The following parts are taken from PEU:1
122.2 common or typical
We often use can to say what is common or typical.
Scotland can be very warm in September.
Ann can really get on your nerves sometimes.
345.2 'general' possibility: can/could, not may/might
We normally use can/could to say that things are possible in general: people are able to do them, the situation makes them possible, or there is nothing to stop them. May/might are not used in this way.
These roses can grow anywhere. (NOT ••• These roses may grow anywhere.)
Can gases freeze? (NOT ••• May gases freeze?)
In those days, everybody could find a job. (NOT ••• In those days, everybody might find a job.)
339.10 another use of may/might: typical occurrences
In scientific and academic language, may is often used to talk about typical occurrences - things that can happen in certain situations.
A female crocodile may lay 30-40 eggs.
The flowers may have five or six petals, pink or red in colour.
Children of divorced parents may have difficulty with relationships.
With this meaning, might can be used to talk about the past.
In those days, a man might be hanged for stealing a sheep.
These explanations made me puzzled. Since they can both relate to typical occurrences, is it possible to substitute can/could for may/might in PEU 339.10 if the context is not written in scientific and academic language?
1. PEU = Michael Swan's, Practical English Usage.