Competency at fatherhood is the most desirable quality in males for females in pair-bonding species. Females select capable fathers by judging their paternal skills demonstrated in courting. A large study about desirable attributes in partners showed that human females were more likely than human males to consider
The likelihood of a good treatment of themselves and their offspring was the main factor for females of social species that do not pair with males to reproduce. Good genes are the only preference for the females in societies where males are not socially integrated and do not provide any help with young. Males then advertise their genes to mate, often displaying ornamental beauty that might say something about their genetic health.
Fancy looks should discourage females due to the significant energy expenditure it requires that is not directed toward survival. Male guppies with the most attractive color patterns are most desirable by the females. Their sons tended to inherit the attractiveness but are significantly less likely to survive than average males even before coloration appeared. Colorful patterns are coded by genes of Y chromosome.
Studies of birds showed that even initially indifferent to a male females became attracted to him after observing interest from other females of their social group. It suggests that they want to have male offspring that are attractive to females to propagate their own genes with more likelihood. A trait can become desirable because it is already desirable, and so on.
Another explanation for female choices of better looking mates could be recognition of health. An attractive individual could be free of parasites, not have sexually transmitting diseases that could endanger the life of the female, and have some extra energy to support unnecessary splendor. Females might have evolved the skill to differentiate between signs of good genes and of bad ones. A number of studies have shown that attractive males have more fit offspring. Female ducks that mated particularly attractive males laid larger eggs and it seemed to be the only factor that increased the fitness of the offspring compared to the kids of ugly ducks, one study has shown. Scientists in Scotland studied zebra finches and found that eggs from attractive male birds contained more growth-stimulating hormones. Barn swallows take better care of chicks from handsome males, according to another study.
It seems like if most members of your species believe that more reproductively attractive males can provide better genes, then in females' best genetic interest is to invest maximally into the offspring of such males. This distal level of explanation in biology deals with evolutionary concerns. However, on the proximal level that translates evolutionary logic into mechanics of hormones and neural pathways in a particular animal, how a female translates the knowledge about attractiveness of the father into producing more growth hormones is a mystery. More research is needed.
Self-fulfilling prophecies are rather common. In certain human cultures, because people believe that shamans can induce death, known as psychophysiological, they start treating the person under such spell as already not alive until he actually dies from lack of resources and support
Robert M. Sapolsky. What Do Females Want? Natural History. Dec2001/Jan2002, Vol. 110 Issue 10, p18. 4p.