The eastern phoebe (Sayornis phoebe) is a small passerine bird that breeds in eastern North America. Phoebes are aerial insectivores and often forage by flying out from a perch to snap up insects in mid-flight. They are well-known for their characteristic “fee-bee” call. Phoebes build nests on ledges or other sheltered sites, and typically lay between 3-6 eggs per clutch. The number of clutches and broods a phoebe will have in a breeding season can vary based on food availability, weather conditions, and other factors. In this article, we will take a closer look at phoebe nesting behavior and the number of babies a phoebe pair can produce in a single season.
Phoebe Nesting Behavior
Eastern phoebes are early spring migrants, arriving back on their breeding grounds in March or April. Shortly after arriving, pairs begin searching for suitable nesting sites. Favorite spots include sheltered ledges on buildings, bridges, rock outcrops, or cliff faces. The male will establish a territory and perform a nest-building display to attract a female. Once paired, the female chooses the actual nest site and does most of the construction work.
The nest itself is an open cup made of mud, moss, grass, rootlets, and other plant materials. It is lined with finer materials like hair, feathers, or fur. The female builds the nest in about 5-10 days while the male brings some material. But the male does not actually participate in nest construction.
Once the nest is complete, the female will lay one egg per day until the clutch is complete. Clutch size ranges from 3-6 eggs, with 4-5 being typical. The female does all the incubating, which lasts about 16 days. She develops a brood patch – a bare patch of skin on her belly – to transfer heat to the eggs. The male will bring her food while she incubates.
Number of Broods
Phoebes often raise more than one brood per breeding season. After the first clutch fledges (leaves the nest), the pair will usually build another nest and produce a second brood. Second nestings happen from late May through July. The number of broods a pair has depends on several factors:
| Factor | Effect on Number of Broods |
|---|---|
| Length of Season | More broods in southern range with longer season |
| Weather | Colder spring delays first brood |
| Food Availability | More insects enables more broods |
| Nest Success | Failed nests may force re-nesting attempts |
In optimal conditions with a long breeding season, abundant food, and successful first nests, phoebe pairs in the southern part of their range have been known to raise up to 4 broods. But 2-3 is more common throughout their range. Farther north, the shorter season usually allows just a single brood.
Number of Eggs and Babies
By combining their typical clutch size range, number of broods, and some assumptions, we can estimate the potential number of babies a phoebe pair can raise in a single breeding season:
- Average clutch size is 4-5 eggs
- Phoebes often raise 2-3 broods per season
- Assume 4 eggs per clutch and 2 broods
- 4 eggs x 2 broods = 8 eggs per season
- If all eggs hatch and babies fledge: 8 eggs = 8 babies!
Of course, the actual number of fledglings will often be lower than the number of eggs laid. Incubation problems, nestlings dying, bad weather, predators, and other factors can all decrease reproductive success. However, under ideal conditions, a phoebe pair is physiologically capable of fledging potentially 6-10 or more babies in a single breeding season!
Comparison to Other Birds
Phoebes produce fewer young per season than many passerine birds for several reasons:
| Bird | Clutch Size | Broods/Season | Total Eggs |
|---|---|---|---|
| Phoebe | 4-5 | 2-3 | 8-15 |
| Song Sparrow | 3-5 | 2-4 | 6-20 |
| House Wren | 5-8 | 1-2 | 5-16 |
| Wood Thrush | 3-5 | 2 | 6-10 |
Smaller songbirds like chickadees, titmice, and warblers may have 6-9 eggs per clutch and raise 2-3 broods. Jays, woodpeckers, and other cavity nesters also often have higher reproductive rates. But phoebes and other flycatchers tend to reproduce more slowly since they are aerial insectivores dependent on local prey abundance. Still, with 2-3 broods of 4-5 eggs each, phoebes are capable of fledging a half dozen or more chicks in a good year!
Conclusion
In summary, eastern phoebe pairs typically raise 2-3 broods per breeding season, with clutch sizes averaging 4-5 eggs. This means a productive phoebe pair can potentially fledge anywhere from 6-10 or more chicks in a single season. However, reproductive success depends on many factors, and actual numbers are often lower. Phoebes reproduce relatively slowly compared to other passerines. But their adaptability to human structures and feisty personalities have allowed phoebe populations to remain stable across their range. Understanding details of their breeding biology provides insight into the natural history of these charismatic flycatchers.
