Control of Invasive Phragmites Increases Marsh Birds but not Frogs

Posted on Oct 30, 2019

Author

by Douglas C. TOZER and Stuart A. MACKENZIE
CWBM 8 (2): 66–82

Correspondence: Douglas C. Tozer, Long Point Waterfowl and Wetlands Research Program, Bird Studies Canada, P.O. Box 160 (Courier: 115 Front Road), Port Rowan, Ontario, N0E 1M0, Canada.

Email: dtozer@birdscanada.org


Abstract

The non-native invasive form of common reed (Phragmites australis australis; hereafter “invasive Phragmites”) negatively affects certain flora and fauna throughout North America. As a result, much effort is spent in some locations controlling invasive Phragmites, although few estimates of the expected benefits of these efforts are available. We used data from Bird Studies Canada’s Great Lakes Marsh Monitoring Program and Central Michigan University’s Great Lakes Coastal Wetland Monitoring Program to estimate changes in 1) species richness, 2) total abundance, and 3) occurrence of 9 breeding marsh bird species and 8 breeding marsh frog species before and after control of invasive Phragmites. Our study took place between 2011 and 2018 throughout 3 Great Lakes coastal wetland complexes located on Lake Huron and Lake Erie in southern Ontario. We found at sample sites where invasive Phragmites was controlled that species richness of 5 breeding marsh bitterns (e.g., Botaurus sp.) and rails (e.g., Rallus sp.) of conservation concern increased by 1.1 species, and that total abundance of these species combined increased by 1.8 individuals. By contrast, we observed no change in these responses at nearby sample sites where no Phragmites control occurred. We found no change in occurrence of any frog species or species richness or crude calling frequency of all frog species combined in relation to control of Phragmites, although we lacked the ability to detect subtle changes in abundance of frogs, so more information would be helpful before firm conclusions can be made in relation to frogs and control of invasive Phragmites in our study system. Our study shows that control of invasive Phragmites has a significant positive effect on breeding marsh bird species of conservation concern and suggests that continued effort to restore habitat for these species is warranted, particularly in areas where former breeding marsh bird biodiversity was high.

Key Words: Common Reed, Frog Abundance, Great Lakes, Herbicide, Invasive Species, Marsh Birds, Phragmites australis australis, Wetland

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