Barn swallows are small, sparrow-like birds known for their long forked tails and their habit of building nests on porches, barns, and other structures. They are highly social and migrate in large flocks, spending the breeding season in the Northern Hemisphere and migrating south for the winter.
Barn swallows build their nests out of mud pellets and line them with feathers. The female typically lays 4-5 eggs which hatch after about 14-15 days. Once the chicks hatch, they remain in the nest for approximately 18-23 days before fledging and leaving the nest.
Nesting and Egg Laying
Barn swallows arrive at their breeding grounds in spring, usually between March and May depending on latitude. Soon after arriving the females begin building nests out of up to 1000 mud pellets. They construct the nests on vertical surfaces such as cliff faces, building eaves, or porches.
The nest is cup-shaped and about the size of half a coconut shell. The interior is lined with grasses and feathers which provide insulation and cushioning for the eggs. Females often reuse and repair old nests rather than building an entirely new one each year.
Egg laying begins as soon as the nest is complete, usually in May or June. Barn swallow clutches typically contain 4-5 eggs that are 0.75 inches long and elliptical in shape. The eggs are creamy or white colored with reddish-brown spots.
The female lays one egg per day and incubates them for about 14-15 days before they hatch. Incubation doesn’t start until the clutch is complete, so all the chicks hatch around the same time. Both parents take turns incubating the eggs, sharing the duties of keeping the eggs warm.
Hatching and Development
After two weeks of incubation the chicks begin to hatch. Hatching can take up to 3 days as the chicks use their egg tooth (a sharp protrusion on their beak) to break out of the shell. Once free they are blind, naked, and completely helpless.
For the first week the chicks are brooded almost constantly by their mother. She provides warmth and protection until they develop feathers for insulation. The father helps gather food and defend the nest from predators.
Chicks grow quickly and pins begin emerging from their wings within just a few days. By two weeks old their eyes are open and they have a full coat of downy feathers. At this stage they are already quite active in the nest and may beg or jostle for position with their siblings.
By 3 weeks their flight feathers begin to grow. These long stiff feathers on the wings and tail eventually allow the chicks to fly. They go through a rapid growth phase and are nearly adult sized by 4 weeks old.
Fledging and Leaving the Nest
Barn swallow chicks are ready to fledge (leave the nest) approximately 18-23 days after hatching. This is a dangerous time as the juvenile birds make their first flight attempts. Initially they are clumsy fliers and very vulnerable to predators.
Fledging often occurs incrementally over several days. The chicks will perch on the rim of the nest, stretching and flapping their wings to build flight strength. Eventually they take short hops and glides, returning to the nest for safety.
As their flying improves the chicks begin venturing further away for longer periods. They stay in the vicinity of the nest for up to a week, still depending on their parents for food. Eventually they gain full independence and leave to join migratory flocks in the fall.
Typical Timeline
Here is a typical developmental timeline for barn swallow chicks:
| Age | Milestones |
|---|---|
| 1 week | Covered in down, eyes closed |
| 2 weeks | Eyes open, wing feathers emerging |
| 3 weeks | Flight feathers growing, nearly adult size |
| 4 weeks | Fully feathered and ready to fledge |
| 4-5 weeks | Leave nest and fly independently |
So in total, barn swallow chicks remain in the nest for approximately 3-4 weeks from the time they hatch until they are ready to fledge.
Factors Affecting Nest Duration
While 3-4 weeks is typical, the exact duration in the nest can vary slightly. Some factors that influence growth rate and fledging age include:
- Brood size – Chicks in larger broods may fledge sooner due to more competition for food.
- Weather – Cold temperatures or rain can slow development.
- Food availability – Abundant food enables faster growth.
- Health – Sick/weak chicks may take longer to fledge.
- Predators – Risks prompt early fledging.
As a general rule though, barn swallow parents will not push chicks out of the nest until they have gained enough flight proficiency to survive. So even with variances, the nesting period is usually 18-23 days.
Fledgling Care and Independence
Once they leave the nest, barn swallow fledglings still depend on their parents for 2-3 more weeks. The parents continue bringing food and leading them to good foraging spots. The young birds follow their parents closely, begging for food.
During this period the fledglings improve their flight skills and learn to hunt insects on the wing. They also join small flocks of other young swallows for safety in numbers. Barn swallows are highly social and juveniles benefit from mixing with others their age.
Within a month of fledging the young birds feed and fly skillfully. They become fully independent and go their separate ways to join large migratory flocks heading south in the fall.
Conclusion
Barn swallow chicks are born helpless but grow rapidly under their parents’ attentive care. After hatching, they remain in the nest for about 18-23 days, developing feathers and flight ability. Once fledged, they are independent within 3-4 weeks.
Understanding the nesting habits and development timeline of barn swallows provides insight into their breeding biology. This small migratory songbird leads an action-packed life in the few short weeks between hatching and fledging!
