Grassland Restoration Results

Grasslands Restoration Results

Wildflowers thrive in restored grassland. Adam Mitchell Photo

By any measure, the Conservancy’s Grassland Restoration project is a success. But how do we quantify that success? There are three ways to test the progress of restoring native plant communities:

1. Compare non-native plants to what is there now.

2. Measure the number of insects eating the plants.

3. Measure the things that eat the things that eat the plants.

Grassland flowers

Wildflowers not far from Par Course. Adam Mitchell Photo

Compare non-native plants to what is there now:

Our native grasses are becoming established, spreading on their own without requiring significant reseeding. These grasses will keep the invasive plants out, provided we continue to promote optimum conditions for grasslands, i.e., prescribed fire.

We have four species of native grasses that are important for grassland birds, and these are the ones people tend to think about when we talk about “warm-season bunch grasses” (WSBG). This includes Big bluestem (Andropogon gerardii), indiangrass (Sorghastrum nutans), little bluestem (Schizachyrium scoparium), and switchgrass (Panicum virgatum). There are other species of grasses and wildflowers in the Parade Grounds that will vary in numbers, but these four grasses will be the dominant members of the community.

Pitfall trap

A Barber pitfall trap collects insects in undergrowth as part of program to measure diversity of insects on Fishers Island.

Measure the number of insects eating the plants:

We use many techniques to measure the diversity of insects on Fishers Island. These include a timed hand-collecting method and a modified leaf vacuum to remove plant-feeding insects and their predators from host plants. We place pitfall traps around the base of plants to collect insects in the undergrowth, and we gather soil beneath plants to collect insects that might feed on plant roots. Finally, we set up mercury vapor lamps to attract moths and other nocturnal insects that feed on a variety of host plants on the Island.

In 2015, we collected around 110,000 arthropods, representing over 1,200 species. The 2016 results are still being processed.

Where invasive plants are dominant, we see mostly insects that feed on dead plants and fungi. Insects that prefer feeding on live plants find invasives distasteful, allowing those plants to grow unhindered, because normal plant consumption by insects is designed to keep plant growth in check. The few species of insects that feed on invasive plants are invasive insects, garden pests or nuisances to the Island. In contrast, our restored grassland now hosts many more plant-feeding insects, pollinators and the predators that feed on them, contributing energy to a healthy, growing food web.

American Redstart

American Redstart. Adam Mitchell Photo

Measure the things that eat the things that eat the plants:

In recent years, we have observed an increase in the number of key fauna to the Island. The return of insect-eating warblers, like the common yellowthroat and blue-winged warbler, are a welcome sight, as they are both residents and migrants to the Island. Another encouraging sign is the arrival of state-threatened and endangered species like the American kestrel and northern harrier.

In addition to birds, there are many other animals that eat insects. Frogs, toads and salamanders feed on insects during both their adult and larval stages. Snakes and turtles will do the same. Mice and squirrels may feed on seeds and fruits, but they consume a lot of insects, especially in the winter. This is also true for moles, shrews, voles and, of course, bats. Possums consume a lot of ticks as well as other arthropods. Raccoons, skunks, weasels, ferrets, and the like could be on the Island and would eat insects if they had the chance. Foxes and coyotes will eat insects when they are young and to supplement their diet when larger prey are scarce, especially in the winter.

Two grassland success stories are the monarch butterfly and the eastern bluebird.

Photos and story by Adam Mitchell, Associate Wildlife Biologist®
PhD Candidate, Department of Entomology and Wildlife Ecology, University of Delaware