Passing the shelves of supermarkets during and well before Easter arrives, the most common object you would see is an egg. Big eggs, small eggs, eggs filled with cream, eggs with luxurious Dubai pistachio filaments; chocolate eggs that cost twenty pounds and weigh one… In short, the moment when the first rays of spring reach our lands and the days become a little longer, everything is suddenly egg shaped. It makes perfect sense; spring is the time when nature renews itself and every wild animal’s instinct makes it completely focused on nesting. And what better visual representation of all this vernal magic than a smooth, shiny, round-ish egg hiding new things inside?
When I talk about magic, I am being a little fanciful. I now know that rabbits don’t lay eggs, despite my most cherished moments of childhood when my grandfather and I looked for chocolate eggs in a local woodland, which were ‘left there for me by a rabbit’. Unfortunately, the rabbit never remembered the locations of all of them, so some are probably still there, 40 years later, confusing new generations of children.
Just consider this: We now know that the egg came first (before the rabbit and the before the chicken) as birds evolved from egg laying reptiles about 66 million years ago. Instead of carrying their babies inside their bodies and waiting weeks or months for them to develop, reptiles and birds take a couple of days to create this wonder capsule packed with nutrients, which support the embryo, leaving them free to move independently. They still need to incubate their eggs, but many species, like our shore birds, take turns, so one parent can always look for food and defend the nest.
The eggshell consists of 95% calcium carbonate, 3.5% organic proteins and 1.5% water and other elements. The camouflaging pigments, so important to protect them from predators, are added by a specialised gland when most of the egg is done. As a final step, an organic coating that protects against harmful bacteria and UV radiation is deposited around the shell, and the egg is ready to roll! The more developed the new-born chicks are, like those of ducks and waders who can walk and feed themselves straight away, the higher the percentage of yolk is contained in the egg.
Newly hatched ringed plover chicks are ready to look for food within hours
And why do eggs come in all those fascinating shapes?
Well, it appears that the shapes are influenced by how much different types of birds fly. Long distance migrants have more elongated eggs, so they can fit better into the streamlined female bodies without being too wide. Another factor in the egg shape is the nest location. Eggs of cliff nesting birds such as guillemots are the most elongated ones. It reduces their chance to roll down and fall into the abyss. Birds whose eggs are safely contained in cupped nests or in cavities are generally rounder like those of owls and birds of prey.
The beach laid eggs we in Bird Aware look after, are generally quite narrow and pointy. They are often arranged in a perfect circle with their ‘tips’ pointing towards the centre to reduce rolling and maximise heat distribution. Ringed plovers usually settle for the sweet spot of four eggs, which seems to work best for them. When they opt for a fifth, it costs them three extra incubation days, smaller size eggs and smaller and more vulnerable chicks. This is probably not worth the effort as it makes both the chicks and parents more vulnerable. Oystercatchers generally make do with 3 and little terns with 2-3 eggs. There is an occasional ‘egg dumping’, cuckoo style, when an extra egg becomes someone else’s responsibility but it’s quite rare. Unlike the chocolate eggs left behind by the forgetful rabbit, most of these wonder capsules are well looked after, and by mid-May, we usually see self-sufficient chicks running around, looking for insects. It’s all completely real but no less magical.