With training now complete, most of the past week has been dominated by the construction of a 600 ft long network of tunnels in the cormorant colony on East Sand Island. Unlike the unassuming albatrosses that allowed us to walk straight up to their nests on Tern Island, Double-crested Cormorants are especially sensitive to human disturbance. We simply can’t just strut about the colony during breeding season. If we did all the birds would flush and abandon their nests regardless of their contents, leaving any eggs or chicks exposed to the ravenous Glaucous-winged/Western Gulls that also breed on East Sand. The tunnels will allow us to navigate the colony and access observation blinds without causing disturbance. Special capture spurs outfitted with trap doors will also permit us to temporarily remove birds from their nests to be outfitted with tracking devices like satellite tags. The Google Earth image of the cormorant colony on East Sand shows the old network of tunnels similar to what we are building this year on a different part of the island. The black dots are Double-crested Cormorants on nest bowls made of sticks and debris. The white coloration is cormorant shit that I will coat everything, including me, by the end of the season.
As you can imagine building over 600 feet of tunnels on a cold sandy island at the mouth the Columbia is not the easiest of tasks, and requires a fare bit of labor. We first had to construct the vertebrae and framework of the tunnels back in Astoria, and move all materials by boat across tidal flats and onto site. An ATV helped with moving some of the heavier gear like generators and air compressors. A-frames roughly four feet high make up the backbone of the tunnels spaced about 15ft apart, held together by 2x4’s running along the apex. Silt fencing draped over the skeleton provides the skin, anchored into the sand by burying the edges. The fencing is pulled tight and tacked into place with slats and staples. Access points in and out the tunnels are caped with wooden blinds and the terminal ends contain capture spurs that branch like arteries into the colony. Double-crested Cormorants apparently like to nest in old tires, which are strategically placed near the capture spurs to encourage birds to nest near the trap doors. We are nearly finished with laying out the framework and fencing, and should have the entire network ready for use by the end of the week. There is also a Caspian Tern colony on the opposing side of the island that will require some set up as well before the birds begin to arrive sometime next month.