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Galapagos Blue-footed Boobies

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Iconic Galapagos' Species: Blue-footed boobies

Galapagos Islands map of the blue-footed boobies

Galapagos map of blue-footed boobies population
An illustration showing the locations of blue-footed boobies in the Galapagos Islands. The Blue Footed Booby is an expert diver because it is a marine bird that can only rear its young on land. With their torpedo-shaped bodies and sharp, tapering bills, these birds were made to pierce both air and water. The booby’s light, long tail, and short upper limb allow it to dive and maneuver exceptionally well in shallow waters. They also have expandable air sacs between their skin and muscles and their skulls that serve as shock absorbers.  By absorbing the shock of their fall, they protect their brain from the intense pressure they encounter. By closing their noses, they also prevent water from entering their nose. With the aid of this useful Galapagos map, you can locate the locations of these birds throughout the archipelago.

Watching these birds in action is incredible because of their powerful, straight flight. In search of food, the booby plunges headlong into the water. This dive typically begins at 10–30.5 meters (33–100 feet) but can fall as high as 100 meters (330 ft). They accelerate their dive by flying into the sea; then they turn into arrows by folding their wings into their bodies and hitting the water at about sixty miles per hour (97 km/h). They can swim rather well, and once in the water, they can go down to a depth of 25 meters (82 ft).

The booby often hunts in groups of twelve or more birds and favors areas of water with large schools of small fish, though it will sometimes hunt by itself or in pairs. It’s interesting to note that, in order to survive competition from other species, every booby species on the Galapagos Islands seems to have carved out an ecological niche for itself. Compared to the blue-footed booby, which fishes nearer the coast, the red-footed booby’s fishing range is considerably further from land. Further out to sea, the Nazca booby fishes.

The birds fly together in a jagged line when they are fishing. Upon spotting a school of fish, one bird signals to the others, and they all dive at the same time, racing for the sea. It’s interesting to note that men and women fish differently due to their slightly varied body types. Because of his smaller height and enormous tail, the male can be caught in shallow and deep seas. Nonetheless, the female can store more food since she is more considerable. Possibly distinct techniques employed by each sex, in contrast to other boobies, enable the birds to raise a large number of offspring.

Though its movements on land are less well-known, boobies are a symbol of grace and power in the sea and the air. The moniker “booby” comes from the Spanish word “bobo,” which can indicate “dumb,” “fool,” or “clown.” This is also due to their seeming lack of fear of people, which is sadly now regarded as absurd. However, this term’s origin is more likely from their land behavior. This bird, evolved for air and water, twitches so clumsily that it almost resembles a clown.

Google Street View of the Galapagos Islands

Risks affecting the population of blue-footed birds

Unfortunately, worries have been raised regarding the decline of the blue-footed boobies population throughout the island in recent years. Because of this, detailed research is necessary to ascertain the exact population size and the reasons behind the decline. The most recent study, published online in the journal Avian Conservation and Ecology in April 2014, confirms the loss and suggests that it may be connected to the decline in clupid fish, particularly sardines.

According to this study, their numbers rapidly decrease even if adult birds lead everyday lives. This is a result of the difficulties the birds are having procreating. Although recent data suggests that this reduction is long-term, experts are uncertain whether it represents a permanent shift or only an occasional variation.

The precise instant a blue-footed booby prepares to dive for its meal
The precise instant a blue-footed booby prepares to dive for its meal

Instead of their incapacity to properly rear their offspring, many birds need to make an effort to breed due to a food shortage. Previous studies on Española have shown that when sardines are readily available to the birds, successful breeding takes place. However, severe sardine shortages have been in the waters surrounding Española Island since 1997. This is evident from the fact that, although they prefer sardines, Nazca boobies may breed while consuming other foods. It seems that blue-footed boobies have enough prey to meet their demands for survival but not enough for reproduction, based on the evidence.

Besides the cause of recent declines, the blue-footed population faces few obstacles, with silicide being one of the worst. But sometimes, short-eared owls pursue them, and they become targets of shark attacks. Moreover, it has been shown that drastic and adverse environmental changes significantly impact blue-footed boobies. In 1992, El Niño, for example, stopped an Isabela Island colony from reproducing. El Niño had subsided, and the population was growing, with high successful reproduction rates in the next year.

Although the precise cause of this event is unknown, scientists believe that the significantly lower concentration of the hormone corticosterone may be involved. Corticosterone plays a significant part in energy management, immune response, and stress response.  The birds’ immune systems were probably compromised by acute stress, but fortunately, this was a short-term condition.

