Blue tits and nesting boxes

Having just pulled down an old shed I found myself with plenty of odd lengths of timber so I’ve been busy with my circular saw and drill making and erecting a selection of nest boxes for garden birds. Of course, I could have bought some nest boxes - there are plenty of unnecessarily ornate and quite expensive ones available from my local garden centre, but fortunately the birds are not too fussy about what the boxes look like so long as they are of a suitable size.

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Building a nesting box

One of the most important features is to make the box from fairly thick wood, this is better for insulation from cold and hot weather. I use sawn timber of 25mm thickness. Another key feature is the diameter of the access hole which should be about 25mm for a blue tit; 28mm for a great tit and 32mm for both nuthatches and house sparrows. 

The base of the nestbox should be 150mm to 180mm across and the hole should be at least 150mm from the base. It’s a good idea to fasten the top on in such a way as it is easy to take it off to clean the box each winter and it’s best to face the hole away from the prevailing wind.

In our garden we find blue and great tits are the commonest occupants of nest boxes. Just outside our conservatory we have had a pair of blue tits using the same box for the last three seasons and I have already seen them prospecting again this winter. It’s fascinating to watch this pair as they go through the regular annual rituals.

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Blue tit mating rituals

By late winter we see blue tits starting to display to each other. It isn’t easy to recognise a male from a female blue tit but in the early spring he is the one who puffs himself up and rotates back and forth with his breast feathers fluffed out and head cocked slightly back. He is at his absolute colourful best in spring. His blue head and wings contrast remarkably with a vivid yellow breast and belly.

To impress her further the male blue tit occasionally brings her a caterpillar or other morsel. 

The nesting habits of blue tits

As soon as the female blue tit feels confident in her mate she starts collecting nesting material to part-fill the nest box. The male does help with this task but he spends far too much time reminding her how handsome he looks. I can’t be sure but I think she finds him a bit narcissistic at this stage. Anyway, to help with their efforts I usually put out some of my own hair or that of our dog in an old peanut feeder. They find this fairly quickly and it must save them a lot of time and make a very comfortable warm nest.

Blue tit nesting season is February to June, with the birds finding a safe spot in February and then starting to build their nest in March and April. For this reason it's traditional to put your nesting box up before Valentine's Day.

In early May the female blue tit will lay her eggs one at a time until she has a clutch (usually 8-12 eggs, but sometimes more), and they'll hatch at the end of the month. Blue tit chicks fledge in early June, but the parents will continue to feed them for several weeks after fledging.

Feeding blue tits and other garden birds

People often ask me about feeding birds and when to start and stop each year. One thing I always suggest is to keep feeding them well into spring. I think February and March are the times of greatest need but I always continue feeding birds until the end of April. 

I’m sure this saves time for the blue tits and great tits at a time when they are building their nest and the female will need to expend a lot of energy on creating about eight eggs which she will lay in April or May.

When the young hatch we always notice a change in feeding behaviour. The adult birds will search for natural food to take back to the nest. 

I’ve put a branch in front of the nest box and they invariably land there before entering the box. This gives me a chance to see what they are carrying in and usually it will be a spider or a caterpillar.

It’s amazing that the adults can find enough food to satisfy the demand from inside the box. Returning with food every minute or two through the day keeps them incredibly busy. No wonder then that by early summer the adults are starting to look a bit tatty!

When blue tits leave the nest box

The blue tit parents' last job is to encourage the youngsters out of the box. This always takes me by surprise because suddenly the adults stop flying back and forth freely with food, instead they sit on the outside perch and call. 

It should be the most satisfying moment of the cycle and yet I also find it quite sad. I won’t be able to watch them any more and the youngsters are heading out into a dangerous world. I wonder how many of them will survive to breed next year?

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