Radio tracking eases minds on crane drought issue

Radio tracking eases minds on crane drought issue
The majestic Whooping crane in flight.Photo by Klaus Nigge.

Radio-tagging and careful preparation against a suspected drought have quelled biologists’ fears of an expected drop in the whooping crane population at their wintering grounds in Aransas, Texas.

The birds migrate from wetlands in the northern part of Wood Buffalo National Park (WBNP) to the Aransas Wildlife Refuge (AWR) each fall. Last year, the southern point of Texas where AWR is located was issued a D4 rating (drought exceptional) by the US Drought Monitor. D4 is the most serious level of drought, making conditions for the whooping cranes extremely difficult.

“Initially we were deeply troubled about the conditions in Texas. We have tried to keep track by putting radio-tags on the young chicks to get an accurate count of the route down to AWR,” said Stuart MacMillan, manager of resource conservation for WBNP.

The birds summering in WBNP just outside Fort Smith are the only wild population of whooping cranes left in North America.

“We were expecting the drought to affect the birds, so to prepare we have built windmills to replenish water, and have strategically burned habitat to allow food like acorns and crispy critters to be available for the birds,” said Vicki Muller, a wildlife refuge specialist for AWR.

Preparations by the Texas-based biologists seem to have helped. Data provided by AWR indicates that of the approximately 300 birds migrating to Texas, only two have died.

Twenty-one birds from WBNP have been radio-tagged to get data on their migratory patterns.

“It is a lot easier for us to keep an accurate count of the birds here, since they are mostly stationary. We work with the WBNP and Canadian Wildlife Service (CWS) radio-collar program to provide accurate data on how the migration is going,” said Muller.

“The goal of this study is to get a better picture of the dangers of the migration process to AWR and to better be able to map the migration,” said MacMillan.

Two dangers presently known to WBNP and CWS are power lines and either accidental or malicious hunting (due to the birds’ endangered status, it is illegal to hunt whooping cranes). There is no word yet on how to best prevent the birds from hitting power lines, but MacMillan notes that this is a concern to be taken very seriously.

Unexpected amounts of rainwater flowing in through Aransas and Copano Bays have also helped the birds stay in one place, conserving energy for their spring flight back to the Canadian North.

Without a supply of rainwater, the birds would have to constantly travel in search of fresh water and their diet staple, blue crabs. Blue crabs tend to be smaller in size, with decreased populations, in drought conditions.

“Fronts moved in from the northwest, and rains also came from the south, which is very unusual,” said Ruben Solis, of the Texas Water Development Board.

The birds arrived at AWR in mid October and will stay until the end of March.

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