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Locating, Constructing, and Managing Islands for Nesting Waterfowl

Monitoring Islands

Maintaining Permanent Records

The relative value of each island or potential island site for nesting waterfowl should be determined from a field reconnaissance. A permanent record should be maintained for each island or potential site visited to register location, habitat, and predator use (Figure 5 and Appendix C). Information from the record can be stored as a paper file, entered into a computer file, or both. Any distinct code can be used where only a few islands need to be identified. Where numerous islands are included in a survey, the Universal Transverse Mercator (UTM) coordinates taken at the center of the island can be used for the identifier. UTM coordinates can be determined on 1:24,000 maps from the U.S. Geological Survey, Denver, CO 80225 and on 1:50,000 maps from Energy, Mines & Resources, Ottawa, Ontario, Canada K1A 0E9. UTM coordinates should be measured to the nearest 10 meters (32.8 feet) in both the United States and Canada.

Figure 5: Island Survey Form.
Figure 5.  This is an example of a form that can be used to record information about nesting islands. The same form found in Appendix C can be photocopied and used to start a permanent record.
  • Information regarding UTM coordinates included under Maintaining Permanent Records.
  • Use an aerial photo or NWI data to count wetland numbers and acres.
  • During the initial island visit or during spring visits to managed islands record number of predators, scats, and tracks.
  • Use a nest card such as the one developed by the Northern Prairie Wildlife Research Center (8711 37th Street SE, Jamestown, ND 58401) to record data on individual nests.

Monitoring Predators

Each year on large islands (≥3.5 acres), and every few years on small islands, predator activity should be monitored in spring after the wetlands are free of ice. Islands should be examined by walking in the uplands and along the shoreline to locate fresh animal tracks, trails, dens, scats, or food remains. Information collected during each visit should be recorded on the island register (Figure 5). If bare soil or sandy shorelines are absent on large islands, track plots (3 feet × 6 feet) can be constructed by removing all vegetation from an area with loamy soil. During each visit, the plots should be examined for tracks and other predator sign and then raked clean.

Monitoring Nesting

Every few years, waterfowl nesting use and nest success should be appraised on islands by conducting nest searches. Two nest searches should be conducted, including one in May and one in June, the peak months for waterfowl nesting in the northern plains. Each nest search should be completed by ≥2 people walking within a few feet of each other through all available nesting habitats. Searchers should use switches or dragging ropes to help flush nesting hens. Each nest location should be marked by placing a wire survey flag or slender willow stake a set distance and direction from the nest bowl. The nest number should be written on a cloth attached to the marker. The nest location and number should also be plotted on a map or aerial photo of the island. For each nest, the waterfowl species, number of eggs, and incubation stage should be recorded. Observers should also record information on nesting shorebirds or colonial birds encountered during the surveys.

The best estimate of nest success is obtained when each nest is revisited every 7 to 10 days. However, when the number of workers or time available is limited, nests found during the first search can be checked 2 weeks later and during the second nest search. Nests found on the second search can be checked once when all nest histories are completed. On small islands with moderate cover, both active and inactive nests are usually found. Apparent nest success can be calculated for these situations by dividing the number of successful nests by total nests. On large islands or on islands with dense vegetative cover, many nests are not found and the Mayfield estimate of nest success must be used (Klett et al. 1986).

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