I've compiled a spreadsheet of bird decors and how to obtain them. The list is sorted by obtainment method and contains excerpts about the birds from wikipedia.

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https://docs.google.com/spreadsheets/d/1MGUHvNhT_3RdUpxTqzzkTUFVbKt-PMWZnEW1RTGj9rg/edit?usp=sharing

If you have information on obtaining birds that are missing obtainment information, please tell me so I can add it to the spreadsheet. The list is currently incomplete and has not been updated in some time now, and may not be updated again for a while, so exercise caution and recognize that this is not a 100% comprehensive resource. The list also excludes decors that are merely animals with bird parts and not whole birds.

Edited Dec 8th 2019 to amend.