Black oystercatchers are a conspicuous bird found along the west coast of North America from the Aleutian chain to Baja California. They are a keystone species largely dependent on rocky marine shorelines for food and nesting. Because of their dependence on intertidal areas, they are particularly vulnerable to habitat degradation, oil spills, as well as sea level rise and ocean acidification associated with climate change. They are considered a species of conservation concern. The main objectives of this project are to 1) Estimate the breeding population size of oystercatchers in Oregon and to compare with previous estimates to better understand the population trend of this vulnerable species; 2) Describe spatial distribution of oystercatchers along the coast; 3) Document oystercatchers abundance in habitat adjacent to the marine reserves and protected areas (MR/MPAs; 4) Document nest locations and reproductive success of Oregon’s oystercatchers; and 5) Promote community engagement through citizen science participation. We targeted rocky shoreline habitat along Oregon’s coastline to perform both abundance surveys and reproductive success monitoring. Observers surveyed routes during the month of May at least two times and monitored nests for hatching and fledgling success. N-mixture modeling was used to estimate oystercatcher population size and probability of detection.
In both 2015 and 2016, 60 and 74 survey routes covering >95% of available habitat (each season) were surveyed for oystercatcher abundance by over 50 trained citizen scientist volunteers and biologists. A negative binomial N-mixture model provided a population estimate of 629 (CI 547-739) in 2015 and 506 (CI 463-560) in 2016. Our findings suggest that Oregon’s population of black oystercatchers is still small but has grown since the estimate from ten years ago (~311 birds in 2006 estimated using same modeling procedure). Oystercatchers using the MR/MPAs ranged from 52-91 individuals which is similar to the coast-wide density. We found that the south coast of Oregon seems to support a higher average density of oystercatchers compared to central and north coast sites. A total of 73 and 68 nests were discovered by volunteers during the 2015 and 2016 field seasons, respectively. In general, we documented higher reproductive success in southern Oregon and for island versus mainland nests. Employing trained citizen scientists enabled the successful execution of this project and engaged members of the public with conservation and science.