Article by:Julia Shewan, B.Sc, RPBio
Conservation Programs Assistant, CVWMA
This E-News is for all the die-hard rookery fans. Some of you may have missed seeing the double-crested cormorants and great blue herons nesting at the Leach Lake rookery as access into the unit this spring was cut off by road/bank erosion along Summit Creek. The lack of access made it slightly more difficult for us to complete our annual survey of the rookery in June,  where we engage Harrier Aerial Surveys out of Nelson to fly a drone over the rookery to take photos and we count the nests from these images. Thankfully, a good neighbour allowed us to launch from their property adjacent to the rookery on the other side of the Kootenay River; thank you again – you know who you are! This year is the 9th of the 10 year monitoring project of the rookery for the Pacific Flyway Non-Game Technical Committee. We will likely continue monitoring the rookery beyond the life of this project as it is a unique feature and one of its kind across the entire Creston Valley Wildlife Management Area (at least that we know about, these birds could be hiding in more inaccessible areas!).
We counted a total of 216 double-crested cormorant nests and 41 great blue heron nests from images taken over the rookery. For those who keep tabs on numbers, these results are pretty similar to last years, though with a few more heron and a few less cormorant nests counted (30 and 222, respectively). In general, cormorant nest counts have been increasing over the life of this monitoring project while heron nest counts are quite variable by year.
This year we tried some new image technology – thermal imaging! (purple and pink image seen above) We wanted to see whether this technology could allow us to more accurately assess nest numbers. Check out the side-by-side images! The rough area captured by the thermal imaging camera is depicted on the wide angle camera image. The results are mixed. Nests at the rookery are built at a variety of heights in the tree canopy, depending on where there are suitable nooks along branches and tree trunks to anchor nests. It can be hard to tell nests apart from one another on thermal images when they are vertically stacked along the same tree truck, as seen in the middle of the thermal image. However, when nests occur under the canopy, such as those in the top right of the images, using thermal images definitely helps us “see” birds hidden beneath the leaf cover. So we may continue using this technology in the future to ensure we have counted nests across the entire rookery. It’s definitely an interesting way to view the rookery, wouldn’t you say?
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