This week, we at Dispatches from the Field are very excited to welcome guest blogger Amy Strauss, a fantastic field biologist and a former field assistant for resident Dispatches blogger Catherine Dale. Amy, who is now pursuing her own graduate work, shares stories of deception and duplicity from her fieldwork studying song sparrows in Massachusetts.
Fieldwork is about beautiful landscapes, vibrant sunrises, and becoming one with the great outdoors. It’s about pursuing scientific exploration in a natural setting, free from the limitations of a superficial laboratory environment.
My fieldwork is also about trickery.
A thick morning fog begins to burn off just as the sun rises over Wentworth Farms Conservation Area in Amherst, MA.
I am a behavioral ecologist, driven by an intense curiosity about what evolutionary and ecological factors have shaped the behaviors exhibited by animals today. Why do some species hibernate and others don’t? Why do we see such elaborate courtship displays exhibited by some animals and not others? Why is it adaptive for some lizards to squirt blood from their eyes when threatened, and for some female spiders to eat their mates after sex? This is the sphere of biology where my intellectual curiosity peaks.
One way to try to understand the biological function of a particular behavior is to manipulate something in an animal’s environment and see how the animal behaves in response. I study singing in birds, a communication behavior used in social interactions, so I get to manipulate birds’ social environments to figure out how song functions. And that’s where the trickery comes in.
Envision a team of field biologists – clad in full nerd attire, binoculars dangling around their necks, and each toting multiple large bags of equipment. This brigade of researchers woke up at 3:30am, bathed themselves head to toe in DEET, and are all geared up for a day in the field. Their goal? To fool unsuspecting little song sparrows into perceiving the presence of birds that aren’t really there.
Let me explain.
Song sparrows are territorial during the breeding season, which means that in areas of adequate habitat, individual males claim space and resources and then fiercely defend them. Those males then work to attract a female to their territory – and fiercely defend her as well. Land gets divided up amongst song sparrows in more or less the same way we humans divide up land amongst ourselves: ‘what’s mine is mine, and what’s yours is yours’. Neighbors are just fine as long as they don’t cross over the designated property line – or in the case of birds, the designated territory boundary. And just like in humans, anyone who crosses into another’s territory is considered an intruder and an aggressor.
Song sparrows use song in this context to negotiate territory boundaries in the springtime, and to maintain those borders throughout the breeding season. Have you ever taken a stroll through the woods or through a meadow in the spring and summer months? If so, you’ve probably heard the perpetual, beautiful singing of many songbird species. What they’re saying, essentially, is: “This is mine! I’m here! Stay away! Back off!”…a loud chorus of self-promoting, resource-hungry birds all broadcasting their positions outward to a network of listening competitors.
I, a human researcher interested in some of the finer points of birdsong biology, can take advantage of this vocal communication system by posing as a song sparrow and attempting to infiltrate established song sparrow neighborhoods. And this is my mission each day in the field: to manipulate the social environment of these birds by masquerading as a rival male song sparrow and observing the birds’ responses.
How do I pull of such a disguise? Good question. No, I don’t try to pass for a song sparrow by gluing feathers onto my head or taping wings onto my back or rigging up some fancy flying machine, although that sounds like fun. I do it entirely through sound. It’s convenient for me that birds rely so heavily on acoustic communication, though it’s not a coincidence at all; their reliance on song is precisely what got me interested in singing behavior in the first place. So my disguise in the field consists of song sparrow song recordings played through a camouflaged speaker connected to – you guessed it – my iPhone.
Amy and her field assistants raise a net and plot their strategy for capturing their next song sparrow. Can you spot the net?
Using this simple system, there is a whole lot I can do with a population of song sparrows, and a lot of fascinating biological hypotheses that I can test. A favorite trick of field ornithologists everywhere is to catch birds from the air, using song to lure birds into their nets. Remember: a bird that crosses into the territory of a conspecific, when detected, will be challenged by the territory-holder. And an audio speaker playing conspecific song from inside the boundaries of a song sparrow territory, when detected, will be challenged by the territory-holder. And so the poor suckers fly right into our nets! [Side note for the wary: birds are not injured during this process.]
A banded male song sparrow, fashionably clad in hot pink bands!
Once the bird is in hand, there are many things that researchers can do – take morphological measurements, gather DNA/blood/tissue samples, or attach GPS trackers to the birds. As a behaviorist, what I do next is place small bands around the bird’s legs that will stay on over time so I can identify that individual in the future. One band has a unique identification number on it, and the other bands are a combination of bright colors that allow me, even from afar, to determine the identity of the bird. Once they are banded and released, I can track individual birds as they fly around their territories, allowing me to create very precise maps of territory boundaries and to learn “who’s who” in the song sparrow neighborhood. I’m now further equipped to meddle in the social lives of these song sparrows.
A portable speaker broadcasts recorded song sparrow vocalizations, fooling the (real) sparrows of the neighborhood.
The real meat of my work comes next – when I throw on my audio-disguise again, this time not to catch birds, but to investigate the function and relevance of variations in song sparrow singing behavior. My field assistants and I, in the form of a portable audio speaker, work together to simulate a trespassing song sparrow intruding on another’s territory. From this speaker, we can present a range of vocal recordings and closely monitor how a bird responds to each. Because we can identify individuals by the colored ID bands affixed to their legs, we are able to perform repeated experiments on the same individual song sparrows to compare responses over time or across treatments. We can vary the song stimuli presented, we can vary the location of the speaker, and we can vary the time of presentation – to see what effect these changes have on the unknowing, outwitted song sparrow. Across these and many more axes of variation, big questions can be asked about the factors that affect avian vocal behavior, territoriality, and aggression. All with just a speaker posing as a song sparrow and some super stealthy field assistants.
Fieldwork is just trickery…in the name of SCIENCE.
Amy Strauss is currently working on her PhD in Organismic and Evolutionary Biology (OEB) in the Podos Lab at the University of Massachusetts – Amherst. Prior to joining the OEB community, Amy worked as a Scientic Assistant in Vertebrate Zoology at the American Museum of Natural History, where she did things like inventory elephant skulls and read through curator field notes from the 1920’s. Amy was inspired to work on birdsong after assisting on a few song-related field projects during and after college — including a summer job in the Dominican Republic working for Dispatches co-creator Catherine Dale!
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