Bewick’s Wrens (Thryomanes bewickii) are small, inquisitive songbirds found across much of North America. These active birds have loud, melodious songs and readily use nest boxes, making them popular with bird enthusiasts. But do Bewick’s Wrens actually utilize nest boxes? Here we’ll examine the key questions around Bewick’s Wrens and nest boxes:
Do Bewick’s Wrens use bird houses?
Yes, Bewick’s Wrens will readily use nest boxes for breeding. These cavity nesters naturally nest in cavities in trees, rock crevices, old woodpecker holes, and other natural cavities. However, they have adapted well to using artificial nest boxes provided for them.
What kind of birdhouse do Bewick’s Wrens prefer?
Bewick’s Wrens have relatively small entrances to their nest cavities, preferring a 1-1.5 inch diameter entrance hole. The nest box should be made of untreated wood and have a volume around 3 liters. The ideal nest box has a removable front panel for easy monitoring and cleaning. Placement is also important, with boxes placed 5-10 feet high on a tree trunk, pole or building.
When do Bewick’s Wrens start using nest boxes?
Bewick’s Wrens will start seeking out nesting sites in early spring. Having nest boxes up by late February – March will allow pairs to find them and start building their nests. The female builds an enclosed, domed nest out of twigs, grasses, feathers and other materials.
How many broods do they have?
Bewick’s Wrens are prolific, having 2-3 broods per breeding season from late March through July. Each brood may have 5-8 eggs that incubate for 12-15 days. So each pair can fledge 15 or more young from one nest box in a season.
Nesting Habits
Now that we’ve covered some key questions, let’s dive deeper into the nesting habits of Bewick’s Wrens and how they utilize nest boxes:
Nest Construction
The female Bewick’s Wren does most of the nest construction work. She builds an enclosed, domed nest with a side entrance hole. The nest is composed of twigs, grasses, feathers, moss, leaves, fur, paper, and other materials she can find. The nests fill up the internal cavity, with a cup shape made inside with softer materials. Nest building takes 2-4 weeks.
Eggs
Once the nest is built, the female lays a clutch of 5-8 tiny white eggs, often with reddish-brown spotting. The eggs measure about 0.6 x 0.5 inches. She lays one egg per day until the clutch is complete.
Incubation
The female incubates the eggs for 12-15 days until they hatch. She brooding them almost continuously, leaving only for short periods to forage. The male may occasionally deliver food to the female while she incubates.
Nestlings
Both parents feed the nestlings as they grow over a period of 14-17 days. The young birds leave the nest at this fledgling stage, but may still be fed by the parents for several more weeks as they become independent.
Number of Broods
Bewick’s Wrens commonly raise 2-3 broods per breeding season. They may reuse the same nest, or build a new one nearby or in another nest box. Each brood may have up to 8 young, so each pair can fledge 15+ birds in one season.
Ideal Nest Box Design
To best attract nesting Bewick’s Wrens, nest boxes should follow these guidelines:
Entrance Hole
– 1-1.5 inches diameter
– Circular or oval shape
– No perch needed
Box Size
– 3-4 inches deep
– 4×4 to 6×6 inch floor
– Volume around 2.5-3 liters
Construction
– Made of untreated wood
– Removable side or front panel for monitoring/cleaning
– Drainage holes in bottom
Placement
– 5-10 feet high
– On tree trunk, pole, or building
– Prefer open deciduous woods
Following these nest box dimensions and placement guidelines will create an attractive nesting site for Bewick’s Wrens.
Monitoring and Maintenance
To get the most out of your Bewick’s Wren nest boxes:
Annual Cleanup
– Clean out old nests after breeding season
– Remove any parasites or debris
– Make any repairs needed
Nest Checks
– Monitor weekly when active
– Record first eggs, clutch size, hatch date
– Avoid visiting too frequently
Predator Guards
– Attach predator guards if needed
– Metal collars can deter climbing predators
Data Collection
– Record nest successes and failures
– Band nestlings to track individuals
– Provide info on nesting biology
Proper monitoring and maintenance will allow the nest box to be safely reused for many seasons.
Benefits of Nest Boxes
Providing nest boxes for Bewick’s Wrens has many benefits:
Increased Nest Sites
Extra nesting sites are limited in many habitats, so nest boxes provide more opportunities for breeding pairs.
Native Cavity Nesters
Supporting native cavity nesters helps restore their populations as habitat is lost.
Insect Control
Bewick’s Wrens are voracious insect eaters, consuming pest insects and spiders around homes and gardens.
Enjoyment of Birds
Seeing wrens raise broods of charming, vocal nestlings in the boxes provides enjoyment.
Citizen Science
Nest box programs allow amateurs to contribute useful data on nesting and biology.
With a properly built and placed nest box, anyone can gain these benefits of hosting breeding Bewick’s Wrens.
Other Species Using the Boxes
While Bewick’s Wrens readily use nest boxes, other species may occupy them at times:
House Wrens
House Wrens are close relatives of Bewick’s Wrens and compete for nest sites. They will gladly use any vacant nest boxes.
Carolina Chickadees
Chickadees prefer smaller 1-1.25 inch entrance holes, but may still nest in Bewick’s Wren boxes on occasion.
Western Bluebirds
In the West, Western Bluebirds may take over boxes intended for Bewick’s Wrens.
Deer Mice
Mice often build nests inside boxes during winter for shelter and warmth.
Invasive Species
European Starlings and House Sparrows may occupy boxes meant for native birds.
With proper care and placement, desired species like Bewick’s Wrens will be the primary occupants of nest boxes. Exclude invasive species where possible.
Data From Nest Box Programs
Scientific nest box programs have provided useful data about Bewick’s Wren nesting biology and behavior:
Location | Clutch Size | Number of Broods | Fledglings/Brood |
---|---|---|---|
California | 6.1 | 2-3 | 4-6 |
Missouri | 5.5 | 2-3 | 4-7 |
Michigan | 6.4 | 2 | 5-6 |
Key findings:
– Average clutch size 5-6 eggs
– Typically 2-3 broods per season
– 4-7 fledglings per successful brood
Detailed long-term data helps us understand breeding biology and productivity.
Conclusion
In summary, Bewick’s Wrens are highly amenable to using nest boxes for breeding. With a properly designed and placed nest box, following their preferences for cavity dimensions, one can expect this active little songbird to readily take up residence. Boxes should be monitored and maintained to ensure successful nesting. Given appropriate habitat, providing nest boxes is an excellent way to support breeding populations of these native cavity nesters and gain enjoyment observing their nesting behaviors. Carefully collected data from nest box programs provides valuable information to help understand the biology of Bewick’s Wrens. So if you want charming songbirds nesting actively in your backyard, put up a nest box this spring and see if Bewick’s Wrens move in!