Master Naturalists: White-wing dove is migrant, immigrant and urbanite
By Paul and Mary Meredith
July 10, 2014 at 2:10 a.m.
The U.S. Fish and Wildlife Service as well as Texas Parks and Wildlife classify the white-winged dove as upland migratory game birds.
That is partially a historical accident because before the 1950s, they were migratory - crossing back and forth from Mexico to Texas' banks of the lower Rio Grande Valley for food, water and shelter. Agricultural successes and failures have had a major impact on the white-wing population over the last century.
As irrigation and row crops were introduced in the lower Rio Grande Valley, populations exploded because grains and seeds are white-winged doves' food. With agriculture expansion, most - almost 90 percent - nesting habitats were destroyed, and unrestricted hunting also took its toll.
From 1920s populations estimated at 4 to 12 million, numbers dropped to a 1939 estimate of one-half million. As citrus became a major crop, white-winged doves shifted from brush to citrus groves because they preferred colonial nesting areas. When Paul was in high school in Corpus Christi, he and his friends tried to "get invited" to lower Rio Grande Valley leases to hunt, both white-winged and mourning doves.
Freezes nature's curve ball
The '50s, '60s and '70s were disasters for lower Rio Grande Valley citrus farmers and white-winged doves. Crops were lost, and entire groves were destroyed by repeated freezes. Roost-less, white-winged doves could either return to Mexico, die off or immigrate beyond the subtropics of the lower Rio Grande Valley. A massive movement north started; nesting locations changed again.
First to the Edwards Plateau oaks and then to mature trees in cities in what parks and wildlife calls Upper South Texas. Those cities - San Antonio, Austin, Corpus and Victoria - host massive white-winged dove populations.
According to Texas Parks and Wildlife biologists, they are urbanites. More than a million live in San Antonio and Austin, with the state's population center now in the region. How many? Estimates range between 7 million to 18 million residents and migrants. They are hunted. Only mournings are harvested more than white-winged. Estimated harvest was 5 to 6 million last year in a regulated 70-day fall season, with somewhere around 70 percent being hatched the same year.
Regulating a short-life-cycle
White-winged doves are short-lived, estimated average life span of 18 months. To compensate, they are prolific. Cooperatively parenting, a pair can breed, hatch - males sit the midday shift, raise and fledge a pair of eggs up to six times a year. Some early-season hatches even mate and breed in the same season. In spite of massive nest predation by grackles, crows, snakes, raccoons and feral cats, a pair can produce in excess of five over-wintering survivors.
This massive replacement cycle makes monitoring both adult and hatch-year birds by biologists imperative. Statewide, biologists trap, band and release thousands of birds. Records stored at the United States Geological Survey Bird Banding Laboratory provide data for population-trend forecasts, information for setting hunting seasons, bag limits and total take by hunters.
Hunters report recovered bands and counts, too, so harvest rates can be monitored. Recovered bands confirm most are shot within 20 to 25 miles of their banding location. Although, a Hidalgo County bird showed up 1,400 miles away in Central America.
Tagging in Victoria
The Texas Parks and Wildlife Department in Victoria began banding in June in Riverside Park and at several residences. Milo placed daily trains birds to feed there at banding sites. Subsequently, cage traps are placed over piles of milo. Birds enter the traps to feed. When traps fill, the biologist and an assistant, a Master Naturalist this year, block the entrances to prevent escape.
Birds are removed and placed in sacks, two to a bag. In turn, each bird receives a numbered leg band, is evaluated as adult or hatch-year based on coloration and is aged based on numbers of flight feathers molted - the more new feathers, the older the bird. Data is recorded and birds are released. Birds are baited and are banded again a week later. In between, feeding is observed daily; banded and unbanded birds are counted, aiding in colony-size estimation. Our Woodway colony estimate exceeds 300.
Sources: tpwd.state.tx.us; hunting-in-texas.com; allaboutbirds.org; pwrc.usgs.gov; The Journal of Wildlife Management 9999:1-6; 2012; DOI: 10.1002/jwmg.371 "Survival, Fidelity and Recovery Rates of White-Winged Doves in Texas"
Paul and Mary Meredith are master naturalists. Contact them at firstname.lastname@example.org.