the bohemian waxwing (bombycilla garrulus) is a starling-sized passerine bird that breeds in the northern forests of eurasia and north america .
it has mainly buff-grey plumage , black face markings and a pointed crest .
its wings are patterned with white and bright yellow , and some feather tips have the red waxy appearance that give this species its english name .
the three subspecies show only minor differences in appearance .
females are similar to males , although young birds are less well-marked and have few or no waxy wingtips .
although the bohemian waxwing's range overlaps those of the cedar and japanese waxwings , it is easily distinguished from them by size and plumage differences .
the breeding habitat is coniferous forests , usually near water .
the pair build a lined cup-shaped nest in a tree or bush , often close to the trunk .
the clutch of 37 eggs is incubated by the female alone for 1314 days to hatching .
the chicks are altricial and naked , and are fed by both parents , initially mostly with insects , but thereafter mainly fruit .
they fledge about 1416 days after leaving the egg .
many birds desert their nesting range in winter and migrate farther south .
in some years , large numbers of bohemian waxwings irrupt well beyond their normal winter range in search of the fruit that makes up most of their diet .
waxwings can be very tame in winter , entering towns and gardens in search of food , rowan berries being a particular favourite .
they can metabolise alcohol produced in fermenting fruit , but can still become intoxicated , sometimes fatally .
other hazards include predation by birds of prey , infestation by parasites and collisions with cars or windows .
the bohemian waxwing's high numbers and very large breeding area mean that it is classified as being of least concern by the international union for conservation of nature .
the waxwings are a family , bombycillidae , of short-tailed stocky birds with soft plumage , a head crest and distinctively patterned wings and tails .
there are three species , the bohemian , cedar , and japanese waxwings .
dna studies and shared features such as a relatively large size , grey underparts and similar undertail patterns suggest that the japanese and bohemian waxwings are most closely related within the genus .
although only the cedar and bohemian waxwings normally have red tips on their wing feathers , this feature is occasionally shown by the japanese waxwing , suggesting that this was originally a whole-family characteristic that has been lost in one species , rather than an indicator of a close relationship .
dna analysis confirms that the cedar waxwing diverged early from the other members of the family .
outside the genus , the closest relatives of the waxwings are believed to be the silky-flycatchers , the palmchat , and the grey hypocolius , all of which have sometimes been included in the bombycillidae .
the bohemian waxwing was described by linnaeus in his systema naturae in 1758 as lanius garrulus .
the waxwings were moved to their own genus , bombycilla , by vieillot in 1808. the genus name bombycilla comes from the greek bombux , "silk" and the modern latin cilla , "tail"; this is a direct translation of the german seidenschwanz , "silk-tail", and refers to the silky-soft plumage of the bird .
the species name garrulus is the latin for talkative and was applied to this bird , as "garrulus bohemicus", by conrad gessner in 1555; the term is a reference to a supposed likeness to the eurasian jay (garrulus glandarius) rather than to the waxwing's vocalisations .
the english name "waxwing" refers to the bright red tips of the secondary feathers on its wings , which look like drops of sealing wax , while "bohemian" follows gessner's usage , and may refer to the romani , alluding to the bird's wanderings , or to its presumed origin from bohemia .
"waxwing" and "bohemian waxwing" were first recorded in 1817, the former as a reference to vieillot's separation of this bird from the "chatterers" .
there are three recognised subspecies:the differences between these forms are small and clinal , and the species could be possibly considered as monotypic .
the fossil record includes pleistocene deposits from the uk and the carpathian mountains .
the bohemian waxwing is a starling-sized bird 1923 cm (7.59.1 in) in length with a 3235.5 cm (12.614.0 in) wingspan , and an average weight of 55 g (1.9 oz) .
it is short-tailed , mainly brownish-grey , and has a conspicuous crest on its head .
the male of the nominate subspecies has a black mask through the eye and a black throat .
there is a white streak behind the bill and a white curve below the eye .
the lower belly is a rich chestnut colour and there are cinnamon-coloured areas around the mask .
the rump is grey and the tail ends in a bright yellow band with a broad black border above it .
the wings are very distinctive; the flight feathers are black and the primaries have markings that produce a yellow stripe and white "fishhooks" on the closed wing .
the adult's secondaries end in long red appendages with the sealing wax appearance that gives the bird its english name .
the eyes are dark brown , the bill is mainly black , and the legs are dark grey or black .
in flight , the waxwing's large flocks , long wings and short tail give some resemblance to the common starling , and its flight is similarly fast and direct .
it clambers easily through bushes and trees but only shuffles on the ground .
the soft , dense feathers are kept in good condition by preening .
