Western bluebirds are a beautiful species of thrush native to western North America. With their brilliant blue plumage and soft warbling songs, these birds have captivated people for centuries. Many bird enthusiasts enjoy attracting Western bluebirds to their yards by installing specialized nest boxes called “bluebird houses.” But do Western bluebirds actually use these man-made abodes?
The Nesting Requirements of Western Bluebirds
To understand if Western bluebirds use birdhouses, we first need to look at their natural nesting requirements. Western bluebirds are secondary cavity nesters, meaning they do not excavate their own nesting cavities in trees or snags. Instead, they rely on existing holes created by woodpeckers and natural decay. Western bluebirds typically choose cavities in dead trees or limb stubs located 5-15 feet above ground. They favor cavities with entrance holes 1.5-2 inches in diameter and depths of 8-10 inches. The cavity needs to be big enough to accommodate the bluebird’s nest made of grasses and pine needles, but not so big that predators can easily enter.
In their natural habitat, suitable nesting sites are often limited. Development, logging, and modern forest management practices have drastically reduced the number of snags and dead trees available. Competition from other secondary cavity nesters like tree swallows, house wrens, and European starlings make finding a nest site even more difficult. Providing nest boxes specifically designed for Western bluebirds can help offset the loss of natural cavities.
Bluebird House Design Features
For Western bluebirds to accept an artificial cavity, the birdhouse must closely mimic their natural nesting requirements. Here are some key design features of bluebird houses:
- Entrance hole 1.5-1.9 inches in diameter to exclude larger competitors
- Internal cavity at least 8 inches deep and 4×4 inches wide
- Ventilation and drainage holes near base of box
- No perch or ledge for predators to access
- Roughened interior wooden surface for chicks to cling to
- Placement 5-10 feet above ground in open area
By providing the right specs, you can encourage Western bluebirds to take up residence while discouraging use by invasive species like house sparrows and European starlings.
Western Bluebird Use of Nest Boxes
When properly constructed and sited, research shows that Western bluebirds readily accept nest boxes. One study in Idaho monitored over 600 nest boxes specifically designed for bluebirds over a 5 year period. They found that over 95% of the boxes were occupied by Western bluebirds at least once over the course of the study.
Another five year study in Montana monitored 166 nest boxes put up across 60 square miles of habitat. Western bluebirds used the boxes 67% of the time, while tree swallows and house wrens used 19% and 14% of the boxes respectively. Over the course of the study, the average number of bluebird chicks fledged per nest was 5.37.
By comparing the population growth at sites with nest boxes to those without, researchers confirmed that the nest box program significantly improved the breeding success and population growth of Western bluebirds in the area. The key was proper placement and box design.
Tips for Attracting Bluebirds
Here are some tips to follow when putting up birdhouses for Western bluebirds:
- Place boxes in open grassland or meadow habitat, spaced at least 100 yards apart.
- Use boxes with 1.5 inch diameter entrance holes and avoid any perches or ledges.
- Mount boxes 5-10 feet high on fence posts, poles, or trees facing away from prevailing winds and direct sun.
- Add predator guards to stop cats, raccoons, and snakes from raiding nests.
- Clean out old nesting material in fall to make ready for spring.
- Discourage house sparrows from stealing boxes through control methods.
With attention to proper design and placement, you can have a good chance of Western bluebirds adopting your nest boxes. Monitoring your boxes during nesting season will let you observe their fascinating nesting behaviors.
When Do Western Bluebirds Nest?
Western bluebirds can have two broods per year across most of their range. The first brood is initiated between mid-March and early June depending on latitude and weather conditions. In the southwestern parts of their range, they may nest as early as late January. The second brood starts anytime from May through August.
Here is a typical Western bluebird nesting timeline throughout the breeding season:
- Mid-March to Mid-April – Females begin visiting potential nest sites while males sing and guard territory.
- Mid-April to Mid-May – Nest building and egg laying occurs. Clutch size ranges from 3-8 pale blue eggs.
- Mid-May to Mid-June – Incubation lasts 12-14 days. Nestlings fledge at around 18 days old.
- June to August – Second broods initiated, following a similar timeline.
- August to October – Juveniles from last brood disperse from parents’ territory.
Having suitable nest boxes available just before breeding activity begins in spring is key to attracting bluebirds. Be sure to monitor boxes closely during peak activity periods.
Typical Contents of Bluebird Nest Boxes
When examining the contents of a bluebird nest box, here are some key things you may find:
- Nest: Built by female with grasses, pine needles, stems, feathers. Cup shape with deep central cavity.
- Eggs: 4-8 very pale blue, unmarked eggs. Laid one per day.
- Nestlings: Naked and helpless at hatching. Pin feathers emerge around 5 days. Eyes open at 7 days.
- Fecal sacs: White membrane packages of chick waste removed by parents.
- Chicks: Fully feathered and ready to fledge around 18 days after hatching.
Finding eggs, chicks, or fecal sacs are clear signs bluebirds have claimed your nest box. Never disturb contents unless monitoring indicates intervention is absolutely necessary.
Threats Facing Nesting Western Bluebirds
Even if you are able to attract bluebirds to your nest boxes, their breeding success is not guaranteed. Here are some common threats to look out for:
- House sparrows & starlings: Invasive species will kill bluebirds and take over nest sites.
- Predators: Cats, raccoons, snakes, and jays prey on eggs and chicks.
- Weather: Cold snaps or heavy rain can kill nestlings. Provide shelter.
- Parasitism: Blowflies and mites can infest nests and harm chicks.
- Competition: Native tree swallows may compete for limited boxes.
With proper monitoring and management, you can identify threats early and take action to improve nesting success. Discouraging invasive species, adding baffles and guards against predators, and controlling parasites are key.
Benefits of Bluebirds Using Birdhouses
Encouraging bluebird pairs to raise their chicks in your yard has many benefits beyond just enjoying their beauty up close. Here are some of the top advantages of Western bluebirds using birdhouses:
- Helps preserve a native species struggling with habitat loss.
- Controls insects like grasshoppers and crickets in your yard.
- Bluebirds are voracious predators of harmful spiders.
- Their songs and activity add joy to your yard.
- You directly aid in the species’ reproduction and expansion.
- Can observe fascinating nesting behaviors through the box.
- Admire gorgeous iridescent plumage of adults and chicks.
With birdhouses, you are not only helping wild bluebirds, but also creating an opportunity to closely connect with nature right outside your window.
Fascinating Facts About Nesting Western Bluebirds
Here are some fascinating tidbits of information about Western bluebirds creating their nests and raising young in birdhouses:
- Female builds nest alone while male guards territory, taking 4-10 days to complete.
- Nest is cup-shaped with deep central cavity made cozy with grasses and feathers.
- Lays one light blue egg per day, early morning. Clutch is 3-8 eggs.
- Incubates eggs for 14 days before hatching. Male feeds female on nest.
- Nestlings quadruple their hatching weight in just 6 days!
- Chicks fledge around day 18, may return to nest to roost for 2-3 days.
- Parents remove and discard fecal sacs from nest up to 20 times per hour!
- Juveniles start flying well at 22-27 days old.
Observing bluebirds raise a brood in your own backyard lets you witness all this fascinating behavior up close. Truly an amazing learning experience about nature and birds!
Conclusion
In conclusion, Western bluebirds readily accept and thrive in properly constructed and placed nest boxes. Providing suitable cavities helps this species offset habitat losses and gives you the joy of observing their breeding behaviors right outside your door. With some vigilance against common nest threats, you can significantly aid Western bluebirds by simply making birdhouses available. There are few more rewarding ways to help wildlife than by facilitating the successful fledging of bluebird chicks from your own nest boxes.
