Life

Things you didn't know about eggs

June 10th, 2016 5:00 PM

By Southern Star Team

A guillemot's eggs are pear-shaped to help prevent them from falling off cliff ledges. (Photo: S Franks)

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We are very fortunate in our townland to have a neighbour who keeps hens and ducks and we get to eat wonderful fresh eggs as a result. 

After a bit of persuasion, Pat (the neighbour!) got me to try out his duck eggs and I’ve been eating them ever since. Not only are they nutritious and fresh, the eggs themselves are quite beautiful objects in their own right, many of them the delicate hue of the popular ‘duck-egg’ paint colour.

Birds lay eggs in a variety of colours, shapes and sizes. Some of them, like the duck eggs, are quite extraordinarily beautiful. The custom of collecting and displaying bird eggs was widespread in times past, particularly during the nineteenth century. Thankfully that practice is discontinued and the collection of wild bird eggs is illegal. But the design and shape of birds’ eggs is certainly interesting, as is the way man has interacted with them over the millennia.

The hard porous eggshell is designed to protect the contents of the egg from injury. The pores allow air but not water in and prevent the egg white from evaporating.

The first birds’ eggshells were probably white and many birds today still lay pure white eggs. Most of these species build their nests in holes or burrows so do not need to camouflage their eggs. The white eggs are more easily seen in the darkness by the incubating bird and so are less likely to be broken. 

Colouration protects the eggs from predators by camouflaging them. Eggs laid in open nests or scrapes on the ground are particularly effectively camouflaged. While basically similar, tints and markings may vary a lot within the same species, even in eggs laid by the same female.

The shell shape and size varies according to the species. The egg shape is generally related to the type of nest or nest-site. A guillemot’s eggs are pear-shaped, an adaptation which prevents them from falling off their precarious cliff ledge nest sites and smashing on the rocks below. 

The pear-shaped eggs of waders, and other birds that nest in a scrape in the ground, helps stop them from rolling away if left unguarded. The eggs of birds which build cup-shaped nests, like many songbirds, or nest in holes, like puffins, are often oval or spherical as they are in no danger of rolling away. 

While the egg is developing within the female, the watery jelly egg-white (albumen) is deposited around the yoke. The albumen is surrounded by two soft membranes and successive layers of a chalky deposit which harden to form the protective shell. 

The two membranes lie close to the shell except at its broadest end where there is an air pocket. This is where the hatching chick will eventually draw its first breaths.

 

Laying and Incubation

Unevenly shaped eggs are often laid broad-end first – however painful that may seem – but some birds lay them pointed end first. The female, together with the male in some species, incubates the eggs by sitting on them and warming them with her body heat. This allows the embryo to grow. 

Many birds have a feather-free patch under their bodies, known as a brood patch. This patch allows the eggs make to direct contact with the bare skin that has well developed blood vessels which allow the heat to transfer easily from parent to egg. In species where male and female both incubate the eggs, the males may also have brood patches. Other species, gannets for example, use their fleshy feet to incubate the eggs and so they lack brood patches. 

Incubating periods vary considerably according to species. On the whole, when birds have long incubation periods, the young are generally well developed when hatched. For example, newly hatched ducklings are active, covered in down and able to feed themselves straight away. In contrast, the nestlings of songbirds, which hatch after relatively short periods of incubation, are naked and blind and totally dependent on their parents for food.

The chicks escape from the eggshell either by chipping out a small hole or a line of weakness in it, depending on the species. They use an ‘egg-tooth’ to do so – a small knob on the upper mandible – which falls off after hatching.

 

Folklore 

Eggs of many species were widely eaten in times past. Domesticated chickens and ducks of course, but also wild birds’ eggs. The eggs of black-headed gulls and lapwings were considered good eating and were sold at a high price in markets and fairs. Dove eggs were also popular and swan eggs were particularly valuable. In 1496, during the reign of Henry VII, anyone who stole or took a swan’s egg would be imprisoned for a year.

There are many beliefs associated with eggs too. The ancient Greeks believed that anyone that ate an owl’s egg as a child could not later become an alcoholic. The Greeks also believed that eating a raven’s egg could restore hair colour to those who’d gone grey. 

While Pliny, a Roman naturalist, believed that bringing an egg of a raven into the house would result in a very difficult labour for any woman in that house. 

There is a lot of folklore associated with eggs in Ireland too. For good luck, an egg would be marked with a cross as it hatched, however, putting rotten eggs in a neighbour’s haystacks would bring them bad luck. After eating the egg, the eggshell would be crushed and thrown in the fire – otherwise it would provide a home for the fairies. 

On the Beara peninsula, it was believed that the first egg laid by a black hen was good for the voice. If a person drank such an egg raw, for three mornings in a row, they would attain a good singing voice. Another West Cork belief said that eggs should only be put under a hen for hatching when the tide was coming in, otherwise they would not hatch.

Perhaps my favourite of the many myths and fables that feature eggs is the story of St Kevin of Glendalough who had a very close relationship with nature. He lived as a hermit and it was said that birds would come and perch on his hands and shoulders as he prayed. One Lent, a blackbird came and laid its eggs on his palm while he was praying. The saint was so patient and kind that he kept his hand outstretched in the same position until all the blackbird’s eggs had hatched.

Then we have, of course, the tale of the goose who laid the golden eggs and also the story of a duck who flew out to sea carrying an enchanted egg.

However, we’ve run out of space again so we’ll save the last words for my neighbour  – thanks Pat for the lovely duck eggs!

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