SPES’s 2023 Heron Report is now available

Another Stanley Park heron breeding season has come to an end. SPES staff successfully monitored the Pacific Great Blue Heron (Ardea herodias fannini) colony located at the Vancouver Park Board office along Beach Avenue, adjacent to Stanley Park. SPES personnel noted another year of the herons returning to this colony, with sightings and behaviour consistent with previous years. 2023 represents the 23rd consecutive year the great blue herons (GBHE) have returned to this location since 2001. 2023 saw a continuation of an increase in Park visitorship, as numbers return to pre COVID-19 levels. Additionally, the Festival of Light fireworks returned for a second year in English Bay, after a two-year hiatus during the COVID-19 pandemic. It is important to consider changes in human activity in these surveys as the Pacific Great Blue Heron can be vulnerable to anthropogenic disturbance (Vennesland, 2006).

This year also marked a significant change in the survey methodology used by SPES. To minimize sampling bias and improve accuracy in heron productivity estimations, SPES shifted to both rootop and ground surveys. This change allowed us to monitor the entire colony, and derive metrics without the need to make sampling estimations, which can introduce bias and influence overall accuracy of results. This change was necessary as the colony itself has greatly changed in the past 20 years, and our previous methodology was not capturing such shifts. This change in how surveys are conducted and analyzed has led to some novel results, which we feel are more closely representative of the actual population metrics for this heron colony.

The 2023 monitoring results differ from previous years in various regards and must be compared within the context of these methodological changes. Previous heron report metrics are therefore not as easily comparable with the 2023 dataset. This is because
the way we measure productivity, nest success and general sampling metrics have changed. Our updated methodology overhaul was done to reflect changes in the colony since the formation of this survey back in the 2000s. In addition, by updating our methodology to be more in line with methods used in surveys of other colonies in the Lower Mainland (eg. Jones et al. 2013), our data can be used in contrast to other colonies and can help us compare the Stanley Park colony to other nearby colonies. Importantly, we will better detect changes in trends related to breeding productivity.

These changes have resulted in different population estimates and other metrics relative to past reports, however we feel this change was necessary. By updating our protocols and methods, SPES will have the ability to make more confident recommendations to the Vancouver Park Board with respect to heron management. New methodology suggests that the heron population at the colony is smaller than previously estimated. However, the findings from this year also provide evidence that the colony remains

To view the full report, click here.

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