Effects of Two Haying Provisions on Duck Nesting in Conservation Reserve Program (CRP) Fields in South Dakota

Duck nesting in Conservation Reserve Program (CRP) fields was evaluated in 1989 and 1990 to determine the post year effects of emergency haying. Due to severe drought some CRP fields were released in 1988 for emergency haying with the provision that 10% be left in idled strips and some fields were released in 1989 with the provision that 25% be left in idled blocks. Visual obstruction readings were used to index vegetation height-density. A cable-chain drag was used to find duck nests, and flush ring-necked pheasants (Phasianus colchicus) and white-tailed deer (Odocoileus virginianus) in 27 CRP fields in 5 eastern South Dakota counties. Duck nesting data in hayed and idled strips, hayed and idled blocks, and idled fields (not released for haying) were used to evaluate post-year haying effects on duck nest density and success. In 1989 mean residual and mean peak green growth vegetation visual obstruction readings in idled strips were significantly greater (P50.05) than hayed strips. Nest densities in idled strips and idled fields were significantly greater (P50.05) than in hayed strips. Nests in idled strips and idled fields were primarily of mallards (Anas platyrhynchos), nests in hayed strips were primarily of blue-winged teal (Anas discors). In 1990 mean visual obstruction readings of residual and peak green growth vegetation were significantly greater (P50.05) in idled blocks than hayed blocks. Nest densities in idled and hayed blocks were similar (P\u3e0.05) but significantly greater (P50.05) than densities in idled fields. Nests in idled and hayed blocks were primarily of mallards; nests in idled fields were mainly of blue-winged teal. Nest success in CRP fields averaged 23.4% for both years but varied among haying provisions and years. Nest success was lowest in idled strips (7.9%). Daily survival rates of nests in idled strips were significantly less (P\u3c0.05) than in other strips, blocks, or fields. Idled strips apparently attracted predators as well as ducks. In 1989 nest success of gadwalls (Anas strepera) exceeded the rate thought necessary to sustain their population, rates of mallards and blue-winged teal were below necessary threshold levels. In 1990 nest success of mallards, gadwalls, and blue-winged teal all exceeded rates necessary to sustain their population. If haying of CRP or other planted cover is warranted, I recommend against haying provisions that leave cover in narrow idled strips six meters or less wide and recommend that a minimum of 25% of each field be left in an idled block