Muth and Healy carried out their experiments on zebra finches,
a bird species native to Australia, in which it is the males who take
building material to the nest, even though both males and females
manipulate building material already brought to the nest. Two tests
were carried out. The aim of the first testwas to determine whether
male zebra finches prefer green or brown nest material in the form
of hay and coconut fibres.