Aussie Finch Forum

My gouldians are aggressive to the zebra finches, as the male gouldian doesn't let the zebra finches near his seed container or his and hers perch

Birds have a need for personal space too, and different species exhibit this to varying dergrees. Zebs like to get up close to one-another - especially with those of their own kind. Gouldians are generally more stand-offish and have a greater need for personal space. Less so with their own kind but rarely if ever to the same degree as Zebs. So it's not surprising that you are observing the sort of aggressive interactions you describe. This does not invalidate the advice already given regarding breeding territories. Rather, one could argue that if such interactions are observed regularly, which I suspect is the case, that would support the notion that they are feeling overcroweded.