Actually, I think the caps appear in series WRT the relevant oscillation circuit...
You may have other 16Mhz crystals that need require a different load capacitance
My understanding of crystal/cap selection goes like this: "picking a correct crystal and capacitors for a particular micro is more complicated than most people think. You can't just lay down a "generic" crystal and a couple of 22pF caps and expect everything to operating within the manufacturers specs. You have to know things about the particular crystal and its load capacitance, along with the inherent capacitance of the circuitry in the microcontroller and board traces, and probably you should pay attention to drive levels too. However, the typical consequences of doing it "not quite right" are either non-oscillation, or operating at a frequency slightly off specification. Assuming the microcontroller operates at all (which means the crystal IS oscillating), it is probably operating close enough to the desired frequency that few applications will notice the difference. So in theory, you can't just use a "generic" crystal circuit, but in practice, it almost always works anyway."
Microchip is supposed to have some good app notes on crystal selection and oscillator design. I found:
AN826 - Crystal Oscillator Basics and Crystal Selection for rfPIC? and PICmicro® Devices
and AN849 - Basic PICmicro® Oscillator Design
Each goes into some detail on how the oscillator works, how you should pick caps and crystals, and how to tell whether it's working right.