Predation by the hoopoe (Upupa epops) on pupae of Thaumetopoea pityocampa and the likely influence on other natural enemies

The hoopoe (Upupa epops L.) is an insectivorous bird often preying on larvae and pupae of the pine processionary caterpillar (Thaumetopoea pityocampa Denis & Schiffermuller), the most important defoliator of pines in Southern Europe and Northern Africa. The first half of the breeding season of this migratory bird coincides with the pupal stage of the insect. Bird predation of pupae was quantified in two years in a Pinus nigra stand of northern Italy by periodic counting of the empty cocoons left on the soil surface after extraction. The predation rate, estimated on 20 pupation sites representing the whole stand, was 74.1% in 1993 and 68.3% in 1994. Predation was higher in the upper part of the soil and then progressively decreased with increasing depth. The hoopoe may also prey on cocoons containing pupae infected by pathogenic fungi or parasitoids. An exclosure experiment showed that the bird may interfere with these other mortality factors. Three pupal parasitoids, the ichneumonids Erigorgus femorator Aubert and Coelichneumon rudis (Boyer de Fonscolombe) and the pteromalid Conomorium pityocampae Graham, were significantly less frequent in the exposed sites. The fungus Beauveria bassiana (Balsamo) Vuillemin and the most abundant pupal parasitoid, Villa brunnea Becker (Diptera: Bombyliidae), caused the highest pupal mortality at both protected and exposed sites. The bird seems to be an incompletely additive mortality factor acting on the pest and it can also alter the relative mortalities imposed by the other natural enemies.