Backyard Biodiversity
Songbird decline in North America and what homeowners can actually do
March 16, 2025 · 6 min read
The 2019 Rosenberg paper documented that North America has lost about three billion breeding birds since 1970 — nearly a third of the total. The causes are numerous and largely landscape-scale, but individual yards, aggregated across a continent, matter more than any one owner realizes.
Keep cats indoors
Free-roaming domestic cats kill between one and four billion birds a year in the United States alone — the largest direct human-caused source of bird mortality. Every indoor cat is a measurable, immediate conservation act.
Native plants and caterpillar hosts
Ninety-six percent of terrestrial birds feed their young insects, mostly caterpillars. Native oaks, cherries, willows, and birches host hundreds of caterpillar species; non-native ornamentals host almost none. Replacing even one non-native shade tree with a native equivalent produces real gains.
Prevent window strikes
Window collisions kill up to a billion birds a year in the U.S. External patterns applied to problem windows — dot arrays with 2-inch spacing — reduce strikes by 80 to 90 percent. Focus first on large picture windows near feeders and on reflective corner windows.
Cut pesticides
Neonicotinoids and other systemic insecticides move up the food chain into birds. Reducing chemical inputs preserves the invertebrate biomass birds depend on and directly reduces bird poisoning.
Measure what visits
You cannot manage what you cannot measure. Merlin acoustic recording combined with periodic bark and cavity eDNA gives a real inventory of what your yard supports, including secretive species that visual surveys miss.