Elegant tern (aka Charran elegante) tracking in the Gulf of California
The Elegant Tern or Charran elegante is a crested tern that is considered by the IUCN to be listed as near threatened due to the fact that it has a very restricted breeding range. Besides Isla Rasa, there are only three other locations in Southern California that the terns breed at. They have only one chick per brood; and once the chicks are old enough, the chicks begin to crèche and are cared for by a group of adults so the parents can both fly off to forage for themselves and the chick. The idea is to feed the chick as much as possible so they can fledge as soon as possible. I began to wonder how they seemed to be so successful nesting in such large aggregations and wouldn't the excessive amount of competition for food in these large groups translate to poor reproductive success?
In 2015, we began a pilot study to assess whether the use of platform transmitting terminals (PTTs) would be a potential method of tracking daily activities and also last long enough to track migration of these terns to South America. In 2016, we added more terns to the tracking database. We have managed to track both posy-breeding dispersal movements and migration routes to both Central and South America.
Recently I had an opportunity to travel to Baja California Norte to deploy more PTTs on Elegant terns nesting at their historical breeding grounds on Isla Rasa in the Gulf of California. Isla Rasa is a small island that is a part of the Gulf of California Islands Biosphere Reserve. It is only 17 acres in size but is breeding grounds for 90% of the world's population of Heerman's gulls and Elegant terns. It was paradise for me! I slept with the sound of terns and gulls calling, and I swam in the lagoon while several hundred terns and gulls would be bathing only 20 feet away.
Enriqueta Velarde, who has been studying the terns and gulls at Isla Rasa for over 39 years was a wonderful and gracious hostess and quite the professional tern catcher. I was able to deploy the PTTs with assistance from Enriqueta, Daniel Mancilla (a PhD student working on Heerman's gull genetics), and Yanell (Enriqueta's assistant). Soon we shall be able to compare movements of terns breeding in Southern California with movements of terns breeding in Mexico. Stay tuned for more!