Harms, Tyler

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Evaluating the effects of landscape configuration on site occupancy and movement dynamics of odonates in Iowa

2014-01-01 , Dinsmore, Stephen , Kinkhead, Karen , Dinsmore, Stephen , Harms, Tyler , Natural Resource Ecology and Management

Odonates contribute highly to global biodiversity and are considered good indicators of environmental quality, but they are under-studied and quantitative information on their habitat associations is lacking. Our objective was to examine the effects of landscape configuration on site occupancy and movement dynamics of four odonate species in Iowa: Tramea onusta, Epitheca princeps, Pantala flavescens, and Calopteryx maculata. We conducted standardized visual encounter surveys for odonates at 233 public properties in Iowa from 2007 to 2011 and computed landscape variables within a 200, 600 m, and 1 km radius of each surveyed site. Using a robust design occupancy model in Program MARK, we estimated detection probability and site occupancy, site extinction, and site colonization probabilities for each species. We found few significant effects of landscape variables on site occupancy, extinction, or colonization, although landscape variables at 600 m were included in the best model for all species. Detection probability (SE) ranged from 0.30 (0.04) for Pantala flavescens to 0.49 (0.04) for Calopteryx maculata. Our study provides information to aid habitat restoration and management efforts on sites having suitable characteristics in the surrounding landscape and ultimately help conserve odonates.

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Habitat Associations of Secretive Marsh Birds in Iowa

2013-01-01 , Dinsmore, Stephen , Dinsmore, Stephen , Harms, Tyler , Natural Resource Ecology and Management

Drastic losses of wetland habitats across North America over the past century have resulted in population declines of many marsh birds therefore emphasizing the need for proper management of remaining wetlands for the conservation of marsh birds. Our objective was to evaluate the probability of site occupancy of secretive marsh birds in Iowa in response to habitat variables at multiple scales. We conducted call-broadcast surveys for eight species of marsh birds at wetlands in Iowa from 16 May–15 July 2009 and from 20 April–10 July 2010. We utilized occupancy models in Program MARK to estimate site occupancy probability based on habitat covariates for four species with the most detections (Pied-billed Grebe [Podilymbus podiceps], Least Bittern [Ixobrychus exilis], Virginia Rail [Rallus limicola], and Sora [Porzana carolina]). Wetland size had a positive effect on site occupancy for Least Bitterns, water depth positively affected site occupancy for Pied-billed Grebes and Least Bitterns, and percent cover of cattail positively affected site occupancy for Virginia Rails. Knowing habitat associations of secretive marsh birds in Iowa will allow us to provide guidance on wetland restoration and management decisions that will aid the conservation of these birds.