Interesting Creatures…The Blue-footed Booby (Sula nebouxii)

Oct 27, 2013 Features / Columnists, Interesting Creatures in Guyana

---

 
The Blue-footed Booby (Sula nebouxii) is a marine bird in the family Sulidae, which includes 10 species of long-winged seabirds.  It belongs to the genus Sula, which comprises six species of boobies.
It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait. Males display their feet in an elaborate mating ritual by lifting their feet up and down while strutting before the female.

The natural breeding habitats of the Blue-footed Booby are the tropical and subtropical islands of the Pacific Ocean. It can be found from the Gulf of California down along the western coasts of Central and South America.
Its diet mainly consists of fish, which it obtains by diving and sometimes swimming underwater in search of its prey. While it sometimes hunts alone, the Blue-footed Booby mainly hunts in groups.
They usually lay one to three eggs at a time. The species practices asynchronous hatching, which means that eggs that are laid first are hatched before the consequent eggs, resulting in a growth inequality and size disparity between siblings. This results in facultative siblicide in times of food scarcity, making the Blue-footed Booby an effective model for studying parent-offspring conflict and sibling rivalry.
It is on average 81 cm (32 in) long and weighs 1.5 kg (3.3 lbs), with the female being slightly larger than the male, measuring up to 90 cm (36 in) long with a wingspan of up to 1.5 m (4.9 ft). Its wings are long and pointed, and are brown in colour.
The neck and head of the Blue-footed Booby are light brown with white streaks while the belly and underside exhibit pure white plumage. Its eyes are placed on either side of its bill and are oriented towards the front, enabling excellent binocular vision. Its eyes are a distinctive yellow, with the male having more yellow in its irises than the female. Blue-footed Booby chicks have black beaks and feet, and are clad in a layer of soft white down.
Since they frequently obtain fish by diving headlong into the water, it has permanently closed nostrils for this purpose, necessitating breathing through the corners of its mouth. Its most notable characteristic is its blue-coloured feet, which can range in colour from a pale turquoise to a deep aquamarine.
Males and younger birds have lighter feet while females have darker feet. Its blue feet play a key role in courtship rituals and breeding, with the male visually displaying its feet to attract mates during the breeding season.
It is strictly a marine bird. Its only need for land is to breed and rear young.
A Booby may use and defend two or three nesting sites, which consist of bare black lava in small divots in the ground, until they develop a preference for one a few weeks before the eggs are laid. These nests are created as parts of large colonies. While nesting, the female will turn to face the sun throughout the day, so the nest is surrounded by excretion.
Females start breeding when they are one to six years old, while males start breeding when they are two to six years old. There is very limited natal dispersal, meaning that young pairs do not move far from their original natal nests for their own first reproduction, leading to the congregation of hundreds of boobies in dense colonies.
The benefit of limited dispersal is that by staying close to their parents’ nesting sites, the boobies are more likely to have a high quality nest. Since their parents had successfully raised chicks to reproductive age, their nest site must have been effective, either by providing cover from predation and parasitism, or by its suitability for taking off and landing. Bigamy has been observed in the species, and there are known cases where two females and one male all share a single nest.
The blue colour of the Blue-footed Booby’s webbed feet comes from carotenoid pigments obtained from its diet of fresh fish. Carotenoids act as antioxidants and stimulants for the Blue-footed Booby’s immune function, suggesting that carotenoid-pigmentation is an indicator of an individual’s immunological state. Blue feet also indicate the current health condition of a booby. Boobies who were experimentally food-deprived for 48 hours experienced a decrease in foot brightness due to a reduction in the amount of lipids and lipoproteins that are used to absorb and transport carotenoids. Thus, the feet are rapid and honest indicators of a booby’s current level of nourishment. As blue feet are signals that reliably indicate the immunological and health condition of a booby, colouration is favoured through sexual selection.
The Blue-footed Booby’s diet consists mainly of fish. It is a specialized fish eater, feeding on small school fish such as sardines, anchovies, mackerel, and flying fish. It also feeds on squid and offal. The Blue-footed Booby dives into the ocean, sometimes from a great height, and can swim underwater in pursuit of its prey. It hunts singly, in pairs, or in larger flocks. Boobies travel in parties of about 12 to areas of water with large schools of small fish. When the lead bird sees a fish shoal in the water, it will signal to the rest of the group and they will all dive in unison, pointing their bodies down like arrows.
(Source: Wikipedia – The Free Online Encyclopedia)

---

---