An ongoing banding and radio tracking study and a wide-ranging mitigation effort to reduce T38 bird strikes at Joint Base San Antonio-
Randolph illustrates white-winged doves’ overwhelming preference for urban areas while more-hardy mourning doves prefer the country. The base offers the perfect habitat for whitewings – about 8,700 mature live oak and pecan trees that provide roosts, nesting and protection from predators just a few miles away from food in agricultural areas and water from stock tanks and Cibolo Creek to the east and southeast.
From a peak population estimated at 12,000-15,000 whitewings, there still are about 10,000 while mourning doves number around 1,000, said Lt. Col. Scott M. Di Gioia, the 12th Flying Training Wing’s chief of safety. When whitewings expanded their range from the Lower Rio Grande Valley in the 1980s after freezes decimated citrus groves, they
discovered a paradise had evolved in the Randolph area. “If you look at an aerial photo of Randolph and the surrounding community in the 1920s, you would see a nearly obscure landscape in regard to trees. There were really only trees near Cibolo Creek Randolph was covered in grass and Cibolo and Schertz were grasslands,” Di Gioia said. “Now, anywhere there is any kind of urban growth it’s full of live oaks, pecans and assorted non-native species.” The trees at Randolph were planted to help shield buildings from
Texas’ brutal summers.
“However, a hundred years later, there literally is a forest on the base. Most of it is concentrated in the central housing area,” Di Gioia said. “There are trees every 15 feet that create a canopy and a tremendous volume to roost, reproduce and keep predators away. “We have Cooper’s hawks, red-tailed hawks and peregrine falcons, but the canopy was so thick that there was no pressure from predators.” Whitewings leave in flocks of 50-60 every morning over the north/south runway at the same point and altitude as the 40-50 daily
flights of T38s on takeoff, Di Gioia said.
When a plane flies through a whitewing flock, they cause multiple strikes, which are counted as only one strike for statistical purposes. DNA testing showed whitewings accounted for about 30 percent of the damaging strikes to canopies, engines and structure, which peaked at a cost of more than $1.1 million for all bird species in fiscal year 2014, Di Gioia said, adding that analysis indicated that if a plane lost both engines it likely would go down in an areas with proposed development.
Mourning doves, which tend to fly in pairs, rarely leave the base and are responsible for some strikes. The base also is home to more than a million perching birds such as barn swallows and western kingbirds. They are responsible for the most strikes, but they are smaller and have the lowest damage rate, although one chimney swift caused the most costly impact last year – $312,000 – by taking out an engine, Di Gioia said. Whitewing mitigation plans were developed by Di Gioia, Maj. Jason Powell, who heads Randolph’s Bird/Wildlife Aircraft Strike Hazard program, along with a study by Michael Pacheco, wildlife hazard management biologist with the USDA’s APHIS Wildlife Services, who works at the wing’s flight safety office. At a cost of $793,000, 100 live oaks were removed and 1,350 live oaks were trimmed, reducing the habitat about 20 percent.
Flights before 9 a.m. were banned.
Every morning, personnel fire shotguns with screamers and bangers at the south end of the runway to change whitewing flight patterns. Another team goes to the housing areas to fire paintball guns to try to make doves leave in smaller groups. An avian radar system was installed to track birds and determine trends. Last summer, some 500 whitewings were netted for the banding study, and 41 were implanted with radio transmitters.
Reports from hunters shooting banded doves showed that almost all were within five miles of the base to the south and southeast along Cibolo Creek and down Interstate 10, Di Gioia said. Radio tracking echoed the reports. By reducing dove density, damage from whitewings in fiscal year 2015 was reduced from $338,000 to $44,000, Di Gioia said, adding
that there have been no damaging whitewing strikes since last October, partly because of luck. Another round of tree trimming is in the works while more whitewings will be banded and implanted with radio transmitters in time for the 2016 dove season. “My advice for hunters is look – don’t miss,” Di Gioia said. “We’re highly supportive of dove hunters in the area. The pressure they put on the birds at food and watering areas is important to help control their numbers and their activity.”
He encourages hunters who down whitewings with bands to report not only where they were shot but also to examine the gizzard contents
so they can learn what they are eating.
Story and Photos By – John Goodspeed