the migration simply late this spring? Would that explain why
so few people reported monarchs until this past week?
this is a detection issue? That is, did it take longer this
spring for each observer to see his/her first monarch because
there are fewer monarchs in the populatoin this spring?
we expect the number of sightings reported to correlate with
the size of the monarch population? After all, each observer
only reports one butterfly, their first of spring, regardless
of the number of monarchs they see.
Did the number of observers change, or their level of enthusiasm?
How might these things affect our results?