Experts are working to discover a solution for the problems that blue-footed boobies face in the following years to stop any significant losses and keep these incredible birds on their incredible blue feet. 

Dances of courtship and blue feet

Probably the best opportunity to see these awkward actions is during the famous blue-footed booby courtship dance. The main attraction of the dance is the male’s blue feet, so to best display this highly sought-after feature, he parades around the possible nest site, showing them off and lifting them high in the air while beak-down to the female. Then, whistling, he raises his beak and spreads his wings after giving the female the materials for the nest. To complete the task, there’s one more fantastic foot performance.

Following their matching, two mates “sky-point” to each other. The movements of the birds’ heads and wings as they look up into the sky during this act indicate the strength of the relationship. In other words, the union’s power is shown by how far they can spread their wings; the limitations are explained below.

The feet of a male blue-footed booby are essential for both dancing and the female’s mating selection. When selecting a mate, women choose guys with larger, more luminous feet, and these men also tend to have more offspring. Broader feet allow the bird to span a wider circle and incubate a larger egg area, so male foot size counts when hatching eggs. On the other hand, a booby’s ability to rear its offspring and the color blue have an exciting relationship.

The carotenoid pigments that give the birds their stunning blue color come from their diet of fresh fish. Apart from its potent antioxidant properties, carotenoid also fortifies the immune system. Because only strong-willed birds can afford to add a lot of pigment to their foot color, it is believed that the pigmentation acts as a proxy for the bird’s immune system.

Blue-footed boobies of the Galapagos mating
Blue-footed boobies of the Galapagos mating

In addition, the color expresses information about the body’s condition. In a recent study, birds were experimentally fed nothing for 48 hours, and the outcome was a decrease in the brightness of the birds’ feet. In a similar vein, the feet of young male birds are the brightest, whereas the feet of older birds are much duller. As stated differently, a bird with bluer feet is both healthier and more visually appealing. Research has demonstrated that a person’s foot color may indicate how a father raises his children. Foster fathers who had more colorful feet than their less colorful counterparts had children who grew up faster, according to the findings of a cross-fostering investigation. This is most likely because of the bird’s better health, greater capacity to acquire food, and safer environment.

Even more impressive is that women adapt to the color of their partner’s foot medically and psychologically. Birds’ feet have extremely sensitive pigmentation; females may recognize color changes in as little as 48 hours. As a result, the mother can modify her investment in the child based on daily assessments. According to a study, some birds whose partners had already laid one egg had cosmetics applied to lighten their color. This is most likely because of the bird’s better health, greater capacity to acquire food, and safer environment.

Similarly, the female’s condition influences the male’s choice to invest in the chick. The larger and more vivid eggs healthier females produce have a higher reproductive value. More giant eggs attract men’s attention since they indicate a female with superior genetic quality. However, studies have shown that males pay equal attention to little and large eggs if their partner has brightly colored feet.

However, what may make blue-footed boobies even more impressive is their ability to improve the color of their feet—a capability that very few animals share—and, consequently, their sexual success through abstinence. Studies reveal that blue-footed birds with duller feet reproduce successfully, but those with brighter feet are infertile for a year. As a result, the birds unable to procreate succeed more in the following breeding season. This is because men expend more energy than women, courting and rearing their offspring. As a result of their efforts, they have less carotene left to transfer to their feet. In many species, a male’s most energetic behavior is his sexual presentation, and blue-footed boobies are no exception.

Nurturing the youth

Once paired up, a nesting location needs to be established and secured. Blue-footed boobies are opportunistic breeders, meaning they will wait to procreate until the ideal conditions arise. As a result, breeding begins as soon as there is enough food. The three primary breeding areas for blue-footed boobies are the Galapagos Islands, the islands in the Gulf of California, and the islands and headlands in the eastern Pacific Ocean, primarily between Ecuador and Peru. Blue-footed boobies typically defend several possible nest sites before deciding on one; they usually make this decision only a few weeks before the eggs are laid. The nests grow in large colonies of raw black lava divots.

When visiting the Galapagos, you may likely witness blue-footed boobies with their nests.

After being deposited, the eggs must be kept at a constant temperature. The boobies are surprisingly adept at maintaining the temperature of their eggs at almost precisely 39C, either by nesting against the eggs or by raising their bodies to allow cold air to flow within the nest. Additionally, while it is nesting, the bird faces the sun nonstop.

