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The winter of 2008/2009 was the worst in recent history for the whooping crane, the icon of federally protected endangered species. The flock had grown from 16 birds in 1941 to 270 birds in the fall of 2009. However, last winter seven adults and 16 chicks died, totaling 23 birds and 8.5 percent of the flock. This is rivaled only by the 1990/1991 winter when 11 birds out of 146, or 7.5 percent of the flock died.
Most of the birds from this past winter were believed to have died from a lack of suitable protein and fat in their diet as well as from stress associated with daily flights to sources of fresh drinking water. Stressed and emaciated birds are less likely to have reproductive success. Thus the toll from this hard winter is yet to be fully realized.
The bays and estuaries that are the winter home of the crane are being hard hit by human water management decisions. In both 1990/1991 and 2008/2009, Texas was experiencing a drought and the flows in the Guadalupe and San Antonio rivers that feed San Antonio Bay and adjacent bays were very low — arguably due in part to our abuse of these river systems. Less fresh water reached the bays and estuaries upon which the cranes depend than can be explained simply by the drought. Our water withdrawals further lessened those flows and magnified the crisis.
Lower flows have a direct effect upon the natural productivity of the bays and estuaries. Species such as blue crab spend much of their lives moving from one portion of the estuary to another, in large part following or seeking a preferred salinity level. Except during spawning, when the female migrates to saltier water, the ideal salinity for the blue crabs is less than 15 parts per thousand (ppt).
Salinity levels in the whooping crane wintering grounds were high this year. An April 7, 2009, report revealed measurements at Aransas National Wildlife Refuge of 29 ppt at the refuge boat ramp and 39 ppt in the adjacent marsh. The Gulf of Mexico typically is 32 ppt whereas the estuary is usually much lower.
It is also clear that the marshes typically used by the cranes were devoid of blue crabs. In good years, crabs make up 85 percent of the whooping crane diet. Yet in January through April of this year, field surveys showed that there were alarmingly few blue crabs in these marshes. There is a strong correlation between the increased salinity and the absence of blue crabs as well as between the absence of crabs and the cranes dying of malnutrition.
On the basis of these relationships, it is important to understand the extent to which the human use of the Guadalupe and San Antonio river water increased the salinity in the bays and estuaries, thereby reducing the number of blue crabs and ultimately causing the cranes to be weakened or to die of malnutrition. Computer modeling indicates that human uses of fresh river water have worsened this salinity problem over that which would have occurred naturally in 1990 and in 2008. Additionally, proposed future uses of these rivers promise to further reduce these inflows, leading to even greater reductions in blue crab production and further increases in whooping crane mortality.
If the scenario described above is correct, then under the terms of the Endangered Species Act, the deaths of the cranes this past winter could be considered a “take.” A “take” is prohibited by the terms of the Endangered Species Act. In other words, human usage of water from the Guadalupe and San Antonio river systems may be seen as violating the Endangered Species Act. This bad situation will only be worsened if more water is removed from the already overdrafted river system.
Groups are fighting to obtain water rights for the bays and estuaries, but virtually no water is currently dedicated to that purpose. The San Marcos River Foundation filed a permit application to set aside water for San Antonio Bay — water that could have been used to support the crane — but that request was denied by the state. The planning process put in motion by the Texas Legislature is moving at a snail’s pace.
To date, reason and persuasion have fallen on deaf ears. The bottom line is that the policies of the state of Texas and of those authorities that are managing the Guadalupe and San Antonio rivers are killing the whooping cranes. And that is simply not acceptable and must stop.