Bird banding can provide valuable data on several fronts. From monitoring populations in an area, studying migration and various other study and research programs.
So how does bird banding work? A typical day of bird banding for passerines (songbirds) starts before the sun rises, and in our case, that means 4:45 am. It’s still dark out, so everyone grabs either a flashlight or headlamp then heads out to set up the mist nests, which are used to safely catch birds. How often the nets are checked can vary, but in our case it’s every half an hour. After all the nets are set up, we head back to our work area to wait for the first check of the day. These mist nets that were just set up, are special nets created specifically for safely catching birds, made of thin material so fine that they appear as nearly-invisible to birds as they are flying through an area. When they hit the net, they fall down into the loops or pockets formed in the net, trapping them until a bander comes along and removes them.
Todays banding session is being conducted by licensed banders and assistants through MAPS. MAPS stands for Monitoring Avian Productivity and Survivorship, the purpose of this project is to create a database to monitor bird population trends. Here we are documenting birds in the area, and if they are breeding here.
Its been a half hour since the nets have been set up, so its now time to go check them and see if any birds have gotten caught. The banding team splits up with half going to check one set of six nets, while the other goes and checks the other. At the first net, there are two birds, the most common species captured in this area, the Gray Catbird and Song Sparrow.
Carefully, the bander will access what side of the net the bird flew into, as that is the side of the net they will have to be on to successfully get the bird out. After this is figured out, the bander will start to carefully work the thin wire of the net off and away from the bird. Slowly freeing the bird’s wings, neck and feet from the net. After the bird is completely free, they will be carefully placed in a cloth bag and a wood clip will be put on the bag handle, indicating what net the bird was caught in, another bit of information used to help track birds and how the habitat is being used by different bird species.
Once all the birds in the nets have been extracted, everyone heads out, birds in bags, back to the banding station. At the station, all the necessary equipment has been laid out, bands are set in order and the paperwork all prepped for the day of data collection.
The first bird of the day to be banded in the Gray Catbird. As the bander is removing the catbird from its bag, another person, who will be writing down the information collected, starts filling out the information on this individual bird. Data such as the current date, the station name, time the bird was collected from the net, what net the bird came out of, and when the bander is ready, will read off the nine number band combo that is going to be attached to the leg of the catbird.
There are many bird band sizes though, so how do the banders determine which is the correct size for the bird they have in their hand? Even in one species, a bird’s leg can vary in thickness, requiring the use of different sized bands. A crucial tool for bird banders comes in the form of Peter Pyle’s bird guide. So now they turn to the page about the Gray Catbird, where the recommended band size is listed. To double check the size, the bander grabs a leg gauge, this tool has many different sized notches all along its sides, each correlating to a different band size. After the proper band size is confirmed, the aluminum band is placed on the bird with special banding pliers.
After that information has been recorded and band attached, the bander will double check to make sure that the band is fully closed, as if it wasn’t, there would be a chance that grass, depri, or other materials could get stuck in it, or the band itself could cut the bird’s leg. As the bander firmly grabs the bird’s legs between their thumb and index finger, they pull the legs downwards towards their tail, gently blowing on the bird’s belly to part the feathers. They are now checking to see if the bird has a brood patch present. This catbird shows a large bare patch on their belly, based on how vascular or fluid filled this area is, they will give it a code of 1-4, this allows them to determine how far along in incubation of their eggs this particular bird is. This also tells them that the catbird is a female, though to double check, the bander raises the bird’s legs up to check their vent. The bander blows on the vent area to part the feathers, they are now looking to see if this bird has a cloacal protrusion. In this case the bird does not, if it did, they like the brood patch would rate the size from 1-3 based on shape and size. The presence of a cloacal protrusion would indicate that the bird is male, and would also tell the bander if the bird was most likely currently breeding in the area. So now we know that this catbird is female, and the transcriper would write down F for female, along with a B for brood patch under how the sex was determined.
Next they want to see how much fat the bird has stored on its body. Since it is breeding season, most birds have little fat stored, once migration comes though, then they start storing fat for their long migration south. Once again, the catbirds legs are carefully pulled down towards their tail and a puff of air is placed over where their fircula is, it would be the collarbone area in us humans. Once the feathers are parted, the bander looks in the divit where their neck meets the body to look for any visible fat deposits, this bird has just a light trace of fat and is given a code of 1.
