The little blue eggs found in the UK belong to a few common small bird species. The most likely candidates for the small blue eggs are blue tits, great tits, robins, wrens, and finches. These birds all lay small blue or blue-green eggs and are widespread across the UK.
To identify the specific bird species, we need to consider the nest location, size and shape of the egg, time of year, and any distinguishing markings. But in general, the little blue bird eggs seen in gardens, hedgerows, and woodlands in the UK will come from one of those common species.
What UK birds lay blue eggs?
The most common UK birds that lay blue eggs are:
Blue Tit
The blue tit is a very common garden bird in the UK. It lays small blue or white eggs with red speckles in an oval nest box or hole in a tree. The eggs are approximately 18 mm long.
Great Tit
Very similar to the blue tit, the great tit lays cream or pale blue eggs with reddish speckles. Their eggs are slightly larger at 22 mm long. Great tits nest in holes in trees or nest boxes.
Robin
The robin is another widespread garden bird in the UK. It builds an open cup nest and lays blue eggs without markings that are 21 mm long.
Wren
The wren builds a domed nest and lays tiny unmarked white or pale blue eggs around 14 mm long. Wrens nest in shrubs, walls, and other concealed locations.
Finches
Finches like chaffinches, greenfinches, goldfinches, and bullfinches build cup nests and lay blue eggs with dark speckles. Their eggs range from 19-25 mm long depending on species.
So in summary, if you find a small blue egg of around 14-22 mm long, it likely belongs to one of those common UK garden birds. To identify the specific species, you’d need to look at nest location, size, markings and time of year.
When do UK birds lay eggs?
Most small birds in the UK breed between March and August. Here are typical egg laying seasons:
Species | Breeding Season |
Blue tit | April – June |
Great tit | April – June |
Robin | March – July |
Wren | April – July |
Chaffinch | April – June |
Greenfinch | April – July |
The exact timing depends on weather conditions each year. But you’re most likely to see small blue eggs in UK gardens and woodlands between April and June. Outside of those months, it’s less likely to be a blue tit or other common species.
Where do blue tits nest in the UK?
Blue tits are very adaptable and exploit many nesting sites across the UK, including:
- Nest boxes – easily take to nesting in boxes, holes, and tubes in gardens
- Tree holes – natural holes and cavities in trees
- Wall crevices – nest in gaps in walls, crevices, and under eaves
- Bird boxes – readily use open-fronted boxes fixed to walls and trees
- Old nests – may renovate and reuse old nests of other species
The most common places to find blue tit nests and eggs are in nest boxes in gardens. But they make use of many habitats and are found nesting across the UK.
Nest box requirements
If providing a nest box for blue tits, the ideal nest box is:
- Small – base 8×8 cm, height 15-25 cm
- Has a 32 mm diameter hole about 15 cm from base
- Made of untreated timber
- Has a sloping roof and front panel that opens for monitoring
Placing the box 3-5 metres up on a tree trunk or wall, facing between north and east gives the best chance of blue tits finding and using the box.
How to identify blue tit eggs
To confirm if the small blue eggs you’ve found belong to a blue tit, look for:
Size and shape
– Oval shaped
– 14-18 mm long
– 12-14 mm wide
Color
– Pale blueish-green or white background
– Tiny reddish-brown speckles concentrated at the wider end
Nest location
– In a nest box, wall hole, or tree cavity
– Nest is moss, hair, wool lined
– Found 3-10 m above ground
Number of eggs
– Lays large clutch of 8-14 eggs
– May be many eggs in nest
How many broods do blue tits have?
Blue tits typically raise one brood per year. The breeding season lasts from April to July.
Key stages are:
- Nest building in April
- Egg laying in April – May
- Incubation for 13-15 days
- Chicks fledge after 16-22 days in nest
They may lay a second clutch if the first fails early in season. But usually blue tits only have time and resources for one successful brood in a year.
The chicks leave the nest in May – June. Adults and juveniles form flocks in summer before winter territories are established.
What do blue tit chicks eat?
The blue tit chicks hatch blind and helpless but develop quickly in the nest. The parents provide a diet of small caterpillars and insects to feed the chicks, including:
- Caterpillars – moth, butterfly
- Spiders
- Flies
- Aphids
- Beetles
- Ants
The parents make frequent trips to deliver tiny portions of food to each chick. The rich protein diet allows the chicks to grow rapidly.
Once they fledge the nest, the parents continue providing food as the juveniles learn to forage. They depend on their parents for 2-3 weeks after fledging.
Threats and conservation
Though widespread, blue tit populations face some key threats:
- Climate change – affects prey abundance and timing of breeding
- Habitat loss – needs nest sites and insect-rich feeding areas
- Predators – eggs and chicks vulnerable to jays, squirrels, cats
- Disease – prone to avian poxvirus and fleas
Providing nest boxes, avoiding pesticides, keeping cats indoors, and planting insect-friendly plants can all help support blue tit populations.
As a common garden visitor, they give people an up-close look at bird behaviour and biology. Protecting this special small bird is important for its own sake and for connecting people with nature.
Conclusion
The little blue eggs commonly seen in UK gardens, trees, and nest boxes in spring and summer likely belong to blue tits, great tits, robins, wrens, or finches. The blue tit is most strongly associated with small pale blue eggs speckled red, laid in tree holes or nest boxes from April to June. Identifying the nest location, size, color, and quantity of eggs can help confirm the species. Though widespread, blue tits face threats from climate change, habitat loss, predators, and disease. Providing suitable nest sites, avoiding pesticides, and planting wildlife-friendly gardens can help support these special birds that provide delight and connection with nature for many across the UK.