After determining the initial sex ratios of a series of clutches, the researchers added or subtracted chicks to increase or decrease the father's workload (a standard trick in avian ecology, made possible by the fact that parents do not recognise their own young until close to the time at which they leave the nest).

ECONOMIST: Sexy sons, dutiful daughters | The

This suggests than it may have something to do with the fact that the sex-determining chromosome is carried by males in mammals and females in birds.

ECONOMIST: Sexy sons, dutiful daughters | The

The lawsuit also argues that the law forces Massachusetts to treat same-sex married couples differently from heterosexual married couples, particularly through determining who qualifies for the state's Medicaid program, known as MassHealth, and whether a same-sex spouse of a veteran can be buried in a veteran cemetery.

CNN: Massachusetts sues federal government over marriage law