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Date of this Version

6-2003

Comments

Published in The Prairie Naturalist 35(2): June 2003. Published by the Great Plains Natural Science Society http://www.fhsu.edu/biology/pn/prairienat.htm

Abstract

We related American avocet (Recurvirostra americana) nesting on 30 earthen constructed islands in wetlands of the Prairie Pothole Region of North Dakota to characteristics of the islands and the surrounding landscape. We found 174 American avocet nests on 10 of the 30 islands; eight islands had four or more nests each. Most (85.9%) clutches contained four eggs. The majority of nests were found in upland graminoids (57.9%) or on unvegetated ground (31.6%). We found little evidence of nest predation or abandonment and concluded that most (84.5%) clutches hatched. Islands with beaches had a higher nest density (mean number of American avocet nests per kilometer of island shoreline) (76 ± 56 SD nests/km) than islands without beaches (4 ± 17 SD nests/km). Islands located in wetlands classified by Cowardin et al. (1979) as L2ABF had a higher nest density (88 ± 92 SD nests/km) than did the wetlands classified as L2ABG (15 ± 30 SD nests/ km) or L2UBGh. Larger islands (≥ 0.3 ha) had a higher nest density (46 ± 56 SD nests/km) than did smaller islands « 0.3 ha) (5 ± 19 SD nests/km). Islands in shallow water (≤ 1 m) were almost twice as large (0.42 ± 0.13 SD ha) and had a higher nest density (48 ± 58 SD nests/km) than did islands constructed in deep water (> 1 m) (5 ± 19 SD nests/km). Seven of the 11 islands in shallower water also had beaches, whereas none in deeper water did. In general, nesting American avocets appeared to favor islands that were large, islands with beaches, islands located in shallow water, and islands built in wetlands classified as L2ABF.

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