I sent a query to jagex, they said they are related to farming but can't tell me anymore.
runescape support wrote:
Dear Shane12088,
Thanks for your message.
Birds Eggs are currently a random result from a nest found for woodcutting. As of this time, we are unable to disclose what there use is, or what they are planned to be used in/for.
Happy gaming!
Sincerely,
Mod Chris L
RuneScape Customer Support
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On 13th July 2005 you sent us the following:
Hi,
I know people have been getting coloured eggs from nests. I was wondering if you guys would be able to tell me if they have any use towards farming as of yet.
Shane
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