So after they have determined those data points, next is to try and age the bird. Generally they can be given the label of hatch year, after hatch year, second year or after second year. Looking at the overall feathers of this catbird, we can tell it’s at least an after hatch year, it has dark eyes, the inside of its mouth is black and its feather quality looks like an adult. To get a more specific gauge of the bird’s age, the bander carefully extends the bird’s wing to look for a molt limit. Looking over the bird’s wings, we see that all of the wing feathers appear silvery except the primary coverts, which are more brown than the rest of the feathers. Those brown feathers are their juvenile feathers from last year, indicating that this female catbird is a second year bird.
Going over every feather group, the bander will tell the person jotting down the data what each group is. If that feather group is the bird’s Juvenile plumage, basic plumage, or alternate plumage. In this bird’s case, all feather groups are B for basic except the primary coverts which are J for Juvenile. This is called a molt limit and is the primary way of aging a bird.
After these steps, there are a few other data points that need to be collected. A puff of air will be blown under the bird’s wing, to look and see if the bird is molting their body feathers or their flight feathers, which in this case, the bird isn’t.
Next, the bird’s wing will be extended again and the bander will closely inspect the ends of the first five primary feathers of the bird. Here they are looking for feather wear, the birds feather tips look very new and don’t show much wear except for a nick in the second primary feather. So for feather wear, a code of 1 is written down out of 5.
Now the last two data points that need to be collected are the bird’s wing chord measurement and its weight. Carefully, a ruler is placed under the bird’s folded wing to get its measurement, from their wrist to the tip of their longest wing feather. This measurement is written down and now for the last step of weighing the bird. The catbird is carefully placed in a roll of lightweight panyhose after the scale is zeroed out with the weight of the panty hose so just the weight of the bird will be shown. Depending on the banding station, there are many different ways to weigh a bird including a paper towel tube or in the bag itself.
Now both the catbird and song sparrow have been banded, information recorded and now its time for release. The bander carefully holds the birds and places their feet on their other flat extended hand, they carefully loosen their grip on the bird’s body and the bird flies off quickly. The catbird of course makes sure it gets in another quick bite to their hand before it flies off. The last thing written down for the catbird is its release code, which is 300, indication it was released unharmed. There are different codes used if the bird is captured injured, or was injured in the process of banding.
Now it’s time for another net check. Several birds are in the nets this time, including 2 catbirds, a Song Sparrow, a female Common Yellowthroat, and a male American Goldfinch.
Next we will band that American goldfinch that came out of net 6. This bird doesn’t have a band, so we look in the Pyle guide and determine it needs a size 0 band and attach it. Just by looking at this bright yellow bird we know it’s a male, so we write down M for male and determined by Plumage (P). To double check, we check to see if it has a brood patch (nope) so we put down a 0 for that and look for a cloacal protrusion. It does have a small one so we write down 1, American goldfinches are one of the latest breeding songbirds in our area so it’s not usually that it would just be just developing a protrusion at this time of year. So since this bird was also determined to be a male by cloacal protrusion, after the P for plumage we will write down C for cloacal protrusion. Next this bird needs to be aged. Their wing is uniformly black along with strong contrast between the black and white on the tail, no brown plumage present on either location. These features tell us that this bird is at least a second year bird. Since nothing more specific can be determined, we will call this bird an after second year (ASY). Since this male goldfinch is in its bright yellow breeding plumage, called its alternate plumage, for molt limit, every feather category will be getting an A placed on it. The rest of the data points are gone over and then this bird is also successfully released unharmed along with the other birds.
Net checks are done often for the safety of the birds. Everything is done with the safety of the birds in mind, to avoid as much stress as possible and avoid injury to the birds. If the weather turns bad, the nets will be closed. Sometimes predatory birds will catch onto small birds being stuck and may show up hoping for an easy meal, at this point the nets will be taken down to protect the birds from becoming prey to the raptor or other predators.
Bird banding can be a critical tool for collecting important data on many subjects including migration. Even if you aren’t part of a scientific program doing the studies, I highly recommend checking out any program that may be going on in your area. It’s one thing to see a bird high up in a tree through binoculars and a completely different thing seeing it up close. You will have a much bigger admiration for the beauty of this amazing group of species.