When individuals are free to choose between producer and scrounger, frequency dependent selection results in a stable mixture of both behaviors where each receives similar payoff.
If the scrounger tactic is compatible with antipredatory vigilance, then an increase in antipredatory vigilance should lead to the detection of more joining opportunities, and hence more joining.
When the seed distribution made the scrounger tactic unprofitable, the frequency of hopping with the head up diminished and appears to support the predictions of the producer-scrounger model.