If I'm not mistaking herbivores are primary consumers
In bird, females are heterogametic, produce two type of gametes. The two different sex chromosomes of a female bird has been designated to be the Z and W chromosomes. Whereas males have a pair of Z- sex chromosomes. Males are homogametic produce only one type of gametes with Z-sex chromosomes. Thus sex determination is ZW-ZZ type. In humans sex determination is XX-XY type. Males are heterogametic produce X and Y gametes and females are homogametic produce one type of gametes. Therefore, in bird sex are determined by female gametes.
Organisms that possess heritable traits that enable them to better adapt to their environment compared with other members of their species will be more likely to survive, reproduce, and pass more of their genes on to the next generation.