Building for Bluebirds

Warden Isett shared some bluebird basics with the Grier community.  Though technically omnivores, up to 80% of the bird’s diet is bug-based!  Smooth green caterpillars are the bird’s favorite meal followed by grasshoppers and spiders. How is that for pest-control? Bluebirds help out mother nature by dispersing seeds after they consume fruit. 

While the native bluebirds were once plentiful in the US, they have been declining as they struggle to complete with invasive species like starlings and house sparrows, face a loss of habitat to human construction projects, suffer poaching for their features, face increasing numbers of predators, harmful chemicals and pesticides, and climate change. 

Some bluebirds migrate from Pennsylvania to Mexico for the winter, while others remain in the keystone state year-round. Of those that migrate, the brightly colored males will return to Pennsylvania for the breeding season ahead of the females. After selecting a nesting site, the male will fluff his feathers and sing to attract his mate.  

As secondary cavity nesters, the birds inhabit hollows made by other creatures, like woodpeckers. The birds will build a clean nest for each of the two broods they hatch. Each next takes 2-6 days to construct. Females lay 3-7 blue eggs, one per day. All the eggs will hatch on the same day and the babies will be the same size as their parents in as little as two weeks!  While the duller colored females remain hidden to incubate the eggs on the nest, the males stand guard and collect food.  Once the babies have hatched, both parents work to deliver food to their babies. 

Once the first clutch has left the nest, the process will restart for a second round, including securing the location of a second nesting site to construct a fresh, clean nest. 

Along with predators like snakes, cats, and racoons, bluebirds contend with cowbirds. These absentee parents have a nasty habit of laying their eggs in other birds’ nests. The worst thing is when the baby cowbird hatches, they tend to kill their bluebird nestmates. 

By constructing birdhouses like the ones made by Grier students, people can help offset the loss of natural habitat. The nesting boxes should be placed 5’ from the ground and 100’ apart. Installing barriers for predators can be a good idea as well!  Other ways to help the bluebird population is by planting fruit trees, providing  meal worms at feeding stations, removing cowbird eggs from bluebird nests, and cleaning out the nest boxes between broods. 

Thank you to Warden Isett and the PA Game Commission for providing Grier students with this informative session and the satisfying activity of building a birdhouse!