I have a chestnut TB and I've noticed a few white spots on her hind end. After we clipped her, I could really see them, and today I counted seven of them, all behind her shoulder. Are these birdcatcher spots? They're pretty small...
What causes these? I'm assuming it's genetic, and she has The Tetrarch several times in her pedigree. He was covered in them so is it possible that that is where she gets it from? From what I can tell her sire does not have them, but I'm not sure what her dam looks like.
Here is her pedigree for anyone who's interested: Sunny Smiles Horse Pedigree
From what I've seen, The Tetrarch is in her Northern Dancer lines (through Almahmoud), and Bold Ruler lines.
This is one of her spots:
And this is her normal color (unclipped). You can't even see them unless you know where to look: