Presentation Abstract

The effectiveness of using seabirds as indicators of marine conditions is predicated on the idea that focal species are sensitive to changes in environmental parameters. Species with more behavioral plasticity may be less sensitive to and presumably buffered from a wider range of environmental conditions, thereby compensating for potential perturbations in the system. Rhinoceros Auklet (Cerorhinca monocerata) breeding populations in Washington State typically show little interannual variability in reproductive parameters, suggesting that they are relatively insensitive to the range of conditions that they typically experience. However, in 2016, we documented a highly anomalous breeding season for Rhinoceros Auklets on Protection Island (PI), WA, in the Salish Sea but not on Destruction Island, on the outer Washington coast. We continued our long-term breeding season monitoring at both breeding colonies in 2017, providing us with the opportunity to evaluate the population-level response to the 2016 season. On Protection Island, burrow occupancy (the proportion of burrows that were reproductively active) was the lowest recorded in 12 years of monitoring (58% vs. long-term mean of 72%). In contrast, hatching and fledging success were both comparable to the 12-year mean values, 85% and 78%, respectively. As in 2016, none of the three reproductive parameters differed from long-term mean values for the Destruction Island breeding population in 2017. In stark contrast to 2016, nestling provisioning, as measured by fish per bill load and bill load weight, on PI was comparable to long-term values. The lower burrow occupancy on PI suggests a population-level effect from the 2016 breeding failure and a concurrent adult mortality event. This depressed breeding effort may have been driven by elevated adult mortality the previous summer and/or birds deciding not to breed during the 2017 season.

Session Title

Transboundary Monitoring of Marine Birds and Mammals in the Salish Sea

Keywords

Seabirds, Indicators, Rhinoceros auklets, Forage fish

Conference Track

SSE7: Monitoring: Species and Habitats

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE7-163

Start Date

4-4-2018 2:30 PM

End Date

4-4-2018 2:45 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

Share

COinS
 
Apr 4th, 2:30 PM Apr 4th, 2:45 PM

Where have all the forage fish gone? Response of rhinoceros auklets to an anomalously poor breeding season

The effectiveness of using seabirds as indicators of marine conditions is predicated on the idea that focal species are sensitive to changes in environmental parameters. Species with more behavioral plasticity may be less sensitive to and presumably buffered from a wider range of environmental conditions, thereby compensating for potential perturbations in the system. Rhinoceros Auklet (Cerorhinca monocerata) breeding populations in Washington State typically show little interannual variability in reproductive parameters, suggesting that they are relatively insensitive to the range of conditions that they typically experience. However, in 2016, we documented a highly anomalous breeding season for Rhinoceros Auklets on Protection Island (PI), WA, in the Salish Sea but not on Destruction Island, on the outer Washington coast. We continued our long-term breeding season monitoring at both breeding colonies in 2017, providing us with the opportunity to evaluate the population-level response to the 2016 season. On Protection Island, burrow occupancy (the proportion of burrows that were reproductively active) was the lowest recorded in 12 years of monitoring (58% vs. long-term mean of 72%). In contrast, hatching and fledging success were both comparable to the 12-year mean values, 85% and 78%, respectively. As in 2016, none of the three reproductive parameters differed from long-term mean values for the Destruction Island breeding population in 2017. In stark contrast to 2016, nestling provisioning, as measured by fish per bill load and bill load weight, on PI was comparable to long-term values. The lower burrow occupancy on PI suggests a population-level effect from the 2016 breeding failure and a concurrent adult mortality event. This depressed breeding effort may have been driven by elevated adult mortality the previous summer and/or birds deciding not to breed during the 2017 season.