This insulates the nest from the outer world by forming an equivalent wall of excrement surrounding it. After the 41–45 day incubation period, which takes place between May and August, the eggs begin to hatch. The parents of blue-footed booby pairs share the responsibility of parenting their young until they are old enough to be left on their own. Both parents sit on the nest throughout the first few days of the egg’s incubation; one partner incubates the eggs while the other keeps an eye on the nest. Moreover, this reciprocal assignment of duties continues after the eggs hatch. Throughout the first several months of the young’s life, the male provides food for them with his unique diving ability.

When old enough to leave the nest, the chicks rarely go far from it. Couples of blue-footed boobies seldom travel from their original nest locations due to their relatively low incidence of natal dispersion. Consequently, hundreds of boobies inhabit extraordinarily dense colonies. However, it benefits the birds since they can raise their young there and are likely to have a high-quality nest because of its closeness to their natal nest, which benefits their growth and safety.

Siblicide

The blue-footed booby is one of only two species of booby that, as was previously mentioned, produces many chicks during a reproductive cycle. It raises two chicks on average, but sometimes it raises three. However, the eggs are not laid simultaneously; they are separated by around five days. Blue-footed people will benefit immensely from this. Owing to their asynchronous hatching, the parents may provide extra care in the early stages of the chicks’ life when they are too weak to regurgitate food. Since the chicks are hatched at different times and do not go through this period simultaneously, the parents are not required to care for them. This approach also increases the chances that at least one brood member will survive significantly.

Furthermore, studies show that asynchronous hatching lessens sibling rivalry. Compared to asynchronous broods, experimentally induced synchronous brood chicks exhibited higher levels of aggression. Asynchronous broods gain from subordinate chicks dying sooner because they are less aggressive. This helps the parents by partially relieving them of the responsibility of providing for the chick in times of scarcity.

Nevertheless, this hatching method causes the chicks to establish a pecking order. Due to its immediate incubation, the first egg will hatch approximately five days before the second, allowing it an additional five days to mature. As a result, the oldest chick outcompetes the second to take home a more significant share of what the parents provide. It can acquire food before it is complete by using its size to draw its parents’ attention away from the more petite chick.  If there isn’t enough food for the whole brood, the larger chick won’t leave the younger one with adequate food, or the parents may just stop feeding it, which frequently results in the subordinate chick dying. In the event of a severe food crisis, the dominant chick is likely to commit siblicide by killing the weaker one.

Although this may sound harsh, sibling rivalry and siblicide are crucial to the survival of blue-footed boobies because they allow the parents to focus their limited resources on only one chick. The adult chick becomes more antagonistic during prolonged shortages until it eventually chases its younger sister out of the nest or pecks it to death. It is important to note that booby chicks do not exclusively apply the Leftover Hypothesis, which postulates that more petite chicks are fed only after the older ones are delighted. Studies have shown that the older chick will put up with the younger one when there is a brief food shortage.

To prevent the younger ones from starvation, the firstborn will reduce their food intake to some extent. There is a strong correlation between the weight of the dominant chick and the siblicide rate. If the subordinate chick’s weight falls below 20–25% of its potential, it will become exceedingly hostile and might even die. However, there is minimal likelihood that the older brother will harm the younger if this isn’t the case. Interestingly, inferior chicks have been shown to construct their nest before their dominant sibling, suggesting that this behavior has no lasting effect on the chicks.

This does not, however, mean that parents go through this process motionless. Studies have indicated that in times of food scarcity, parents will choose to have children depending on what will help them grow up. Put another way, the parents would prioritize the more petite chick since it requires less money if they couldn’t afford to feed the others. The size differences between the chicks are most significant during the first two months; after that, sex, not age, dictates the chicks’ sizes. Because they grow faster than boys, girls frequently develop larger than boys, indicating a higher parental commitment. As a result, the parents start focusing on the boy instead of the unfortunate lady (if that’s the case). However, in siblicide, the parents neglect the weaker chick and encourage inequality by feeding the dominant chick more than the submissive one. As a result, scientists believe that siblicide is advantageous to the parent and that the second egg mainly functions as insurance if the first one fails to hatch.

On the other hand, research indicates that parents do try to stop siblicide on their own. The blue-footed booby parents reconstructed their nests after they were purposefully crushed. For instance, they construct their nests with steep edges to keep the dominant one from displacing the inferior chick. In addition, it is possible that females purposefully produce a more significant second egg to increase the chance of the second chick surviving. Analyses show that the second egg in a nest weighs 1.5% more on average than the first at the beginning of the breeding season, which eventually produces a more muscular chick.
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Updated:June 5, 2024

Published:January 26, 2016

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