The Marsh Monitoring Program (MMP) is designed to assess and improve the conservation and management of Great Lakes wetlands and their wildlife. Data from the MMP help build our understanding of the habitat requirements of marsh-dependent amphibians and birds and provide information on species abundance, status and distribution needed for good conservation. Because the Great Lakes basin covers a huge expanse, and because species’ ranges and habitat requirements are extremely variable, the conservation of Great Lakes wetlands and their wildlife is a complex challenge. With data from about 800 routes (that’s nearly 3,000 stations surveyed since 1994!) across the Great Lakes basin, the MMP provides a unique and powerful tool for meeting this challenge. The 1999 data make an important contribution to the growing MMP database.

In 1999, a total of 52 bird species was recorded by MMP surveyors across the Great Lakes (Table 1), with the most species recorded in the Lake Ontario basin (36 species) and the fewest in the Lake Superior basin (25). Not surprisingly, the most commonly recorded species were Red-winged Blackbird, Tree Swallow, Swamp Sparrow, Common Yellowthroat and Yellow Warbler. One species that is quite rare on MMP routes was recorded in 1999. A King Rail was recorded in the Grand River Marshes near Dunnville, Ontario. Although the bird was not present during MMP surveys, a King Rail was also observed (a very rare occurrence!) strutting its stuff in a Long Point, Ontario wetland – right here in Bird Studies Canada’s backyard.

A review of bird species occurrence and numbers across the lake basins reflects species range limits, geographic variation in wetland types, and other influences on wetland habitat. The Yellow-headed Blackbird, typically a species of western prairie wetlands, occurred only on the western edge of the Lake Michigan basin. American Black Duck and Alder Flycatcher tend to breed in the northern portions of the Great Lakes and, as expected, were recorded most frequently in the Lake Superior basin. Perhaps reflecting the relative scarcity of their preferred rich cattail marshes, Red-wings tended to occur less frequently on Lake Superior routes than on routes in other basins. The Mute Swan, an introduced European species and one quite comfortable with intensive human development, was recorded in the Lake Ontario basin only. Purple Martin, Northern Rough-winged Swallow and Cliff Swallow were recorded only in the Erie and Ontario basins. Black Terns were observed most frequently in the Lake Huron basin. As summarized in the 1998 MMP Newsletter, Black Terns tend to favour large wetlands with a mix of emergent vegetation and open water areas. Routes in the Lake Huron basin may include more of these types of wetlands than routes in other basins.

Overall habitat quality in a lake basin is reflected not only in species frequency of occurrence but also in the number of individuals. For example, Virginia Rails occurred most frequently on routes in the Lake Huron basin. Where they were observed, however, they tended to be found in higher numbers in the Lake Michigan and Superior basins than in the Lake Huron basin. Where Black Terns were observed, they tended to be found in the highest numbers in the Lake Ontario basin. Habitat information provided by MMP volunteers will help determine the wetland characteristics that are most important to bird numbers.

The amphibian data also show some patterns relating to species ranges limits and species rarity (Table 2). The average call code used in this summary does not reflect actual counts of individuals (which is impossible to determine for large calling choruses) but instead uses the three-level call code index to help make relative comparisons among basins and species. For example, an average calling code of around 3 indicates that, on average, the species was recorded in full chorus (i.e. with calls continuous and overlapping). Although the actual numbers of individuals is unknown, an average near 3 probably reflects more calling males than an average call code close to 1.

A total of 13 amphibian species was detected in 1999, with the most species occurring in the Lake Michigan basin (12 species) and the fewest in the Lake Superior basin (5). The most frequently recorded species, and the one with the highest average call code by far, was the Spring Peeper. Green Frogs occurred on about half of all MMP stations. There are several amphibians that were detected at only a few stations. For instance, the Blanchard's Cricket Frog was detected at only 5 stations – 4 stations in Indiana, and one in Oak Harbor, Ohio. This species is rare across the Great Lakes and may even be extirpated from Ontario. The Mink Frog, a species with a more northerly range than most, was detected at only 4 stations, 2 of which were in the Lake Ontario basin and two more outside of the Great Lakes basin. The Pickerel Frog was also detected infrequently, but the records were spread across the lower lakes.

Bullfrogs, although not uncommon, showed an interesting pattern of distribution. They were most frequently recorded in Lakes Erie and Ontario. The surveyed wetlands in these lake basins may be, on average, more nutrient rich than those in the other lake basins – resulting in a more bountiful food supply for Bullfrogs. The milder climate typical of the lower latitudes may also be a bit easier on overwintering Bullfrog tadpoles.

Upcoming analyses of MMP data will explore in more detail these and other patterns in species distributions and numbers. Because species vary in their habitat needs, a variety of wetland types are needed to ensure healthy and sustainable populations of wetland birds and amphibians. The MMP data from 1999 will join the information collected in previous years to help ensure that restoration and conservation efforts are directed toward providing the needed wetland habitat for all Great Lakes wetland species.

— Sandy Dobbyn & Russ Weeber

* Based on data received before February 2000.
** Values are based on all MMP routes (inside and outside Great Lakes basin).