Falcons use old nests of other species. All other birds build stick nests either in trees, on cliffs, on humanmade platforms, or on the ground. Many species line the nest with greenery before the eggs are laid. Some pairs use the same nests year after year. Bald eagles reuse nests, adding sticks and greenery each year.
Pairs often maintain two or more nest sites per territory, alternating nests between years.
The use of different nests may prevent the build up of nest parasites, and provide an alternative location if the first nest is disturbed or destroyed. E. Clutch frequency and size. Most species raise one brood per year. If the season is long, smaller species with short breeding cycles can sometimes raise two broods. A few species, such as the California condor, lay one clutch every two years.