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Ecology of the Atlantic Brant



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Reports from the Arctic 2003 (Field Journal link)

Brant Patch Program
Closeup of Brant
Photo by Kim Annis
Reports from the Arctic 2003 (Field Journal link)

Atlantic brant (Latin scientific name: Branta bernicla hrota) are a member of the goose family. Brant typically weighing 3 lbs. or less, much smaller than their close cousins the Canada goose (Branta canadensis). The distinctive white cheek patch found on the Canada goose is replaced on the brant by small white bars forming a ring around the neck. In flight, the brant has a very fast wing beat similar to ducks.

Atlantic brant mate for life unless one mate is lost, and begin breeding around 3 years of age. Brant migrate to the arctic circle and beyond to breed. Major breeding colonies are located in the Foxe Basin west of Baffin Island. This study may identify previously unknown breeding colonies. On the breeding grounds snow melts in mid-June, and winter returns in early September. In an average year this leaves just enough time to lay a clutch of eggs, incubate them and raise goslings to flight stage. In years when snow melt is late female brant reabsorb eggs to retain nutrients that would otherwise be lost in an unsuccessful breeding attempt. This process is known as atresia.

Breeding Distribution
Distribution Map
Click to enlarge

Little food is available when brant arrive on the breeding grounds. In fact, female brant utilize nutrients stored in body fat to produce eggs and to sustain them during incubation. They obtain these nutrients while feeding at migration stop-over sites. This study will document the location of stop over areas that are critical to brant reproduction and survival. James Bay is believed to be one of the most important spring staging areas for brant. Little is known about staging areas in the United States

Brant nest in low areas along the arctic coastline. Females lay 4 to 6 eggs in a bowl shaped depression lined with down. Eggs hatch after 24 days of incubation. Once the eggs hatch, the male assumes the leading role in herding the brood, with the female following close behind. Young brant feed on marine invertebrates, mosquito larvae, and various plants. As the brant age their diet shifts to one of almost all plant matter consisting of sea lettuce, eelgrass, and widgeon grass.

Atlantic brant winter in large flocks along the Atlantic Coast from Massachusetts to North Carolina. On average 70% of wintering brant occur in New Jersey. The south shore of Long Island, New York winters the second largest population. The 2002 brant surveys estimate the population of wintering brant number around 181,000 birds.

Note: Information on Atlantic brant ecology was derived from Ducks, Geese and Swans of North America by Frank C. Bellrose.

State Count   State Count
MA 3,025   NJ 124,590
CT 500   MD 535
RI 940   VA 14,355
NY 37,675   FL 11
 

Atlantic Brant Telemetry Study


There has been little recent research on the ecology of Atlantic brant. Current infomation regarding migration routes, timing, and stop over sites is lacking. This information, along with current breeding colony locations would be valuable to biologists for making better management decisions.
The purposes of this study are:
  1. Clarify migration routes and the timing of migration,
  2. Identify staging areas used by brant during migration,
  3. Clarify boundaries of the breeding range,
  4. Search for previously unknown breeding colonies.
pic of field work

Females and young are released immediately after banding. Mature males are fitted with either a satellite transmitter or a VHF radio transmitter. They are held for 24 hours to ensure that they are healthy, and that there are no adverse effects from the transmitter application. They are then released at the same location in which they were captured. Observations of radioed males show they quickly rejoin their family groups and otherwise act normally.
While brant are on the wintering grounds, biologists at various locations in New York, New Jersey, and Virginia will use decoys to lure brant to rocket nets for capture (See 3 photos below). Once captured all are banded with U.S. Fish and Wildlife Service aluminum leg bands (See left). Each band is engraved with a unique number which is reported to the Bird Banding Laboratory located in Laurel, Maryland. If a band is reported by a hunter or a person who finds a dead bird, biologists can determine vital statistics used for managing the population.

Click to enlarge pictures

Most radioed brant receive a VHF transmitter weighing approximately 33g (1.16oz.). Each VHF transmitter emits a unique signal at a specific frequency. Biologists, use a special receiver and antenna to monitor radioed brant. The signal can be heard up to 2 miles away on the the ground, and up to 5 miles away when using aircraft. When a signal is heard the location of the brant is recorded on a map.

Some of the brant receive a satellite transmitter, which weighs approximately 30g (1.06oz.). The satellite transmitters send their signal to satellites orbiting the earth. These transmitters are programmed to turn on several times a week. The satellite calculates the position of the transmitter. This information is then downloaded from the satellite to a computer, where they are plotted on maps.

Tracking Picture/Transmitter closeup

Brant with Satellite Transmitter

Both types of transmitters are attached around the body using a soft cloth harness that is similar to a backpack carried by children. The transmitters are designed so that they do not interfere with the birds daily activities such as swimming or flying. The weight of the transmitter is less than 3% of the birds total body weight.

Brant in flight
Photo by Kim Annis
During the spring migration, aerial surveys will be flown along the Atlantic coast from Virginia to Maine to locate brant with radio transmitters. These surveys also serve to identify staging areas, which are areas where brant congregate in large groups, and gather nutrient reserves before making the final trip to the breeding grounds.
In May, and June Canadian Wildlife Service biologists will conduct aerial surveys over the Gulf of St. Lawrence and eastern James Bay. During late June biologists from the Ontario Ministry of Natural Resources will survey western James Bay. The Foxe Basin will be surveyed by a joint team of biologist from New Jersey and the Canadian Wildlife Service.

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