I recently received an email from a friend who told me about a Northern Cardinal building a nest in a bird seed feeder, a hanging platform feeder with a roof. Cardinals normally build their nests in shrubs, small trees or vine tangles, so this bird stepped outside the box of instinct to do something different. A normal cardinal nest would rely on vegetation to provide some overhead protection from the elements.
In my years of birding observations and research, the closest analogy of this “nest with a roof” concept is that I once observed a cardinal nest in a hanging basket on a porch. I have never heard of a cardinal using a bird house, such as wrens use for their nesting sites. Placing a nest in a bird feeder rather than in a shrub causes me to ponder the question – why? Did this cardinal figure out that this feeder offered better protection from the weather, or was the selection just a convenient selection? We will not ever know the answer, but it is interesting to consider potential factors in the bird’s decision making progress regarding self-protection.
Another email came from a friend showing photos of a Lark Sparrow’s nest hidden in a small hole in the ground in my friend’s back yard. Many birds build their nests in shallow holes in the ground, but in the case of the Lark Sparrow, and several other ground nesting sparrows, they also choose other types of nesting sites. The Lark Sparrow may choose to build its nest in shrubs and trees, as does the Northern Cardinal, or in a partial cavity in a rock crevice. What factors may have led to the Lark Sparrow’s adapting to a variety of nest sites?
I read that Lark Sparrows might build the first nest in the ground and then build a second nest in a shrub or tree. I can understand that the bird could likely hide its nest in ground cover, grasses and forbs, in the early spring growing season for plants. As the plants mature, or die from the heat because of lack of summer rains, less ground cover would be present for hiding the second nest site. Placing the second nest in a shrub would offer a safer and more secure site than ground with limited cover. Birds and mammals have adapted ways, such as having two nesting venues, to improve their chances of survival.
The chances of survival for birds and mammals increase greatly if they have the ability to adapt to changes in their environment. The Edwards Plateau once had more grasslands and savannah habitats before European settlement. Prairie Chickens, pronghorns (antelope) and bison lived here. As the grasslands and savannahs gave way to more woody plants, these birds and mammals were not able to adapt to the changes, and either moved to other areas with suitable habitat, or faced possible extinction, as do the Prairie Chickens now.
Having the ability to alter nesting sites or styles of nests may increase birds’ immediate chances to survive. Large scale changes in the natural world are subtle and require long periods of time to occur. I do not expect cardinals to change their nesting habits any time soon, but it is interesting to see a pair of cardinals do something different. In the case of Lark Sparrows, the selection of nesting venues evolved over eons of time so that they could adapt to subtle seasonal changes in ground cover.
Enjoying birding as an avocation is much more than learning the identities of hundreds of species; recognizing changes in their life styles, movements, behavioral habits and food consumption adds to the enjoyment of being a birder. Because changes in the environment are slow and subtle, we can only speculate as to what the long term effects will be on our feathered friends. If you see birds doing something unusual and you might not understand the process, send me an email and/or a photo and we can discuss facts or possibilities.