Proposed Abstract Title

What’s happening with Harlequin ducks in the Salish Sea?

Type of Presentation

Snapshot

Session Title

Local Stories and Results

Location

2016SSEC

Description

White Rock B.C. supports a relatively small population of Harlequin ducks during the non-breeding period. From the 1980s to the mid-2000s, males consistently returned to White Rock during June-July to complete their body and wing molts, followed by females 1-2 months later. However, by 2006 all males stopped molting at White Rock, returning instead 2+ months later in pre-alternate plumage. Associated with this change in behavior the number of overwintering males declined and this contributed to a local population level effect. Causal factors are unknown but the following are suspected: 1) increasing levels of disturbance from kayakers and paddle-boarders, and/or 2) increasing levels of predation risk from river otters and bald eagles. Surveys were initiated at two nearby sites (Point Roberts and Birch Bay in WA State) to determine if the same pattern of delayed return is occurring, and that definitely seems to be the case. In spring 2015 we marked Harlequin ducks at White Rock (7M/7F) and Hornby Island (14M/8F) with satellite transmitters to describe winter-breeding affiliations and site-fidelity, and to track male molt migration patterns. The resulting Argos data showed that the large majority of the tagged birds bred in the Rocky Mountain-Kootenay Mountain region, all signaling birds returned to their capture sites by the end of October indicating a high level of site-fidelity, and the males migrated north of the Salish Sea to molt, from northern Vancouver Island to Prince Rupert BC. This large-scale molt migration was unexpected and raises the following questions: Why is it occurring? Is it happening throughout the Salish Sea? Is this a recent phenomenon or has it always occurred? Finally, what are the population implications for Harlequin ducks and other marine birds in the Salish Sea? Plans are to mark breeding birds in Alberta and northern US Sates to further describe connectivity and migration patterns.

Comments

Key words: Harlequin ducks, migration, satellite transmitters,molting, breeding, connectivity.

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What’s happening with Harlequin ducks in the Salish Sea?

2016SSEC

White Rock B.C. supports a relatively small population of Harlequin ducks during the non-breeding period. From the 1980s to the mid-2000s, males consistently returned to White Rock during June-July to complete their body and wing molts, followed by females 1-2 months later. However, by 2006 all males stopped molting at White Rock, returning instead 2+ months later in pre-alternate plumage. Associated with this change in behavior the number of overwintering males declined and this contributed to a local population level effect. Causal factors are unknown but the following are suspected: 1) increasing levels of disturbance from kayakers and paddle-boarders, and/or 2) increasing levels of predation risk from river otters and bald eagles. Surveys were initiated at two nearby sites (Point Roberts and Birch Bay in WA State) to determine if the same pattern of delayed return is occurring, and that definitely seems to be the case. In spring 2015 we marked Harlequin ducks at White Rock (7M/7F) and Hornby Island (14M/8F) with satellite transmitters to describe winter-breeding affiliations and site-fidelity, and to track male molt migration patterns. The resulting Argos data showed that the large majority of the tagged birds bred in the Rocky Mountain-Kootenay Mountain region, all signaling birds returned to their capture sites by the end of October indicating a high level of site-fidelity, and the males migrated north of the Salish Sea to molt, from northern Vancouver Island to Prince Rupert BC. This large-scale molt migration was unexpected and raises the following questions: Why is it occurring? Is it happening throughout the Salish Sea? Is this a recent phenomenon or has it always occurred? Finally, what are the population implications for Harlequin ducks and other marine birds in the Salish Sea? Plans are to mark breeding birds in Alberta and northern US Sates to further describe connectivity and migration patterns.