The Aransas-Wood Buffalo flock, the only naturally occurring Whooping Cranes in the world, produced 97 nests this year, second only to the 98 nests of 2017. It’s great news, certainly, but the more important number is the tally of fledged young. In August, Parks Canada and the Canadian Wildlife Service reported that 37 young birds had fledged from 36 nests. Put another way, it means that 61 nests failed to fledge chicks this year.
In 2017, a record 63 chicks fledged at Wood Buffalo. In 2018, 87 nests were counted but led to only 24 fledglings — a low number but “still within the natural range of variation that we would expect from this species,” according to Rhona Kindopp, manager of resource conservation with Parks Canada.
The other key metric is the annual winter survey of Whoopers at Aransas. Six years ago, the Fish and Wildlife Service changed from an actual count of every bird to a method known as distance sampling. It aims to count most cranes and produces an approximate total.
In the last couple years, the agency has switched from using a Cessna aircraft to a Quest Kodiak, which provides better visibility of the 115,000-acre refuge. And it’s conducting the surveys in late January and early February instead of mid-December because biologists found that not all Whoopers make it back to the Aransas area until later in the winter.
The estimate for the winter of 2017-2018 was 505 cranes, although the authors report the number could be as low as 439 or as high as 576. A further 21 birds were assumed to be outside the primary survey area, based on reports from eBird, a GPS tracking study, and other sources.
The numbers for the 2018-2019 winter were similar: an estimate of 504 cranes and a range of 412-660 birds. During the survey period, approximately 12 cranes were reported on eBird beyond the primary survey area.