This year, I’ve decided to keep a nature journal. As I already have this (previously dormant) blog, I’ve decided I’ll just post my entries on here. The plan is to write once a week, loosely basing my entries off prompts from Margaret Renkl’s new book Leaf, Cloud, Crow.

Here’s my first entry:

Our backyard has a tyrant. Marty the Northern Mockingbird is the undisputed despot of our birdfeeder. A flash of white and a flutter of wings mean that Marty has once again descended from a high oak or holly branch to reign terror upon all feathered foes. Yet again, another poor bird is prevented from nabbing a tasty sunflower seed or nutritious bit of suet. What a jerk!

I’m not proud of it, but it’s time to admit to everyone that I’m biased against mockingbirds. They are extremely loud vocalists, especially in the spring, with the annoying habit of beginning their continuous singing before sunrise They are common in suburban landscapes; thus, if I’m seeing a lot of them, it means I’m not in my preferred wilderness habitat. Plus, I really do hate a bully.

I readily admit feeling animosity toward Marty and kin is ridiculous. Mockingbirds have a lot to like. As both their common name and scientific epithet (Mimus polyglottos, the many-tongued mimic) imply, they have the amazing ability to incorporate the songs of other birds, frog calls, or even car alarms into their acoustic repertoire. While omnivorous, they are important seed dispersers of native plants, especially in fall and winter, as their diet shifts to mainly fruit. And they are willing to fearlessly take on potential predators, harassing hawks and ousting owls. I seem to be quite alone in my distain for the species, as evidenced by numerous positive references in art and literature (think, To Kill a Mockingbird). In fact, five US states have chosen the mockingbird as their official bird, trailing only beloved cardinals and meadowlarks by that popularity metric. Even Marty specifically has an admirer. My partner loves watching Marty splashing around in the bird bath that is the outside dog bowl, or hopping from fence to tree-trunk and back, head cocked at a jaunty angle, or scampering across our outdoor table, feet pattering and golden eye gleaming intelligently.

What is going on inside Marty’s little bird brain? After an hour of observation, I began to wonder if this bird is, like me, a biased creature. I started to think Marty wasn’t treating all birds equally. Carolina Wrens, in particular, seem to invoke Marty’s wrath. When a wren stopped by, not only did Marty immediately swoop in with wings outstretched, a chase often ensued, with both birds acrobatically weaving chaotically across the backyard. While Marty often displaced finches, nuthatches, and titmice from the feeder, both the intensity and duration of the rage appeared greater when a wren is involved. At the other end of the spectrum, Carolina Chickadees seemed to get a free pass as they snuck seed after seed right out from under Marty’s watchful gaze.

I wonder what forces are driving Marty’s differential treatment of competitors. Maybe Carolina Wrens, another common omnivorous resident here in North Carolina’s suburbs, share more overlap in diet, habitat, and behavior with mockingbirds than any other species. If so, then it would make evolutionary sense for Marty to pay more attention to their biggest rival! But before I build a complicated story that explains Marty’s actions, I need to check my facts. Is Marty really chasing wrens more aggressively and more often than any other species? Or are my observations of Marty’s biases themselves biased?

I came up with my wren prediction based on some initial observations. Without rigorously collecting additional data, I may subconsciously favor evidence that supports my claim. This tendency of conformation bias is why we shouldn’t just rely on antidotes when stating conclusions. In fact, as I continued to watch, Marty began aggressively chasing Eastern Bluebirds, a species that simply wasn’t around earlier in the morning. I also started noticing times when a wren snuck an unmolested snack.

So is Marty biased? In order to test my hypothesis, I would need many more observations of interactions between Marty and each species of bird. I could then statistically test if the likelihood of being chased off the feeder by the mockingbird depended on species. I probably would also need to account for things like the time of day, the length of the visit, and the number of other birds present. Then, if I wanted to make the claim that all mockingbirds (not just Marty) were biased in which species they chase, I would need to watch different mockingbirds across multiple locations. And even after all that, I still couldn’t be 100% certain in my claims. This time-consuming process is why people can get annoyed with scientists. We can’t quickly give a straight answer without couching it with an “it seems” or a “probably!” But it’s also why people can trust the conclusions of peer reviewed studies much more than their own gut feeling or the claims of a TV talking-head. We systematically eliminate sources of observational bias to get closer to the objective truth. What’s more–this careful accounting of the natural world has great side effect. It almost inevitably leads to a greater appreciation of the being you are watching. Even after just a morning of observation, I can already conclude that Marty is more beautiful, charismatic, and maybe even benevolent than my biased perspective initially had me believe.