An elegant if faintly comic looking bird given its name from the Spanish "bobo" meaning clown or foolish from their awkward movements on land. Their most striking characteristics are of course those large blue feet which are displayed with great pride during courtship rituals.
They are large diving birds with dagger like bills that catch their fish by plunge diving from up to 30m, when they can reach 97 kmh and swim down to 25m beneath the surface chasing and eating fish underwater often as part of a large flock.
Blue Footed Booby / Boobies - Sula nebouxii
Profile - Animals of the Galapagos
Both sexes look very similar, females are larger than males, their eye pupil is larger (evident in the first two pictures, below) and they have feet that are somewhat darker than the male. They are easier to tell apart when they are together for a comparison. They make different sounds too, the males make a whistling sound and the females a honking sound.
blue footed boobies facts - Basics
Weight: 1.5 kg (3.3 lb) on average, females are slightly larger than males.
Length : 81 cm (32 in) Wingspan: up to 1.5m (5ft)
Breeding: An opportunistic breeder in common with many tropical birds, breeding can happen at any time of the year often prompted by plentiful food. After an elaborate courtship ritual 1 to 3 eggs (80% of the time it is 2) are laid 4 to 5 days apart in a system known as asynchronous hatching. This provides some defence against predators , if food is not sufficiently plentiful, the larger earliest hatched chick will eat its smaller siblings. There is no nest, the eggs are laid on bare ground, though over time the nest area becomes surrounded by a circular wall of dried excrement. Egg incubation takes 41-45 days, fledging happens after about 102 days and sexual maturity is reached in 3-4 years.
Feeding: Fish are the main food, usually caught while fishing in a flock by plunge diving. The birds fold their wings back and plunge from 10-30m (33-100ft) reaching up to 97 kmh (60 mph) and can reach depths of 25m (82 ft), fish are eaten while underwater, fishing dives may also occur from a starting point of swimming on the surface of the sea. Blue-footed boobies feed inshore sometimes in spectacular numbers and sometimes in conjunction with other predators such as other sea-birds from above and tuna from below. Air sacs in the skull between muscles and the skin act as shock absorbers during dives to prevent injury, specifically to the brain.
Conservation status: Least concern, though the population in the Galapagos is feared to be in a slow decline. They are found in tropical and sub-tropical regions of the Pacific coast of the Americas, with about 50% of all breeding birds on the Galapagos Islands.
Predators: They have been hunted by humans at various times, though this has largely stopped now. No other predators on the adults, like any birds the eggs and young chicks may be vulnerable to native and introduced predators.
What are Blue Footed Boobies Like?
These really have to be one of the most remarkable birds in the world with their almost unreal large sky-blue feet and a mating dance which entails lifting the feet in a very solemn manner, one at a time showing them off to the prospective mate.
Odd as it may seem the feet are actually a very good indicator of these birds state of health and their suitability as a reproductive partner for both males and females with the key factor being the brightness and intensity of the blue colour. Research has shown that both males and females with the brightest and bluest feet are more attractive to the opposite sex and also are the most successful in rearing chicks.
The feet are used in the mating ritual (video above) where they are each lifted very deliberately in turn, this is then followed by 'skypointing" - tails and beaks are pointed vertically upwards, the wings are brought forwards and half opened while the birds make a honking noise.
Another unusual element of the birds behaviour is the asynchronous hatching of the eggs. One to three eggs are laid, but usually two, 4-5 days apart which results in chicks of different ages and sizes. As they are opportunistic breeders at times of apparent food abundance, it is not always certain that once breeding has begun, there will be enough food to grow and sustain more than one chick. So in times of shortage, the parents will feed the larger chick more which may oust its smaller sibling from the nest or even eat it itself. This is not unique amongst birds, but makes the "brood reduction" process in the face of a limited food supply more efficient in Blue Footed Boobies. reference
Top banner credit - Ndecam from London UK, used under CC2 Attribution Generic license.