Some Birds Have Multiple Broods in One Season
Some songbirds have multiple broods or clutches in one season, including northern cardinals, American robins, mourning doves and eastern bluebirds. Other species have only one clutch per season, like tree swallows and American goldfinches. Based on data gathered during the District’s bluebird monitoring program, tree swallows have one peak nesting during the growing season. In contrast, eastern bluebirds have two peaks about one month apart, which is sufficient time to hatch eggs, rear young and try for a second nest.
A number of factors can influence the number of broods an individual bird can have each season, such as:
Location: Some species lay more eggs in fewer clutches in northern latitudes, but more clutches with less eggs in southern climates.
Time of year: Some species nest early in the breeding season, making it possible to raise two sets of young. Because American goldfinches nest very late in the season, they only have time for one clutch.
Food supply: Weather, periodic cycles and timing impact the food supply available for parents to develop the eggs and/or feed the nestlings. The more food available, the greater the potential to have multiple clutches.
Experience/family: Age can play an important role in how successful a parent is in raising their young. Inexperienced parents may not know how to properly care for their young, make strong nests that withstand the weather or have fewer clutches than more experienced birds in the same area. Also, some young from previous broods may assist in raising of future broods, easing the parents’ workload.
Personality: All birds exhibit their own personality traits when it comes to nurturing their young, aggressively protecting their brood and foraging for food. Whether genetically inherited or learned, all of these traits impact the success of multiple clutches.