By Dannie Piezas, Urban Wildlife Coordinator
At the writing of this article, there remains one last observable nest in the Stanley Park Heron colony that still has chicks yet to fledge, but for the most part, we have reached the end of yet another Great Blue Heron breeding season.
This is a summary of what SPES’s heron monitors observed this year:
- We counted 109 total nests among the trees around the Stanley Park Tennis Courts that comprise the Stanley Park heronry. They have been here since the spring of 2001. When the nests get abandoned at the end of each season, most are reused in the next, while a handful of new ones get built each year and some similarly get destroyed, often by falling branches or high winds. (last year’s count: 106 total nests)
- Some of the new nests that we found were built in the trees closest to the then-unfinished Stanley Park Brewing Restaurant & Brewpub. They had not established nests in these trees in previous years.
- Among the total counted nests, we approximated 90 active nests—they were used, whether successfully or unsuccessfully, by a breeding pair to raise a clutch of young. (last year’s count: 85 active nests)
- We conducted 13 rooftop surveys at a nearby residential building affording a good view of some nests. These surveys were done every two weeks to follow 41 sample nests from beginning to end of the breeding season, and we recorded the number of active nests, numbers of eggs, timing of the young’s growth, chick mortality, and fledging success of these visible nests to the best of our ability.
- We found 34 successful nests with young that survived to fledge, and a total of 76 fledglings among the sample nests. (Last year, we found 24 successful nests, and 46 fledglings in the sample.)
- Recognising that the sample size is quite small to confidently derive total numbers, the sample nest fledging success lets us approximate 90 total fledgings from this year’s breeding population of herons in Stanley Park.
Suffice it to say, if these numbers are accurate, our colony has done quite well this year, especially compared with previous years! Some events of note that we were keen to keep an eye on this year included the Stanley Park Brewing Restaurant & Brewpub construction and service line renovations in the area, but operations were undertaken under rigorous environmental monitoring and consultation and did not result in flushing events (mass take-offs) among the herons. The usual potential disturbances of the area continued to be present—most impactful of all was eagle predation, alongside daily activity from cars and pedestrians, sport events, and nearby fireworks displays.
Studying the colony this year presented some unique challenges, with new staff taking on the work of monitoring and reporting on them. We are much beholden to our volunteers Maria Morlin, Julie Emerson, Frank Lin, and many more who helped both in the field and office for the continued stewardship of our resilient colony!
You can expect a more detailed report on this year’s heron colony sometime this next month. Hear it first by following the hashtag #herontalk on Twitter and Facebook, or by donating to our Adopt-a-Nest program to receive heron updates and reports.