Interstate Island Habitat Restoration: Phase III – Long-Term Monitoring and Maintenance Plan Common Tern Monitoring & Migratory Shorebird Assessment 2023 Final Report

Abstract

The goal of the Interstate Island avian habitat restoration project was to restore and enhance critical breeding habitat for the Common Tern (Sterna hirundo) and Piping Plover (Charadrius melodus) in the St. Louis River Estuary (SLRE). The primary objective of the habitat restoration was to maintain and increase the population of Common Terns breeding at the Interstate Island colony. To assess the effectiveness of the restoration, post-restoration field surveys were conducted to document the breeding status of Common Terns relative to pre-restoration averages. To document breeding population size and productivity, we followed the long-term monitoring protocol developed by the

Wisconsin Department of Natural Resources (DNR), to ensure comparability between pre- and post- restoration monitoring. There were no monitoring objectives related to Piping Plover since this species

has not been documented on Interstate Island. A secondary objective of the project was to document shorebird use of the island during migration to determine if this species group was utilizing the restored

habitat. To meet this objective, researchers developed a shorebird monitoring protocol, conducted in- person surveys, and utilized remote camera traps to observe and quantify shorebird species diversity,

abundance, and spatial and temporal use of Interstate Island. Based on post-restoration surveys, population targets are not currently being met for Common Tern, with the number of nesting pairs currently at some of the lowest recorded since the island was colonized. However, post-restoration productivity is above the range deemed necessary to sustain a viable population and above pre-restoration averages. The overall quality of the nesting habitat for Common Terns was greatly improved. If habitat quality is the primary factor limiting the size of the breeding population, we anticipate the restoration actions will result in an increase in breeding numbers but there may be a lag in response time. We also documented 22 shorebird species and 38 other avian species using the island during our surveys. Our results indicate that shorebirds as well as many other species of birds will readily use the newly restored habitat at Interstate Island, habitat which is much needed in this important bird region. Continued monitoring and management will be necessary to determine long-term effects of restoration for both Common Terns and migratory shorebirds.