Birding is a popular hobby worldwide and many enthusiasts have explored all aspects of birds, researching how they live, breed and nest. One aspect of this is identifying bird eggs, as many birds can be identified solely by the shape, colour and markings on each of their eggs. This knowledge and skill has helped not only birders, but naturalists identify the regions certain birds live in and how they survive and interact with their natural environment.
Size of Eggs
Size is the first thing to look at when trying to identify which bird laid a particular egg. Most small birds that are common in different regions and suburban neighbourhoods have, not surprisingly, small eggs. Most are a little bigger then a dime, ranging from the house wren to sparrow to the tree swallow. The Eastern bluebird's egg is generally bigger, as the bird is bigger then all of the smaller bird's eggs and the robin's egg is about twice the size of that one.
Number of Eggs
After settling on size, the number of eggs is also a good indicator as to what kind of bird it is. While you will probably never see it, some birds like the albatross only lay one egg every two years, so the number of eggs vary per bird species. Hummingbirds, for example, lay two eggs about the size of a jelly bean. House sparrows usually lay 5 eggs on average and the house wren lays 6 to 8 eggs. So you can immediately narrow down what kind of bird eggs you are dealing with based on sheer number of eggs alone.
Colour of Eggs
The colour of the eggs widely varies from species of bird to species of bird, and this where the really serious birding enthusiasts can really flex their knowledge. Birds know these colours and patterns so they can identify their own eggs or other eggs they are dealing with when they come across them. Some birds will destroy the eggs in another bird's nest. However, humans knowing the specific bird species based purely on the colour and patterns on the eggs is a true study, as they all range from white to yellow to blue to brown to grey to olive. They are all unique and pretty in their own ways and those who appreciate birding always have their favourite eggs.