Considering how often I am out, I don't often see butterflies totally consumed with nectaring. My preferred hiking conditions run cloudier, cooler, and earlier than prime nectar flow, aka prime butterfly sipping activity. My goal this year is to see more butterflies and to get to know, really know, our local spp. So, I've adjusted my outings to a little later in the day and for warmer temperatures, which include inland locations away from the coastal cool, like Pinnacles National Park. Thus far, I've had a fair bit of success in finding more butterflies that hold still long enough for me to take a good look at them and a couple of pictures. I haven't netted in over a decade, because I know I am not a gentle netter and it pained me to injure butterflies just so I could look at them up close.
For Pinnacles, the only 2 reported spp. of striped, yellowish swallowtails are the pale swallowtail (aka Pterourus eurymedon - why? someone wanted to make it a thing?) and the western tiger swallowtail (Papilio rutulus). The slightly twisted tail-detail view from on top and from below don't match and can be visually confusing on a quickly moving animal. Plus, the tails are sometimes broken off. Here's my cheat sheet to tell the two apart:
true, creamy butter color (real butter, not what you imagine is a butter color)
often with orange coloring in last crescent next to the tail, sometimes yellow
western tiger swallowtail
deeper yellow, like buttercups
always yellow in last crescent next to tail
I've read that the width of their stripes is thicker in pale versus western tiger, but that's tricky to tell when they're not side-by-side to compare. Although, they reportedly often fly together.