

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“When the female of this species is satisfied that she’s found just the right home for her chicks in a tree, rock face or another nest, she gives it her final seal of approval—literally,” said Kathy Brader, bird keeper. “Using mud, droppings and food, the male helps the female wall herself into the nest, leaving a narrow vertical slit as her only opening to the outside world. Due to the nature of the way she is sealed in, we could only verify one chick, but there is a good possibility there may be another.”

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(Photo by Mehgan Murphy)

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When it comes to attracting a mate, flowers and sweets often do the trick—even for one of the world’s smallest birds—the purple throated carib, a hummingbird species native to the mountainous islands of the Eastern Caribbean. Scientists recently discovered that it is in the best interest of male purple-throated caribs to defend and maintain a territory with a high density of nectar-producing flowers. Why? Because it is the quality of this territory—rather than flashy plumage or elaborate courtship displays—that attracts the most females.

Image right: A male purple-throated carib perches on a Caribbean heliconia plant. Click to enlarge. (Photo by John Kress)

John Kress, a botanist at the Smithsonian’s National Museum of Natural History, and Ethan Temeles, an ornithologist and biology professor at Amherst College in Massachusetts, have spent several years researching purple throated caribs (Eulampis jugularis) in the wild on the island of Dominica. What they observed was unique among all bird species: successful male caribs maintained and defended territories with nectar supplies that were two to five times greater than their daily needs and also isolated part of their crop for the exclusive feeding rights of visiting females. The key to this female-only feeding area was the presence of heliconia flowers.

“This is the first time such behavior has ever been observed in a bird species,” said Kress. “Not only is the male defending a huge territory from competing males, but he’s also defending a big chunk of it exclusively for females who he is trying to attract as potential mates. He is farming the nectar for these dual purposes.”

Image left: A female purple-throated carib (Photo by Ethan Temeles)

Male and female purple throated caribs are alike in plumage, but males are considerably larger and have longer wings than females. Females, however, have bills that are 20 percent longer and 30 percent more curved than the bills of the males, meaning that they are physically able to feed from flowers that males cannot. This is also known as “sexual resource partitioning” and for the purple throated carib it applies to two species of Heliconia, a primarily neotropical genus of plants. Male caribs feed from the Caribbean heliconia (Heliconia caribaea), while females feed primarily from the lobster claw heliconia (Heliconia bihai).

This close correspondence between the physical traits of the two different heliconia flowers and the bill morphology of each sex of purple-throated carib strongly suggests that the process of coevolution (the evolution of two or more species that interact closely with one another, with each species adapting to changes in the other) is the cause of this fit between the birds and the flowers. Furthermore, this process is strongly reinforced by the fact that the different energy requirements of the male and female carib are uniquely matched by the energy rewards in the nectar of their respective heliconia flowers.

Image right: A male purple-throated carib sips nectar from a Caribbean heliconia plant. (Photo by Ethan Temeles)

The scientists report that a female’s choice of a male depends on the nectar supplies within his territory, which in turn depended on his prevention of nectar losses to competing male purple-throated caribs and other nectar feeding intruders.

“One of the most important aspects of maintaining an abundant nectar crop for the male carib is keeping intruders out,” Temeles said. “We found that males that were most successful at defending their territories from intruders also were the ones that were most successful at dominating neighboring males and at feeding on neighbors’ territories.”

The male’s reward for spending the time and energy in defending his territory was, of course, the attraction of potential mates. Temeles and Kress observed that the rates of female intrusions to feed on defended territories were highest in late morning and early afternoon, at times when the amount of nectar in undefended plants was lowest.  “Once the females are in the territories they are allowed to “sip from the male’s wine cellar.” If she likes what she is sampling, then mating takes place,” Temeles said.

Kress and Temeles plan to extend their studies to other islands in the Eastern Caribbean to test how this plant-pollinator system has evolved in different regions and in different ecosystems.  —Johnny Gibbons

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Recently they discovered that in late spring and early summer, more than half of the birds bitten by mosquitoes were American robins, even though robins make up only four percent of the bird population. Once the robins finish nesting in late summer and disperse from their breeding areas, the mosquitoes turn to their second favorite blood source: humans.

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Photo: A double-wattled cassowary, a flightless ratite native to New Guinea and Australia. (Photo by Jessie Cohen)

New research using DNA from ratites and other bird species is providing some surprising answers. Ornithologists now know that despite their appearance, the ratites are not as closely related as once believed. In fact, some ratite species are more closely related to certain flying birds, the quail-like South American tinamous for example, than they are to other ratites, says Michael Braun, a research scientist in the Department of Vertebrate Zoology at the Smithsonian’s National Museum of Natural History.

Braun and his colleagues at the Smithsonian and other institutions reached this unanticipated conclusion while working on Early Bird, an ongoing study that is part of the broader Assembling the Tree of Life initiative of the U.S. National Science Foundation. Under this initiative, systematic biologists from around the world are using DNA and other data to reconstruct the evolutionary origins and relationships of all living organisms.

Photo: An emu, the largest bird native to Australia. (Photo by Jessie Cohen)

“For the last 40 years, most people have believed that ratites were more closely related to each other than to any other birds,” Braun says. “But historically, the relationships of the ratite birds has been a hotly debated issue, not only in ornithology but in evolutionary biology overall.”

