The Blue-footed Booby’s Baja Boogie

Blue-footed Boobies at Isla La Gaviota in the Sea of Cortez. Photo by Colin Ruggiero

Bryan Jáuregui, co-owner/operator of Todos Santos Eco Adventures in Baja California Sur is at it again with another informational and humorous article – this time focused on the antics of the Blue-footed Boobies! Most people don’t know that these lovely and awkward birds make their home within the near vicinity of Camp Cecil, on Isla Espiritu Santo in the Sea of Cortez. Read on of contact us to learn a little more!

By Bryan Jáuregui
This article was originally published in Janice Kinne’s Journal del Pacifico

At a time when over half the single people in the Americas have created an online dating profile through which they send out their virtual avatars to court potential partners, it may be difficult to remember the days of Saturday Night Fever and Strictly Ballroom when plumage and dance moves were everything.  But off the coast of Baja California Sur on islands like La Gaviota, Isla Isabel, and Isla San Pedro Mártir, dancing to show off mating suitability is alive and well, although the practitioners looked so silly to early outside observers that they earned themselves the name of Booby, from the Spanish word bobo meaning “stupid” or “clown”.  Pretty much your worst dancing-in-public nightmare.

But the Blue-footed Boobies of Baja remain unruffled, secure in the knowledge that shaking their tail feathers has resulted in what is possibly the largest Blue-footed Booby colony in the world. And it’s not just the moves that are important in their dance, but the exact cerulean hue the footwork displays. Blue-footedness, it turns out, is enhanced by the bright yellow pigments found in the carotenoids of the fish the birds consume, so those who catch and eat more fish get bluer feet. Ipso facto bluer feet connote better health, better health connotes greater ability to provide for a nest, and as every dancer in life thinking about raising a chick knows, those are the moves that really count in a mate. So the booby dance includes a series of steps in which the feet are raised up to allow potential partners to inspect their blue-ness (apparently a vibrant aquamarine is the most desirable) and determine if that’s the blue they want to get tangled up in. And unlike in some species in which only the male sports the color, in boobies both sexes are focused on the blue tones of a potential partner’s feet. In fact, males will avoid mating with females whose blue feet have been dulled with paint. With boobies, it definitely takes two to tango.

Blue-footed Boobies. Photo by Colin Ruggiero

And in many cases, three. Researchers have found that Blue-footed Booby rookeries could easily provide source material for the most salacious telenovelas; in over 50% of booby couples one or both partners engage in what scientists call extrapair behavior (what the rest of us would call an extramarital affair), and it is not at all uncommon for a booby to toddle off for a quickie with the neighbor while its mate is out foraging at sea. Dr. Hugh Drummond, Professor of Biology at the National Autonomous University of Mexico (UNAM), who has studied the Blue-footed Boobies at Isla Isabel for the last 37 years, notes his education on this point. “There was a time when we thought that all bird species were monogamous and mated for life. This couldn’t be further from the truth. The majority of studies indicate extra pair behavior in birds. This is not surprising in males as this behavior can provide them with extra offspring at no cost. What is surprising is that in the vast majority of bird species, including the Blue-footed Booby, the females stray. It’s surprising because this behavior can be accompanied by some fairly high costs.”

Scientists, being scientists, have been searching for a rationale for the female booby’s lustful leanings as “because she can” doesn’t square in a world in which behaviors are generally explained by survival and advancement of the gene pool. The working hypothesis was that a female who is nest hopping with the neighbors must be doing so because she is not paired with the ideal biological partner, and is therefore driven to hook up with a better set of genes. But, as Dr. Drummond notes, “Most studies have found no difference in the success of the mated pair’s offspring versus the success of the extra pair’s offspring. The extra pair males have not consistently proven to provide better genes than those of the mates. So we have to consider that the female’s behavior may not be for the benefit of the offspring after all.” Have female boobies liberated themselves from the Darwinian grind?

Blue-footed Booby. Photo by Colin Ruggiero

Possibly, but the males aren’t taking it lying down. They will destroy an egg in their nest if they suspect it was fertilized by another, and if the female was out of their observation range for a few hours or more during the 5 days of fertility prior to egg laying, then they are definitely suspicious. Dr. Drummond and his colleagues tested this by “kidnapping” males during the 5 critical days. Under these circumstances, the males destroyed the first egg subsequently laid, ensuring that they didn’t have to raise some other guy’s chick. If they are kidnapped prior to the fertile period they leave the egg alone. Male boobies will actually abandon particularly perfidious partners, and seek out others to soothe their ruffled feathers. Says Dr. Drummond, “Isla Isabel has roughly 2,000 pairs of Blue-footed Boobies, and at the end of every season half of the pairs break up.”

