How many eggs or clutch size varies among bird species. Depending on food and calcium availability, latitude, age of the female, weather, and time of year. The Black Swift lays just one egg, but a Wood Duck may lay 7-14 eggs per clutch. Birds incubate their eggs to keep them at the proper temperature to ensure normal development. Many songbirds begin incubation after laying all their eggs so they hatch around the same time. Common Ostriches can have about 50 eggs in a single nest, but they are laid by several females. An ostrich egg is also the heaviest, with an average weight of 1.36 kg. The Vervain Hummingbird, found in Jamaica and two nearby islets, lays an egg weighing 0.365 grams. The Mallard Duck, shown in the picture with 11 ducklings, can lay up to 13 eggs. The newly hatched birds are covered in down and are alert; they are ready to leave the nest within 13-16 hours of hatching.
