Use and selection of sap trees by White fronted Woodpecker, Melanerpes cactorum, in the Semiarid Chaco, Argentina

NUÑEZ MONTELLANO MG; BLENDINGER PG; VATTUONE MA; ROTA G

Campos do Jordão

Congreso; 25th International Ornithological Congress; 2010

Melanerpes cactorum drills holes on different species of trees and feeds on the exuded sap, mainly in times of low resource availability. Sap is a major constituent of its diet, 79% and 42% of the foraging records respectively during winter and spring were on sap. We investigated the factors that determine the selection of sap trees by M. cactorum during 2008 and 2009. To investigate if M. cactorum selected tree species based on their availability in the environment or on tree species-specific attributes, we measured the plant density and structural and morphological attributes of 8 used sap-species trees and 9 unused species. Also, we estimated sap flow and sap-sugar concentration of each tree species. M. cactorum selected some trees species (mostly Prosopis ruscifolia), while most other species were consumed in lesser quantities respect to their availability (eg Bulnesia sarmientoi) or were not consumed (eg Ruprechtia triflora). Relationships between frequency of consumption and structural attributes, bark morphology, sap-flow volume and sugar concentration explained a smaller fraction of species selection for sap consumption. We suggest that harmful secondary chemicals could play a role in the tree selection. In addition, morphological and chemical attributes of the selected sap trees were evaluated at the intraspecific level. Sap flow and sugar concentration were higher in the individual trees consumed, especially in the most consumed species. Overall, our findings suggest that chemical cues, more than the bark morphology, promote selection of sap trees