Clutch Size – The number of eggs laid in a single brood by a nesting pair of birds. Some species of birds will lay only one or two eggs while others will have clutch sizes to as many as 20.
Brood – The group of young produced or hatched at the same time. Some species of bird will only have one brood in a year while others may have multiple. When species have multiple broods, some will re-use the nest and others will make a completely new one.
Incubation – The act of sitting on the eggs to keep them warm to allow them to hatch.
Incubation Period – The period over which eggs are incubated by a parent. In general, birds do not begin incubating until the clutch is complete and the incubation period is defined as the period from the laying of the last egg of the clutch until that egg hatches.
Nestling Period – The number of days between hatching and leaving the nest or fledging.
Fledge – To leave the nest.
Brood Parasitism – A form of social parasitism practiced by certain birds, such as cuckoos and cowbirds, in which eggs are laid in the nests of other birds, causing them to be hatched and the young reared by the hosts, often at the cost of the hosts’ own young.
Parasitism – A type of symbiotic relationship between two species in which one member, the parasite, benefits at the expense of the other, the host, sometimes without killing the host organism.