Action: Mowing roadside verges
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A single replicated, controlled study in the USA found that more ducks nested on unmown roadside verges, but that over four years, nesting success on unmown verges fell to below that on mown verges.
Roadside verges could potentially act as a valuable nesting or foraging habitat for many species of birds, but can become overgrown with rank vegetation. Mowing, therefore, may increase the value of this habitat.
Alternatively, conservationists may want to limit the number of birds using roads verges, to reduce the risk of collisions with vehicles.
Supporting evidence from individual studies
A replicated, controlled trial in 1969-72 in North Dakota, USA (Voorhees & Cassel 1980), found that more ducks nested in unmown than mown road verges (although this difference was not significant in 1972). However, nesting success remained between 40-60% in mowed strips, whereas it fell from >70% to <30% in unmown strips due to an increase in mammalian nest predation. Alternate mowed and unmown 1.6 km strips of roadside vegetation were compared along 37km of Interstate 94. The 23 mowed strips (totalling 123 ha) were mown once in autumn. Six duck species nested over the four years: blue-winged teal Anas discors, mallard A. platyrhynchos, gadwall A. strepera, northern shoveler A. clypeata, pintail A. acuta and lesser scaup Aythya affinis.