Behavioral Responses of European Blackbirds and Australasian Silvereyes to Varying Acid and Sugar Levels in Artificial Grapes

Abstract

Diminishing acid concentrations have long been thought to be one of the effects of ripening grapes that leads to increased bird pressure approaching harvest. Blackbirds (Turdus merula) and silvereyes (Zosterops lateralis) were offered in a field context varying concentrations of tartaric and malic acids in artificial grapes, where sugar and all other ripening grape parameters were controlled. No linear response of consumption to varying acid concentration was found for either species. A response to rising sugar was confirmed, but diminishing acid concentrations in ripening grapes appear not to be a contributing factor to increasing bird pressure approaching harvest.

Iodine application in Vitis vinifera L. cv. ‘Cabernet Sauvignon’ improve bioactive compounds and enzymatic activity in berries

“…The parameters such as pH, TSS and TA are used as maturity indices to define the optimal time of harvest. The pH indicates the strength of acids in the must (Blouin and Guimberteau, 2003) and it is estimated that at harvest time it should have on average a pH of 3.66, TSS for wine grape varieties should be between 12-24 °Brix (Cabeller, 2017); TA is a component of flavour, composed mainly of organic acids such as malic and tartaric (Saxton et al, 2009), which are used as metabolites during respiration during fruit growth and ripening (Dorey et al, 2016) and the MI for this variety is between 3 and 3.5 indicating commercial maturity (Walteros et al, 2012). The results show that foliar spraying with I affected these oenological parameters (Table 2).…”