the red waxy tips are the extended and flattened ends of feather shafts , pigmented with astaxanthin and enclosed in a transparent sheath .
a study of the cedar waxwings showed that the red tips are few or absent until the third year of life for that related species .
all adult waxwings have a complete moult annually between august and january .
juveniles moult at the same time but retain their flight and some other wing feathers .
the female bohemian waxwing is very similar to the male , but has a narrower yellow terminal band to the tail , a less defined lower edge to the black throat and slightly less distinctive wing markings .
juveniles are duller than adults , with whiter underparts , only a few red wing tips , no black on the throat and a smaller black face mask .
compared to the nominate subspecies , eastern b .
g .
centralasiae is paler , greyer and has little reddish-brown behind the bill .
the american subspecies b .
g .
pallidiceps has more colouring on the cheeks and forehead than the nominate form and is otherwise generally duller in appearance .
the range of the bohemian waxwing overlaps those of both the other members of the genus .
the cedar waxwing is smaller than the bohemian; it has browner upperparts , a white undertail and a white line above the black eye patch .
adult cedar waxwings have a yellowish belly , and all ages have less strongly patterned wings than the bohemian waxwing .
the japanese waxwing is easily distinguished from its relatives; it has a red terminal band to the tail , the black mask extends up the rear of the crest , and there is no yellow stripe or red tips on the wings .
the bohemian waxwing's call is a high trill sirrrr .
it is less wavering and lower-pitched than that of the cedar waxwing , and longer and lower-pitched than the call of the japanese waxwing .
other calls are just variants of the main vocalisation; a quieter version is used by chicks to call parents , and courtship calls , also given during nest construction , have a particularly large frequency range .
although not a call as such , when a flock takes off or lands , the wings make a distinctive rattling sound that can be heard 30 m (98 ft) away .
the bohemian waxwing has a circumpolar distribution , breeding in northern regions of eurasia and north america .
in eurasia , its northern nesting limit is just short of the treeline , roughly at the 10 c july isotherm , and it breeds south locally to about 51n .
most birds breed between 6067n , reaching 70n in scandinavia .
the north american subspecies breeds in the northwestern and north central areas of the continent , its range extending southwards beyond the us border in the rocky mountains .
this waxwing is migratory with much of the breeding range abandoned as the birds move south for the winter .
migration starts in september in the north of the range , a month or so later farther south .
eurasian birds normally winter from eastern britain through northern parts of western and central europe , ukraine , kazakhstan and northern china to japan .
north american breeders have a more southeasterly trend , many birds wintering in southeast canada , with smaller numbers in the north central and northeastern us states .
birds do not usually return to the same wintering sites in successive years .
one bird wintering in the ukraine was found 6,000 km (3,700 mi) to the east in siberia in the following year .
in some years , this waxwing irrupts south of its normal wintering areas , sometimes in huge numbers .
the fruit on which the birds depend in winter varies in abundance from year to year , and in poor years , particularly those following a good crop the previous year , the flocks move farther south until they reach adequate supplies .
they will stay until the food runs out and move on again .
in what may be the largest ever irruption in europe , in the winter of 20042005, more than half a million waxwings were recorded in germany alone .
this invasion followed an unusually warm , dry breeding season .
in 1908, an american flock 6090 m (200300 ft) wide was noted as taking two to three minutes to fly over .
the breeding habitat is mature conifers , often spruce although other conifers and broadleaf trees may also be present .
more open , wet areas such as lakes and peat swamps with dead and drowned trees are used for feeding on insects .
lowlands , valleys and uplands are used in eurasia , although mountains tend to be avoided .
however , the north american subspecies nests in canada at altitudes between 9001,550 m (2,9505,090 ft) .
outside the breeding season , the waxwing will occupy a wide range of habitats as long as suitable fruits such as rowan are available .
it may be found by roads , in parks and gardens or along hedges or woodlands edges .
it shows little fear of humans at this time .
in winter , waxwings roost communally in dense trees or hedges , sometimes with american robins , fieldfares or other wintering species .
bohemian waxwings start their return from the wintering grounds in february or march , but northern breeders do not reach their breeding areas until april or early may .
this monogamous species nests mainly from mid june to july .
waxwings are not highly territorial , and , although normally solitary breeders , several pairs may nest close together where there are a number of good nest sites .
males may sometimes deter rivals from approaching their mates , and females may squabble over nest sites .
aggression is shown by sleeking down the feathers and crest , showing the black throat , and opening the bill .
the breeding display is almost the opposite of this; the male erects his body and crest feathers , and turns his head away from the female .
the male may repeatedly present a gift of a small item , often food , to his partner , placing it in her open bill .
in about 90% of cases , this display does not lead to copulation .
