Protecting threatened Over-seas biodiversity

Easter weekend: what if we learn more about eggs ?

Whether they are blue like those of the White-breasted trasher, two like the Tuit-tuit or millions like the Atlantic goliath Grouper, the eggs never cease to amaze us.

The color of the eggs

White-breasted trasher nest and eggs © Laurent JUHEL / PNM

Blue, white or brown, the color of eggs in birds varies in the natural environment. Contrary to what the scientific community thought for years, the color of these eggs is not due to the species but indeed in part to the temperature of the environment and the exposure to the sun in which the animal evolves. American scientists have shown that in cold regions, eggs often have a dark brown tint while in hot regions, the latter are lighter, and sometimes blue. Indeed, darker eggs will absorb more solar radiation allowing the baby to develop properly.

The blue-green color comes from a biliary pigment called biliverdin, it ensures a parasol effect by masking ultraviolet radiation thanks to its dark shade without inducing too much absorption of infrared radiation caused by too much dark color which would overheat the bird.
Other factors could also influence the color such as the need for certain species to hide the eggs from predators.

The records

Ostrich male and his eggs

Size contrasts

Among vertebrates, the animal that produces the largest number of eggs is the Ocean sunfish with more than 300 million eggs made during each breeding period. In birds, many species lay only one egg like the Vulture while some can lay up to 17 eggs like the Grey partridge.
But which animal lays the biggest eggs? Not surprisingly, the Ostrich is the bird that lays the biggest eggs. Measuring 18 cm long by 14 cm wide, it can weigh up to 1.8 kg. This egg is 5000 times larger than that of the Bee hummingbird whose egg size is 1cm for 0.35g, which can be similar to a pea.

The amazing incubation period

Not all species incubate their eggs in the same way and some species even display amazing characteristics.
In the Surinam Toad, called Pipa-pipa, the female will incubate the eggs under her skin on her back for several months. Between 60 and 100 pockets welcoming eggs then tadpoles thus garnish his body. Once mature, the young will pierce the pocket and emerge from the back of their mother in the form of young toads.

In some fish species, eggs are incubated in the mouth. The best known species of fish performing this oral incubation belong to the family of Cichlids, freshwater fish living in African lakes.
Some species incubate their eggs for years. This is the case for the octopus Graneledone boreopacifica, which holds the record for the animal kingdom with an incubation greater than 4 years observed in California. In birds, the longest incubation period without interruption is that of the Emperor Penguin, which can reach 67 days.

Even more amazing

What if eggs could communicate?

A Spanish study has shown that birds can communicate through their shells and inform other eggs of potential danger thanks to vibrations directly produced in the shells. A French study has also shown that the eggs of snakes use their heartbeats to communicate with each other but also to accelerate the growth of certain eggs.
Certain bird species such as the Superb fairywren, an Australian passerine, learn to sing in the bud. A study has shown that the mother emits a specific melody during the brood, and that the more the song of the baby bird resembles the melody, the better she takes care of it. And the less accurate the reproduction, the more it tended to abandon the nest.

Different strategies

Two reproduction strategies are visible in the natural environment and are linked to environmental characteristics: strategy K and strategy R.
Strategy K is a strategy for the development of populations of living beings adopted when living conditions are predictable and risks low: animals invest in the survival of young people, fertility is therefore limited and populations present few eggs, few young people, but adults provide parental care. This is the case of the White-breasted trasher, the Reunion cuckooshrike and the Madagascar pond-heron.
Strategy R is a strategy for the development of populations of living beings adopted when the habitat is variable or disturbed and the risks high: the species then present a high growth rate, high fertility and low chances of survival until sexual maturity. Populations thus present many pups and adults provide little or no parental care. This is the case of the Atlantic goliath grouper and the Nassau grouper.