Effect of dilution degree of commercial nectar and provision of fruit on food, energy and nutrient intake in two rainbow lorikeet subspecies

Abstract

A feeding trial was performed on adult rainbow lorikeets of two subspecies: six green-naped lorikeets (Trichoglossus haematodus haematodus) and six red-breasted lorikeets (T. haematodus mitchellii). Throughout the entire trial, half of the birds from each subspecies had ad libitum access to water-diluted commercial nectar powder and drinking water only, whereas the other half also received ad libitum apple pieces. During three consecutive 14-d periods, the nectar powder was diluted to a different degree: 1:3 (low), 1:5 (high) and 1:4 (medium) (v:v). Diluting nectar to a higher degree resulted in both subspecies in a decrease in voluntary energy intake. Next, nectar intake significantly decreased when apple was available and apple intake significantly increased when fed higher-diluted nectar. In green-naped lorikeets fed nectar and apple, energy intake was similar between dilution degrees of nectar but was lower compared with feeding only low- or medium-diluted nectar. Whereas, in red-breasted lorikeets, provision of apple next to medium- or high-diluted nectar resulted in higher voluntary energy intake compared with feeding solely nectar of any degree. Overall, protein and thiamine intake as well as Ca:P ratio of the ingested ration were lowest when fed highly diluted nectar and apple. Yet, minimal requirements were still covered. Because energy content of fruit can be higher than liquid diets, in this case medium- or high-diluted nectar, ad libitum provision of fruit as a means to lower voluntary energy intake in lorikeets, for instance in case of obesity, needs to be considered with care.