Puget Sound Great Blue Heron 2020 Status Update


The Puget Sound Great Blue Heron Update 2020 is a volunteer effort to update existing Great Blue Heron (Ardea herodias) colony locations and nesting numbers in order to determine the current status of the breeding population and breeding distribution within the Puget Sound region.

The Puget Sound regional Great Blue Heron breeding population and colony locations were last assessed in 2004-2005 and published in 2007 (Great Blue Herons in Puget Sound).  No effort has since been made to update this information or track the heron colonies within Puget Sound.  Great Blue Herons are currently recognized as a Priority Species in Washington State by the Washington Department of Fish and Wildlife (WDFW) and have management recommendations to guide the management of nesting colonies and associated habitats.

In 2015, the Great Blue Heron was removed from the WDFW Species of Greatest Conservation Need (SGCN) list.  This removal was based on commonality, the appearance of stability, Breeding Bird data (which is a poor representation of the heron population), and the lack of data to indicate the need for conservation.  As a consequence of its removal from the SGCN list, the Great Blue Heron is no longer recognized in the State Wildlife Action Plan, and thus does not receive funding to support staff time or conservation efforts.  As a result the WDFW no longer updates or tracks heron colonies.

Great Blue Herons are vulnerable to a number of environmental impacts and changes within the Puget Sound Basin.  These generally include: habitat loss due to expanding human development, pollution and environment toxins, colonial nesting and susceptibility to disturbance, depredation by Bald Eagles, unknown status of prey and availability, close association with eelgrass, and climate change. Considering these factors, it is easy to recognize that the population of Great Blue Heron in Puget Sound and the Salish Sea as a whole is under constant human pressure and is at risk of decline.

In order to define and understand the status of Great Blue Herons in Puget Sound, we will utilize the previous 2000 and 2004-2005 data as a baseline to compare current breeding and colony numbers.  To accomplish this, we will examine existing data sources including WDFW, eBird, and request data and sightings from local conservation organizations, including each Audubon Chapter within Puget Sound, and other groups associated with heron colony protection and monitoring.  Field observations and nest counts will also be needed to update existing data.  A colony profile form will be available for recording colony specific information.  All data will be compiled in a database for analysis and results reported following the project.

Study Area:  Puget Sound – 11 counties including: Whatcom, San Juan, Skagit, Island, Snohomish, King, Pierce, Thurston, Mason, Kitsap, and Jefferson.

Data and Records obtained:

  • WDFW: Great Blue Heron colony records from 2010 through 2019
  • eBird: Observational data from the 11 Puget Sound counties from 2017-2020

Data and Records Requested:

Individuals, Agencies and Conservation Organizations: all relevant heron colony information and data from 2015-2020 for known or new heron colonies including: nest numbers, colony activity, colony location, and associated supporting habitat descriptions, etc. (see Heron Colony Profile form for more detail and instructions)

Analysis and Results:

We will use simple computation, with graphs and spatial mapping to illustrate total active colonies, nests per colony, colony location and distribution, concentration by county, extrapolate breeding population, and compare with previous data to determine trends.  Colony abandonment between 2004-2020 will also be addressed if information is provided.

Project Duration:

January 2020 to June 2021.


Online report – possible publication

Sponsors and Cooperators:

Project Lead

Ann Eissinger, Wildlife Biologist
PO Box 2891
Corvallis, OR 97229

Project Outreach

Brian Zinke, Executive Director
Pilchuck Audubon Society
1429 Ave. D, PMB 198
Snohomish, WA 98290

Please contact us for more information.


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