older males have more red tips to the wings and are preferred by females .
the nest , built by both sexes , is a cup of thin twigs lined with softer material such as fine grass , moss , fur or lichen .
it is constructed 1.315 m (450 ft) above the ground in a pine or scrub , commonly close to the trunk .
the eggs are a glossy pale blue spotted with black and grey and the clutch is 37 eggs , although five or six is most common .
the average size of the egg is 24 mm  18 mm (0.94 in  0.71 in), and it weighs 3.8 g (0.13 oz), of which 5% is shell .
the eggs are incubated for 1314 days by the female alone .
she is fed regurgitated berries by her mate , and rarely leaves the nest .
the chicks are altricial and naked , and have bright red mouths; they are fed by both parents , although the male brings most of the food , mainly insects , in the first few days .
the young are subsequently fed largely with fruit .
the chicks fledge about 1416 days after hatching .
they are fed by the adults for about two weeks after fledging .
breeding densities of this waxwing are typically low compared to other passerines , usually less than ten birds per square kilometre (26 per square mile) even in good habitat , although up to 356 birds per square kilometre (92 per square mile) have been found in russia .
one brood each year is normal .
maximum recorded ages are 5 years 10 months in north america and more than 13 years 6 months in europe .
the average life expectancy is unknown .
significant causes of death include predation , collisions with windows and cars , and poisoning by road salt consumed when drinking .
waxwings are primarily fruit eaters , but also consume insects during the breeding season .
mosquitoes and midges are the most common prey , but many other insects and some spiders are eaten .
they are caught mainly by flycatching from an open perch , but some may be picked off vegetation .
fruit is normally picked from trees , sometimes from the ground , and is usually swallowed whole .
in the summer , vaccinium and rubus species and canada buffaloberry are important items of their diet , while cotoneaster , juniper , haws , rose hips and apples predominate outside the breeding season .
rowan berries are a favourite food , and are eaten whenever available .
waxwings can eat huge numbers of berries , each bird sometimes consuming several hundred a day , more than double its own weight .
one individual was recorded as eating between 600 and 1,000 cotoneaster berries in six hours , and defecating every four minutes .
waxwings travel significant distances when feeding and help to disperse the fruit seeds .
waxwings forage in large flocks , sometimes of several hundred birds , which enables them to overwhelm birds such as mistle thrushes attempting to defend their fruit trees .
fruit is rich in sugar but deficient in other nutrients , so it must be eaten in large quantities .
bohemian waxwings have a large liver which helps to convert sugar to energy .
they can metabolise ethanol produced from the fermentation of those sugary fruits more efficiently than humans , but may still become intoxicated , sometimes fatally .
waxwings often drink water or eat snow in winter , since the sugar in their fruit diet tends to dehydrate the birds through an osmotic effect .
in the summer , the fruits are juicier and water is less of a problem .
in the past , the arrival of waxwings sometimes coincided with epidemics of cholera or plague , and led to the old dutch and flemish name pestvogel , "plague bird" .
the juniper berries on which they fed were thought to offer protection , and people consumed the fruit and burned branches to fumigate their houses .
waxwings are preyed upon by birds of prey including rough-legged buzzards , eurasian sparrowhawks , prairie falcons , and great grey shrikes .
merlins attack winter flocks , including those in cities .
when alarmed , bohemian waxwings "freeze" with bill and neck pointing upwards .
if this fails , they fly , calling noisily .
bohemian waxwings are not brood parasitised by the common cuckoo or its relatives in eurasia because the cuckoo's young cannot survive on a largely fruit diet .
in north america , the waxwing's breeding range has little overlap with brown-headed cowbird , another parasitic species .
nevertheless , eggs of other birds placed in a bohemian waxwing's nest are always rejected .
this suggests that in the past , perhaps 3 million years ago , the ancestral waxwing was a host of a brood parasitic species , and retains the rejection behaviour acquired then .
parasitic mites include syringophiloidus bombycillae , first identified on this species , and the nasal mite ptilonyssus bombycillae .
blood parasites include trypanosoma species , and a leucocytozoon first identified in this waxwing .
bohemian waxwings may carry flatworms and tapeworms , but levels of parasitic worm infestation are generally low .
the global population of the bohemian waxwing has been estimated at more than three million birds , and the breeding range covers about 12.8 million km2 (4.9 million mi2) .
although this species' population , as of 2013, appears to be declining , the decrease is not rapid nor large enough to trigger conservation vulnerability criteria .
given its high numbers and huge breeding area , this waxwing is therefore classified by the international union for conservation of nature as being of least concern .
the woodlands used by this species are well to the north of major human populations , and the birds can use disturbed habitats , so there are no serious long-term threats to this species .
