By Keith L. Bildstein, Ph.D.
Sarkis Acopian Director of Conservation Science
Hawk Mountain Sanctuary
27 June 2016
We’ve all seen the Gary Larson cartoons of vultures perched or soaring above one or two desiccated cowboys insightfully expounding on something comical. Truth be told however, vultures are rare inhabitants of most of the world’s deserts. Fortunately, this is not so in the Sonoran Desert of the southwestern United States and northwestern Mexico.
The Sonoran, a fascinating and ecologically rich region, is an important go-to place for vacationing Canadian and US snow birds, as well as home to 10 species of amphibians, 100 or so reptiles, 60 mammals, and more than 350 species of birds, including the world’s most northern breeding populations of Cathartes aura aura, a largely Neotropical subspecies of Turkey Vultures. Investigating raptors at the limits of their geographic ranges has been a fascination of mine for more than 40 years, and this explains why I traveled to Buckeye, Arizona, 30 minutes west of Phoenix on Interstate 10 just before midnight on the night of Tuesday 17 May 2016.
Hawk Mountain’s Senior Research Biologist Jean-Francois Therrien and I landed at Sky Harbor Airport in Phoenix with an ambitious agenda. The following day I would travel two hours south to Tucson to give a talk on our vulture work at the world famous Arizona Sonora Desert Museum, while at the same time Jean-Francois would hook up with Rich Glinski, the editor of The Raptors of Arizona, and try to catch vultures at a dairy facility outside of Buckeye. Dairy farms are large in Arizona, and still-born calves would be the bait at our desert trap site.
Both Black and Turkey Vultures occur in Buckeye, and although we had begun our studies in the state in 2014 focusing solely on the latter, we have recently expanded the work to both species, as both were feeding, interacting at, and fighting over at the same nutritional resources, and fully understanding the feeding ecology of two species was only possible if we studied both of these competitors.
My talk at the museum was set for noon and a group of 40-plus museum workers and volunteers were eager to what I had to say as the museum had open an exhibit featuring both Black and Turkey Vultures a few months earlier. Half way through the talk my mobile phone vibrated in my pocket. Unfortunately, I ignored it as I didn’t want to interrupt the presentation. That was a mistake, as Jean-Francois was calling from Buckeye to let me know that he and Ron had just caught and placed a satellite tracking device on an adult Turkey Vulture they had decided to call “Moo Moo,” the name the young daughter of our host blurted out when she first laid eyes upon it. (Most of our trapping sites are on private land, and we always make certain to engage the land owners in all aspects of our field work, including watching us place tracking devices on the birds we catch and tag and helping us name them.) The next phone call came two hours thereafter when JF called to let me know that he and Rich caught and tagged a second Turkey Vulture named “Gash.” Both individuals, while quite healthy, weighed less than 70% of the Turkey Vultures we catch in Pennsylvania, which were members of the considerably more massive septentrionalis subspecies. Needless to say we celebrated the day over dinner at a “wings” restaurant close to our motel. We had brought four tracking devices with us, and after just one day of the four that we had allotted to trapping and tagging birds, we were half way to our goal. The pressure was still on, but reaching our goal certainly appeared doable, and we were pleased.
We caught Turkey Vulture number three, “Calm Lady,” early afternoon the next day, and caught our fourth Turkey Vulture, “Early Bird,” before eight the following morning. Four birds after a little more than two days in the field. Not bad… not bad at all. We took time off from the field the rest of day three while planning our work for the remaining two days we had scheduled to be in Arizona. When we first started working in Arizona in May of 2014, our plan was trap and tag at least a dozen Turkey Vultures, and the four we caught in May of 2016 brought our total 15. We also planned to conduct a series of six seasonal road surveys totaling 1,061 miles in southern and western Arizona. The surveys would allow us to estimate the sizes of the wintering and summering populations there, providing us with critical information on regional numbers.
The next morning we set off a 166-mile road survey that began at Gila Bend and meandered through the towns of Ajo, Why, and Sells Arizona, while circling back toward Tucson. We counted 63 Turkey Vultures and 3 Black Vultures along the way. After overnighting in Tucson, we conducted a second, 152-mile survey that began at Three Points and continued south to Nogales on the border with Mexico, before turning north to Continental. On that survey we counted 30 TVs and 1 BV along this route. After finishing the survey we scurried back to Sky Harbor Airport in Phoenix to catch a red-eye flight back to Newark, New Jersey. It was then onto Hawk Mountain by car, where we arrived mid-morning on Monday the 23rd.
Although we had spent but five days in the field, we had managed to catch and tag four new Turkey Vultures and had conducted two full-day roadside counts. Our next trip to Arizona will be in January 2017, when we hope to catch and tag at least three Black Vultures and conduct as many as six road surveys. Although the work—if you want to call it that—might seem tedious to some, for me and my colleagues it was as close to heaven as one comes in raptor biology… a chance to catch up on all things “vulture” while trapping and tagging a few birds, surveying an important regional populations of two species, and getting the word out to the public about why we are studying Turkey and Black Vultures and what we are finding out about them.
In my next blog, which I hope to have out in several weeks, I will update you on our Arizona findings to date.
To learn how you can help support our studies, email me at Bildstein@hawkmtn.org or call me at 570 943 3411 ext. 108.