Do most orchids have bloom triggers like temp or light?

[nogreenthumbs]

I think we mostly all know that a Phal usually wants some cool weather before it'll bloom. What about the other (more common) orchids. Yeah, I know there are something like 25,000 species and another 65,000 hybrids or something crazy like that, but it seems like most of the common orchids fit within a few (relatively) common groups. Do those common groups share the same or similar triggers. IE, Catts, Cymbidiums, Dendrobiums, Oncidiums, etc....

Is there a general guideline that you can use for the groups and then assume there will be a ton of exceptions. I would assume they should almost all have some sort of trigger since in nature, the same kinds of plants would all want to bloom at about the same time to increase their chances of reproduction.

It seems like the most likely candidates are temperature (cooling down in the fall or winter or just after cool weather in the early spring) or it seems like I've also heard about hours of daylight (presumably the plant then knows what time of year it is and is ready to go).

What about the really tropical varieties? I visited the Amazon in Brazil. All year long, the amount of daylight varies by about 10-15 mins, and the temp probably doesn't vary by much more that 5-10°. They do have quite variable rain patterns though. Dec/Jan-May/Jun it rains, and the rest of the year it rains less.