We have been studying birds as part of our nature study in the past few weeks. In particular, we have been focusing on the Bluebird. Bluebirds are secondary cavity nesters meaning that they can not build their own nests. Instead they find homes that woodpeckers (primary cavity nesters) or humans leave behind for them. Bluebirds are part of the Sialia genus of the thrush family. Gardeners love Bluebirds because they are primarily insectivores (insect eaters) and dine on garden pests.
The trouble is that many other birds will also reside inside of a Bluebird house, so it is important to be able to identify birds by their nests. Some other birds that can make their home in a Bluebird house are House Wren, Tree Swallow, Carolina Chickadee, or House Sparrow. For the Bluebird enthusiast, there is only one type of bird that really poses a threat and that is the House Sparrow. The House Sparrow is not native to the US and is very aggressive. The House Sparrow can and will kill a Bluebird. The House Sparrow has been partially blamed for declining Bluebird numbers along with humans destroying their habitat.
To help Little BBQ learn about potential birds that can make their home in small cavities we decided to do a hands on project where a built sample nests from secondary cavity nesters. Each type of bird has an unique nest. We built out nests in foam cups with one side cut open so you can see inside the "cavity."
Eastern Bluebird Nest
One or both types of materials maybe used depending upon availability. The nests do not fill up the entire cavity, so there is plenty of head space in this cavity.
finer plant material (we used crumbled leaves)
feathers (we used paper feathers since we could not find any real ones outside)
The bulk of the nest is composed of twigs with some feather and finer plant material lining the inside of the nest as well. The cavity is usually filled to the top.
feathers (we used paper feathers)
The bulk of the nest is made out of grass with feathers lining the top. The nest has lots of head space and does not fill up the entire cavity.
very fine plant fibers (we used crumbled leaves)
A Carolina Chickadee is flexible about what type of material the bird is willing to use to build its nest. We used animal hair, dryer lint, and crumbled leaves for our nest since we could not find any moss in the backyard. A Carolina Chickadee builds small soft nests that are meticulously built. A Carolina Chickadee is most likely to settle in a Bluebird house.
The House Sparrow will fill their cavity to the brim with a wide assortment of found materials.
"House Sparrow Kills Eastern Bluebirds" Journal of Field Ornithology. Summer 1984. pp 378-380.
North American Bluebird Society Educational Packet: information on nests found on pages 18-19
All "nests" were taken by me
Bluebird Photo: Ken Thomas released to public domain
House Wren Photo: Calibas released under GNU Free Documentation License
Tree Swallow Photo: John Benson released under Creative Commons
Carolina Chickadee Photo: Dan Pancamo under Creative Commons
House Sparrow Photo: Photo by DAVID ILIFF. License: CC-BY-SA 3.0