The Pacific or Great Blue Heron fannini subspecies winters and breeds on Vancouver Island, within 10 km of the marine shoreline. Its visibility and close connection to the Salish Sea make it an important conservation species, and it is listed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as a Species of Special Concern due to population concerns and threats associated with urban development. The Province of B.C. has coordinated monitoring of Pacific Great Blue Heron colonies on Vancouver Island and the adjacent Gulf Islands from 1997 through 2015. We trained volunteer stewards and technicians to follow a standardized methodology for locating and assessing heron colonies and counting active nests. We follow a sample of visible nests to determine nest success and productivity of young herons (those that lived until fledgling-age). The data are housed at the B.C. Ministry of Environment Wildlife Species Inventory website and are provided to local governments and interested parties to support conservation bylaws and urban planning.
Each breeding season, we assessed between 19 and 37 colonies and analyzed the population variables to provide indications of Pacific Great Blue Heron population viability. This report focuses on the survey results from the 2013?2015 Pacific Great Blue Heron breeding season. Long-term trends from 2002 to 2015 are also included. From 2002 to 2015, overall colony success rate ranged from a low of 43% in 2008 to 90% in 2010 with an average of 66 ? 7%. The number of active nests in the study area does not show a significant trend with a mean of 540 ? 26 active nests annually. Nest success in sampled nests ranged from a low of 30% in 2005 to 100% in 2015 with an overall average of 65% ? 11%. Vennesland and Butler (2008 COSEWIC report) estimated that at least 63% of active nests would need to fledge young to maintain Pacific Great Blue Heron populations. This occurred in 9 of 14 years analysed. As well, the average annual productivity on Vancouver Island was 1.4 chicks per sampled nest. In only three years (2006, 2010 and 2012), the productivity exceeded the 1.9 chicks per nest population maintenance threshold estimated by Henny and Bethers (1971). Immigration of breeding adults from large colonies on the Fraser Delta could be helping to maintain Pacific Great Blue Heron populations on Vancouver Island.
Bald Eagle predation on chicks and adults appears to be responsible for lower productivity and nest success and colony failures. Another factor in the annual variation of nesting success appears to be cool wet springs, which affect egg production and timing of nesting. Pacific Great Blue Heron colonies on Vancouver Island appear to be locating closer to urban centres possibly to deter Bald Eagle predation, but this poses vulnerabilities due to disturbance from noise, tree cutting and various development pressures. We recommend continuing monitoring of Pacific Great Blue Herons on Vancouver Island and Gulf Islands and working with local governments to encourage conservation. Public support could be encouraged through installation of a heron webcam at either the Beacon Hill Park or Cowichan Bay heron colonies. More research on Pacific Great Blue Heron life history is recommended in order to provide valuable population parameters and provide direction for management.
Chatwin, Trudy, Travis Heckford, Emily Barnewall. 2017. Pacific Great Blue Heron Population and Monitoring Vancouver Island and the Gulf Islands 2013 - 2015. Province of British Columbia, Ministry of Forests, Lands and Natural Resource Operations, Heron Working Group. Wildlife Working Report. WR124