Upper Midwest Environmental Sciences Center
Terrestrial Wetland Global Change Research Network
Fig. 14. The sounds recorded at site SC4DBI2 in the St. Croix National Scenic Riverway during April 2008, depicted as a response surface. The subtle peaks near the base of the frequency range in early April represent the earliest calls of wood frogs (Rana sylvatica). The highest peaks centered at near 4000 Hz later in the month, for example, represent calls of spring peepers (Pseudacris crucifer) and chorus frogs (Pseudacris triseriata/maculata).
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