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Browsing by Author "Hamilton, Derek"

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    Monitoring American White Pelicans and Double-crested Cormorants in Minnesota: Assessing Status of Populations and Exploring New Survey Methodologies
    (2016-12) Hamilton, Derek
    North American populations of American White Pelicans (Pelecanus erythrorhynchos) and Double-crested Cormorants (Phalacrocorax auritus), at one time depleted by human actions, have increased in abundance and distribution over the last 40 years. These changes resulted in a greater overlap of resource use between these bird species and humans (e.g., consumption of fish, use of islands), and managers must now balance conservation with public interests. My research informs management decisions by improving understanding of the status of these species, specifically of populations nesting in Minnesota, and by highlighting resources that can reduce cost and increase frequency of monitoring efforts. Nesting censuses conducted in Minnesota during the summer of 2015 found cormorant and pelican populations (15,421 pairs and 16,406 pairs respectively) to be comparable to previous reports. This suggests populations in the state have reached carrying capacity, at least at present, but vacation of cormorant depredation orders in 2016 may impact future populations of one or both species. In July of 2015, surveys of pelican fledglings were conducted in Minnesota as a follow up to a report released by the Minnesota Department of Natural Resources that found contaminants from the 2010 Deepwater Horizon Oil Spill in pelican eggs. We found no evidence that fledging rates observed during our survey (avg. 0.54) were below expected ranges, but cannot rule out long-term effects of contaminant exposure. Inspired by the high costs of aerial photography and manual counting employed during our studies, I also investigated alternative sources of colony imagery and computer aided analysis techniques. I found that images acquired from sources such as DigitalGlobe and Google Satellite can be used to estimate abundance of pelicans and potentially cormorants at select colony locations. I also showed that object-based image analysis can provide an estimate of pelican abundance quickly and with accuracy comparable to manual counts. Although not feasible to use at all locations, satellite imagery analysis has great potential as an inexpensive method to regularly track bird numbers at selected colony sites in Minnesota and elsewhere if images are available and meet analysis requirements.