This is the time of year to keep an eye out for bird nests that were hidden by leaves all summer. Their location can reveal more than one might guess. As with many bird species, the female Northern Cardinal does most of the nest-building herself, usually selecting a site that is in dense shrubbery, often in a tangle of vines. Frequently there are two broods, but rarely is a nest reused. Instead, a new nest is built for the second clutch of eggs, and it can intentionally be located quite close to the first nest.
The two pictured Cardinal nests were both built this year, only four feet apart in a grape vine-covered stand of Staghorn Sumac. Two different birds would not have nested so close to each other due to territoriality; thus, the same bird most likely built both nests. Ornithologists feel that the presence of old nests may function as protection against predation. They found that when they placed an empty Cardinal nest adjacent to a Cardinal nest containing plastic eggs, there was significantly less predation than with single Cardinal nests. (Thanks to Jody Crosby for photo opportunity.)
(NB: Even though most songbirds only use their nest once and then abandon it, one needs a federal permit to collect bird nests.)
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.