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Biology

Parental Care Strategies and Offspring Sex Ratios in Great Tits

Quick fact

In years with abundant food, great tits may produce more sons (the larger, costlier sex), while in poor years they produce more daughters, who are cheaper to raise and more likely to survive.

Why this is interesting

Every spring, great tit parents face a hidden choice: how many sons and daughters should they raise? And why might they favor one sex over the other depending on the weather?