Bluebirds and Company: What’s Chirping at the Smithsonian Gardens’ Greenhouses

The summer season brings new life to the Smithsonian Gardens’ greenhouses. As you might expect, much of this new life is the result of staff work to produce plants for our gardens. However, there are also a surprising number of winged, chirping occupants on the greenhouse property this season. As a part of the Bluebird NestWatch effort organized by the Cornell Lab of Ornithology, Smithsonian Gardens has set up ten specially-designed bluebird houses around the greenhouse property. The greenhouse staff visits each birdhouse weekly and unscrews a side wall to make notes of the visitors and nest progress. Often times they find other species of birds occupying the houses, so it’s really a fantastic glimpse at a variety of bird life. During the past several weeks of collecting data, we’ve seen Bluebirds, Wrens, Tree Swallows, and Robins making their nests in these houses.

Greenhouse staff member accessing bird house

We also regularly see ground-nesting Killdeer around the greenhouse. Preferring ground mobility to flight, these birds are fast runners from an early age. This makes them difficult to approach especially as they are easily spooked. Though not one of our birdhouse residents, the Killdeer nest quickly became a weekly checkpoint for our observation tours and we were able to see four chicks this year.

It’s easy to imagine that the parents of these chicks were not particularly pleased with our weekly interruptions. As a result, we rapidly learned each bird’s defense strategy. Bluebirds are often shy creatures and the parents would fly to a vantage point to watch us with a keen eye while we conducted our research. Tree Swallows, on the other hand, are a little more aggressive and would dive-bomb us to get us to leave their nest alone. Adult Robins and Wrens would often just flee the coop entirely and wait for a quiet time to revisit their brood.

Bluebird fledgling

Wren chicks

Killdeer, on the other hand, have developed a pretty impressive show to protect their young which uses camouflage, predator calls, and distraction performances. Killdeer often hang out near our gravel walks or driveways where, as seen in the picture below, their neutral colored feathers help them blend into the background. Under the cover of camouflage, the adults would use alarm calls to attract attention to themselves and away from their babies when we approached the nest. When that failed, the adults would lay down and stretch out their wings like they had been injured to make themselves appear an appealing victim to the perceived predator. Once the threat (in this case the greenhouse staff) was fooled by the adult Killdeer’s show and moved to approach, the adult would wait for the the chicks to be safely out of reach before miraculously “recovering” and flying away to safety. There’s nothing more humbling than being duped by the oldest trick in the book.

An alert Killdeer adult

All in all, it’s been a terrific and refreshing few weeks for the greenhouse staff to get outside and witness the beauty of avian life. During this project we’ve not only seen countless chicks and eggs, we’ve also seen the these young birds develop from day-old hatchings into fledglings ready to fly. Despite being attacked by adults aggressively protecting their young and mocked by flawless Killdeer performances, it’s been a pleasure seeing the diversity of bird life out at the Smithsonian Gardens greenhouses.

– Alan Marcus, Smithsonian Gardens Intern

Newly hatched Robin chicks

Update on the Eastern Bluebird Trail

The green roof Eastern bluebird nesting boxes before installation on the trail.

In 2012, the Smithsonian Gardens Green Team developed an Eastern Bluebird Trail at our greenhouse complex in Suitland, Maryland. The trail of ten paired nest boxes was designed to support and expand the year-round resident Eastern Bluebird population. By the end of the 2013 nest season, the bluebird population had expanded to about thirty birds.

What happened in 2014? We began monitoring the trail in March, looking for the first signs of nesting behavior. The monitoring continued through July and in that time, no Eastern Bluebirds have been seen at or around the greenhouse complex. We believe the resident population migrated to another location due to a harsh winter of repeated deep Arctic cold blasts starting in late November and persisting through March. In addition to the cold, we believe the bluebirds did not have enough food to support their population.

American beautyberry (Callicarpa americana, top) and flowering dogwood (Cornus florida, bottom) are bluebird favorites!

Bluebirds rely on fruit for more than thirty percent of their diet. In the winter, when insects are scarce, they depend on persistent fruits more than at any other time of year. The SG Green Team is committed to planting more native tree and shrub species around the facility to provide a sustainable winter habitat for the birds. Planting trees and shrubs not only provides food for birds but also provides shelter from harsh winds and cold temperatures.

-Sarah Hedean, SG Green Team Member

Smithsonian Gardens Greenhouses Welcome Bluebirds

The installed nesting boxes on the Eastern Bluebird Habitat Trail.

Working in collaboration with Richard E. Gies, lead volunteer of the Longwood Gardens Bluebird Project, Smithsonian Gardens established an Eastern Bluebird Habitat trail around the perimeter of the Greenhouse facility in Suitland MD.

Eastern Bluebird. Photo Courtesy of U.S. Fish and Wildlife Service. Dave Menke, photographer.

Why Bluebirds?

A native songbird, the Eastern Bluebird (Sialia sialis) is a member of the thrush family (Turdidae). They eat insects and berries and require open grassy areas and meadows with low groundcover for feeding. These beautiful birds breed in all eastern states from Maine to Florida. They are considered to be secondary cavity nesters in that they traditionally nest in holes made by woodpeckers and other birds.

The nesting boxes were installed to benefit an existing population of Bluebirds as well as to encourage more bluebirds to nest on site. Eastern Bluebird populations are on the rise thanks, in part, to efforts like this one. The lack of suitable nesting cavities caused by changing land use patterns, increasing urbanization, and competition from introduced European starlings and house sparrows has been responsible for the decline of Eastern Bluebirds populations in the past.

Tree Swallow. Image courtesy of the U.S. Fish and Wildlife Service. James C. Leupold, photographer.

When is a pair of nesting boxes better than one?

In areas where Eastern Bluebirds coexist with Tree Swallows (like Maryland) it is recommended that two boxes be placed 15-20 feet apart. Tree swallows will select one box for nesting and defend the other against use by other swallows thereby allowing Bluebirds to claim it.

Green roof nesting boxes waiting to be installed at the Smithsonian Gardens greenhouses in Suitland, Maryland earlier this winter.

A Green Roof: for style and comfort.

The roofs on these nesting boxes have been planted with a variety of stonecrop (sedum) plants. The purpose of the “green roof” is to help keep the interior of the boxes cool during the hot summer months.

The temperature inside these nesting boxes will be monitored in an effort to ensure the safety of the fledglings (baby birds).

The green roof nesting boxes were designed Richard Gies for Longwood Gardens. You can download a PDF of his instructions here:

Green Roof Eastern Bluebird nesting boxes