Before egg incubation starts, nearly all male boobies on Isla Isabel court extra pair females, while roughly one third of the females develop sexual relationships with one or more male neighbors. But booby mates who retain the same partner for successive years definitely reap gene pool rewards – Dr. Drummond has found that they produce 35% more offspring those who change partners. And while all booby couples share in parental duties, longtime mates spend equal time caring for their young. They are completely in it together, with males spending just as much time as their mates on household duties. Female boobies. Has their behavioral long game all along been shaping male boobies into the perfect domestic partner? That would be a remarkable evolutionary feat!

While longtime mates may cohabit harmoniously, harmony is definitely not a word one would associate with their offspring in the nest. Dr. Dave Anderson, Professor of Biology at Wake Forest University, has studied boobies in the Galapagos Islands for most of his adult life. He explains. “Nazca boobies (the Blue-foot’s cousin) only want one chick but they sometimes have two by mistake when their extra insurance egg hatches. In such cases, 100% of the time the older (or healthier) chick will force the other one out of the nest with no parental interference, and perhaps even some parental facilitation. Once out of the nest, a chick has no way to survive on its own. Nazca boobies nest on the ground in such a way that the nest is essentially a gladiatorial arena that the parents observe from on high.”

“The Blue-footed Boobies, on the other hand, do want the option of having two chicks. So they will give the first egg a head start of 3-5 days before laying the second egg, such that a natural dominance hierarchy is established among the resulting chicks. If food is abundant, they will raise both chicks. However, the first-hatched chick fiercely beats up the second-hatched, and the second-hatched survives only by adopting submissive behavior.” Dr. Anderson points out that the parents help the subordinate by building nests that are bowl-shaped, which means that when the older chick is pecking the younger one, at least for the first ten days or so, the poor little guy generally doesn’t fall out of the nest like its hapless Nazca counterpart – there are walls to keep it hemmed in. Further, unlike the murder-permissive Nazcas, murder-restrictive Blue-footed Booby parents will actually sit on their chicks to prevent the dominant from killing the subordinate.

Dr. Anderson tested what would happen when the constraints of the parents and the bowl-shaped nest are removed. “What is really interesting,” says Dr. Anderson, “is when we put Blue-footed Booby chicks in Nazca nests with Nazca parents. They are much more aggressive than when in their own nests. And when we put Nazca chicks in Blue-footed nests with Blue-footed parents, they still want to kill each other but can’t because of the shape of the nest and the murder-restrictive Blue-footed parents.” They may fool around like mad, but the Blue-footed Boobies do draw the line at siblicide, unless of course, food is scarce – as in an El Niño year – and subordinate chick sacrifices must be made.

Blue-footed Boobies. Photo by Colin Ruggiero

Now you may well imagine that the poor second-hatch chicks, having been so horribly abused by their siblings and practically starved to boot, would turn into physically stunted adults, emotionally crippled by their circumstances and consigned to a lifetime of failure. “Not so!” says Dr. Drummond. “We compared 1,167 fledglings of two-chick broods for 10 years and found few differences between first-hatched and second-hatched birds. Even more surprisingly, where there were differences these tended to favor subordinates.” By almost every measure that counts in a booby’s biological life, Dr. Drummond found that the subordinate chicks matched or bettered those of their dominant tormenters including survival, defensive ability, brood size, nest success, and cumulative brood size over the first ten years of life. Blue-footed Boobies. Liberated females, progressive males, bullies not allowed to flourish over others. What else can we learn from our blue-footed friends?

Every mating season the Blue-footed Booby males stake out their territories and wait for females to come by and notice them. “The males then fall all over themselves trying to demonstrate their suitability as a mate” says Dr. Drummond. One would think in such circumstances that younger, more virile (and of course bluer-footed) birds, would rule the day. But once again, things are not always as one would imagine in the booby world. Dr. Drummond and his colleagues have found that May-December romances among the boobies, i.e., partnerships in which one bird is old and one bird is young, produce offspring that are significantly more likely to later become parents themselves compared to the offspring of parents of a similar age. And it doesn’t seem to matter which sex is at which end of the age spectrum, old mothers and young fathers or old fathers and young mothers, the results were the same in the 3,361 booby offspring that Dr. Drummond and his colleagues studied – breeding in age-mismatched parents provides greater success in contributions to the gene pool than those of similarly aged parents. In fact, the advantage to the chicks born of May-December parents was almost as great as those conferred on chicks whose parents are in long-term partnerships. Why this is so remains a scientific mystery. Could it simply be that Blue-footed Boobies are as socially evolved as the French?

So now we know that these dancers who looked so silly they earned themselves the name of Booby may actually have some elegant lessons to share across species: 1. A rough start in life need not define your later years; 2. Sharing equally with a long-term partner produces better health for the family; 3. Age does not necessarily define your ability to contribute to society; and 4. Dancing your heart out no matter what you look like to strangers is one of the keys to a successful life. In fact, the future of the species depends on it.