Bewick’s wrens (Thryomanes bewickii) are small songbirds found in western North America. They build intricate nests incavities to raise their young. Here is an overview of where Bewick’s wrens nest and their nesting habits.
Natural Nesting Locations
Bewick’s wrens nest in naturally occurring cavities and crevices. Some of their preferred natural nest sites include:
- Tree holes – Abandoned woodpecker holes are a prime nesting spot for Bewick’s wrens. They seek out holes in dead trees or dead limbs of live trees.
- Rock crevices – Cavities and cracks in rocky cliffs, outcroppings, and boulder fields provide nesting sites.
- Brush piles – The spaces within piles of brush and branches create cavities for nests.
- Cornices – They will nest inside openings under the eaves and cornices of buildings and sheds.
- Nest boxes – Bewick’s wrens may occupy nest boxes intended for other cavity nesting birds like chickadees.
The availability of natural cavities limits the population size in many areas. Bewick’s wrens compete with other secondary cavity nesting birds for these scarce nest sites.
Nest Construction
The male Bewick’s wren builds multiple nests, up to a dozen, in his breeding territory. The female then selects the nest she prefers in which to lay eggs. Nest building takes 10-12 days on average.
Bewick’s wren nests are ellipsoid in shape with a side entrance hole. They construct nests out of a variety of natural materials including:
- Twigs
- Bark strips
- Grass
- Feathers
- Spider egg sacs
- Plant down
- Tree resin
The nest cup is lined with finer soft materials like fur, fine grass, and feathers. The male weaves these materials into a thick, durable nest. The entrance hole is barely large enough for the adult to pass through.
Nesting Materials Table
| Nest Structural Materials | Nest Lining Materials |
|---|---|
| Twigs | Fur |
| Bark | Fine grass |
| Grass | Feathers |
| Feathers | |
| Spider egg sacs | |
| Plant down | |
| Tree resin |
Nest Sites by Region
The specific nest sites used by Bewick’s wrens vary across their range. Here are some details on nesting habits in different regions:
Southwestern United States
In the arid Southwest, Bewick’s wrens are found in riparian woodlands along streams and rivers. They nest in natural tree cavities along the waterways. Nest boxes may be used where natural sites are limited.
California
California wren populations nest in oak woodlands. They nest in cavities of oak trees and attics and crevices of rural buildings. Nest boxes are readily used where available.
Pacific Northwest
In the Pacific Northwest, Bewick’s wrens breed mainly in coniferous forests. They nest in holes in dead snags and stumps of trees. They may also use nest boxes, particularly those made of weathered wood to mimic snags.
Midwestern United States
Midwest wrens nest in a variety of woodland edges, hedgerows, and suburban parks. Natural cavities in dead limbs and tree holes are used. They also nest in crevices of human-made structures like nest boxes, fence posts, and buildings.
Nesting Season
Bewick’s wrens can raise multiple broods per breeding season. Their nesting period varies across the range:
- Southwest: late March to early August
- California: early March to mid-July
- Pacific Northwest: May to July
- Midwest: late April to late July
They often re-nest following a failed nest attempt. The male continues building replacement nests through the season to allow for re-nesting.
Clutch Size
The typical Bewick’s wren clutch is 5-6 eggs. The female incubates the eggs for about 14 days. Both parents feed the nestlings. The young fledge the nest at 14-16 days old.
Here is the typical Bewick’s wren clutch and nesting timeline:
| Clutch Size | 5-6 eggs |
| Incubation Period | 14 days |
| Nestling Period | 14-16 days |
Parental Care
Bewick’s wrens are dedicated parents and work together to raise their young. The male feeds the female while she incubates. The parents both bring food to the nestlings frequently, up to 35 times per hour. Nest sanitation is important and the parents remove fecal sacs to keep the nest clean.
Both parents remain involved in feeding the fledglings. The young stay with the parents for up to four weeks after leaving the nest while they learn to forage independently.
Threats to Nests
Bewick’s wren nest success averages around 50%. Here are some top threats that lead to nest failures:
- Predators – Snakes, squirrels, and chipmunks may invade the nest cavity and prey on eggs or young.
- Weather – Cold snaps or heavy rain can lead to starvation or loss of nestlings.
- Nest parasites – Blow flies and mites sometimes infest nests.
- Tree trimming – Removal of nest site trees and snags causes nest loss.
- Habitat loss – Logging, development, and conversion reduce nesting locations.
Ensuring adequate undisturbed nesting habitat is key to Bewick’s wren conservation. Monitoring and actively managing nest sites in an area can help improve productivity and allow populations to thrive.
Conclusion
Bewick’s wrens are highly adaptable, using a wide variety of natural and man-made cavities across their range for nesting. Their small size and love of cover allows them to take advantage of small crevices in trees, rocks, brush piles, and human structures. Maintaining habitat with available nesting locations is important for the reproductive success of these busy little cavity nesters.
