We have not received any satellite-tracking data for the Lake Woodruff kite since Sunday, September 17, 2000. There are a number of possible explanations, although at this point, we are not able to say which is the most likely. Because the transmitter is a prototype design, there may be a malfunction in the radio itself, although a similar transmitter on another migrating kite has been performing quite well. And, of course, the bird may have died, leaving the transmitter's solar collector unable to gather enough light to power the radio. Migration is a very challenging time for birds and it can be a substantial source of mortality. Although the kite encountered favorable winds when it left the Florida Keys and it made a remarkable passage across the water to Mexico (even bypassing Cuba, a regular stop-over point), it arrived on the northern shore of the Yucatan Peninsula just as a tropical storm - which soon became Hurricane Gordon - was developing in the area. The kite no doubt encountered strong winds and heavy rains once onshore, which could have limited its ability to forage after its arduous flight. In fact, September 13, when it arrived in Mexico, until we last heard from the bird on September 17, it remained in roughly a 50 square mile area rather than continuing its southward migration.

The effects of the long over-water flight and the subsequent bad weather, in combination with any possible lingering effects from the original wing injury, could have put the bird at risk even after it reached the relative safety of Mexico. But did these factors, or others unknown to us, result in the bird's death? At this stage, and based on what we have learned from prior satellite tracking of Swallow-tailed Kites, there are several other things to consider before we attribute the lack of data to either radio failure or mortality.

The transmitter is programmed to broadcast for 10 hours, then to be off for 20 hours. While off, it has an opportunity to recharge. At various times, the 20-hour recharge stage will include nighttime and/or periods of continuous cloudy weather, preventing the radio from attaining a sufficient charge to transmit during the next "on" stage of the cycle. The Yucatan Peninsula and northeastern Central America have been under substantial cloud cover for much of the last week.

Another random factor that can periodically interrupt the flow of data is the positions of the orbiting satellites relative to the bird when the transmitter turns on. If the satellites happen to be low in the sky, or on the other side of the earth, at that time, it will not be possible to get good location data - or perhaps any data at all. This becomes more of a problem as the bird approaches the equator, since the satellites are in polar orbits and, thus, are farthest apart in their paths near the equator. Much of the variation in the performance of the transmitters is related to these characteristics of the tracking system.

In the past, yet another phenomenon probably has resulted in extended loss of contact (sometimes permanent) with tagged kites. When the transmitter turns on and the system goes to work at determining its location, the tracking analysis may use the last known location as a starting point, thus saving time and making better use of what may be a small temporal window of opportunity for deriving a fix. If it has been a long time since the last location was determined, and if the bird has moved a long distance during that period, the system may have trouble obtaining a fix. The next time the transmitter turns on, with the bird still farther along its path, it would be even more difficult to obtain a fix, etc. We suspect that this contributed to the poor performance of the battery-powered satellite transmitters that we used to track migrating kites in previous years.

Obviously, any of these technical factors could work in combination to limit our ability to obtain data. Is this the explanation for the recent lack of information from the Lake Woodruff kite? We just do not know. With luck, we will hear from the bird's transmitter again and gain some insights. We may not, however, and we may never know the reason why. Nonetheless, the bird certainly demonstrated that it had the ability to survive in the wild, and we have already learned valuable lessons from the three weeks of data that it provided. For now, we will continue to monitor satellite activity every other day, and any noteworthy news will be posted on the observations page.

Special thanks to all of you who have followed along in the journey, and to those who have helped promote awareness of the Kite Site 2000 project. Please "stay tuned" for further developments.

Send questions or comments to kitesite@adoptabird.org Return to Kite Site 2000 - http://www.adoptabird.org/kitesite