Aim for 70% Native Plants

In 2018, graduate student Desirée L. Narango and Douglas W. Tallamy, professor in the Department of Entomology and Wildlife Ecology at the University of Delaware, collaborated on a study that indicates that when the proportion of native plants in an area reaches or exceeds 70%, there is a significant positive impact on bird populations.

Food Web Supported by Native Plants

The reason for this increase is mainly due to the food web supported by native plants. Native vegetation supports a greater diversity and abundance of insects than non-native plants. Since many bird species depend on insects as their main food source, particularly during the breeding season to feed their young, the availability of native plants has a direct impact on their reproductive success.

By maintaining or restoring native plant diversity above the 70% threshold in landscapes, particularly in suburban and urban areas, it is possible to create more favorable environments for local bird populations. This research highlights the importance of considering plant selection in landscaping and urban planning to support biodiversity and ecosystem health.

Carolina Chickadee

The study, focusing on the Carolina chickadee (Poecile carolinensis), describes the direct relationship between native plant abundance and the reproductive success of these birds. Narango and Tallamy found that breeding success of Carolina chickadees was significantly higher in areas where native plant biomass was greater than 70%. This success was measured by the number of fledglings produced per breeding attempt. Specifically, they observed a 20% increase in the number of fledglings, indicating a higher reproductive rate.

The research also highlighted the importance of caterpillars, which are more abundant in areas with native plants, as an essential food source for chickadee chicks. The availability of caterpillars is directly linked to the presence of native plants, influencing chick survival rates and overall reproductive success.

The article introduced a critical threshold, suggesting that landscapes with less than 70% native plant biomass are not sufficient to support self-sustaining populations of Carolina chickadees. This is due to the lower availability of caterpillars in these environments.

The results suggest that urban and peri-urban landscaping practices have a significant impact on local biodiversity. By increasing the proportion of native plants in these environments, it is possible to support not only chickadees, but also a wider range of insectivorous birds and other wildlife.

Limitations of the Study

While Narango and Tallamy’s study provides a clear target for those seeking to design bird-friendly habitats, it presents several data points that influence its wider applicability.

Its geographical scope is limited to certain suburban areas, potentially influencing the relevance of results in varied ecosystems, climates and urban patterns, and generalizability to other regions and environments.

The fact that the research is primarily focused on a single bird species means that the results may not be universally applicable to other birds with different ecological requirements and behaviors, as species respond uniquely to their habitats.

The study also simplifies ecosystem interactions by emphasizing the role of native plants in supporting caterpillars and, subsequently, chickadees, without getting into the complex web of factors such as predation, competition for resources and human disturbance that also affect bird populations.

In addition, the research presents a temporal snapshot, examining the reproductive success of chickadees during a specific season without considering long-term environmental changes.

It also measures success primarily by fledgling production, ignoring other vital indicators of ecological health, such as genetic diversity and long-term survival.

These limitations suggest the need for broader and more inclusive research to fully understand and apply the implications of the study in different contexts.

A Growing Body of Evidence

Desirée L. Narango and Douglas W. Tallamy’s research aligns with a broader scientific consensus. While I’m not aware of any specific studies that replicate their results identically, the basic tenets of their research are widely supported. Various studies have demonstrated that native vegetation is essential for maintaining and enhancing biodiversity, providing essential habitat and food resources for a multitude of species, including birds and insects. This work underlines the fact that landscapes rich in native plants can support more diverse and robust wildlife populations.

The Benefits of Native Plants Highlighted

Research in areas such as insect biomass and diversity, bird population success, urban and suburban biodiversity and ecosystem services reinforces the benefits of native plants. Collectively, these studies underline that native plants are integral to ecosystem services such as pollination, water filtration and carbon capture, beyond their role in supporting flora and fauna. The emphasis on increasing the proportion of native plants to improve biodiversity and ecosystem health is a key element to remember, reflecting the call to action launched by the work of Narango and Tallamy. This burgeoning field of research underscores the essential role of native plant-based landscaping in promoting ecological balance and sustainability in human-dominated landscapes.

While it may not be suitable for all situations and requires further study, this research offers practical and achievable guidelines for homeowners, landscapers and planners wishing to support wildlife. The 70% threshold provides a clear target for those seeking to design bird-friendly habitats, making it easier to implement biodiversity-friendly practices.

Not Just for Birds

Increasing bird populations is essential to maintaining ecological balance and biodiversity. Birds play a key role in pest control, pollination and seed dispersal, contributing to healthy ecosystems and plant diversity. They are indicators of environmental health, their presence signalling a healthy ecosystem.

Beyond ecology, birds offer significant social and economic benefits, enhancing human well-being through their cultural and aesthetic value, supporting nature tourism and providing educational opportunities. Promoting bird-friendly environments through conservation efforts and planting native species is essential for restoring ecosystems, conserving biodiversity and maintaining the myriad benefits that birds bring to ecosystems and human communities.

So the next time you have an empty space in your flower beds, think of the birds and opt for a native plant.