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Ecology and Management of Islands, Peninsulas and Structures for Nesting Waterfowl

Establishing Low Shrubs on Islands to Provide Waterfowl Nesting Cover

John Lokemoen and Robert Woodward
Northern Prairie Wildlife Research Center
Jamestown, North Dakota 58401

One key habitat requirement for breeding waterfowl using islands is nesting cover that is preferred by breeding hens and is perennial. Research studies at Miller Lake in North Dakota and at islands in Canada found found that Woods rose (Rosa woodsii) and snowberry (Symphoricarpos occidentalis) were preferred by nesting mallards (Anas platyrhynchos) and gadwalls (Anas strepera).

We initiated a study in 1986 to determine the feasibility and cost of establishing low shrub cover on islands. Woods rose and snowberry were planted during May on 1 upland and 4 island sites in 1986 and 1987. The species were set alternately at a 2-foot spacing. Each plot was hoed 3 times during the growing season to reduce weed competition. We used power augers, KBC bars, OST bars, steel bars, and tile spades to plant shrubs.

Survival of snowberry was 50% after the 2 growing seasons and plant height averaged 8.9 inches. Woods rose survival averaged 74% after 2 growing seasons and plant height averaged 14.6 inches. Shrub survival was only 17% for snowberry and 70% for rose at Medicine Lake where weed control was ineffective. Only 30% of the snowberry and 47% of the rose survived at the Thacker Waterfowl Production Area where weed control was adequate but plants were placed into subsoil. At 2 sites where there was good topsoil and good weed control, shrub survival and growth was excellent. At these sites plant survival was 98% and the average height of Woods rose exceeded 19 inches after 1 growing season.

It would require 3,484 seedlings to plant 0.5 acre plot if shrubs were spaced 2.5 feet apart. Using our average cost of 0.29/plant the total expense for shrubs would be $1,001.65. An estimated 16.9 man-days would be required to plant the shrubs and 3 visits for weed control would involve another 15.6 man-days.

As a result of trials we make the following recommendations for establishing low shrubs on islands:

  1. Plant in early May after the last threat of severe frost.
  2. Plant into topsoil where the weeds have been eliminated.
  3. Space plants 2.0 to 2.5 feet apart so a dense canopy forms when plants reach full growth.
  4. Use a KBC bar for planting and pack soil tightly around the plant roots.
  5. Maintain the shrub Plots as weed free as possible during the first 2 growing seasons. Eliminate weeds in the first year by hoeing and apply Dichlobenil in the fall of the first year to aid weed control the second year.

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