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So red corundum is a ruby, and pink corundum is still a sapphire. Where exactly do they draw the line between lighter rubies and darker pink sapphires? What would you call something that straddled that line, anyway? Suby? Rapphire? Is it possible for jewelers to disagree on what category a stone is?
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In English, we’ve decided that red corundum is its own thing, but other colors are lumped together as types of sapphire (with the possible exception of padparadscha). Do other cultures divide them up differently?
Wikipedia indicates that the ruby/pink sapphire distinction is a relatively recent thing that’s limited to the US, and that “a minimum color saturation must be met to be called a ruby”. I’d take that to mean there’s some sort of standard for what shades are considered rubies vs. pink sapphires, but the Wikipedia article doesn’t provide any specifics about this.
Huh. I was reading the Wikipedia article on corundum, not rubies, they didn’t mention it there that I saw.
Since when are sapphires pink? I know they can be different colors, but I always think of blue.
And indeed, a few moments with Google confirms that blue is the most common color.
Sapphire is a variety of aluminum oxide. It’s valuable when it has clear and consistent color. Blue sapphires are the most recognized but they come in many colors.
And in fact, pure sapphire is colorless.
So they’ve stopped killing pigeons? 
I assume this is some sort of joke, but in case it’s not, “pigeon’s blood” is a term used to describe the color of the reddest rubies. This is a metaphor and does not involve actual pigeons.
I don’t know if there’s any objective standard for what counts as a pigeon’s blood ruby.
Show a few to a pigeon and see if it faints?