Assessing the Role of Conspecific Attraction in Habitat Restoration for Henslow’s Sparrows in Iowa

The presence of conspecific individuals may provide important cues about habitat quality for territorial songbirds. We tested the ability of a conspecific song playback system to attract Henslow’s sparrows to previously unoccupied restored habitat. We successfully attracted Heslow’s sparrows to 3 of 7 treatment plots using conspecific song playbacks and we found no Henslow’s sparrows in control plots. The addition of social cues using playback systems in restored grassland habitats may aid conservation efforts of Henslow’s sparrows to available habitat

Effects of Field Size and Landscape Composition on Grassland Birds in South-Central Iowa

Many species of grassland birds have been shown to avoid smaller fields. The avoidance of smaller fields, however, has not been consistently reported; avoidance may occur in one study, but not in another. To examine one possible reason for these inconsistencies, we examined how landscape composition influenced the relations between occurrence or abundance and field size. The study took place during the 1998 breeding season on 44 Conservation Reserve Program (CRP) fields located in Adair, Ringgold, and Union counties. The relations between occurrence, abundance, and field size were not influenced by landscape composition for any species. Grasshopper Sparrow, Ammodramus savannarum, Bobolink, Dolichonyx oryzivorus, and Eastern Meadowlark, Sturnella magna, were more likely to occur or were more abundant in larger fields. Field Sparrow, Spize!la pusilla, Western Meadowlark, Sturnella neglecta, Brown-headed Cowbird, Molothrus ater, and American Goldfinch, Carduelis tristis, were less likely to occur or were less abundant in larger fields. Field size is an important factor influencing the occurrence and/or abundance of grassland songbirds in fields. Future studies that investigate the effects of landscape composition on area sensitivity should use landscapes that have similar habitat compositions other than the habitat being varied, and use similar sized fields in each landscape

Could the Area-sensitivity of Some Grassland Birds be Affected by Landscape Composition?

Several grassland bird species have been shown to be area sensitive. This area sensitivity occurs when a species\u27 frequency of occurrence, or relative abundance, tends to be lower in smaller fields. The detection of area sensitivity, however, is not consistent among studies because a species may exhibit area sensitivity in one study, but not in another. We tested the hypothesis that a species\u27 area sensitivity varies depending on the amount of grassland in the landscape. The study took place in central North Dakota during the 1996 and 1997 breeding seasons on 46 fields enrolled in the Conservation Reserve Program (CRP). One species, the bobolink (Dolichonyx oryzivorus), displayed variable area~sensitivity consistent with our predictions. In landscapes with greater amounts of grassland, the species\u27 relative abundance in smaller fields was higher. Thus, the species\u27 area sensitivity decreased in landscapes with greater amounts of nesting habitat. This finding suggests that use of small prairie remnants by area~sensitive species may be enhanced by increasing the amount of grassland in the surrounding landscape

Assessing the Role of Conspecific Attraction in Habitat Restoration for Henslow’s Sparrows in Iowa

The presence of conspecific individuals may provide important cues about habitat quality for territorial songbirds. We tested the ability of a conspecific song playback system to attract Henslow’s sparrows to previously unoccupied restored habitat. We successfully attracted Heslow’s sparrows to 3 of 7 treatment plots using conspecific song playbacks and we found no Henslow’s sparrows in control plots. The addition of social cues using playback systems in restored grassland habitats may aid conservation efforts of Henslow’s sparrows to available habitat

Long-Term Declines in Nest Success of Prairie Ducks

Increased predation on nests of ducks in prairie uplands, as a result of habitat alteration, has been hypothesized to cause decreased nest success and population sizes. We tested whether, and by how much, nest success declined using data compiled from 37 studies conducted between 1935 and 1992 at 67 sites in the Prairie Pothole Region of Canada and the United States. Nest success declined (P = 0.0002) over time, but time explained only 10% of the variation; precipitation (P = 0.79) did not account for additional variation in nest success. Nest success declined at similar (P = 0.13) rates among 5 species, but late nesters (gadwall [Anas strepera], blue-winged teal [A. discors], and northern shoveler [A. clypeata]) had higher success (P = 0.004) than early nesters (mallard [A. platyrhynchos], and northern pintail [A. acuta]). Populations of gadwalls and northern shovelers, however, have not declined, indicating that declines in nest success may not be related causally to population change. Long-term population declines in blue-winged teal, northern pintails, and mallards coincide with large-scale temporal declines in nest success. Declines in nest success were parallel in parkland and grassland regions, suggesting a causal agent (or agents) that act(s) at a broad scale, despite inherent differences in the composition of the predator communities and habitats between regions

Appendix A. A table showing characteristics of fields in study areas in central North Dakota during the 1996 and 1997 breeding seasons.

A table showing characteristics of fields in study areas in central North Dakota during the 1996 and 1997 breeding seasons