The mammal people have it easy - they can slap a big ol' collar on one of their gigantic animals, with a honking huge battery, plenty of battery life and a huge signal range. They can have movement sensors, GPS devices, automatic collar-releases, light sensors, all kinds of stuff. But birds are different. Our birds only weigh about 30 grams (lighter than an iPhone, to put it in terms that modern folks can understand). And they fly. So the transmitter has to weigh very, very little, and has to be attached somewhere near the bird's center of gravity and somewhere where it won't mess up its flight ability. Usually the transmitter is glued to the feathers of the back, like a tiny fanny pack, or sometimes mounted in a teeny-tiny backpack. These transmitters are designed for birds, and they are miniaturized miracles - an infinitesimal battery, a little radio crystal and a few other micro components, encased together in a minute teardrop of acrylic, with a long antenna sticking out the end:
The worst culprit, for weight, is the battery. Generally we have to keep the battery so small that it will only work for a couple of days.
The next worst culprit, for weight, would be a sturdy switch to turn the radio off. So there is just the tiniest, flimsiest little magnetic switch, deep inside. When the transmitter arrives, it's attached to a little magnet that keeps the switch shut and the battery off. As soon as you take off the battery, the radio springs to life. But the little switch is so flimsy that once it turns on, often it won't turn off. And there's so little battery life that if your radio won't turn off, you can burn right through the battery in a couple days. And so much for your $600 transmitter.
Maybe you can see what I'm getting at: We can't test the radios beforehand. The risk is too great that if we start them up, we won't be able to turn them off and we'll immediately burn through the precious battery life.
And maybe you can see what's coming next. There we were, out in the early dawn light by Signal Mountain with our mist net set up and our 5 precious radiotransmitters carefully taped to pieces of cardboard with their frequencies, and weights, scribbled by each one - and we had no idea if any of the 5 would work. The problem was, we had ordered 20 new radios that hadn't arrived yet (due to the fact that there is only 1 fellow in the entire universe who knows how to make them, and, how shall I put this, meeting deadlines is not one of his most prominent work habits.) All we had was our 5 backup radios, of uncertain vintage.
Anyway, the moment came - we caught a crossbill! We pulled the little magnet off radio #1. Jamie aimed an antenna at it, punched the right frequency into it, and immediately we heard the reassuring "WOOOOOOOOOO" hum of a working radio. Yay!
Now came the really tricky part: attaching it to the bird. Our radios are unusual: they are heart rate transmitters. That means they have two tiny, almost invisible copper wires that have to make contact with the bird's skin. So we had (1) securely sew a tiny bit of cotton fabric to each radio, (2) clip off some back feathers, (3) make two tiny pinpricks in the birds skin, to either side of the back feathers, (4) slip the two slender, fragile, copper threads into those two minute, microscopic pinpricks in the bird's skin so that the electrodes will stay put - while both electrodes are trying to spring in the wrong direction, tiny feathers are blowing everywhere and the whole radio is trying to flip suddenly out of your fingers onto the ground and the bird is, at this point, staring at you with a certain baffled look that clearly means it is wondering what the H*** you are doing; (5) glue the cotton fabric to the bird's back feathers (with cosmetic eyelash glue).
After all of that, it actually ends up very tidy and aerodynamic, right above his center of gravity, and with the antenna sticking out right along his tail feathers. It's an awfully clever rig, and I admire whoever thought this up. It's also relatively low-impact for the bird. He'll shed the whole thing in a couple weeks when he re-grows those back feathers in August.
But it was an intense two-person production. I was holding the crossbill in my left hand, bracing one wing out of the way with my other hand and holding his left wing down with my other other hand. (if you are counting hands, you start to see the problem, right?) while Jamie was using one hand to hold the radio, her other hand to clip the feathers and her other other hand to put the electrodes in place. (In bird work, every finger is doing double duty - you get used to doing 1 job with the base of each finger and a different job entirely with the fingertip.) We were both hunkered down over the little fellow, and he was so tiny that all of our fingers were constantly colliding with each other. We were both practically holding our breath.
Jamie got the first electrode in place. Beautiful. Perfect placement. The bird was fine - tense, of course, and obviously confused, but he was alert and seemed comfortable. (Birds that are not comfortable will let you know it, very clearly.) The radio was still working. "WOOOOOOOO..."
Then Jamie slipped the second electrode into position, and instantly the radio went dead silent.
What the ... ? We stared at each other. The radio had died!! We tried pushing the radio around, repositioning the electrodes, fiddling with the frequency, switching to a different antenna, changing batteries in our receiver... nope, it was dead. DAMNATION! And just when it was all glued on, too, and in perfect position, and the bird was all ready to go.
Dismally we peeled the radio back off and removed the electrodes. We tried another radio... This one was dead. It wouldn't even come on at all.
At this point we'd had the little guy for an hour and we didn't want to stress him out further, an hour being sort of a mental tipping point that Jamie and I both have, when dealing with wild birds. We let him go (with his female - I'll write later about how his female came back looking for him).
They both flew away. Immediately the radio - sitting on our pickup tailgate - said "WOOOOOOO..." It had just started working again. WHAT THE...?? Now the bird was gone... and we only usually catch 1 or 2 crossbills per day. Sure enough, we caught no more that day and returned home discouraged.
Long story short, we eventually verified that that particular radio had a short. Its signal came on and off whenever it was jostled, whenever an electrode was touched, whenever we shook it. Well, that's not a very useful radio to put on a live, flapping, jostling, moving bird, is it?
Three of the other radios were completely dead. Dead batteries.
By the time we figured this out, it was late on Wednesday and we'd spent three days testing useless radios on puzzled birds.
That left ONE WORKING RADIO. Un-be-lievable.
But one is better than zero! And that one radio set us off on our Signal Mountain Adventure the next day. More about that later.
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