Connecting with Nature: Eastern Bluebird (Sialia sialis)


Eastern bluebirds are permanent residents of Florida. They have beautiful blue plumage that extends from head to tail, with rust-colored feathers on the chest. Males are a deep, chalky blue and more vibrant during mating season, while females have a faded bluish/gray coloration. Eastern bluebirds are known as secondary cavity nesters, meaning they seek out previous nesting sites dug by primary cavity-nesting birds, such as woodpeckers. Nesting cavities can be in live trees, snags (dead standing trees), or fence posts.

From the 1920s to the 1970s, their population began to decline. There was a lack of nesting sites due to territorial competition with other secondary cavity nesters like Carolina Chickadees, House Wrens and some owl species. But that’s not all that played a role in the decline. The reduction of their natural habitat and habitat fragmentation were also important factors. Habitat fragmentation is the breaking up of a largely undisturbed area of ​​habitat into smaller, isolated patches.

Besides the reduction in natural habitat, other factors contributing to the decline of the eastern bluebird population were the loss of snags as nesting sites and the increase in predators, such as cowbirds, snakes and raccoons. Additionally, they have faced aggressive competitors in other bird species such as house sparrows and starlings. Both of these bird species have been documented killing eastern bluebirds, adults and young, in order to claim their nesting site.

In June of last year, the behavior of a male Eastern Bluebird caught my attention. He was checking the snag in our garden. This snag has previous nesting cavities and we had never noticed any birds occupying them.

Male eastern bluebirds need to find a suitable home for the female to raise their young, and we have seen this happen in our backyard. The male checked the pre-excavated cavity, flew away, came back to perch on the neighboring branch. It was singing and flapping its wings. When the female appears, she checks the nest site. If she accepts, she will start bringing nesting material. Unfortunately, a Carolina Chickadee took an interest in this particular nesting site. But eventually, a pair of downy woodpeckers moved in and raised two healthy chicks.

Quick nature notes about Eastern Bluebirds:
The eastern bluebird is a member of the thrush family
They only weigh about an ounce – the weight of an AA battery or dime
They are sexually dimorphic, meaning the male and female look different
They prefer open grassy areas
The female will build a cup-shaped nest constructed with pine needles, twigs, and grass. She will also add animal hair and feathers.
Their nesting begins in mid-February (for Florida) and mid-September in the northern states.
Bluebirds are territorial when nesting and will re-nest two to three times a year
Females lay between three and five beautiful blue colored eggs, although there has been documentation of white eggs
Chicks hatch within a week and fledge (leave the nest) within twenty days
The main diet of bluebirds consists of fruits and insects
They can spot an insect from around 50 feet away, which is why they are classified as sit-and-wait predators.

Bluebirds may rarely visit bird feeders. Providing native Florida plants that produce berries would be beneficial and limit the use of pesticides because, after all, eastern bluebirds and other birds need insects to survive and feed their young.

When the bluebird population was in decline, conservation pioneers got to work trying to preserve the species. In the 1970s, Wisconsin residents began building artificial nesting sites called bluebird-boxes, to replace the loss of natural nesting sites. Their action created a new bluebird box building movement across the United States. Their efforts and commitment helped raise awareness of the plight of this avian species and the Eastern Bluebird population began to recover.

February is when bluebirds search for nesting sites and providing a nesting site on your property can help your neighboring eastern bluebirds. You can build a bluebird-box or place a pre-built one on your property. But before you do, a few things to consider are location and engagement.

Location is extremely important. The eastern bluebird needs mowed open spaces and no or limited feeders for successful nesting. It is recommended that nest box placement be more than 50 feet from any brushy or wooded areas. If you decide to place more than one, the distance between the two must be 330 feet.

There are a few models of nesting boxes suitable for bluebirds. Here is a link to a website for those who want to build their bluebird box: or buy a prefab from one nature/wildlife bird Supply store.

Having a birdhouse also comes with a great commitment and responsibility for cleaning. After the bluebird chicks have all fledged, it is recommended to clean the nest box. Cleaning involves removing all nesting materials, and this should be reasonably accessible since the height placement of the bluebird box is usually at eye level.

While the nest is in use, enjoy the view from afar!

An example of a store-bought Bluebird box. Photo by Alice Mary Herden.


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