The head crest, orange in the male and yellow in the female, is displayed during breeding, and gives rise to the English and scientific names for the species.

This bird superficially resembles the goldcrest, which largely shares its European range, but the firecrest's bronze shoulders and strong face pattern are distinctive.

The common firecrest breeds in broadleaved or coniferous woodland and gardens, building its compact, three-layered nest on a tree branch.

Despite some possible local declines, the species is not the subject of significant conservation concerns owing to its large European population and an expansion of its range over the last century.

The head pattern is striking, with a black eye stripe, long white supercilium, and a crest which is bright yellow in the female and mainly orange in the male.

[20] The common firecrest breeds in lowland broadleaf forest, preferring cork oak and alder where available, otherwise beech and holly.

It also uses mixed broadleaf and conifer woodland, and stands of spruce, European silver fir, cedar and pines, often with undergrowth of juniper, ivy and wild rose.

[3] Unlike more specialised birds such as Eurasian nuthatch and common treecreeper, both of which forage on trunks, the crests do not need large woodlands, and their population density is independent of forest size.

It occurs singly or in pairs, spending much time in the tree canopy, although frequently venturing into bushes and other lower vegetation.

[2] Southern birds are largely resident, unlike northern and eastern populations which are migratory, wintering mainly in Mediterranean areas and the far west of Europe from Portugal north to Britain.

[15] Laying starts in western Europe at the end of April, and in the east of the range in late May; second clutches, which are common, commence in June to July.

[2] The eggs are pink with very indistinct reddish markings at the broad end,[29] unlike those of Madeira firecrest which are described as like those of a Phylloscopus warbler (white with some brown speckles).

Even in aviary studies in which a female goldcrest was given an artificial eyestripe to facilitate mating with a male firecrest, the chicks were never raised by the mixed pair, and appeared to be poorly adapted compared to the parent species.

In winter, flocks of common firecrests cover a given distance about three times faster than do goldcrests, and ignore the smallest prey items preferred by their relative; large invertebrates are killed by beating them repeatedly against a branch.

Firecrests forage more often while standing, and have a foot better adapted for perching, whereas the goldcrest's longer hind toe reflects its habit of moving vertically along branches while feeding.

[31] Young common firecrests are fed almost exclusively with springtails; larger food items are not accepted, and spiders are occasionally regurgitated.

From the fifth day onwards, the nestling diet includes aphids and a high amount of snail shells, the latter being needed for bone growth.

After the second week, the food includes larger moths and caterpillars, as well as various arthropods typically avoided by adults, such as harvestmen, earwigs, and centipedes.

[3] This kinglet, like other species that prefer mixed-species foraging flocks in winter, hunts over a greater range of heights and vegetation types than when feeding alone.

The results showed that, relative to body weight, the insect-eaters had shorter intestines, but longer gut passage times than the Sylvia species.

[33] The contact call is three or four thin high notes, similar to that of goldcrest, but slightly lower in pitch,[34] zit-zit-zit rather than see-see-see.

[13][26] Throughout the firecrest's range, the main predator of small woodland birds is the Eurasian sparrowhawk, which takes avian prey as up to 98% of its diet.

The reduction in prey items is greatest in the tree canopy, and has a greater effect on species like the firecrest that feed high in the foliage.

[40] Data on specific parasites of the firecrest is lacking, but the widespread moorhen flea, Dasypsyllus gallinulae has been recorded in a related Regulus species.

[44] The common firecrest expanded its range in the nineteenth and twentieth centuries,[20] colonising northern France, followed by first breeding in the Netherlands in 1928 and Denmark in 1961.

[2] Population growth may be limited by lack of suitable habitat, and there may be local declines due to loss of conifers through storms or replacement by plantations of native deciduous trees.

[47] There may also be localised losses in areas of high heavy metal pollution, which particularly affects ground feeders like thrushes and conifer foliage gleaners, including both European Regulus species.

[52][53] The confusion was assisted by the similarity and consequent interchangeability of the Ancient Greek words for the wren (βασιλεύς basileus, "king") and the crest (βασιλισκος basiliskos, "kinglet").