Are Condors Blown By the Wind?

Posted at 9:31 am June 4, 2008 by James Sheppard

The animal carcasses that condors rely on for food are widely distributed across the landscape and are relatively unpredictable in their occurrence. Condors must regularly make long-distance foraging flights over large areas to maximize their chances to detect a suitable meal. Because of their large size condors can conserve energy by soaring for long periods without flapping their wings, similar to albatrosses. Condors require strong and consistent thermal winds to achieve the altitudes needed to make these long-distance soaring flights in search of food.

Consequently, the wind conditions within a condor’s habitat are likely one of the principle determinants of condor foraging ability, which is why condor introduction programs have been sited in mountainous regions with strong updrafts. Enhanced understanding of the meteorological conditions that determine the flying ability and foraging success of condors is vital to tailoring reintroduction programs to the bird’s habitat needs. No formal analysis of the characteristics of the winds that shape condor movements has yet been conducted.

weathershepardequipment.jpgWe recently installed the first of an array of remote weatherstations that will be placed throughout the expanding ranges of the condors that are being reintroduced to Baja California, Mexico. The units include an anemometer to measure wind speed and direction and a thermometer to measure air temperature. The weather data is stored in a data recorder and can be downloaded at the end of the recording period (limited to about six months of memory capacity) using a handheld shuttle. Rather than choosing arbitrary locations, the sites where the weatherstation are to be installed were selected by overlaying the home ranges of 14 birds that were GPS-tracked for three years. This way the climate data we record will be taken from habitats that have actually been used intensively by the birds themselves. The big challenge to our team is that the weatherstation sites are in very remote and inaccessible areas, which presents considerable logistic difficulties for equipment installation and data acquisition.

weathershepardtree.jpgThe site for the installation of our first weatherstation was only half a mile from the Baja base camp, which certainly made it easy for us to carry the units and all of the equipment needed to set them up. Once at the site we selected a suitable tree on which to mount the weather sensors. The stations must be installed well off the ground to sample the strongest wind flows while minimizing ground-based turbulence and interference. We also need the units to be high enough to deter interference by curious animals (and curious people!). We needed climbing ropes and harnesses to bolt the unit 33 feet (10 meters) off the ground onto the main trunk of the tree. This was not an easy task, and was complicated by the fact that each unit must also be precisely calibrated to compass directions, often while the units were recording wind velocities of more than 33 feet (10 meters) per second.

The second weatherstation was placed at Venado Blanco, at the crest of a steep ridge overlooking a series of valleys back toward the condor campsite, which was about three miles to the southwest. The reintroduced condors have been tracked coming to this site many times over the past three years, and during our journey to the site we encountered a herd of deer and noticed the hoof prints of cattle and scats from various animals – the kinds of things that attract inquisitive and hungry condors. Getting to the Venado Blanco site required some serious off-roading and a hike with the weatherstations and their installation equipment across steep chaparral covered slopes.

weatherlandscape.jpgThe site itself was a picturesque study in contrasts, with colorful desert flowers in bloom beneath blackened pine trees that had been scarred by numerous lightening strikes and wildfires. The frequent storm activity in the area is of particular concern, since a high voltage blast of static electricity could have some serious negative consequences for one of our little weatherstations! To reduce the possibility of lightening strike we grounded our units to a long copper rod that we hammered into the ground. Needless to say, trying to find sufficient earth in which to hammer a six-foot rod into in a rocky granite peak also presented a physical challenge.

The remaining weatherstations are soon to be installed across the remote eastern canyons of the Baja reintroduction site that face the open deserts towards the Gulf of California. This network of canyons includes Picacho Del Diablo, which is the steepest peak in Baja. The sheer difficulty of reaching these sites necessitates the incorporation of a remote data uplink system into the weatherstations, to beam the climate data directly to us via a satellite modem. Once installed, we will be able to access the weather information provided by the units via the Internet. By matching the wind conditions and air temperatures with the movement patterns of the ranging condors we will be able to build an extensive and accurate picture of the environmental factors that shape condor habitat use and foraging success. This is another example of how cutting-edge technology can contribute highly valuable information to enhance management programs designed to conserve threatened species.

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