Predation by birds in relation to the population density of cardiaspina albitextura (Psyllidae)

Abstract

Field observations suggest that in areas in which the numbers of Cardiaspina albitextura remained low, birds tended to destroy an increasing percentage of late instar nymphs and adults with increase in psyllid numbers. However, when other environmental influences strongly favoured psyllid multiplication, birds were unable to prevent increase to the outbreak level. The response of birds to change in psyllid numbers was functional (not numerical), and depended partly on factors other than psyllid density. In areas in which C. albitextura maintained a high mean level of population density, the percentage destruction due to birds tended to vary inversely with psyllid numbers.