in a sheltered environment. Depending on weather conditions, shadecloth may be used to cover the holding cages. The aim is to minimise stress to the birds. Processing. This includes the attachment of individually numbered bands to the birds' legs, sometimes with site-specific colour-bands, plastic leg-flags, or light level geolocators to track migration routes. Measurements are made of wing-length, head and bill length, weight, as well as degree of moult or signs of breeding plumage. Retraps of previously caught birds have their band numbers recorded and are similarly processed. Evidence of age is noted in order to estimate seasonal breeding success. Sometimes blood samples or cloacal or tracheal swabs are taken for epidemiological studies, such as government programs monitoring the incidence of avian influenza. All data are logged on field datasheets and later entered on a computer database. Details of catch conditions are also recorded. Following processing, all birds are released. Modifications Over the years, biologists have modified this basic set up to catch various animals (Schemnitz et al. 2012). Portable platforms have been built to capture birds over open water. Boxes have been modified to capture wild turkey. Rocket nets have been fired from portable platforms to capture birds in water. References External links Australasian Wader Studies Group Victorian Wader Study Group Wash Wader Ringing Group Broome Bird Observatory BirdLife International - Avian Flu surveillance Ornithological equipment and methods Bird hunting Nets (devices)