Unwrapping eggs for Easter
9 Apr 2019
Allan Archer, our Wildlife Education Officer, talks about eggs
For a lot of people Easter is all about hollow chocolate eggs, wrapped in colourful foil and sometimes containing a small bag of additional treats on the inside. For me it is about emerging butterflies and other insects, returning migrant birds and new life; be it plant or animal.
A large percentage of this new life is hatched from eggs. In the UK, they range in size from those of insects, which are smaller than a pin head to over 11cm belonging to the mute swan a bird which lays the largest egg in this country. The swan’s egg is by no means the largest of the birds’ eggs. That accolade goes to the ostrich with an egg size of 15cm x 13cm. Compare that to the average chicken egg at 5.5cm x 4.2cm.
However even the ostrich egg pales in comparison to the largest eggs ever laid. These measured a whopping 30cm in length with a circumference of 71cm! These were laid by elephant birds which are, unfortunately, now extinct.
At the other end of the scale, the smallest egg laid by a bird in the UK is that of the goldcrest (1.4cm x 1cm), but that is still around half a centimetre longer than a bee hummingbird egg!
Not all birds’ eggs are ‘egg-shaped’. Those of the tawny owls are almost round, others are oval and the guillemot’s egg is pointed at one end. Initially it was thought that the pointed shape of the guillemot egg meant that it would roll in a circle if knocked, thus preventing it from falling off the cliff ledge where the bird nests. Research has now shown that this is not the case. The shape of the egg makes it very stable on the ledge and prevents it from rolling at all.
Birds have evolved other strategies to protect their eggs. Little ringed plover eggs are extremely well camouflaged to blend in with the shingle they nest on. African jacana eggs are water-proof because their nests are built on water and spend a lot of the time submerged. One bird, the hoopoe goes even further; coating its eggs in a smelly, stick secretion which acts as a shield against infection.
Whilst some birds go to extremes to protect their eggs, one of our UK migrants leave all the hard work to others. Cuckoos don’t build nests, but instead lay their eggs in those of other species. dunnock, pied wagtails, meadow pipits and reed warblers are the main species to fall fowl of this practice.
To end, here is an excellent pub quiz question.
How many holes are there in an unbroken chicken egg?
If you said up to 17,000, you are right! These tiny micro-pores allow the flow of air through the egg and for moisture to be expelled, which are vital for the chick’s development.
So this Easter, spare a thought for the egg – a fascinating, highly adaptable, some would say perfect, object that gives rise to real treats.
During the Easter holidays, to complement our egg trail and crafts, we will have a display of replica eggs on show in the Wildlife Education Centre. Come along and find out even more about the fascinating life in and from the egg.
Allan Archer: Wildlife Education Officer