A Day in the Life of a Monster: How to Make Better Bestiaries

From JA Baker's The Peregrine:

[A] peregrine's day usually begins with a slow, leisurely flight from the roosting place to the nearest suitable bathing stream. This may be as much as ten to fifteen miles away. After bathing, another hour or two is spent in drying the feathers, preening, and sleeping. The hawk rouses only gradually from his post-bathing lethargy. His first flights are short and unhurried. He moves from perch to perch, watching other birds and occasionally catching an insect or mouse on the ground. He reenacts the whole process of learning to kill that he went through when he first left the eerie: the first, short, tentative flights; the longer, more confident ones; the playful, mock attacks at inanimate objects, such as falling leaves or drifting feathers; the games with other birds, changing to a pretence or attack, and then to the first serious attempt to kill. True hunting may be a comparatively brief process at the end of this long re-enactment of the hawk's adolescence.  

Hunting is always preceded by some form of play. The hawk may feint at partridges, harass jackdaws or lapwings, skirmish with a crow. Sometimes, without warning, he will suddenly kill. Afterwards he seems baffled by what he has done, and he may leave the kill where it fell and return to it later when he is genuinely hunting. Even when he is hungry, and has killed in anger, he may sit beside his prey for ten to fifteen minutes before starting to feed. In these cases the dead bird is usually unmarked, and the hawk seems to be puzzled by it. He nudges it idly with his bill. When blood flows, he feeds at once.

Imagine if RPG bestiary entries were written like that.

Now, we can't all be JA Baker, widely thought of as one of the greatest nature writers to have ever lived, and I suppose at some point length becomes an issue. But what we can think about is how to actually describe monster behaviour which is relevant and interesting to the players - such as, what a monster generally does over the course of a day or night. That allows them to learn patterns of activity through observation and/or listening to experts, and to plan accordingly if they are clever enough. If you know that orcs usually nap mid-morning after their breakfast of elven infants' livers on toast, or whatever, you also know when to plan your attack on their village for best effect.

That may be too Gygaxian-naturalistic depending on the style of game you're going for, but the idea that a DM can predict what a monster is likely to be doing at a given time of day is also useful for interesting encounters on the cuff and adding depth to the randomness of the reaction dice: imagine if each monster had a different set of reaction dice values depending on the rough time of day - not all that hard to pull off, and not requiring two paragraphs of Barkerian purple prose either.