Last month, we conducted an expedition to install a series of meteorological stations on the remote and inaccessible eastern escarpment of the Sierra Mountains of Baja California, Mexico. This rugged region of spectacular natural beauty is the release site for the San Diego Zoo’s California condor reintroduction program. This site was chosen because of its status as a pristine, protected area of the condor’s former range. Condors existed in the mountains of Baja until they disappeared in the 1940s, only to reappear in 2002 when the San Diego Zoo released captive-bred birds back into their former habitat.
The mountainous terrain of the Baja reintroduction site provides ideal habitat for the wild condors. The birds must range over extremely wide areas to detect the carcasses of the animals that they scavenge upon for food, such as mountain sheep, goats, and pigs. California condors are extremely efficient fliers, and they are able to glide for long distances without flapping their wings, much like an albatross does when flying across the open ocean. This efficient soaring enables the birds to successfully search for food without expending too much energy. Condors gain lift by catching thermal updrafts, and these wind currents often form alongside mountains. Thermal winds are especially frequent along the Baja Sierra ranges, when warm air from the valleys and deserts below forms a rising column. The strong winds and frequent thermals that occur in this area make it an ideal location for condor habitat, and the birds have been tracked making long-distance exploratory flights whenever wind conditions seem to be suitable.
Defining suitable (or even optimal) wind conditions in condor habitats is key to successfully managing wild condor populations and reintroduction programs. The importance of wind in determining condor foraging success means that a habitat that may seem ideal to conservation managers (i.e., due to high densities of food items or good roosting and nest sites) may actually be inferior in the eyes of a condor because the winds are too weak, erratic, or unstable to sustain efficient condor flight over long distances. In fact, the condor population that was released by the Zoo on the western escarpment of the Baja Sierras now makes frequent and unforeseen use of the eastern ridges 12 miles (19 kilometers) away, where strong, hot winds roar up from the scorching Laguna Salada desert below.
To gain a better understanding of the climate conditions that drive condor movement patterns and modify condor habitat preference, we installed remote-operated meteorological stations within the range of the released condors. These stations are solar-powered and mounted on 10-foot-tall (3-meter-tall) tripods. A logger records climate information from wind and air temperature sensors, and these data are then transmitted via a satellite phone network. This way, the stations can be installed in remote areas without the need to change batteries or download the data by hand, as the climate sensor information can be directly downloaded from the Internet.
The eastern escarpment of the Baja Sierras favored by the wild condors is so steep, rugged, and remote that it is inaccessible by foot. Hence, we had to employ a helicopter to install our meteorological stations (with the kind permission of the Mexican federal government, the local ejido(community), the management department of the Parque Nacional Sierra San Pedro Martir, and the Mexican military). After loading up the chopper with our scientific equipment at San Felipe airport, we flew directly across the desert and high up into the mountains. I had previously determined the location sites for each station using the combined home ranges of the birds themselves: that way, we would be collecting climate data within the areas that the condors actually use. These locations proved to be so steep and jagged that our expert pilot had to search hard for safe landing sites. Often we had to land on the edge of sheer precipices with the chaparral barely feet away from the spinning helicopter rotors!
As soon as we had set down safely, we rushed out to erect each tripod by bolting it onto the top of a flat rock; the incredibly strong winds that occur in the area mean that each station must be robustly secured. Setting up and activating each station took less than an hour, and we had successfully installed each unit by early afternoon. Upon our return, we were able to immediately begin downloading the climate data recorded by each station at five-minute intervals. These highly accurate, high-resolution data will provide invaluable information on how wind patterns shape and modify the movement patterns and habitat use of the reintroduced condors. This information will in turn help managers fine-tune the condor reintroduction program to the specific habitat requirements of this endangered, iconic species.