I'm sorry to see that no one has responded to your question earlier. Different experts come online at various times; I just came online and saw your question.
Unfortunately, there is no sure-fire way to sex doves short of DNA testing. You certainly can't tell by looking at them. Even experienced breeders sometimes accidentally house together what they think is a breeding pair (based on behavior), only to later discover the birds are two males or two females. The International Dove Society states that old-timers in the dove business say, "The only one who can accurately sex a dove is another dove & they sometimes make mistakes".
The pelvic bone method of sexing which you may have heard about is not 100% accurate, and it’s easy to hurt the birds, so it is not recommended.
Some fanciers do a fair job of sexing their doves by watching behavior. The doves must be of breeding age before you can have any success with it. This link will take you to a list of behaviors to watch for:http://www.diamonddove.info/bird11c%20Sex%20Determination.htm
There are several companies that do DNA sexing of birds. Some tests use a blood sample. Others use feathers. They are equally reliable. DNA testing is the most reliable method of sexing birds, and it is very accurate (about 99%), but once in a great while a mistake is made. If you want to do a blood test, you'd need to take the bird to an avian vet. Here are reputable companies where you can order kits for feather or blood test kits. They're under $20.http://www.dnasexing.com/
This one also has explanations of the two types of testing:http://www.avianbiotech.com/SexingCenter.htm
If you have more questions, let me know by clicking on REPLY.
(If you find my answer helpful, please click on the green ACCEPT button. Thank you.)