Bird Banding Station

One day this spring I was fortunate enough to chance upon a bird-banding station during a trip to a state park in Virginia.  The banders had just returned from the nets (where the birds are captured), and they graciously invited me to join them as they processed their latest catch.


The Banding Station
 
The banding station itself consisted of a picnic table strewn with numerous banding tools, including a rugged laptop computer into which is entered information about each bird captured:

The birds are brought back from the nets in small white bags, one bird per bag.  Each bag has attached to it a clothesline clip with an alphanumeric code identifying which net the bird was caught in, since the nets at different heights and locations around the banding station represent different "micro-environments" used by the birds during their various daily activities:

The birds are processed one-by-one.  To make sure the bird can't escape during handling, the bander is very careful to use a safe, but firm grasp, in which the bird's neck is held between two fingers, resulting in something that looks like the avian equivalent of a "headlock":



Note that despite the firm grip used on the bird, the banders are keenly aware of the fragility of their subjects, and are careful to never injure them.  From the image of this warbler's leg and toes (below), you can see just how small and fragile these creatures are:



The first task for the banders is to positively identify the species, gender, and year of the bird (some songbirds look different during their first or second year from how they'll look as adults).  In some cases this requires the use of a thick reference book, to be absolutely certain as to the gender, year, and (in some cases) subspecies or geographical race:

Although other field guides are also occasionally used, the main reference is a thick book that you wouldn't want to try keeping in your back pocket while birding --- it's the Identification Guide to North American Birds, by Peter Pyle:

During the identification phase, some birds (such as this Blue-winged Warbler) pass the time by reading excerpts from this weighty tome*:

Here's another bird (a female Red-winged Blackbird) that appeared to be mulling over a particularly interesting passage in the text*:

Various measurements are taken from the birds during their processing.  These can be used either to aid in identification (i.e., the use of "morphometrics" such as size-weight ratios to distinguish between male and female birds in some species) or simply added to the database entry as additional information about the physical condition of the individuals captured.

One "measurement" is the condition of the bird's plumage.  Here you can see the bander examining the primaries and coverts on a Common Yellowthroat:

The degree of feather wear in a bird's plumage can be an indication of the bird's nutritional state, since birds sometimes delay molting when living in a nutrient-poor environment.  Feather wear can also sometimes help differentiate between an adult bird and a sub-adult.

Another indicator of nutritional state is the amount of body fat present.  Below you can see the bander blowing on the bird's underside so as to expose the bird's skin (which is barely visible on this individual, due to the thick plumage).  Because fat reserves provide energy for the bird during migration, the degree to which a migrating bird possesses subcutaneous fat deposits can indicate how likely the bird is to reach its final destination (or, alternatively, how much time the bird is likely to spend at re-fueling sites along the way).  Blowing on the abdomen can also reveal a brood patch (if present), in the case of birds currently in the breeding state.  

Precisely determining the age of the bird can be very difficult, though determining whether the bird is an adult or sub-adult can often be done reliably.  In some species the plumage differs markedly between adult and sub-adult birds.  In others, the bander has to rely on more subtle clues, such as the pneumatization state of the bird's skull.  By pushing back the feathers on the head (see below), the bander hopes to see through the translucent scalp to determine whether the skull cap is fully ossified as in an adult bird, or if it is still undergoing development (indicating that the individual is a juvenile):

More precise measurements which can be taken from birds in the field include the wing chord (distance from the "wrist" to the tip of the longest primary feather) or in this case the flattened wing length:

Sizes of smaller features such as the length and/or depth of the beak are typically measured with callipers (below) instead of a ruler, for greater precision:

As you can see from the above photo, different-sized bands are used for different-sized birds, and the tool has individual grooves for the different band sizes.

As you can see, the bands fit loosely around the leg, so that the bird will feel no discomfort once it's in place.  It will be closed tightly enough, however, to ensure that it does not slide up over the ankle joint (which in birds is between the lowest and second-lowest sections of the leg), or down over the foot.

Finally, the bird must be weighed.  Different options are available for weighing birds.  In this case, the bird is inserted into a plastic tube (see photo below) which rests atop a digital scale (not visible in the photo).  Since the scale has been "zeroed-out" with the tube in place, the reading with the bird in the tube will give the weight of the bird alone (i.e., not including the weight of the tube).

Once a weight has been read from the scale and entered into the computer, the bird is released.  Below you can see a Blue-winged Warbler that hasn't yet realized he's free to go:

The other major component of a banding operation is, of course, the system of nets in place around the banding station, which are used to catch the birds.  The nets are deployed (i.e., unfurled) only when in direct use, with banding personnel immediately present to ensure that birds caught in the net aren't injured or eaten by a passing predator; when not supervised the nets are rolled up and tied shut to prevent inadvertant capture.  As you can see below, these "mist nets" are made from very tiny filaments, which are difficult to see when you're not focusing exactly on them (hence their ability to catch unwary birds):

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Summary 

So, do the birds enjoy being banded?

I asked this Black-throated Blue Warbler that very question, and he promptly bit the nearest finger in front of him*:

My guess is that they probably do not overly enjoy it, though I don't think they suffer any real trauma from the process.  The data collected during the banding process can inform policy-makers of the need for greater efforts in the conservation of particular species.  Banded birds that are re-captured elsewhere provide vital information about the migration routes and re-fueling sites that are used by the birds during their migration.  Hotspots for re-fueling during migration are obviously of great importance, and need to be identified and protected from environmental degradation.  Finally, the data collected during this process can be useful for the study of bird biology, which can itself benefit the birds in various ways.

Please note that migratory birds are protected by law, and that the banding of wild birds can be legally performed ONLY by licensed banders.  The banders at this site (CVWO / First Landing SP) were both highly trained and federally licensed.  Information on becoming a licensed bander in the United States can be obtained from the U.S. Geological Survey.