A Talk on the Wild Side.
A pair of whooping cranes skim over tidal marsh habitat at Aransas National Wildlife Refuge in Texas. Photo is for USFWS use only.
Even though a record-breaking 281 whooping cranes wintered this past season at Aransas National Wildlife Refuge on the Gulf Coast of Texas, climate change is a major concern for the charismatic endangered species.
The primary threat to the cranes’ survival, according to Aransas Refuge manager Dan Alonso, is rapidly disappearing coastal habitat. Most of the habitat is being devoured by burgeoning real estate development along the Gulf of Mexico, but climate change is exacerbating the problem. A secondary concern related to climate change is the prospect of prolonged drought, which would reduce the flow of freshwater and leave marsh habitat unacceptably saline for cranes.
The Aransas Refuge population – the only natural flock of whooping cranes in North America – nests at Wood Buffalo National Park in Canada in spring and summer. From early fall to December, the cranes migrate in small groups to the Texas refuge. In early spring, they rush 2,500 miles back up to Canada in 15-16 days.
|An adult whooping crane feeds a chick during nesting season at Wood Buffalo National Park in Canada. Photo: Klaus Nigge. Photo is for USFWS use only.|
The 281 cranes at Aransas Refuge this season represent half of all whooping cranes on this continent. Approximately 110 others occur in the human-induced migration route between Wisconsin and Florida, and about 167 are in captivity (many at Patuxent Research Refuge, MD). The Aransas Refuge crane numbers are up from15 in 1941.
“The major climate change impacts are sea-level rise and loss of habitat, and black mangrove encroachment from the south,” says Alonso.
|A whooping crane plucks a blue crab from a tidal marsh at Aransas National Wildlife Refuge in Texas. Climate-related loss of habitat is a major concern for the charismatic, endangered bird. Photo: Steve Hillebrand.|
Sea-level rise results in saltwater intrusion into brackish marsh, erosion of coastal marsh and simple inundation, Alonso says. “The areas are now deeper than they were before. The bird is only so tall. It’s a wading bird, not a diving bird.”
Whooping cranes – which are five feet tall and have a seven-foot wingspan – thrive on open tidal marsh where they can forage for razor clams, minnows, lizards, snakes and, especially, blue crabs. They dislike thick cover. “They don’t fly into trees or densely wooded areas,” Alonso says, “because it doesn’t afford them the opportunity to elude predators” – primarily coyotes and bobcats. So, the climate-related proliferation of black mangroves makes what once was prime habitat undesirable to the cranes. A proposal by University of Texas researchers to study and document the extent and the effect of black mangrove encroachment on Gulf Coast habitat and its wildlife – including cranes – is pending approval.
To counter the effects of climate change, in addition to working with various partners to estimate the amount of additional suitable habitat that is needed in Texas to foster species recovery, Aransas Refuge is monitoring saltwater inundation with the use of Sea Level Affecting Marshes Model (SLAMM) analysis, mapping black mangrove and researching effective control techniques of the woody vegetation, Alonso says.
Author: Bill O’Brian, USFWS