One of the family

NOT a lot of people know this, but... blue tits don't start life blue.

- MIKE LOCKLEY

They're green and gradually develop the trademark colour.

As I type this a pair are frantically flying to and from a nestbox nailed to the shed of my back garden. The frenzied activity has become an annual spring sight.

Dawn to dusk, they never stop. If I walk too close to the nestbox, one, keeping watch from a nearby bush, issues a raucous alarm call.

The hunger of the chicks inside is insatiable, the demand on their parents unrelenting. So unrelenting, if one of the adults dies, the other runs the risk of dying from exhaustion.

The British Trust for Ornithology explains how gruelling parenthood is for these birds: “Feeding chicks takes its toll on the parents as they flit in and out of the nestbox with juicy fat caterpillars. Each chick can eat 100 caterpillars a day, so to feed a brood of ten, adults need to find as many as 1,000 caterpillars a day!

“Adults also need to remove the chicks’ waste from the nest to keep it clean. Baby blue tits produce faecal sacks - strong mucous membranes that keep their faeces neatly encapsulated so the parents can carry them from the nest.”

Each year, I attempt to capture the very moment the brood emerges from the dark depths of the nestbox into the sunlight. Each year I miss that dramatic debut into the wide world.

What has become apparent over the years is the fact blue tits are using my nestbox much earlier.

The activity I'm now witnessing used to begin in mid-May. This pair have been in situ since early April. That poses a problem for parents because caterpillars are in short supply.

The brood will be big. Blue tits lay between eight and 12 eggs and as many as 16 have been recorded. Very few of the emerging chicks will reach adulthood.