To identify the species, sex, and age of a bird, a bird bander in North America relies either on personal experience with the species or on the massive handbook of bird descriptions known as the Pyle Guide. The Pyle Guide is full of confidence-instilling descriptions like “Juvenile rectrices usually pointed, but occasionally truncate” and “Male scapulars brownish-black, compared to blackish-brown in female.” To make matters still more confusing, birds can vary from site to site, meaning that the description in Pyle based on a population 100 miles distant may not be correct for your own local population. One of the best tools a bird bander can have, as they squint at a bird and wonder whether its iris is “red-brown” or “maroon” and whether that is even relevant to their local birds, is a comparison photo showing local birds.
You have to be a bit lucky to capture such photos: you have to happen to catch both birds at the same time. When you usually catch five or fewer birds at a time, as we do, the chances that any two of them will be an informative comparison becomes small. Each of these pair photos is a little special for this reason.
One of the many fun things about bird banding is that you never know who you’ll catch next: every bird is a surprise. To try to share that feeling, I’m running brief profiles of selected birds we’ve caught in a mini-blog called “Notes from the Station.” The birds profiled definitely tend toward the more conventionally “exciting,” but I try not to neglect our good common birds too—they have their own interesting stories. Each profile includes a photo of the bird and some information about it, and every one is a real bird with real data. I try to do a few new profiles each week. Check it out!
Facebird. Instagrebe. Tikstork. Linkedpenguin. Twitter. Only one of these is real, and I’m pretty sure that even on Twitter the number of actual birds participating is negligible. Birds do have social networks though—the old-fashioned analog kind, made up of flockmates and siblings and reproductive partners and rivals. Some species, like the Black-capped Chickadee, have tight-knit flocks with elaborate social hierarchies; others, like the Hermit Thrush, live most of their lives alone. These differences are surely fundamental to shaping the lives of birds, from their mundane daily experiences to how they tackle life-or-death challenges. If you spot a deadly predator like a Cooper’s Hawk, do you try to disappear quietly into the brush or do you risk your safety by giving an alarm call to warn your companions?
It’s been… 20 months (yikes) since my last post, and some stuff has changed! I’m back in the San Francisco Bay Area where the juncos look right – none of this slate-colored nonsense – and I now co-run a bird banding station.
The sun rising behind the mist nets at the banding station.
‘Tis the season for year-end “Best of” lists, so I thought I’d do something of the sort for my 2017 banding station birds. Except it turns out that we had too many cool birds this year to fit in one blog post, so I’ll be doing a series of banding station highlights posts. First up: the small and fuzzy.
It’s the time of year when migrants come through the banding station on their way from their breeding grounds in the north to their wintering grounds in the south. We see a greater variety of species now—not just those who like to breed here, but everyone who thinks our patch of forest looks like a good place to stop for a snack. It isn’t just that these are different species, though: these birds have a different feel to them. These are travelers on a genuinely long and perilous journey. We banders are, I hope, just a blip in any bird’s day—a frightening moment to be shaken off by mid-afternoon—but the days we interrupt for these migrating birds are epic days.
This is physically manifested, on the birds, as fat.
The birds are having babies, those babies are learning to fly, and they are flying into our nets at the banding station. They’re not really babies by this point: most of them are independent of their parents. They may have been out of the nest for a month or more, and are technically “juveniles” or “immatures.”
At the banding station we collect data on each bird we catch, including that bird’s age. It’s important to record the age if we can, because the more accurate we are with the age the first time we catch a bird, the more accurate we can be later. If we caught a bird in 2014 and recorded that it was a juvenile, then when we catch it in 2016, we’ll know it’s exactly 2 years old. If we didn’t bother to age it back in 2014, then in 2016 we would only know that it was at least 2. That maybe seems like a small distinction, but the lifespans of wild birds are still an area in which we lack a lot of information, so knowing exact ages is valuable.
How do you tell if a bird is a juvenile or an adult? In some species, the juveniles are dramatically different colors than the adults. Juvenile juncos, brown and streaky, look distinct from adults even from a distance—until they molt, at least. But the differences can be a lot more subtle.
Here is a Common Yellowthroat from the banding station:
Last year, I waited to order color leg bands (for banding the juncos) until spring. This turned out to be a mistake, since everyone else ordered their leg bands at the same time, so all the good colors got backordered and I spent the first half of the field season banding my birds in just orange, lime, green, light blue, brown, and grey. If you’re wondering whether brown or grey bands show up on a junco leg: well, no, they don’t.
I learned my lesson. I’ll have a full arsenal of colors for this field season:
I think this is the least dignified photo of Limpet I have ever taken