Hi Yuzhan! I am working also with geese and I would answer to your question that yes there is a need if there is a suspicion that geese are limited , for example, by the quality (nutrient content) of the available food, since plants differ in their nutrient contents and thus their nutritive values. so if your research has to do with that, then yes, you might have to work with the specific kinds of plants that your geese eat.

Thanks for your reply. But think about Carex, if there are three or four species of carex mixing together in a wetland, is that possible for geese to distinguish these species? I tend to think they would not do this kind of selection, whilst just pick what they meet. How do you think about this? Do you think geese are super specialist, or they could also adapt to different plants occurring in their habitats?

Hİ

I think geese can separate species, and they can also tell the difference within a species between plants that have a higher or lower quality (e.g. in nitrogen content). See e.g.

Stahl, J., A. J. Van Der Graaf, R. H. Drent, and J. P. Bakker. 2006. Subtle interplay of competition and facilitation among small herbivores in coastal grasslands. Functional Ecology 20:908-915.

But a full answer to your question depends on the objectives of your study, which are not fully clear to me