K.E.
I also have a 13 month old son doing the same thing. He use to take two short naps, one around 10:30am and the second around 3:00pm. He's recently starting merging the two together. He now (usually) takes one long nap a day starting at 1:00pm. Everyone I've talked to said this is normal for his age, plus it makes my life easier since I only have to work around one nap a day instead of two. Hope this helps!