Eastern Bluebirds are not currently considered rare. Their population has significantly recovered from historical lows, presenting a notable conservation success story. These colorful thrushes are now widespread across their range in eastern North America, reflecting the positive outcomes of sustained conservation efforts.
From Scarce to Resurgent: The Bluebird’s Comeback Story
Eastern Bluebirds experienced a drastic population decline between the late 19th and mid-20th centuries, with numbers plummeting by nearly 90%. This downturn was caused by extensive habitat loss, as changing land management practices removed dead trees and old orchards bluebirds relied on for nesting cavities.
Widespread use of pesticides also negatively impacted bluebird populations by affecting their food supply and reproductive success. However, the most significant challenge came from non-native, aggressive cavity-nesting species like European Starlings and House Sparrows. These introduced birds outcompeted bluebirds for limited nesting sites, often destroying nests and killing young.
In response to this crisis, a dedicated conservation movement emerged in the 1960s and 1970s. The formation of the North American Bluebird Society (NABS) in 1978 was pivotal, galvanizing citizen scientists and birders. Key to the bluebird’s recovery was the widespread establishment of “bluebird trails,” networks of species-specific nest boxes.
These nest boxes were designed with entrance holes too small for larger, competing species like European Starlings, providing safe nesting opportunities. Public awareness and involvement grew, leading to the installation and monitoring of thousands of these nest boxes, reducing competition for nesting sites. The bluebird’s rebound exemplifies how focused human intervention can lead to successful species recovery.
Where Bluebirds Thrive Today
Today, Eastern Bluebird populations are stable or increasing in many areas, with an estimated global breeding population of 23 million. This positive trend indicates they are a species of low conservation concern. Males exhibit a brilliant royal blue on their back and head, with a rusty or red-brown throat and chest, and a white belly.
Females are duller in color, displaying a more grayish-blue back and a paler orange-brown breast. Eastern Bluebirds thrive in open country with scattered trees, preferring environments such as pastures, orchards, agricultural fields, suburban areas with open lawns, forest clearings, roadsides, and golf courses.
Their diet primarily consists of insects, including crickets, grasshoppers, beetles, and spiders. During colder months, when insects are scarce, their diet shifts to various berries.
Helping Bluebirds Continue to Flourish
Continued public involvement remains important for the Eastern Bluebird’s ongoing success. A practical way to support them is by installing and maintaining species-specific nest boxes. These boxes should have a 1.5-inch diameter entrance hole, which is large enough for bluebirds but too small for European Starlings.
The interior floor space of the nest box should be approximately 4×4 or 5×5 inches, with the entrance hole positioned 5 to 6 inches above the floor. Nest boxes benefit from proper ventilation and drainage holes, and should not include a perch, as bluebirds do not require one and perches can assist predators. Mounting boxes on a smooth pole, about 5 to 6 feet high, with a predator guard helps deter climbing animals like snakes and raccoons.
Planting native berry-producing shrubs and trees also provides a valuable food source when insects are less available. Suitable options include:
- Winterberry
- Serviceberry
- Nannyberry
- Pagoda dogwood
- Sumac
- Elderberry
- Northern bayberry
- Eastern red cedar
Reducing or eliminating pesticide use in gardens and yards is another beneficial action. Pesticides can directly harm bluebirds or reduce their insect food supply, impacting their health and reproductive success. Providing a clean water source, such as a shallow bird bath or a recirculating stream, offers bluebirds a place to drink and bathe.