Field Fiasco Friday is a weekly segment highlighting the follies, foibles, farces, and failures that accompany any successful field season. Through this segment, we’ll share the stories of scientific data collection that don’t always make their way into the published results.
In early January of 2016, my colleagues and I headed out to South Mountain desert park, just south of Phoenix, Arizona, to capture some wild house finches for our study. Our goal was simple: we wanted to examine the effects of bird feeders on wild bird health and disease. To test this, we planned to bring rural birds, that lived off native desert plants in the surrounding mountains around the Phoenix desert, into captivity where their food source would become bird seed and feeders commonly encountered by their urban conspecifics.
Luckily, house finches are relatively gullible. We set up “basket traps”, wire baskets with a feeder full of delicious sunflower seeds – a finch favorite – in the middle. The finches can enter various funnel-shaped openings without a problem, but they can’t figure out how to get back out.
So, just after sun up, we hung up our basket traps in a tree just out of view from the parking lot and waited in our car to let the finches find the feeder. It was likely to be an uneventful morning. We watched cactus wrens flit from the saguaros while we listened to the radio quietly to pass the time. After a half hour, we checked the traps and decided to wait a little while longer. When house finches find a food source, they omit “contact calls”, little shout outs that attract other finches to the area. By waiting, we would let the finches bring along their friends and increase our yield.
Another half hour passed. It was my turn to check the traps. As I approached, I noticed from a distance that no birds were flying around in it. Had they managed to escape? A closer look revealed that no, they hadn’t. Fifteen finches were out dead at the bottom of our trap! I wasn’t sure what to do, and ran back to the car, bewildered. “Umm, guys? There’s a bunch of dead finches in there!”
Quickly, our field day turned into a forensics investigation. We examined the evidence: most of the finches had no obvious wounds, no blood, and there were few signs of a struggle, just the smallest clump of feathers on the ground. The trap lid was slightly ajar, the only sign of something amiss (apart from the dead finches). We ran through possible explanations. A snake? A raccoon? A villainous hiker laced the sunflower seeds with poison? We were stumped; Occam’s razor eventually led us to the only reasonable explanation: this was the work of a chupacabra.
Hesitantly, we re-set the trap and decided to try again, feeling guilty about the inexplicable loss of so many finches. But we vowed to check it more often, to see if we could catch the chupacabra in the act. Fifteen minutes later, we rechecked the trap only to find two more finches desperately trying to escape their attacker: alas, not a chupacabra, but a loggerhead shrike! This large gray bird, about the size and color of a mockingbird, looked like a villain. The bars around the eyes resembled a bandit mask, and the sinister curve to its bill made sure you didn’t mistake this for just another songbird. Shrikes are songbirds gone rogue and raptorial, and use pointy structures (cactus thorns, barbed wire, or in this case, the wire of trap) to impale their prey. This one had had a heyday attacking our helpless finches.
This mystery was solved and we got to nerd out as only birder can. Loggerhead shrikes are not always easy to sight, much less catch in the act of being little Vlad-the-impalers. But, as cool and curmudgeonly as he was, we knew we couldn’t keep the shrike around if we wanted to accomplish our goal. We bagged him up and drove him 2 miles down the road, where he could terrorize a new territory of helpless fauna and stay away from our finches!
Author Victoria Farrar is a 2nd year PhD student in Animal Behavior. She studies bird neuroendocrinology. This field fiasco occurred during her gap year work in the McGraw lab at Arizona State University.