Detection and density of breeding marsh birds in Iowa wetlands

Abstract

Accounting for imperfect detection is an important process when obtaining estimates of density or abundance for breeding birds, and this is particularly true when researchers are monitoring birds to assess the success of restored wetlands. Due to the dramatic decline in areal cover and habitat quality, wetland restoration in the Prairie Pothole Region (PPR) is critically important to breeding birds. The Shallow Lakes Restoration Project (SLRP), a partnership between the Iowa Department of Natural Resources and Ducks Unlimited, Inc., aims to restore degraded shallow lakes throughout the Iowa PPR. We conducted unlimited-radius point counts with call-broadcast surveys for breeding marsh birds at 30 shallow lakes in various stages of restoration in 2016 and 2017. Our goals were to assess the impact of covariates on detection probability and estimate density of these species at non-restored, younger (1-5 years since restoration), and older (6-11 years since restoration) restorations. Detection probability ranged between 0.07 ± 0.009 (SE) for Red-winged Blackbird and 0.40 ± 0.09 (SE) for Common Yellowthroat. Percent cattail had a positive quadratic effect on detection probability for four species, with detection decreasing sharply as percent cattail increased and increasing slightly with 100% cattail cover. Wind speed negatively influenced the detection probability of Pied-billed Grebes but had a negative quadratic effect on the detection probability of Marsh Wrens. Both restored shallow lakes had greater densities of breeding Pied-billed Grebes, Marsh Wrens, and Yellow-headed Blackbirds than non-restored shallow lakes, but there was no significant difference between younger and older restorations. Including both habitat and environmental covariates on models for detection probability can improve the precision of estimates for density and should be considered when assessing bird populations pre-and post-restoration of shallow lakes.

Springtime bird use of agricultural landscapes examined by using autonomous recording units

“…We examined the utility of ARUs to study springtime avian habitat use within agricultural landscapes. We found that, in addition to documenting species richness of vocalizing species springtime avian communities, ARUs generated species-level detection probabilities similar to or higher than studies on breeding season occupancy of grassland birds (Sidie-Slettedahl et al 2015, West et al 2016, Rigby and Johnson 2019, Vanausdall and Dinsmore 2020, though we conducted more surveys. Several focal migratory species showed significant trends in springtime habitat associations.…”

Habitat preference and abundance of Coscoroba coscoroba and Cygnus melancoryphus in Petrel wetland (O'Higgins region, Chile): Implications in the conservation

“…Regarding the detectability of the species, our results provide relevant information for the development of monitoring programs suitable for the species, since considering the factors that influence the probability of detection can improve the precision of the estimates (Vanausdall & Dinsmore 2020). Furthermore, this is the first study that has examined the importance of considering factors that may influence the probability of detection when estimating the density or abundance of South American swans.…”

Improving waterbird monitoring and conservation in the Sahel using remote sensing: a case study with the International Waterbird Census in Sudan

“…Assuming a detection probability of only 50%, a realistic situation for such large and often vegetated wetlands (Einoder et al . 2018, Vanausdall & Dinsmore 2020), the three most important sites (Tokar game reserve as well as Er Roseires and Khashm El Girba reservoir dams) would then qualify as sites of international importance according to Ramsar criteria 5 (Ramsar Secretariat 2014). They would thus represent a higher priority target in the national IWC programme.…”