Zebra Finches forage on seed from invasive Buffel Grass, but prefer seed from two common native grasses

Abstract

ABSTRACTInland Australia is being transformed by invasive Cenchrus ciliaris (Buffel Grass) which is displacing native grasses. Zebra Finches (Taeniopygia guttata) forage on C. ciliaris seed but it is not known whether native grass seed is preferred. The preferences of captive-bred Zebra Finches for different species of grass seed were investigated using cafeteria trials. An equal volume of unhusked seed from C. ciliaris and one of two common native grasses were offered in each trial. Zebra Finches foraged on C. ciliaris seed, but preferred native seed. They spent approximately 80% of their time foraging on Enneapogon polyphyllus seed, compared to 20% on C. ciliaris, and consumed more native seed. They also spent more time foraging on Triraphis mollis seed compared to C. ciliaris, but the amount of seed consumed was similar. Preferences could not be explained by seed size or accessibility and may relate to nutritional composition. Comparison of the condition and reproductive fitness of Zebra Finches on introduced and native seed diets would determine whether less-preferred C. ciliaris seed is nutritionally sub-optimal and whether there will be detrimental effects on Zebra Finch populations if C. ciliaris becomes the major source of seed across much of their current distribution. Our research contributes to knowledge of avian dietary preference in human-altered landscapes, and represents one of the few experiments published so far that focuses on direct interactions between invasive grasses and native animals to better understand the potential impacts of invasion.