Blue tit colours

The blue tit (Parus caeruleus) has been classified as sexually monochromatic, which means that male and female are the same colour. This classification is based, though, on human colour perception, not on blue tit colour perception.

Like all birds, blue tits can see ultra-violet light and the front of their heads glow brightly under UV light. Researchers have found that it is the males who choose the females with the brightest heads; this is unusual because it is usually the females who do the choosing. Females with bright ultra-violet heads are more successful mothers; they rear more chicks to the point of fledging.

All gallery images taken by DKG in the reserve.

And while we are on the subject of colour, let’s discuss yellow tummies. The reserve’s blue tits can’t produce the pigment carotene that makes their tummies yellow. This is not unusual: most birds can’t create pigments other than melanin.

Blue tits get the carotene they need from pigments in the green winter moth caterpillars they eat at this time of year. The more green caterpillars a blue tit eats, and the brighter yellow its tummy, the more likely he or she is to attract a mate.