Cannon netting
Encyclopedia
Cannon-netting is a method of catching large numbers of animals, often birds, usually to band
them, or otherwise tag them, as well as acquiring biometric data (measurements), in order to find out about their movements, migration
routes, survival rates and metabolism
. It is often used where large numbers of birds, especially wader
s, tern
s and gull
s aggregate on beaches at high tide
, or in places (which may be baited) where waterfowl
or cockatoos feed. Cannon-netting may be used as a capture-for-culling method for perceived pest species such as cockatoos. Mammals such as deer
and macropods may also be cannon-netted.
s, the only significant difference being the method by which the projected nets are pulled over the catching area. In the case of cannon-netting the projectiles that are attached to the net are fired simultaneously from smooth-bore cannon
s by electrically detonated cartridges. A full-sized cannon-net may utilise four or more cannons to pull the net over the target birds. Smaller nets with fewer cannons may also be used.
s, though occasionally other locations, such as salt lake
s or sewage treatment
lagoons, are used.
Bird ringing
Bird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
them, or otherwise tag them, as well as acquiring biometric data (measurements), in order to find out about their movements, migration
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
routes, survival rates and metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
. It is often used where large numbers of birds, especially wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s, tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...
s and gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s aggregate on beaches at high tide
High Tide
High Tide was a band formed in 1969 by Tony Hill , Simon House , Peter Pavli and Roger Hadden .-History:...
, or in places (which may be baited) where waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
or cockatoos feed. Cannon-netting may be used as a capture-for-culling method for perceived pest species such as cockatoos. Mammals such as deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
and macropods may also be cannon-netted.
Methodology
Cannon-nets are nets pulled rapidly by explosively-driven projectiles to cover a pre-determined area of ground and presumptively capture any birds (or other target animals) present before they have time to escape. An alternative is the use of rocket netRocket net
A rocket net is a kind of animal trap used to trap a large number of live animals, usually birds. It consists of an accordion folded rectangular net with one edge attached to the ground. The corners of the opposite edge at the top of the folded heap are attached to heavy tubes with one closed end....
s, the only significant difference being the method by which the projected nets are pulled over the catching area. In the case of cannon-netting the projectiles that are attached to the net are fired simultaneously from smooth-bore cannon
Cannon
A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...
s by electrically detonated cartridges. A full-sized cannon-net may utilise four or more cannons to pull the net over the target birds. Smaller nets with fewer cannons may also be used.
Catching waders
When cannon-netting is carried out for the purpose of catching large numbers of waders or shorebirds for banding and release, it requires an experienced team to coordinate and manage not only the catch itself, but also the subsequent care and processing of the birds to their eventual safe release. Catching is usually conducted on tidal beaches with nutritious tidewrack, or adjacent to coastal mudflatMudflat
Mudflats or mud flats, also known as tidal flats, are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of...
s, though occasionally other locations, such as salt lake
Salt lake
A salt lake or saline lake is a landlocked body of water which has a concentration of salts and other dissolved minerals significantly higher than most lakes . In some cases, salt lakes have a higher concentration of salt than sea water, but such lakes would also be termed hypersaline lakes...
s or sewage treatment
Sewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...
lagoons, are used.
- Planning. In the days preceding a catch, known and likely high-tide roosting sites are reconnoitered to establish the best prospective site for a catch, although a final decision may not be made until immediately prior to net-setting. Consideration of expected maximum tide height and wind direction may affect the precise placement of the net.
- Setting the net. The net is usually set during low tide when the birds are dispersed and feeding. The mesh of the net must be free of any obstacles such as twigs, leaves and shells that might obstruct its deployment when fired. The bunched net is laid in a line with pegged 'jump ropes' attached to the back edge. Markers are set to indicate the extent of the catching area. The heavy iron projectiles are attached to the projectile ropes that will pull the leading edge of the net, and are inserted in the partly buried cannons behind the net. The previously cartridge-loaded cannons are connected by an electrical circuit to a firing box in a hide which may be some distance away, though with a good view of the catching area. After setting, the net is often concealed with sand, seaweed or other light debris.
- Setting up the catch. If the birds do not fly or walk readily into the catching area of the net when coming in to roost, it may be necessary, through the judicious placement and movement of people or vehicles, to encourage the birds to move into position where they can be safely caught. Team members coordinate their efforts through radio contact.
- Firing. The net is fired when it is judged that an appropriate number of birds is catchable, and that none will be endangered during firing. The number of birds caught should not exceed the capacity of the team to deal with them expeditiously.
- Extraction. The birds are extracted as speedily as possible from the net and placed in temporary fabric holding cages to await processing 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 attachmentBird ringingBird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
of individually numbered bands to the birds' legs, sometimes with site-specific colour-bands, plastic leg-flags, or geolocators to track migration routes. MeasurementsBiometricsBiometrics As Jain & Ross point out, "the term biometric authentication is perhaps more appropriate than biometrics since the latter has been historically used in the field of statistics to refer to the analysis of biological data [36]" . consists of methods...
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 bloodBloodBlood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
samples or cloacaCloacaIn zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
l or tracheaVertebrate tracheaIn tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
l swabs are taken for epidemiologicalEpidemiologyEpidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
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.