Frequently Asked Questions: Tracking Marbled Godwits by Satellite

 

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• Why do we care where Marbled Godwits go?
• Why is Bear River Migratory Bird Refuge so important  to Marbled Godwits?
• What happens when you capture a bird?
• Why is there a difference in transmitter weights on different birds?
• How long do the transmitters last?
• How does satellite tracking work?
• How can you tell whether the bird is in flight versus on the ground?
• Is it easy to find the birds on the ground using the satellite coordinates?
• How do you decide what to name the birds?
• How many more birds will you band?
• Where can I get more information on Marbled Godwits?

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• Why do we care where Marbled Godwits go?
  The U.S. and Canadian Shorebird Conservation Plans have identified the Marbled Godwit as a Species of High Concern. To ensure protection of habitats important to this migratory bird, natural resource managers need a clear understanding of linkages between specific breeding areas and wintering grounds, including key stopover sites used during spring and fall migration.
• Why is Bear River Migratory Bird Refuge so important  to Marbled Godwits?
  The Bear River Migratory Bird Refuge is considered the most important migration stopover site for Marbled Godwits in terms of bird numbers, hosting up to 40,000 individuals (about 25% of the total estimated population) during spring and fall migrations. Because of its importance to Marbled Godwits and other shorebird species, the Great Salt Lake, including Bear River Migratory Bird Refuge, has been designated a Western Hemisphere Shorebird Reserve Network Site of Hemispheric Importance (http://www.whsrn.org/).
• What happens when you capture a bird?
  When a bird is captured, it is fitted with two leg bands. The first is a colored plastic band with a large 2-character alpha-numeric code (for example, K2), which is placed on the tibia (upper leg) for visibility from a distance. The second is a smaller metal band associated with the national Bird Banding Laboratory (BBL) at the USGS Patuxent Wildlife Research Center, Maryland. (If a bird is recovered, the metal band bears the BBL phone number for reporting the find.) Finally, a satellite transmitter is affixed to the bird’s back with two elastic bands that fit gently around the bird’s legs, where they won’t interfere with the bird’s movements.
• Why is there a difference in transmitter weights among the birds?
  We used 12-gram transmitters on the first two birds, Sassy and Berta, in 2006, which were the lightest available at that time of the solar-powered transmitters we elected to use. The manufacturer has since pushed the state-of-the-art and developed transmitters weighing only 9.5 grams, so we now use this lighter version.
• How long do the transmitters last?
  According to the manufacturer, Microwave Telemetry*, solar-powered transmitters can last from 3 to 5 years.
• How does satellite tracking work?
  Each bird’s transmitter sends a radio signal to the Argos satellite, which receives and transfers this signal back to receiving stations on Earth. The signals are converted into latitude and longitude coordinates. These coordinates are made available to scientists tracking the birds through the Argos Web site.
• How can you tell whether the bird is in flight versus on the ground?
  The satellite sends a location (in latitude and longitude) as well as an estimated altitude for each location point. Several data points were collected when the birds were apparently in flight during migration, as suggested by great distance traveled in a short time, together with higher altitudes (for example, >100 m).
• Is it easy to find the birds on the ground using the satellite coordinates?
  Finding an individual bird based on the most recent satellite coordinates can be a challenge. The best accuracy currently obtainable with these types of transmitters is 150 m; however, many locations are not this accurate. Still, experienced field biologists can sometimes sight the bird if it is moving around in the general area of the last known location, as Phil Taylor of the Canadian Wildlife Service was able to do when Sassy first arrived on her breeding ground.
• How do you decide what to name the birds? 
  Three of the birds names’ came from wherever turned out to be their ultimate destinations: “Berta” flew to Alberta, “Sassy” to Saskatchewan, and “Sonora” to the Mexican state so named. “Willard,” on the other hand, got his name from his capture location, Willard Bay on the Great Salt Lake. Future godwits outfitted with satellite transmitters will be named via competitions held among schoolchildren in Box Elder County, Utah.
• How many more birds will you band?
  The long-term goal is to place satellite transmitters on at least 30 Marbled Godwits, 10 from each of three breeding populations from Alaska, James Bay in Canada, and the midcontinent of Canada and the U.S. That’s a lot of bird names to come up with!
• Where can I get more information on Marbled Godwits?

1. Marbled Godwit, Limosa fedoa http://www.mbr-pwrc.usgs.gov/id/framlst/i2490id.html
2. Effects of Management Practices on Grassland Birds: Marbled Godwit http://www.npwrc.usgs.gov/resource/literatr/grasbird/mago/mago.htm
3. Marbled Godwit http://fwp.mt.gov/fieldguide/detail_ABNNF08040.aspx

*Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.