Black terns are easily identified as they fly low over large shallow marshes with abundant vegetation adjacent to open water and are enjoyed by many birders. However, sightings of black terns have declined over the past 10-20 years.
Doris Rusch, retired DNR Wildlife Biologist and Red Cedar Lake (Jefferson County) resident, wrote “Every year there are less and less terns. There used to be so many. I count them every time I go out to do the lake survey, so I have some crude documentation as to numbers each month of summer.” The DNR listed the black terns as state-endangered in 2014 as a result of long-term studies which documented state-wide declines and correlate to observations like those from Doris.
Black terns nest in open wetlands on floating bogs or similar habitats and can greatly be impacted by changes in water levels. Heavy rain events raise water levels and can flood out nests. Other problems terns face include predation from great horned owls, great blue herons, and snapping turtles.
David Shealer, Biology Professor at Loras College in Dubuque Iowa, is the national black tern expert. David has banded almost 5,000 black terns in the past 15 years. For many years David has focused his research in south central Wisconsin. Last year with the assistance of Tony Abate, Goose Pond Sanctuary Land Steward, David trapped a black tern at Grassy Lake State Wildlife Area that was 12 years old and was the oldest band recovery in the nation. This year, David trapped a black tern at Horicon Marsh State Wildlife Area that he banded 14 years ago.
The DNR developed Management Guidelines that if implemented could help remove the black tern from the endangered species list. These guidelines include “Use of artificial nesting platforms may benefit black terns and should be evaluated on a site by site basis.” The rational for nesting platforms is that the platform are attached to poles and can rise with water levels and also help provide a solid substrate for nests.
The DNR provided Madison Audubon Society with funds to purchase materials for nesting platforms and Goose Pond Sanctuary staff and volunteers have been busy constructing, placing, and helping monitor nesting platforms. The nesting platforms are made out of plywood, stryfoam insulation, and astroturf. Special thanks to William Damm for coordinating the construction of 150 nesting platforms and Sara Kerli, DNR Columbia County Wildlife Biologist, who coordinated the construction of 40 platforms.
Nesting platforms have been placed at Grassy Lake, French Creek, and Mud Lake State Wildlife Areas; Rowe and Schoeneberg Marsh Waterfowl Production Areas; and Goose Pond Sanctuary.
As of July 1, over 50 nests have been found at the State Wildlife Areas with most of the nests being found at Grassy Lake.
Nine terns were observed at Goose Pond in early June and summer interns placed 10 nest platforms. Friends of Rose Lake made and placed platforms at Rose Lake State Natural Area (Dorothy Carnes Jefferson County Park) and David Shealer recently reported seeing 80-100 terns at the SNA! To see the terns, visit the west side of Rose Lake and head to the observation overlook area.
Only a few nests have been on platforms and David’s recommendation next year is that some platforms be moved to different locations. As your local bird conservation organization, we will continue to provide information on the summer nesting results as the season progresses. We look forward to working on this long-tern project and hopes that tern numbers will recover in future years - but we need your help.
Photo by Arlene Koziol