Sally Lightfoot Crab Expert
Galapagos Sea Birds Have the “Moves Like Jagger”
Poop. It smells like poop, seawater, sunscreen, and hot rock. These are smells that you encounter when the sun is roasting you and your colleagues for hours at a time. But while it might sound as if I’m having a horrendous time at the equator, I’m not. I am actually mesmerized by
all of the stunning sea birds that the Galapagos has to welcome us. So many colors and interesting morphologies grab my attention. The sea birds’ wings and feathers and overall beauty surround me as they call out into the bright blue sky. Have you ever seen a bird with impressive turquoise feet like the blue-footed booby or met a bird with a great red gular pouch like the frigate bird? Not even the extreme heat and unforgiving sun dampens the magic that the birds create and as I sat on this hot rock, I watched the beautiful, yet silly, unique mating rituals many of these birds had!
Here in the Galapagos, most sea birds have courtships dances. They are very amusing and I witnessed a male booby encounter rejection from a female after he performed his courtship dance. This compares a lot to human life. But what is the actual necessity to why they must do such elaborate courtship dances and other mating behaviors?
Usually for humans, all it takes to get a chance for a date is a compliment and a conversation over food. But in the rest of the animal kingdom it is all due to sexual selection, which is broken up into two subcategories, intrasexual selection and intersexual selection (1). When these birds perform and present their best traits, they are hoping that a female will choose them. This is called intersexual selection since it is “female choice”. But intersexual selection can work both ways. An example of “male choice” is when a male blue-footed booby is also choosy with the female’s colored feet (4). Since blue-footed boobies are monogamous, the males display paternal care toward their offspring. With that level of investment by the males, they carefully choose who they display courtship rituals towards (4).
When I was observing a male blue-footed booby, I noticed that his feet were a paler turquoise color. During his courtship dance, he moved on a rock and presented his feet by picking them up slowly, imitating a member of the Rockettes. He opened up his wings and pointed his beak to the sky to create a high-pitched whistle. To finish the visual, he would even present the female with a stick.
To me, the ritual reminded me of a frat guy flexing his muscles to a pack of girls and saying “Which way is the beach?”, but the way the booby presented himself was much more graceful and more vulnerable because he is showing all of his features so the female can critique him and decide whether his traits are something she wants her offspring to have. Intersexual selection, in this instance, is when the female booby chooses the best mate with the best traits that can be passed onto her offspring. With blue-footed boobies, one of the traits that they look for are bright turquoise feet since they find that more attractive and it is an external representation of the how healthy the male is (5). Their foot color is a signal for health because the bright color is due to carotenoid pigments that they obtain from their fish diet; this means the higher concentration of pigments they eat, the brighter their feet.2 If the male is healthy and has brightly colored feet, the women assumes that the male is well fed and can supply for her family (5). This is why the female chooses the best male and why males must perform this courtship dance.
One day as the boat was traveling toward Daphne Major, I decided to go paint on the top deck and just enjoy the breeze. As I sat there, thinking about my day so far and how I can’t figure out how to mix these watercolors to get the exact shade I want, I heard something move behind me. It was a frigate bird! Its brilliant red gular pouch was not inflated so its appearance appeared like a scary, wrinkly old man!
The next time I was so close to one was when we went on land to see nesting sites. When we climbed up toward the nesting site, I felt like we crashed a “frigate and friends” party since there were so many seabirds in the area. I was able to be close enough to observe these birds better. These large birds had a black body with iridescent black feathers. The Great frigate birds had this green sheen to their feathers whereas Magnificent frigate birds had a purple sheen that reminded me of the rainbow sheen oil makes when it is spilled on wet concrete. As I sat there and tried to sketch a male with his pouch inflated, I noticed that there were other frigates in the air looking down. It was the females scouting, looking at the males below her, who presented their red gular pouch as they flap their wings and producing drumming sounds. The females scout for two sexual traits, which consist of the red gular pouch as well as the iridescent feathers of
the male (3). During mating season, the pouch is inflated and usually a rich red but during the off-season, the pouch shrinks and the color reverts back to a skin color. Since the pouch is a temporary signal of the quality of the male, the female scouts the quality of the feathers since that is a more permanent signal of the condition of the male despite what season it is (3). This is how the female selects what male to fly down to.
While observing this interaction, I noticed that the pouch resembled a heart. It made me remember old cartoons when a person would be infatuated with someone and their heart would pop out of their chest. It was amusing to observe a real life interpretation of that since these birds are also displaying courtship displays to a choosy female.
After watching the courtship of two seabirds in the Galapagos, you wonder why would they have such striking features, like colorful feet or bright red gular pouches. It all comes back to sexual selection! Having such ornaments gives an animal more success in obtaining mates and producing offspring.1 These unique traits are what get females excited when finding a mate. It is their dating kryptonite.
However, the females are very choosy and know what they want for their offspring. According to a study led by Alberto Velando, female blue-footed boobies change the amount of reproductive investment they put in due to the male’s foot coloration (5). If it was not a very bright turquoise, the female booby would lay a smaller egg and not as many. This is also how females strategize their decisions so they can put in more investment into their offspring. With frigate birds, the female determines how much energy to commit by the male’s pouch and their iridescent feathers (3). The females know what they need and don’t settle for less. They want the best of the best. That is why, with the ornaments that the males have, there is a courtship display that consists of the males “shaking a tail feather” or in the booby’s case, their feet.
1 -“Sexual selection". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2016. 26 Apr. 2016
2 - Heskell, Pete. "Why Do Boobies Have Blue Feet?" Galapagos Conservation Trust. Galapagos Conservation Trust, 15 Jan. 2016. Web. 13 May 2016.
3 - Madsen, Vinni., Dabelsteen, Torben., Osorio, Daniel., and Osomo, José Luis. (2007) Morphology and Ornamentation in Male Magnificent Frigatebirds: Variation with Age, Class and Mating Status. The American Naturalist 169: 93–111
4 - Torres, Roxana and Velando, Alberto. (2005) Male preference for female foot colour in the socially monogamous blue-footed booby, Sula nebouxii. Animal Behaviour 69: 59-65
5 - Velando, Alberto., Beamonte-Barrientos, René., Torres, Roxana. (2006) Pigment-based skin colour in the blue-footed booby: an honest signal of current condition used by females to adjust reproductive investment. Behavioural Ecology 149: 535-542
6 - Velando, Alberto., Torres, Roxana., Espinosa, Irene. (2005) Male coloration and chick condition in blue footed-booby: a cross-fostering experiment. Behavioural Ecology and Sociobiology 58: 175-180