How many eggs do you think a bird will lay? have a guess for Blue tit, Mallard duck Barn owl, Song thrush and Heron.
Birds laying eggs is another good trick of nature. Birds are creatures that fly, so it would be very difficult for them to fly with their babies inside them because of the weight. Think about how "fat" mammals get when they are pregnant, or how wide frogs can get carrying all those eggs inside. So laying eggs makes sense for birds.
Normally, the shorter a birds life is the more eggs it will lay. This is because the eggs, and chicks, are new lives of that species. So birds like Blue tits lay many more eggs than a Barn owl family. A Blue tit's life expectancy is 2 years, whereas a Barn owl will live *** years in the wild. Wading birds like Lapwings or Avocets can live for 10 years or more. They lay 2 or 3 eggs because their chicks may not make it to adulthood. Also, if a bird migrates (I'll write about this later on) they lay less eggs . A really strange fact of nature is that birds that migrate(like Chiffchaffs and Swallows) to warmer countries, like Africa, are more likely to survive until the next Spring than those species that stay in Britain's cold winter.
Seabirds can live for many years so they usually only lay one egg. The Guillemot, Razorbill, Kittiwake and Fulmar are all sea birds - they get their food from the sea. These birds make their nests on cliffs - sometimes in very small spaces! But luckily their eggs are more of a cone shape so that if they do get knocked they roll around in a circle, rather than fall of the edge. Their main predator will be big sea gulls such as Great black-backed gulls. At least the eggs cannot be stolen by Foxes.
Common Guillemots (left) and Razorbill (right.)