The roundup page for the Eagle Complex says “For the reporting purposes of this gather, all of last year’s weanable foals will be counted as adults,” but it does not supply a definition of ‘weanable.’
Barn witches and other knowitalls would probably put the age at four months but if you followed the development of a mom/baby pair—without interfering—you’d know it’s at least six to eight months before the foal can survive mostly on solid food, or as much as a year, when the next one is born. Nursing can go on for two or three years if there are no more births.
Anyway, if they don’t disclose the number of youngsters found in the traps, you can’t test their assertion that the herd is growing at a rate of 20% per year.
RELATED: Eagle Roundup Day 4.