MIGRATION, MOVEMENT and MONITORING of BLACK OYSTERCATCHERS

The black oystercatcher is large instantly recognizable shorebird with an estimated  global population of 15,000 restricted to rocky intertidal habitat along the Pacific coast of North America from the Aleutian Islands to Baja California.  Migration of some, but not all, individuals link the population in Alaska with the population in BC.  Migrants, that make up ¾ of the birds in Alaska during the summer migrate 130 – 1700 km to winter with year-round residents in BC (Johnson et al. 2010). 

The seasonal partial migration of black oystercatchers is a common phenomenon having been documented in many other birds, mammals, fish and even insects. Individual migration strategies, including whether individuals migrate and the distance they travel, can have a strong genetic component or be canalized and therefore consistent across years, but can also be phenotypically plastic and vary with individual state or local conditions (Chapman et al. 2011). Anthropogenic change in climate or land use that alters the relative benefits of residency versus migration or the costs and benefits of wintering in different locations can select for changes in migration patterns (Parteke & Gwinner 2007) or alter individual behavior (Teitelbaum et al. 2016). Berthold (2001) argued that warmer climatic conditions on shared high latitude breeding grounds would favour a reduction in the relative number of migrants in partially migratory populations. Conversely, predicted increases in the frequency and intensity of winter storms (USGCRP 2009) may favour migrants.    

We, in collaboration with USGS and the National Parks Service (NPS), are using tracking technology to determine the migratory strategies of individual black oystercatchers in Alaska, assess the degree to which migration is canalized or phenotypically plastic, investigate the underlying ecological pressures that promote different migratory strategies and test three hypotheses for partial migration (the body size, dominance and arrival time hypotheses; Ketterson & Nolan 1976, Gauthreaux 1982). 

Migration redistributes individuals in space among seasons with consequences for location-specific population densities and intraspecific competition between migratory phenotypes in partial migrants. Models suggest that the magnitude of density dependence effects on survival will influence the evolution and maintenance of partial migration (Taylor and Norris 2007, Griswold et al. 2010) and the prevalence of different migratory strategies (Reid et al. 2018). In Iberia, Tellería & Pérez-Tris (2004) argued that the arrival of migratory Europeans robins displaced 30% of the resident population (primarily young and female birds) from woodlands to shrublands for the winter. In contrast, Perez-Tris & Tellería (2002) showed that migratory blackcaps were excluded from high quality patches by the larger residents.

Black oystercatcher population densities in BC likely double when Alaskan migrants arrive and join BC residents in the fall.  We, in collaboration with ECCC, are examining if migrants influence the movement, winter habitat use, feeding ecology and demography of resident black oystercatchers.

Black oystercatchers are thought to be an indicator of the overall health of rocky intertidal ecosystems because they are a top predator entirely dependent on a narrow band of shoreline habitat for food (primarily mussels, clams, whelks and limpets) throughout the year. Black oystercatchers are also vulnerable to native and introduced predators (including bald eagles, racoons, mink, and rats), and sensitive to human disturbance and oil spills.  As a result, they are monitored as part of both the Parks Canada Ecological Monitoring Program and the Gulf Watch Alaska long-term monitoring program. 

We are studying the movement and fine-scale habitat use of black oystercatchers in both BC and Alaska in collaboration with ECCC, Parks Canada, USGS and NPS and the assistance of the Raincoast Education Society and Laskeek Bay Conservation Society. Spatial data derived from solar powered GPS and ARGOS satellite tags will be used to assess how movement and habitat selection decisions vary depending on the season, the time of day and the tidal cycle.  This data will also be used to assess black oystercatcher vulnerability to increased marine transportation and support marine emergency response and preparedness of the Canadian Government as part of their Ocean Protection Plan.   

BIRDERS, CITIZEN SCIENTISTS AND PHOTOGRAPHERS.
If you see a black oystercatcher wearing a colour band (usually green with two white letters) and/or carrying a tracking tag we would love to hear from you. Please send us an email (lena_ware_2 AT sfu.ca or djgreen AT sfu.ca) with the following information and/or a photograph
BAND – colour and letters or number
DATE – when you saw the bird
LOCATION– where you saw the bird
Your data will be used in our research examining the movement, habitat use and survival of this iconic coastal shorebird.
We will let you know when and where the bird was banded and keep in touch so that you know when any papers incorporating data from our team of citizen scientists get published.

COLLABORATORS ON THE BLACK OYSTERCATCHER PROJECT