Don't know what it is about me, maybe where I grew up, who my parents were, what I do for a living...but my zucchini plants have always put out the female flowers first. Guess I'm just a maverick in that regard.
After the first couple of years I finally realized that they were just going to shrivel and die because of not getting pollinated, so nowadays I pick them when they're about as big as my finger and put them in the salads. ( as long as I don't see any male flowers) I usually plant Black Beauty, and they are very prolific.
This year I wanted to try a grey zucchini that is advertised to be ready in 45 days, but I just don't have the room. Maybe next year!
Never really noticed if the butternuts do the same with the female flowers. I suspect they put out the males first. All I know is, my butternut vines are loaded with big beautiful green striped squash! Can't wait.