Signals from the Sky: About Those PTTs


It’s anyone's guess as to when the ultralight chicks will start their first journey north. What path will they follow? Will they use safe crane habitat along the way? Crane trackers have help finding out, thanks to the Platform Transmitter Terminals (PTTs) on some of them. The tracking team follows the migrating birds in vehicles equipped with radio receivers. As soon as the young birds head north, ICF trackers hit the road, tracking the youngest birds of the new Eastern flock.

Powered by Batteries

Each PTT is powered by a battery. Because the battery wears down each time it's used, the PTT can't constantly send signals. Experts program the battery to send a specific radio signal according to a schedule set by the WCEP scientists.

For example, the cranes' PTT batteries run 8 hours on a given transmission day. The "duty cycle" affects how long the battery will last. On the current schedule, the batteries in the crane PTTs will probably last at least 750 hours, says project biologist Dr. Richard Urbanek. "But no one would be surprised if the antennae broke off before then and the units stop working", he adds.

crane_Sp04_008 crane_Sp04_009 crane_Sp04_015
A Platform Transmitter Terminal is a satellite tracking device that can be worn/carried by an animal so its position is known.
Why do you think the name and address of Operation Migration is on the PTT?
Photos: Operation Migration

The PTT is light, so it does not hinder the survival prospects for the bird. The bands and transmitters stay on the birds for life. The bands that support the transmitters are part of the color-banding scheme. They are used to individually identify the birds. These bands are fastened securely so that we can identify the birds throughout their lives, even after the transmitters fail.

How Do the Units Affect the Cranes?

Crane #208 with PTT on his right leg and radio transmitter on the left leg (red/white).
Photo Sara Zimorski

"They preen it and pick at it, treating it like any other accessory. Of course, they'd like to be rid of it if they could," said ICF's Anne Lacey, who monitored the 2001 chicks in Florida. "Over the years many birds like cranes have been fitted with PTT’s. Other than a problem with ice forming on the antennas, the PTTs do not seem to bother the birds once they get used to them. The birds will often try to preen the antenna as if it is a feather that will not smooth out, but normally that's all that happens. So far we have not seen any problems and they do not inhibit flight."

The units weigh 30 grams. They are designed for mounting on a leg band for birds like cranes. One PTT costs approximately $2800.00 plus the band and mounting, and the Argos costs.

Satellites: Eyes in the Skies
The crane PTTs broadcast signals to the ARGOS/NASA satellite. According to NOAA, the polar orbiters do more than track migratory species. They are able to monitor the entire Earth, tracking atmospheric variables and providing atmospheric data and cloud images. The cranes' signals are picked up by polar-orbiting satellites when the satellites pass high overhead. Imagine! Zipping through space, the same satellites are picking up signals from other animals wearing transmitters — the manatees in sunny Florida, the caribou in the cold Arctic, and the bald eagles on the East Coast.

But let's step back for a minute. Think about the information the satellite sends us every two days, and the assumptions we might be making when we interpret the data. Now you're ready for our questions:

Try This! Journal or Discussion Questions
  • Close your eyes. Imagine being in your classroom, day and night, with your eyes closed. Every 2 days, you blink your eyes open for a few seconds. You ONLY have that time to see what is happening. The rest of the time, you see nothing but darkness. As a class, consider the conclusions you might draw, based on your limited observations. Think about that image when you interpret satellite data. The satellite only sends a snapshot representing a moment in time. Based on your discussions and what you read above, list in your journal some benefits AND some limitations of satellite tracking.
  • The risk to the birds would be high if anyone were to try and catch the bird to replace the transmitter or recharge it, yet several captures and replacements have taken place through the years of the flock's existence. Do you think the risk is worth the information that might be gained? Explain.

    Journey North is pleased to feature this educational adventure made possible by the Whooping Crane Eastern Partnership (WCEP).

National Science Education Standards

  • Technology used to gather data enhances accuracy and allows scientists to analyze and quantify results of investigations.
  • Tools help scientists make better observations, measurements, and equipment for investigations.