Nonnative plants reduce population growth of an insectivorous bird
Narango, D.L., Tallamy, D.W. and Marra, P.P., 2018. Nonnative plants reduce population growth of an insectivorous bird. Proceedings of the National Academy of Sciences, 115(45), pp.11549-11554. PDF.
Summary
Nonnative plants can be very common in residential yards in part because of the horticultural preferences of homeowners and developers. Yet, these plants do not support the same diversity of insects as native plants and as such could reduce habitat quality for insect-eating consumers like songbirds. In this study, Narango et al. compared the prey availability, diets, reproduction and survival of Carolina chickadees (Poecile carolinensis) across a gradient of nonnative plants from low to high biomass. They found that as nonnative plants increased in abundance, caterpillar and spiders declined and chickadees switched diets to less preferred prey. In general, chickadees avoided breeding in yards with high nonnative plants, however, those that used nonnative yards experienced a reduction in the number of young that fledged from the nest. The authors also show that population growth of chickadees declines as nonnative plants increase and only yards with <30% nonnative plant biomass had the possibility of contributing to a sustainable population of chickadees. The authors conclude that homeowners should plant native, insect-producing plant species to improve habitat for breeding songbirds and support local food webs in urban and suburban landscapes.
Take home points
Insect prey availability is lower in yards landscaped with nonnative plants because evolutionarily novel plant species do not support the same abundance and diversity of insects.
Because reproduction is limited by food availability, insect-eating birds produce fewer young and cannot sustain populations in yards landscaped with nonnative plants
Management implications
To improve the habitat quality of urban and suburban areas for songbirds, homeowners should landscape yards with more than 70% native plant foliage.
Keywords
Impact Study; Observation; Invasive Plant; Terrestrial Habitat