Bridge Piers and Bird Poop: RiverNET sensor maintenance


Getting out in nature is why most of us got into ecology in the first place, so I take every chance to get out of the Bozeman office for some field work. Lately, that’s meant driving down to the Yellowstone River in Paradise Valley, tying a climbing rope off to the Mill Creek Road Bridge, and rappelling down the bridge pier to work on our new cellular-transmitting water monitoring station. And while I do enjoy stepping over the guard rail, loosening my rope-locking belay device, and gliding down to a swallow’s eye view over the Yellowstone, I do end up getting a lot more than I’d like out of the birds than just their vista.

Both the sturdy plastic box housing the sensor’s transmitter, electronics, and battery, and the solar panel powering it all, are perched on the tops of the piers just below the bridge deck. Just overhead, perched on the underside of the bridge deck, are dozens of mud cliff swallow nests. So while the top of the pier makes a convenient (albeit crammed) place for me to stand when I need to calibrate the sensor or adjust the solar panel, it is also a convenient place to collect bird droppings. My helpers up on the bridge deck always think I dropped a tool when they hear the first big splash, but then see it was just a big clump of swallow guano being kicked over the side. Then they realize why I switched from sandals to rubber boots before descending.

But my worst too-close-for-comfort nature experience happened when I was bolting down the stilling well – a vertical PVC pipe alongside the bridge pier that houses the sensor, protecting it and keeping it from moving in the current. I had a cheap plug-in impact drill (we are a non-profit, after all) with a portable generator up on the bridge deck and an extension cord running down alongside my climbing rope, pockets full of expansion bolts and waterproof epoxy, and was hanging nearly upside down inches above the river, rattling away bolt-sized holes in the concrete. I bumped into the PVC pipe, and from behind it came a giant globe weaver spider. Now those things look particularly nasty, but the biologist in me knew they are harmless, plus anyone who has watched them at work weaving a web has at least an admiration for them if not an affection. So I just hung in there (literally) and decided to live and let live. But then, from behind mama spider, came 10 gajillion baby globe weaver spiders. I didn’t like that at all, but there wasn’t much I could do about it either, so decided to just keep drilling away and let them scramble away up the pier.

It’s not all bird crab and arachnophobic nightmares though; far from it. Earlier this spring, I was working there during the “Mother’s Day Caddis Hatch” – any fly fisherperson will know what that is, but for everyone else, it is one of the first trout feeding frenzy-inducing aquatic insect hatches of the year – and noticed a bunch of gardener snakes on the banks eating adult caddis flies. Then I noticed how one of the snakes had a big wound, and was wondering how he came by that, when I saw a red-tailed hawk swoop out of the nearby cottonwood and grab one of the snake’s kin. Just another day in the office – on-budget, on-demand problem solving; challenging workplace conditions; wildlife surprises – for a field biologist!

By the way, stay tuned to our RiverNET project page: we should be getting realtime data from that sensor online any day now, making its installation worth the trouble…

Patrick Cross is YERC’s research director and the RiverNET project manager

Patrick working on the sensor’s solar panel mounted on the bridge pier: the “dirt” under the panel is actually guano from the swallow nest above.

Patrick working on the sensor’s solar panel mounted on the bridge pier: the “dirt” under the panel is actually guano from the swallow nest above.