Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Biology

Brood Parasitism and Host Egg Rejection in Reed Warblers

Quick fact

Reed warblers reject foreign eggs about 60-70% of the time, but they make mistakes—occasionally rejecting their own eggs—illustrating the imperfect nature of recognition.

Why this is interesting

A reed warbler returns to its nest to find an egg that looks slightly different from its own. Why does it sometimes toss the egg out, but other times accept it?