Quarter notes. In fact I think most people whistling will tend to slide from note to note, where possible, rather than jumping cleanly from one note to the other, which means they are in fact whistling quarter notes and such. I suppose people who play musical instruments may be more likely to tend to do it the other way, jumping from note to note.

It's the same difference you get between formally trained singers and many traditional singers, which has often been put down as faulty technique, whereas it is just a different and and often highly effectuve, technique.
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It hadn't occurred to me until we had a thread here about whstling that there are peopel who don't whistle in both directions, on the in breath and the out breath. It must nbe difficult if you only whistle in one direction.

I wonder if there are some people who whistle Anglo Concertina style, with different notes in the different directions, and others who do it the English Concertina style, same notes both ways?