Carolina chickadees are not able to successfully raise enough young to maintain their population numbers in areas where less than 70% of the plants are native species, according to new research from the University of Delaware. The study was conducted in backyards throughout Washington, D.C.
The research looked at the relationship between Carolina chickadee nesting success, percentage of native vs non-native plants within the chickadee’s home range, and the abundance of spiders and caterpillars. Carolina chickadees were chosen for the study because they are common backyard visitors throughout much of the eastern U.S. They are also primarily insectivorous birds, especially during the nesting season.
The researchers found that as the percentage of nonnative plants within a 164 foot radius (average size of a chickadee’s home range) of the nest box increased,
- the number of spiders and caterpillars declined,
- more spiders than caterpillars were consumed by the nestlings, and
- the number of baby Chickadees that survived for 21 days (when they typically become independent of their parents) declined.
In areas where 70% or more of the plants were native, chickadees thrived and the parents were able to raise enough young each year to sustain or grow the population. In areas where less than 70% of the plants were native, the parents weren’t able to raise enough young to sustain the population. The researchers attributed this finding to the decline of preferred prey (caterpillars).
Many species of insects have specialized diets and only eat plants in one genus or family. This is especially true when it comes to caterpillars. The monarch caterpillar is probably the most familiar example of a caterpillar with a highly specialized diet, but they aren’t the only species with a specialized diet.
Unfortunately, many of the non-native plants popular for landscaping aren’t closely related to our native plant species and aren’t used by our caterpillars and other native insects. Therefore, it makes sense that as the number of non-native plants increases, that there would be less food available for our caterpillars to eat. Less food for the caterpillars means fewer caterpillars. Fewer caterpillars means less food for the songbirds and other animals that eat the caterpillars. Less food for songbirds and other animals means fewer of those animals.
Although this study just looked at Carolina chickadees, it is likely that the general findings are applicable to many of our other insectivorous songbirds. Therefore, if you are interested in providing a healthy habitat for the songbirds in your yard, try to have at least 70% of the plants in your yard be native to your area.
This article was part of Shannon’s original Kentucky Pollinators and Backyard Wildlife blog which evolved into the blog for Backyard Ecology.
Backyard Ecology: Exploring Nature in Your Backyard
Nature isn’t just “out there.” It’s all around us, including right outside our doors. Hi, my name is Shannon Trimboli, and I am the host of Backyard Ecology. I live in southcentral Kentucky and am a wildlife biologist, educator, author, beekeeper, and owner of a nursery specializing in plants for pollinators and wildlife conservation. I invite you to join me as we ignite our curiosity and natural wonder, explore our yards and communities, and improve our local pollinator and wildlife habitat. Learn more or subscribe to my email list at www.backyardecology.net.