1. Sex determination in birds is by ZW-ZZ mechanism.
2. In birds, males are homogametic while females are heterogametic.
3. Males produce all similar types of sperms, containing 8 autosomes and ‘Z’ sex chromosome.
4. Females produce two different types of eggs, one containing 8 autosomes and Z chromosome and the other containing 8 autosomes and W chromosome.
5. When Z bearing egg is fertilized by a sperm a male offspring is produced. If W bearing egg is fertilized then female offspring is produced.
[Note : In domestic fowl chromosome number is 18, with 16 autosomes and two sex chromosomes.]
