The House Wren (Troglodytes aedon) is a widespread songbird across North America, known for its small size, energetic behavior, and loud, bubbling song. As a migratory species, its reproductive cycle is synchronized with the arrival of spring in its temperate breeding range. This synchronization ensures that raising young aligns with the seasonal peak in insect availability, their primary food source. The annual timeline involves a precise sequence of events, from the male’s solo arrival to the family’s departure in the fall.
Arrival and Territory Establishment
The House Wren nesting season begins with the arrival of males, typically occurring in the temperate zones of the United States and Canada from late March through early May, depending on the latitude. Males return first from their wintering grounds in the southern U.S. and Mexico, immediately claiming territory through persistent, loud singing from prominent perches. This vocal display warns off rival males and attracts a potential mate.
After establishing a territory, the male secures multiple potential nest sites, which are almost always pre-existing cavities such as old woodpecker holes, natural tree hollows, or human-provided nest boxes. He starts constructing “dummy nests” by filling these cavities with a base of small twigs. He may start up to twelve of these incomplete structures, offering a selection to the female who arrives approximately one to two weeks later.
The Physical Nest Construction
The male’s initial construction is a coarse, bulky foundation of small sticks, which can number in the hundreds and often fills the cavity completely. This stick foundation serves multiple purposes, including territory advertisement, competition with other cavity nesters, and providing a stable base for the true nest cup. Once the female arrives and selects a mate, she inspects the available sites and chooses one of the male’s stick-filled cavities.
The female then takes over construction, often removing some of the male’s sticks before creating the final nest cup in a depression within the foundation. She builds the soft lining from finer materials like grasses, plant fibers, animal hair, and feathers. This final cup is completed quickly, sometimes in as little as three days, and is where she will lay her clutch of eggs.
Incubation and Fledging Timelines
Once the nest is lined, the female begins laying her clutch, typically one egg per day in the early morning, until the clutch size of four to eight eggs (most commonly five or six) is reached. She begins incubation after the next-to-last egg is laid, ensuring the eggs hatch nearly simultaneously. The incubation period lasts approximately 12 to 14 days, though this timeframe can be slightly extended in colder weather.
Hatching occurs over a one- to two-day period. The young are altricial, meaning they are helpless, blind, and require constant care and feeding by both parents during the nestling period, which lasts between 15 and 17 days. The entire nesting cycle, from the laying of the last egg to the young leaving the nest, takes roughly one month. When they fledge, all the young typically leave the cavity within a few hours of each other, marking the end of the first breeding attempt.
Second Broods and Seasonal Departure
House Wrens are frequently multi-brooded, attempting to raise a second, and sometimes even a third, brood during the long breeding season, especially in the southern parts of their range. The second nesting attempt often begins almost immediately after the first brood fledges, starting roughly 50 to 60 days after the first egg of the season was laid. For the second brood, the female may choose a new nest site or renovate the existing one with a fresh lining.
Clutch sizes for the second brood are often slightly smaller, averaging five to six eggs. The parents continue to feed and guide the fledglings from the first brood for up to two weeks after they leave the nest. Sometimes the male takes over primary care while the female prepares for the next attempt. By late August or early September, nesting activity concludes, and the House Wrens begin their fall migration south to their wintering grounds.