Mist-netting...debunked

When I first heard of ‘mist-netting’, my mind swarmed with visions of dewy green glens, delicate birds suspended in shafts of sunlight, and maybe a fairy or two skipping around the scene. The real version is far more nitty-gritty, feces-filled, and challenging. That said, mist-netting will always retain a certain sort of magic. Each bird has a story; we do our best to piece it together, and share it.

Before closing Idaho Bird Observatory's net one, for the end of
the 2009 season. Can you see the mist-net?

Golden-crowned Kinglet banded
at IBO in fall 2009.

I’m guessing mist-netting isn’t an everyday term for most people, and since many a future story to come will require some understanding of the concept, here’s a quick run-down. A standard mist net is 12 meters long and probably about two or three meters high. Usually five or six ‘trammel’ lines run the length of the net. In addition to keeping the net from sagging, they also create a sort of long pocket. The material is very fine, and a dark color. Each net is placed strategically, in a net lane cut amongst vegetation where bird traffic is suspected to be heavy. Because of the fine material, and placement near vegetation, birds don't notice the nets in time to avoid them, fly in, and get caught in the pockets.

Extracting the bird is like solving a puzzle. Some birds don’t struggle and are hardly even in the net (Nashville Warblers!). Feisty birds manage to create some amazing tangles (Chickadees!). Others provide resistance in the form of high pitched squeaking and clamping down on fingers and soft spots with powerful beaks (Grosbeaks!!). Projectile poop abounds as a defense. By the end of the season, you can expect to have poop stains on every article of clothing. But by then you won’t really mind it anyway. The overall goal with extraction, is to do it quickly, gently, and in the safest way possible for the bird.

Nathan Banfield showing off the fat stores of a particularly chunky
Oregon Dark-eyed Junco. October 2009

Caroline Poli with a banded Steller's Jay.

Bird-banding pliers. The good
ones...and last of their kind

Birds are placed individually in cloth bags and carried to the banding station. There, each will receive an appropriately sized aluminum band with a unique number on it. Special pliers close the band around the bird’s tarsus, so that it can slide up and down, but not over the foot or ankle joint (which looks like a backwards knee). We take morphological measurements and give the bird a ‘fat score’. Birds have thin, nearly transparent skin, so when the feathers are parted by blowing on them, fat is actually visible. Migrating birds store and put on fat very quickly, as it fuels their migration (birds can convert fat to water!). Resident birds usually do not have a need for much fat/fuel, so don’t have much.

Measuring tail length at the Lucky Peak Banding Station.

Ageing the bird is both fun and challenging. To determine age we can look at several different things. Skull ossification and molt limits are two main ways, but eye color, bill color, and other characteristics can be telling. For ‘skulling’, remember that transparent skin? When a bird hatches it has one layer of skull bone. Over the next few months as it develops, a second layer grows in underneath (ossification), in a particular pattern. The two layers are connected by columns of bone. Through papery skin and with practice, all of this is visible. Two layers together look white-ish and will have little dots (the columns). One layer looks pink-ish. So a bird that still has only one layer in places is a hatch-year bird. I’m going to glean over molt limits for now, because it takes significantly more time to explain and probably deserves a post in its own. AND it also probably isn’t as fascinating to the average human being as it is to me and other bird nerds!

The afore-mentioned chunky Junco
being weighed. October '09

After the data has been collected, we measure mass and send the bird on its way. Kids like this part in particular because after placing the bird in their palm, we’ll let them do the ‘release’. By mist-netting and collecting data, we learn about life histories of different species, monitor population trends, and have an excellent teaching tool for banding station visitors. The primary focus of the banding station I'll be working at for Rocky Mountain Bird Observatory will be education. In the coming weeks, hundreds of students will pour past the banding station. I’ve banded birds around Boy Scout troops, and kids of all ages, and suffer no illusions about how our feathered friends often weigh-in, in comparison to say, lizard catching or tree branch sword fighting. I can only hope they have a positive experience, and maybe even leave with the same sense of awe for birds that I have.