Sugar preference of common mynas (Acridotheres tristis)
Thobeka Gumede (Honours candidate)
Supervisor: Prof. Colleen Downs
Introduction
Food selection.
Enzyme sucrase- most starlings do not have so cannot digest sucrose (Bizaare et al., 2012).
Sugar concentration.
Daily energy intake.
Previous studies
Starlings (Sturnidae) American robin (Turdus migratorius)
Brown-eared bulbuls (Hypsipetes amaurotis)
Sugarbirds (Promerops)
Sunbirds (Nectariniidae)
Bananaquits (Coereba flaveola)
Common mynas (Acridotheres tristis)
Invasive species.
Broad diet.
Damaging crops.
No study of sugar preference.
Aim and objectives
AimTo examine the sugar preference and digestion. ObjectivesTo determine sugar preference.To determine the presence or absence of sucrose in excreta of common mynas.
To determine if concentration affects sugar type preference of common mynas.
MethodsCapture & maintenance Seven common mynas were caught in Pietermaritzburg.
Housed in aviaries at the University of KwaZulu-Natal, Pietermaritzburg campus.
Fed fruit and vegetables daily as a maintenance diet.
Methods- sugar preferencePairwise choice tests were conducted using the solutions (sucrose, fructose and hexose).
Birds were weighed before and after trials.Trials ran from 06h00-18h00.Sugar solutions were measured each hourDetermined sugar preference.
Methods- effect of concentrationPresented three glucose solutions of different concentrations (5, 10 and 25%) simultaneously to birds.
The trials were conducted from 06:00 to 18:00 hBirds were weighed before and after trials.Consumption of each concentration was measured.
Methods- assimilation efficiency
A tray of liquid paraffin under cages to catch excreta.
Single sugar offered (08:00-12:00 h).Deprived of food for 2h following.Liquid excreta collected using a syringe.Samples were centrifuged and sugar content analyzed using Shimadzu (LC-20AT) high-performance liquid chromatograph (HPLC).
samples
Results – sugar preference
t-test: P = 0.003; t = 8.062; df = 12; n=7
a.Significant difference
t-test: P = 0.008, t = 6.828; df = 12; n=7
b.
Sugar preference
t-test: P = 0.033; t = 6.334; df =12; n=7
c.
Sugar preference
Results- sugar concentration
One-way ANOVA: df = 2; F = 2.468; P =0.113; n=7
a.No significant difference
One-way ANOVA: df = 2; F = 2.565; P = 0.105; n=7
b.
Sugar concentration
No significant difference
Results – assimilation efficiency
90% of glucose and fructose absorbed.10% of sucrose absorbed.
Discussion
Common mynas (Sturnidae) were expected not to prefer sucrose (Brown et al., 2012).
Sucrose intolerance.
Common mynas showed preference for 10% glucose.
Intolerance of high concentrations (Brown et al., 2012)..
Assimilation efficiency of sugars varied.
Lacking enzyme sucrase.
Acknowledgements DST-NRF Centre of Excellence for Invasion Biology
Ebrahim Ally, Ntaki Senoge and Preshnee Singh
Thami Mjwaha
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Bizaaré, L., Coetzer, T. H., & Downs, C. T. 2012. Disaccharidase presence and activities in a range of southern African frugivores. Ostrich, 83, 165-168.
Brown, M., Downs, C.T., Johnson, S.D., 2012. African red-winged starlings prefer hexose sugar solutions, but do not like them too sweet. Journal of Ornithology 153, 265-272.
Jackson, S., Nicolson, S.W., van Wyk, B.-E., 1998. Apparent absorption efficiencies of nectar sugars in the Cape sugarbird, with a comparison of methods. Physiological and Biochemical Zoology 71, 106-115.
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Odendaal, T., Brown, M., Downs, C., Johnson, S., 2010. Sugar preferences and digestive efficiency of the village weaver: a generalist avian pollinator of African plants. Journal of Experimental Biology 213, 2531-2535.
