The Biological Sciences major is offered in both the College of Agriculture and Life Sciences and the College of Arts & Sciences. The major is administered by The Office of Undergraduate Biology.
Christina Mendoza
Blue-footed Booby Expert
Setting the Stage for Evolution: The Blue-footed Booby Mating Dance
6:00AM, somewhere in the Pacific Ocean
Picture this: it’s a little past daybreak and you’re already on a small inflatable zodiac boat, wind tousling your hair as you sail towards North Seymour Island — an island that your naturalist guide told you all about last night. Unfortunately, you were too busy trying not to be seasick on the motor yacht to pay much attention. You look over your shoulder and see the sun climbing in the sky. Breathtaking. You know you shouldn’t look directly at it, but you attempt to take a picture of the landscape anyway, despite the resistance your camera gives as it fogs up. In the distance, you hear whistling— an almost unsettling amount of whistling and honking. What on earth could that possibly be? Cue the blue-footed boobies.
Blue-footed boobies, scientifically known as Sula nebouxii, have a wingspan of nearly 5 feet, are about 33 inches in length, and have bright blue feet (3). These boobies have a long, pointed, grayish bill; a long, pointed tail; and long, pointed wings. Basically, a long, pointed everything
Their plumage is brown above, white below, and the wings are a darker brown than the rest of its body (3). Females are slightly larger, appear to have larger eye pupils, and have a blue feet when they are ready to mate. The juveniles are dark all over and have a white belly.
These funny little creatures are able to plunge gracefully into the water while searching for cold water fish, but walk awkwardly on land with their giant blue feet. I had the fortune (or I guess misfortune) to be able to relate on a much deeper level with these birds. After spending a little over a week living on our boat, The Fragata, I developed a pretty intense case of sea legs. So while I wasn’t seasick, or as some scientists say, “communing with Darwin” on the boat; I was communing with blue-footed boobies on land— clumsily climbing lava rocks, navigating across cliffs, and tripping over my own feet as my colleagues stifled a giggle or two. Honestly, I don’t blame them because I’m sure I was a sight to behold. In fact, the early Spanish explorers who landed on the Galapagos Islands thought the same thing as they watched clumsy blue-footed boobies walking on land. Because of this, it’s believed that their name came from the Spanish word “bobo,” which means “clown, or stupid.” (1)
These otherwise graceful birds breed on the Galapagos Islands south of the Equator, though they have also been known to breed on Genovesa Island. They are best viewed in the coastal waters throughout the islands: Punta Suarez on Island Española, Punta Pitt on San Cristobal Island, Daphne, North Seymour, and Baltra (2,3). For blue-footed boobies, breeding is opportunistic, so they “take the stage” and mate whenever their environment is favorable (3). During courtship, the female booby honks and the male whistles. They perform a dance which includes showing off their feet and “sky-pointing.”
The male, eager to impress the female, flashes his brightly colored feet, and struts around her. Most people think the tango is the most passionate form of dance, but I’d say it comes second to the mating dance of the blue-footed boobies. The courtship ritual continues with the male showing off potential nest building materials. Then, since female blue-footed boobies are essentially podophilists because of their intense sexual interest in feet, the male continues to show off his bright blue feet. However, this heated encounter also features a male displaying its wings and sky-pointing. As the name suggests, in sky-pointing, the male booby points its head to the sky, and as it spreads out its wings, he whistles to the female.
On the seventh day of our trip to the Galapagos, we went to Punta Cormorant Island. We had come to see flamingos but got a glimpse of an even cooler show. The sand was a dark greenish color, and on the edge of a nearby cliff, I observed two males attempting to display to a female bird. The males, trying to out-do the other, each did a few rounds of sky-pointing and showing off their feet, but ultimately, the female was unimpressed with their dance battle. Perhaps sensing the feeling of disgust and disinterest, one of the males flew towards the ocean while the other slowly waddled away. Elizabeth Cady Stanton, a proud women’s right advocate, would be proud. But in all seriousness, it makes sense that females are very “choosy” since they invest a lot of energy in reproduction, given that she actually finds a suitable male to fertilize her egg. A lot of thought goes into choosing a mate. For example, while the male is busy showing off his feet to the female, she’s not judging it based on shape or size; she’s judging it based on color. The brightness of male blue-footed boobies’ feet is dependent on their age and health. Younger males have brighter feet, and healthy birds have dietary carotenoids which make their feet more aquamarine, thus making the color of feet indicative of successful genes; genes that the female would like to pass on to its offspring (2). It’s important for a female to choose a healthy male mate, because both the male and female will raise their chicks (2). This is known as bi-parental care and it leads to males choosing as well. Studies show have also shown that females with brighter feet were more likely to have males display to them, demonstrating that males also invest in this relationship as well (5). However, displaying is only beneficial if both participants are committed.
Female boobies will display back to the male to show their interest. This behavior of blue-footed boobies displaying and engaging in courtship is part of sexual selection. Sexual selection is a form of natural selection, where organisms choose to mate with other members of its species based on favorable characteristics, for example foot color in blue-footed boobies. This “choosing” behavior leads to successful mating, and is passed down to subsequent generations. Foot color is such a favorable trait that even related species, such as the Peruvian booby, can sometimes cue in on the foot color. Normally, Peruvian boobies have dull grayish feet, but a female Peruvian booby may choose a blue-footed booby male to mate with because of its color signaling. On the other hand, a male blue-footed booby will never display to a female Peruvian booby since it will not be attracted to the female’s gray feet.
When people think of the Galapagos, they think of blue-footed boobies. In many ways, it has become the most “iconic” animal of the Galapagos. Sula nebouxii excisa is a sub-taxon of blue-footed boobies that is unique to the Galapagos Islands. One of my TA’s, Dr. Scott Taylor, spent about 5 years studying blue-footed boobies and Peruvian boobies, and even conducted field research in Peru. For one of the classes in our Galapagos Curriculum, I had to choose to become an “expert” on an animal, prior to embarking on our journey to the Galapagos. I chose to become an “expert” on blue-footed boobies, reading dozens of scientific journal articles and writing papers on them, but it was even cooler that Scott (an actual expert on blue-footed boobies) was part of our Galapagos cohort and was always ready to share his knowledge. His insight about how climate change is affecting the blue-footed booby population in the Galapagos was very evident when we visited the Islands. When we got to the Galapagos, we didn’t see a lot of boobies until the last day of our trip, when we landed on North Seymour Island. The combined effects of global warming and El Niño have led to a lack of cold water fish (sardines and anchovies), and have translated to a chronic lack of breeding by blue-footed boobies in the Galapagos. It is important that we take action to decrease humans’ contribution to climate change, because it is a very serious problem that is affecting ecosystems everywhere.
Blue-footed boobies are magnificent animals that are very entertaining to watch. They’re definitely not camera-shy, and love to keep their audience entertained, as you can see a blue-footed booby sky-pointing with our naturalist guide, pictured above. As a former dancer, I can say that evolution is like their dance teacher. Without it, they wouldn’t be the dancers they are today. In the wise words of William W. Purkey, “You've gotta dance like there's nobody watching, love like you'll never be hurt, sing like there's nobody listening, and live like it's heaven on earth." (6) Blue-footed boobies make the world their stage, whistle like there’s no tomorrow, and aren’t afraid to jump head first into the unknown. We could probably learn a thing or two from these admirable creatures.