Wintering Whooping Crane Update Time
Dr. Wade Harrell, U.S. Whooping Crane Recovery Coordinator
We plan to begin our annual whooping crane abundance survey this week, and our goal is to fly a minimum of six survey days. Phil Thorpe, with our Migratory Birds Program, will be piloting us in a wheeled Kodiak. Hopefully our dreary and wet weather as of late will clear enough to allow safe flying conditions.
Recruitment of juvenile cranes
In addition to an overall estimate of the winter population size, the survey provides us an estimate of how many juveniles were “recruited” into the population this year. Simply put, the only way to effectively grow a population is for births to exceed deaths—i.e. recruiting juveniles into the adult population. The past few years’ increases have been tied to high numbers of fledged chicks on the breeding grounds, but Canada only estimated 23 fledged chicks during their survey this past August. For comparison, that is 40 fewer chicks than reported in the August 2017 survey. Annual variation in fledged chicks is to be expected and we’ve seen this amount of fluctuation in the historic survey records dating back to the 1950’s. Weather in the breeding grounds is often a major driver of chick fledging rate in Wood Buffalo National Park. This past June, when most eggs were hatching, was unseasonably cold and wet—not ideal conditions for early chick survival.
Technology allows for better tracking
Efforts to trap and mark whooping cranes here at Aransas National Wildlife Refuge (NWR) for our telemetry study is ongoing, and thus far this winter we have marked 6 adult whooping cranes here on the Refuge with cellular telemetry devices. With these devices providing locations every 15 minutes, we are able to understand daily movements (night and day) and habitat use at a level that wasn’t available even a few short years ago. You can find more about our use of this revolutionary technology to conserve whooping cranes here.
One of the new developments that this technology is revealing is how and when whooping cranes move around here on the wintering range. In the past, we understood wintering whooping cranes, particularly mated pairs, to stay in a “territory” or one general area of a few hundred acres, all winter. With the telemetry data, we are starting to see a much more complex picture of movement, with some whooping crane pairs mostly following our traditional understanding of a single territory and others making multiple movements across the entire wintering range throughout the winter. It is difficult to say whether this is related to food availability or simply individual differences, but it does help us understand the need to focus our conservation efforts at a landscape scale—well beyond Refuge boundaries.
Opportunities for viewing whooping cranes
There are several opportunities for visitors to Aransas NWR to view whooping cranes in publicly accessible areas this winter. Whooping cranes have been consistently sighted from the Heron Flats viewing deck, the observation tower and the tour loop near Mustang Slough. We also consistently observed a family group of whooping crane in the Mustang Lake salt marsh in front of the observation tower, so you have an excellent opportunity to view whooping cranes at a respectful distance. Please come by and say hello to us at this year’s upcoming Whooping Crane Festival starting February 21 in Port Aransas!
Habitat Management on Aransas NWR
No prescribed burns have taken place yet this winter due to the wet conditions. However, we are planning for prescribed burns on the Blackjack Unit of Aransas NWR this winter pending drying conditions.
Recent Precipitation/Salinity around Aransas NWR
December-current precipitation: 6.38” @ Aransas HQ
Salinity at GBRA 1: averaging around 11 parts per thousand.