On a winter morning in Texas, as a pair of whooping cranes and their halfyearold juvenile are wading in a tidal marsh on Aransas National Wildlife Refuge, a scene unfolds that is hard not to anthromorphize. One adult plucks a blue crab from the water, holds it in its bill, walks over to the juvenile, cracks the crab and appears to feed the crustacean to the juvenile.
Blue crabs are a mainstay of the whooping crane diet. This winter was a banner one for cranes at Aransas Refuge, but refuge manager Dan Alonso is concerned about their futurein part because, he believes, blue crabs are being overharvested and in part because Gulf of Mexico coastal habitat is disappearing rapidly. So, the refuge is taking new steps to help North Americas tallest flying bird.
The Aransas Refuge population, the only natural flock of endangered whooping cranes, nests at Wood Buffalo National Park in Canada in spring and summer. From early fall to late December, the cranes migrate in small groups to the Texas refuge. In early spring, they rush 2,500 miles back to Canada in 1516 days. Theyre usually all gone by April 15, says Alonso. They dont want to be taxed.
A recordbreaking 281 cranes wintered at Aransas Refuge this season. Thats half of this continents whooping cranes. Approximately 100 others occur in the humaninduced WisconsinFlorida migration route, and about 167 are in captivity (many at Patuxent Research Refuge, MD).
The Aransas Refuge crane numbers are up from 15 in 1941, but the genetically homogeneous population remains prone to catastrophic disease, and human development is devouring the cranes habitat. That is what has imperiled the species to the degree it is today, says Alonso. Were constantly losing shoreline, either through outright development or bulkheadingputting up a barrier that prevents the water from flowing into the marsh or the estuary. That basically kills the estuary, rendering the habitat unusable for cranes.
Whooping craneswhich are five feet tall, have a sevenfoot wingspan and can fly up to 45 mphthrive on open tidal marsh. They dislike thick cover (or densely wooded areas), Alonso says, because it doesnt afford them the opportunity to elude predatorsprimarily coyotes and bobcats.
A team led by longtime U.S. Fish and Wildlife Service whooping crane coordinator Tom Stehn is working with various partners to estimate the amount of additional suitable habitat that is needed in Texas to foster species recovery.
Cranes are voracious eaters that forage in marsh for razor clams, minnows, lizards, snakes and, especially, blue crabs, Alonso says, but the commercial fishing industry is overharvesting crabs.
Alonso, who came to Aransas Refuge about two years ago, has placed renewed emphasis on enforcing and publicizing regulations that prohibit commercial fishing for blue crabs in refuge waters at all times. We let the commercial fishermen know that this was a longstanding regulation in place, but that it was going to be enforced more strictly than it had been in the past, he says.
A consortium of government and nongovernmental entities that includes the refuge is advocating blue crab conservation. The refuge also participateswith nonprofits, sportfishermen and volunteersin an annual abandoned crab trap pickup. For a nineday period in February, any trap found in the water is considered abandoned and removed. This is important because abandoned traps continue to catch crabswhich then die, unharvested. In nine years, 27,052 ghost fishing traps have been removed. Alonso wants to hold industry accountable for such trapsfor the cranes sake.
Theyre just so majestic, he says of the birds that help attract an estimated 45,000 visitors to Aransas Refuge each winter. Theyre large, theyre aweinspiringbright white with black wingtips. Being as large as they are, theyre still very graceful … highly charismatic, enjoyed by many. And given their state of low numbers, it makes them that much more appealing and sought after.