pegasus and the gender thing
It's commonly believed that pegasus only accept female riders. This is a misconception, but a sticky one:
Pegasus are quicker and more agile in the air than wyverns, but they're also lighter and more delicate. Flying with a heavy or uneven load is exhausting, even dangerous. A strain injury that impairs flight can kill a pegasus.
Consequently, they're very picky about riders, and will reject -- violently, if necessary -- anyone who doesn't meet their standards.
Bottom line, pegasus really care about 1) flight dynamics and 2) confidence.
A pegasus knight should be as light as possible, with a low center of gravity. This selects for short, wide-hipped jockeys; statistically, that describes more women than men.
(Pegasus will also reject taller, heavier, and top-heavy women; this is considered just "not being cut out for it." You'd think somebody would have made the connection, but these things are stubborn.)
Really, most of it's cultural. A quirk of statistics has become a whole self-fulfilling thing.
Pegasus mares are larger than tiercels, and make better mounts. This is offputting to a certain kind of guy, and lends itself to the idea that of course a mare would prefer a woman rider.
"Pegasus attack men" is now a common belief. Men get nervous and uncomfortable around pegasus, which sometimes translates to belligerence. Pegasus react poorly to both, which only reinforces the idea that pegasus hate men.
It's not uncommon that the above produces pegasus which actually do have a grudge against men (by whatever standards a pegasus can tell -- some combination of affect, physical cues, and social cues).
Many men who could physically qualify as pegasus riders aren't interested, because the profession is so associated with women. Even if they were, many pegasus stables refuse to train men, because "men can't ride pegasus" is such a pervasive belief.
A "man" who's committed and dedicated enough to enter a profession generally restricted to women, with women as colleagues, teachers, and peers ... is probably a woman, actually. She's sure as hell not cis.
