Migrating birds, not enough food, and it’s getting colder by the day! What do non-native invasive plant species have to do with that bleak scene? A lot actually, and here’s why.
Although it may be summer, when our bird populations are in breeding season and looking for protein in the form of insects and their larvae (caterpillars), migration season will come as it always does and prompt birds to seek out high-fat seeds and berries for the winter.
Protein in the form of insects and their larvae is especially important to birds raising newly hatched chicks during these warm months. To feed those young birds, many soft, squishy caterpillars are needed. A single pair of breeding chickadees must find 6,000 to 9,000 caterpillars to rear one clutch of young, according to Doug Tallamy, a professor of entomology and wildlife ecology at the University of Delaware. Insects are best for feeding growing fledglings, and our native trees and shrubs provide the leaves that grow this abundant caterpillar buffet.
As birds gear up for their journey south each year, a significant part of their preparations includes finding high-fat foods to build up their stamina for the long flight and keep them warm as cold weather arrives. The flight pathways of migrating birds are anything but random, having been travelled for eons for the valuable, high-fat foods along those flyways provided by regional native plants.
When the native vegetation our avian friends need is replaced by non-native invasive species, vital available food often transitions from high-fat seeds and berries to those with high-sugar content. While plants like nandina may provide edible berries for birds, they are far from winter dietary needs, especially for birds facing that long over-water flight with no place to refuel their bodies. Surviving that grueling trip demands the right food before it starts – from local native food sources the birds expect to find here, as they have for millennia.
Resident fall and winter birds may also suffer in colder temperatures for lack of the high-fat sources when forced to resort to food from non-native plants. Imagine the amount of shivering a chickadee must do overnight in cold weather just to survive until sunrise when it can replenish its strength by finding seeds or berries with high fat content.
Birds aren’t the only wildlife that lose their best food sources when native foods disappear, but as such a big part of the wildlife we see, they serve as a reminder to protect sources of year-round wildlife food. One of the best ways to protect critical food is by removing invasive species from our own landscapes when we can, replacing them with plants that produce the best fall and winter resources. American beautyberry is a sure winner, is easy to grow, plus pollinators will love the flowers that turn into masses of purple berries the birds need through the fall and into winter! Yaupon holly, wax myrtle, and hackberry are all good choices too!
