If you ask any bird-dog enthusiast what they look for when choosing a future upland dog and hunting companion, you are bound to get a wide array of advice. Many bird-dog enthusiasts favor specific breeds and bloodlines that align with the species of upland game they pursue or the hunting methods they use (i.e., walk hunting vs. horseback, etc.). When selecting puppies, they may favor certain mannerisms, such as boldness vs. timidness, or with a preferred conformation or coloration. Most enthusiasts also prefer a specific gender—male vs. female.

https://gundogcentral.com/articles/5135/comparing-performance-metrics-of-bird-dogs-by-gender