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Seasonal variation in food availability is one of the primary limitations to avian populations, particularly during the breeding season. However, the behavioral responses between species may differ based on foraging strategies. I examined the influence of food availability on landscape-level habitat selection, patch-level habitat selection, and movements of two wading bird species with divergent foraging strategies, the Great Egret and White Ibis. On a landscape scale, there appeared to be a relationship among resource availability, the temporal scale of the independent variable, and whether the response was similar or different between species. At the patch level, results demonstrated a relationship between resource availability and the spatial scale of the independent variables selected by birds. Species movements were consistent with the differing strategies. This study is the first to make the link between landscape hydrology patterns, prey availability, and responses in wading bird habitat selection at multiple spatial scales.
The Cackling goose (Branta hutchinsii minima) population has increased from a low of 20,000 in 1984 to the current population of 220,000-300,000 (Stehn 2012, Sanders 2013). As the Cackling goose population began to recover in the late 1990s, the majority of the population relocated from wintering in California to the Willamette Valley, Oregon (Pacific Flyway Council 1999, Mini 2012). Cackling geese in Oregon now commonly use exurban, suburban, and urban areas (Mini 2012). The reasons for Cackling goose use of urban areas are still unclear as they did not commonly use this habitat type on their traditional wintering areas in California or initially upon showing up in Oregon. Given what we know about habitat selection in geese and the Willamette Valley system, we tested three different hypotheses that seem to have the greatest utility for explaining the recent use of urban habitats in Oregon’s Willamette Valley: 1) Foraging opportunity in urban habitats is higher due to lower perceived, or actual, predation risks, 2) Foraging efficiency in urban habitats is higher in urban landscapes due to a difference in forage characteristics between landscape types, and 3) Quality of forage in urban habitats is higher due to a difference in nutritional content and regrowth rate. My field work centered on collecting data to test predictions deduced from my hypotheses. From November 2013-April 2014 and November 2014-April 2015, I conducted a total of 278 hour-long disturbance surveys and 238 behavioral time- activity budget scans in 109 different sites in the Willamette Valley, Oregon within urban areas in Portland, Eugene, and Salem and agricultural areas in the Willamette Valley National Wildlife Refuge Complex and nearby private fields. Consistent with the Safe Habitat Hypothesis, predator-related disturbances in urban landscapes were significantly lower than in agricultural landscapes: only one avian predator-related disturbance was observed in urban landscapes throughout the entire study. Geese spent more time feeding (69.0 ± 1.9% vs. 55.0 ± 2.1%), less time flying (3.0 ± 1.1% vs. 6.6 ± 1.3%) and less time vigilant (2.1 ± 0.2% vs. 5.6 ± 0.5%) in urban landscapes than in agricultural landscapes. The frequency of the eight disturbance types differed between landscape types (n = 988, X2 = 308, df = 8, P
This book is open access under a CC BY-NC 2.5 license. The Gulf of Mexico is an open and dynamic marine ecosystem rich in natural resources but heavily impacted by human activities, including agricultural, industrial, commercial and coastal development. The Gulf of Mexico has been continuously exposed to petroleum hydrocarbons for millions of years from natural oil and gas seeps on the sea floor, and more recently from oil drilling and production activities located in the water near and far from shore. Major accidental oil spills in the Gulf are infrequent; two of the most significant include the Ixtoc I blowout in the Bay of Campeche in 1979 and the Deepwater Horizon Oil Spill in 2010. Unfortunately, baseline assessments of the status of habitats and biota in the Gulf of Mexico before these spills either were not available, or the data had not been systematically compiled in a way that would help scientists assess the potential short-term and long-term effects of such events. This 2-volume series compiles and summarizes thousands of data sets showing the status of habitats and biota in the Gulf of Mexico before the Deepwater Horizon Oil Spill. Volume 2 covers historical data on commercial and recreational fisheries, with an analysis of marketing trends and drivers; ecology, populations and risks to birds, sea turtles and marine mammals in the Gulf; and diseases and mortalities of fish and other animals that inhabit the Gulf of Mexico.
This volume provides information about the terrestrial, freshwater, and marine habitats of Oregon and Washington and the wildlife that depend upon them; it also supports broader and more consistent conservation planning, management, and research. The 27 chapters identify 593 wildlife species, define some 300 wildlife terms, profile wildlife communities, review introduced and extirpated species and species at risk, and discuss management approaches. The volume includes color and bandw photographs, maps, diagrams, and illustrations; and the accompanying CD-ROM contains additional wildlife data (60,000 records), maps, and seven matrixes that link wildlife species with their respective habitat types. Johnson is a wildlife biologist, engineer, and habitat scientist; and O'Neill is director of the Northwest Habitat Institute; they worked together on this publication project as its managing directors. Annotation copyrighted by Book News Inc., Portland, OR