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

Photoperiodism and Seasonal Breeding in Temperate-Zone Birds

Quick fact

A single extra hour of daylight can trigger a cascade of hormonal changes in a bird, causing its gonads to grow up to 200 times their winter size within weeks, prepping the body for breeding.

Why this is interesting

Every spring, robins and sparrows begin building nests—but how do they know that spring has arrived? The secret isn't a calendar or temperature; it's the changing length of daylight.