There tends to be a huge drop in appetite around 1 yr, and that's often when they start eating air for several days only to eat you out of house and home for the next few days. And it's pretty normal to eat progressively less and less throughout the day. Tyler still does this...he'll eat an obscene amount of food for breakfast, an okay lunch, then 2 bites for dinner. I think the intervals between his meals looks fine if you think he does okay without snacks. Some toddlers have tiny tummies and like to eat small bits at a time every couple of hrs, and some do better on a routine like yours. Is he drinking milk in between meals? That can often be very filling and can kill an appetite. Also, how much milk is he having first thing in the morning? Is it formula or whole milk? It's up to you when you eliminate that and the bedtime milk...you might find that his appetite improves once those are gone.
As long as he seems healthy otherwise and isn't losing weight, I wouldn't worry too much. As long as he's eating SOMETHING, he'll probably come around once he hits a hungry phase.
