Wildlife use of terraces in Iowa rowcrop fields

Abstract

The effectiveness of terraces for controlling soil erosion is well documented, but the benefits to wildlife are poorly understood. Our objective was to document wildlife use of terraces in southwestern Iowa. Twenty-six bird species were observed in terraces. The red-winged blackbird (Agelaius phoeniceus) was the most abundant species, accounting for 37% of the total bird abundance (x̄ = 463.O birds/100ha). Five species nested in terraces (64.8 nests/10 ha), and 76% of the nests found were of red-winged blackbirds. Predation was the main cause of nest failure, accounting for 73% of the nests of all species combined. Terraces may act as ecological traps for nesting birds by attracting them to nest in areas where productivity is inadequate to sustain viable populations. Nine small-mammal species were captured in terraces. The deer mouse (Peromyscus maniculatus) was the most abundant (64% of captures). An average of 17.4 mammal dens/km was found in terraces. Dens constructed by the striped skunk (Mephitis mephitis) were the most abundant. Mammals may prefer terraces because they provide cover,food, and protection from cultivation; are seldom burned; and are not mowed. Also, dens may be abundant in terraces because many burrowing mammals prefer sites with steep slopes and well-drained soils. Avian nesting success in terraces is low, likely because of the high level of mammal activity and increased predator search efficiency in such a narrow habitat. To determine potential nest predators in terraces, we evaluated the efficiency of a new hair catcher design consisting of stakes coated with Tangle-Trap [Superscript registered trademark symbol] Insect Trap Coating placed around artificial nests (n = 279) consisting of two Coturnix quail eggs and a plasticine egg. Forty-four percent of the artificial nests were depredated. Predator activity was documented more often with the plasticine eggs (61% of depredated nests) than with the hair catchers (23%), but distinguishing imprints in the plasticine eggs was difficult and some plasticine eggs melted. The most commonly identified hair was that of the striped skunk. The efficiency of the hair catchers we tested was less than that reported for other hair catcher designs.