Hello Smokerbill, welcome to the forum!
The size of the white spot on top of the head of Barred Rock chicks, also known as the "dot on the head" method, is a method for sexing chicks that is often used by backyard chicken keepers. According to this method, smaller and more compact dots are more likely to indicate males, while larger and more oblong dots are more likely to indicate females. However, this method is not always accurate and can vary depending on the breed and individual chick.
Other ways to determine the sex of chicks include:
1. Feather sexing - This method involves examining the wing feathers of chicks and is most accurate between 2-10 days after hatching. Certain breeds, such as Rhode Island Reds and Leghorns, have sex-specific feather patterns that can be used to identify males and females.
2. Color sexing - Some breeds, such as Silkies, have different feather colors for males and females that can be used to sex chicks.
3. Behavioural differences - In some cases, males and females may display differences in behaviour or vocalizations that can be used to sex chicks, although this method is less reliable and can be difficult to differentiate.
It's important to note that while these methods can be useful for sexing chicks, they are not always 100% accurate and it's possible for mistakes to be made. If you're uncertain about the sex of your chicks, it's a good idea to wait until they're older or consult with an expert such as a poultry veterinarian. Good luck with your new flock!