Facilitation of Sap-Feeding Birds by the White-Fronted Woodpecker in the Monte Desert, Argentina

Abstract

In the Monte desert of South America, the overall supply of water and food for birds decreases in the dry, cold season (June through September). During this period the White-fronted Woodpecker (Melanerpes cactorum) drills holes in the trunks and branches of Prosopis flexuosa and feeds on the exuded sap. Other bird species, diverse in ecological attributes and taxonomic affinities, take advantage of this resource which otherwise would be rarely available. Sap is a major constituent of the diet of the White-fronted Woodpecker and 11 other bird species, and sap feeding comprises between 16% to 83% of foraging observations made during June and July. Aggression by White-fronted Woodpeckers significantly reduced the time smaller bird species spent fecding on sap, indicating that White-fronted Woodpeckers actively compete for this resource. Other bird species profit from having access to a resource rich in water and sugar.