We report a mortality event of Red Phalaropes (Phalaropus fulicarius) that occurred from October to November 2016 on the north coast of British Columbia, Canada. All individuals were severely underweight and showing signs of physiological stress. The guts of all carcasses contained ingested plastics (100%, n = 9). Distribution modelling from pelagic bird surveys (1990-2010) indicated that Red Phalaropes are not typically found in the study area during fall months. Ocean conditions during fall 2016 were unusually warm, coinciding with reduced upwelling in the study area. eBird records since 1980 indicated Red Phalaropes are observed closer to shore during periods associated with reduced upwelling. These results suggest that distribution shifts of Red Phalaropes closer to shore, where plastic debris occurs in higher concentrations, may lead phalaropes to feed on plastic debris while in a weakened state, resulting in a combination of two adverse circumstances.

Intertidal biofilm is a thin layer of microbes and meiofauna enmeshed in an extracellular polymeric matrix within and on top of mudflat sediment. This medium provides a dynamic resource for a variety of consumers in estuarine habitats, and is rich in essential fatty acids that birds require for long-distance migration. We measured seasonal changes in biofilm fatty acid content from spring to summer on the Fraser River Estuary, one of the richest and most important ecosystems for migrant and wintering waterbirds in Canada. Fatty acid content in biofilm showed a strong seasonal pattern with a peak in the spring that is associated with the northward migration of Western Sandpipers (Calidris mauri) to their breeding grounds. This peak is linked to the abundance and physiological state, and hence nutritional condition, of epipelic diatoms, which, in turn, depend on a combination of mudflat topography, salinity, temperature, and nutrients that can fluctuate widely with the freshwater inputs from the Fraser River. Specifically, areas with higher elevation (i.e., ∼1 m) had longer periods of exposure to ambient conditions (i.e., light, warm temperatures, gas exchange into/out of biofilms) that facilitated more biofilm growth and higher fatty acid content. Moreover, springtime changes in water chemistry (i.e., salinity/osmotic stresses and nutrients) and temperature facilitated the production of higher overall total lipid/fatty acid contents in the mudflat biofilms compared to summer. Effective conservation of migrating shorebirds depends on the protection of underlying processes at important stopover sites that promote biofilm communities to escalate their production of lipids, including essential fatty acids, during key times of the year.

Stralberg, D., D. Berteaux, C. Drever, M. Drever, I. Naujokaitis-Lewis, F. K. A. Schmiegelow, and J. A. Tremblay. 2019. Conservation planning for boreal birds in a changing climate: a framework for action. Avian Conservation and Ecology 14(1):13. https://doi.org/10.5751/ACE-01363-140113

Estuaries of major rivers provide important stopover habitat for migratory birds throughout the world. These estuaries experience large amounts of freshwater inputs from spring runoff. Understanding how freshwater inputs affect food supply for migrating birds, and how birds respond to these changes will be essential for effective conservation of critical estuarine habitats. We estimated trends over time in counts of Western Sandpiper (Calidris mauri) and Pacific Dunlin (Calidris alpina pacifica) during northward migration on the Fraser River estuary, British Columbia, Canada, where shorebirds feed extensively on intertidal biofilm and invertebrates. We also examined whether counts were correlated with a suite of environmental variables related to local conditions (precipitation, temperature, wind speed and direction, solar radiation, tidal amplitude, and discharge rates from the Fraser River) during a total of 540 surveys from 1991 to 2019. Counts of Western Sandpiper declined ~54% (−2.0% per annum) over the entire study period, and 23% from 2009 to 2019 (−0.9% per annum). Counts of Pacific Dunlin did not show a statistically significant change over the study period. Counts of shorebirds were lower when discharge from the Fraser River was high, which we propose results from a complex interaction between the abrupt changes in salinity and the estuarine food web related to the quantity or quality of intertidal biofilm. Counts were also higher when tidal amplitude was lower (neap tides), potentially related to longer exposure times of the mudflats than during spring tides. Effects of wind are likely related to birds delaying departure from the stopover site during unfavorable wind conditions. The negative trend in migrating Western Sandpipers is consistent with declines in nonbreeding areas as observed in Christmas Bird Counts. Understanding causes of population change in migratory shorebirds highlights the need for research on mechanistic pathways in which freshwater inputs affect food resources at estuarine stopovers.