We've got two 6 week old Black Australorps (supposed to be pullets). As they were day-olds received through the mail I can confirm that the age is accurate. The combs and wattles are pretty well identical to date but "Big Foot" is the largest chick by a good margin (21.2oz today) and has enormous legs and feet.
For Australorps, is leg size (comparative) a good predictor of sex or is it all about the comb/wattles? I wish I had more side by sides but neither is a joy to catch or handle and Big Foot is in a class of his/her own in terms of strength and use of those nails!
Day 39, Big Foot (left), Little Foot (right)
Little Foot, day 42
Big Foot, day 43
Big Foot again, day 43