MIST-NETTING, BANDING, AND MEASURING BIRDS

Objectives:

  1. To learn techniques that are essential for studying population biology or behavioral ecology of birds in the field
  2. To have an opportunity to handle, identify, and measure birds
  3. To mark birds in our study area in preparation for experiments. Note: Ordinarily, we do not capture enough birds to get a sample size sufficient to allow meaningful statistical tests. Therefore, this lab does not require any data analysis. However, if someone sees an opportunity to test a hypothesis and is enthusiastic about pursuing it, feel free to discuss it with us.


Equipment:

Please bring your lab notebook, a pencil or pen, good walking shoes and appropriate clothing. Binoculars are available, if you want them. I will provide field guides to the birds, mist nets and poles, U.S. Fish and Wildlife bands, calipers for measurement, electronic balance or spring scales for determining weight, banding forms, and other materials necessary for bird-banding.


Background:


Without some way of recognizing individual birds, it would be impossible to conduct detailed studies of avian migration, mate selection, demography, abundance, or many other topics in ecology, behavior, and conservation biology. In this lab we will learn two techniques that are widely used in avian behavioral ecology: the capture of birds using mist-nets, and the marking of birds using U.S. Fish and Wildlife bands. We will also gather data that could be used to determine allometric relationships between body mass and a variety of other morphological features or to test other hypotheses about the behavior of migratory animals.


Mist-nets had been used to capture birds in Italy and Japan for many years before the technique was discovered by ornithologists interested in avian migration. Nets consist of delicate dark nylon or monofilament webbing stretched between a frame of stouter horizontal and vertical cords. Nets are set in promising flight paths of birds, near fruiting plants, around nests, or anywhere where birds are likely to fly by. A bird is trapped after it hits the webbing and becomes entangled in the pocket formed by a cross-support cord.


In addition, we may trap individual birds using a specially designed feeder. The feeder has a remote-control door that allows us to selectively capture individuals as they approach bird seed.


Individually numbered aluminum bands serve to mark birds permanently and harmlessly. Bands are issued by the U.S. Fish and Wildlife Service to licensed banders only. In addition, avian ecologists sometimes place plastic color bands on birds’ legs in unique combinations to allow the birds to be recognized at a distance. Some recent studies suggest the possibility that color bands can change birds’ behavior (e.g., females might prefer males with bands of a certain color). How can a field ecologist avoid or at least minimize such potential biases?


Procedure:


Feeders have been placed at the BFEC and near the aviary. With the advent of cool weather, birds come readily to feeders. We hope to be able to capture enough for everyone to see how to extricate them from nets, and handle, band, and measure them safely.


To remove a bird from a mist net, it is important to determine from which direction the bird entered. Work from that side, following the instructions on the next page. WE ALWAYS HANDLE BIRDS WITH EXTREME CARE! Bird bones are generally hollow (why?). Consequently, they are extremely fragile. Until you have had extensive experience, never hold a bird just by its legs, wings, or bill.


Using special pliers, bands can be bent around the unfeathered, distal portion of a bird's leg (tarsometatarsus). When banding a bird, you should hold the bird yourself, grasping it firmly and carefully clamping the band around its leg, making sure afterwards that the band slides easily.


For each bird the following data should be taken: date (including year), time of day, location, habitat, species, AOU No. (the number assigned to the particular species by the American Ornithologists’ Union, band number, and, if possible, age and sex (determined generally by plumage, size, and other features). Morphological measurements that are often taken are weight (to 0.1 g using a scale), wing length and width (to 1 mm using a wing ruler), tarsus length, and, if there is time, bill depth (at the nostril) and length (from the distal end of the nostril to the bill tip) (to 0.1 mm using dial calipers). Additional measurements include presence or absence of parasites, status of molt, and the extent of subcutaneous fat deposits. Fat reserves are scored as follows:

  • 0 (no visible fat in furcular [wishbone] area or abdomen
  • 1 (traces of fat in furcular area or abdomen, but neither completely lined)
  • 2 (furcular area lined but not bulging, little fat on abdomen)
  • 3 (furcular area full, some fat on abdomen but not full)
  • 4 (both furcular area and abdomen full to bulging)
  • 5 (both areas full with fat extending across sternum)
  • A functional morphology analysis of the data could include relative wing loading (body mass/wing area), an allometric analysis of wing length vs. body mass, bill length vs. depth, etc. The morphology of birds with different social systems (flocking vs. solitary), mating systems (polygamous vs. monogamous), phylogeny, or movements (migratory vs. sedentary) could be compared. Sometimes blood samples are also taken to estimate population genetic structure, relatedness between individuals, hormone levels, etc.