Abstract Title

Session S-04D: Marine Birds and Mammals of the Salish Sea: Identifying Patterns and Causes of Change - I

Presenter/Author Information

Sean Boyd, Canada. Environment CanadaFollow

Keywords

Species and Food Webs

Start Date

1-5-2014 8:30 AM

End Date

1-5-2014 10:00 AM

Description

A relatively small population of harlequin ducks overwinters along the shoreline between White Rock and Crescent Beach, B.C. This population has been the focus of hundreds of ground surveys over the last 30+ years. In the 1980s and 1990s, males consistently returned to the study area during the June-July period to molt their body and flight feathers, followed by the females 1-2 months later. Long-term pair bonds were re-established once the females completed their own molts, usually by mid-late October. Over the last 10 years, the male molt pattern has changed considerably to the point where they do not molt in the study area anymore but return ca. 2 months later and in pre-basic plumage. The reason(s) for this rather dramatic change in behavior is not known but the following factors may be acting alone or in concert: 1) increasing levels of disturbance from people (especially boaters, kayakers, and more recently, paddle-boarders), and 2) increasing levels of predation risk (especially from bald eagles). In addition, and associated with this change in molt behavior, the number of males overwintering in the study area has declined significantly. In other words, the change in molt behavior appears to have resulted in a local population level effect. Surveys were initiated in fall 2013 at two nearby coastal sites in WA State (Point Roberts and Birch Bay) to determine if they are experiencing the same pattern of delayed return by males, and that appears to be the case. Important questions stemming from these surveys are: 1) is this change in molt behavior happening throughout the Salish Sea?, 2) if so, is it having similar local population level effects or even larger scale effects?, and finally 3) why is it happening? Detailed monitoring and applied research efforts are needed to answer the above questions but, in the meantime, plans are underway to mark White Rock males with satellite transmitters to track their movements, especially during the molt period.

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May 1st, 8:30 AM May 1st, 10:00 AM

Something strange is happening with Harlequin Ducks in the Salish Sea

Room 611-612

A relatively small population of harlequin ducks overwinters along the shoreline between White Rock and Crescent Beach, B.C. This population has been the focus of hundreds of ground surveys over the last 30+ years. In the 1980s and 1990s, males consistently returned to the study area during the June-July period to molt their body and flight feathers, followed by the females 1-2 months later. Long-term pair bonds were re-established once the females completed their own molts, usually by mid-late October. Over the last 10 years, the male molt pattern has changed considerably to the point where they do not molt in the study area anymore but return ca. 2 months later and in pre-basic plumage. The reason(s) for this rather dramatic change in behavior is not known but the following factors may be acting alone or in concert: 1) increasing levels of disturbance from people (especially boaters, kayakers, and more recently, paddle-boarders), and 2) increasing levels of predation risk (especially from bald eagles). In addition, and associated with this change in molt behavior, the number of males overwintering in the study area has declined significantly. In other words, the change in molt behavior appears to have resulted in a local population level effect. Surveys were initiated in fall 2013 at two nearby coastal sites in WA State (Point Roberts and Birch Bay) to determine if they are experiencing the same pattern of delayed return by males, and that appears to be the case. Important questions stemming from these surveys are: 1) is this change in molt behavior happening throughout the Salish Sea?, 2) if so, is it having similar local population level effects or even larger scale effects?, and finally 3) why is it happening? Detailed monitoring and applied research efforts are needed to answer the above questions but, in the meantime, plans are underway to mark White Rock males with satellite transmitters to track their movements, especially during the molt period.