Early researchers wondered how the ostrich, rhea and other ratites, often assumed to be each other’s closest relatives, ended up on different continents—Africa, Australia and South America—when they could neither fly nor swim.

In the 1960s, the newly accepted science of plate tectonics, or continental drift seemed to explain ratite distribution. Under this hypothesis, the common flightless ancestor of all ratites was living on Gondwana, the single giant supercontinent that made up much of the southern landmass of the Earth more than 167 million years ago. When Gondwana broke apart into what is now South America, Africa, Australia and Antarctica, populations of this early ratite ancestor would have been carried off in several directions on the drifting continental plates. Over millions of years, these isolated populations might have evolved into the distinct, but similar appearing, giant flightless ratites that we know today.

“It is a beautiful, serendipitous theory that is in all the textbooks,” Braun laughs. But it seems to be wrong.

By closely comparing the DNA of a representative sampling of 171 (so far) out of the 9,000 to 10,000 living bird species, Early Bird scientists have gained new insight into the avian family tree, Braun says. One of the most startling findings is that birds of the tinamou family—which can fly—fall squarely in the middle of the ratites, which cannot. Early evidence of this relationship came from work on the c-Myc gene by John Harshman and Scott Steppan, former postdoctoral researchers at the Smithsonian.

“I didn’t believe it at first” Braun says, but with supporting data from 20 genes in the Early Bird project, today the conclusion is inescapable.

Photo: An elegant crested tinamou, a bird native to Argentina and Chile. (Photo by Jessie Cohen)

This discovery led to a new question: Was the common ancestor of ratites and tinamous a flying bird or a flightless bird? If flightless, then the tinamous must have gained the ability to fly at some time during their evolution. If the common ancestor was a flying bird, then ostriches and other ratites possessed, and then lost, the ability to fly.

The latter explanation is by far the more likely, Braun explains. The fossil record holds hundreds of examples of bird species that became flightless over time. No example exists of flightless birds evolving the ability to fly. Therefore, it is most likely that the ancestor of both ratites and tinamous was a small flying bird. Each ratite species became flightless independently in its different geographic area, a location that was reached early in its evolution through flight, not continental drift. Ratite species experienced a minimum of three—and possibly five or more—separate transitions to flightlessness at different times and places during millions of years, Braun says.

Genetic data also show that ostriches are not close cousins of rheas or any of the other ratites, Braun says—another result of DNA analysis in the Early Bird study. The new ratite findings were published last September in the Proceedings of the National Academy of Sciences.   —Harvey Leifert

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Photo: A crane lifts US Airways Flight 1549 from the Hudson River in lower Manhattan on Jan. 17, 2009. Two days earlier it had crash-landed in the river after colliding with a flock of geese.

The US Airways plane took off from New York’s LaGuardia Airport, colliding with a flock of geese approximately 2,900 feet above the ground, extensively damaging both engines five miles from the airport. The pilot conducted an emergency landing in the Hudson River, and all 155 people on board survived with only a few serious injuries. Investigators at the National Transportation Safety Board later sent feathers and tissue extracted from the plane’s engines to the Smithsonian in Washington, D.C., for analysis.

Researchers in the Feather Identification Laboratory at the Smithsonian’s National Museum of Natural History used molecular genetic techniques and feather samples from museum collections, as well as a technique developed for rapid species identification with small genetic samples called DNA barcoding, to determine that the birds involved were Canada geese (Branta canadensis). This is one of the largest species of birds in North America. The birds involved are estimated to have weighed about 8 pounds each.

Photo: An investigator from the National Transportation Saftey Board removes bird remains from one of the jet engines of US Airways Flight 1549. The remains, analyzed by Smithsonain scientists, were determined to be from migratory Canada geese from the Labrador region. (Photos courtesy NTSB)

The next step for the scientists was to find out if these geese were migratory or non-migratory (resident) birds. “Determining whether these birds were migratory or not was critical to our research and will help inform future methods of reducing bird strikes,” says Peter Marra, research scientist at the Smithsonian’s Migratory Bird Center located at the National Zoological Park, and lead author of the project’s paper. “Resident birds near airports may be managed by population reduction, habitat modification, harassment or removal, but migratory populations require more elaborate techniques in order to monitor bird movements.”

The team took their research to a molecular level at the Smithsonian’s Museum Conservation Institute labs in Suitland, Md., where experts examined stable-hydrogen isotopes from the feathers to confirm whether the geese were from resident or migratory populations. Stable-hydrogen isotope values in feathers can serve as geographic markers since they reflect the types of vegetation in the bird’s diet at the time it grew new feathers after molting. Using a mass spectrometer, which measures the masses and relative concentrations of atoms and molecules at high precision, Museum Conservation Institute scientists compared the bird-strike feather samples with samples from migratory Canada geese and from resident geese close to LaGuardia Airport. Their analysis revealed that the isotope values of the geese involved in the crash of Flight 1549 were most similar to migratory Canada geese from the Labrador region and significantly different from feathers collected from Canada geese living in the New York City region.

“Knowing the frequency and timing of collisions is important,” Marra says. “Otherwise we are missing valuable information that could reveal patterns of frequency, location and the species involved.” 

See related video: Scientists Determine Geese in Hudson River Plane Crash

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