Behaviour and ecology Common starling

1 behaviour , ecology

1.1 feeding
1.2 nesting
1.3 breeding

behaviour , ecology


a large flock in rotterdam, netherlands

the common starling highly gregarious species, in autumn , winter. although flock size highly variable, huge, noisy flocks - murmurations - may form near roosts. these dense concentrations of birds thought defence against attacks birds of prey such peregrine falcons or eurasian sparrowhawks. flocks form tight sphere-like formation in flight, expanding , contracting , changing shape, seemingly without sort of leader. each common starling changes course , speed result of movement of closest neighbours.

very large roosts, exceptionally 1.5 million birds, can form in city centres, woodlands or reedbeds, causing problems droppings. these may accumulate 30 cm (12 in) deep, killing trees concentration of chemicals. in smaller amounts, droppings act fertiliser, , therefore woodland managers may try move roosts 1 area of wood benefit soil enhancement , avoid large toxic deposits.

huge flocks of more million common starlings may observed before sunset in spring in southwestern jutland, denmark on seaward marshlands of tønder , esbjerg municipalities between tønder , ribe. gather in march until northern scandinavian birds leave breeding ranges mid-april. swarm behaviour creates complex shapes silhouetted against sky, phenomenon known locally sort sol ( black sun ). flocks of 5 fifty thousand common starlings form in areas of uk before sundown during mid-winter. these flocks commonly called murmurations.

feeding

a flock foraging @ farm in northern ireland

the common starling largely insectivorous , feeds on both pest , other arthropods. food range includes spiders, crane flies, moths, mayflies, dragonflies, damsel flies, grasshoppers, earwigs, lacewings, caddisflies, flies, beetles, sawflies, bees, wasps , ants. prey consumed in both adult , larvae stages of development, , common starlings feed on earthworms, snails, small amphibians , lizards. while consumption of invertebrates necessary successful breeding, common starlings omnivorous , can eat grains, seeds, fruits, nectar , food waste if opportunity arises. sturnidae differ birds in cannot metabolise foods containing high levels of sucrose, although can cope other fruits such grapes , cherries. isolated azores subspecies of common starling eats eggs of endangered roseate tern. measures being introduced reduce common starling populations culling before terns return breeding colonies in spring.

an adult foraging , finding food young chicks

there several methods common starlings obtain food part, forage close ground, taking insects surface or underneath. generally, common starlings prefer foraging amongst short-cropped grasses , found among grazing animals or perched on backs, feed on mammal s external parasites. large flocks may engage in practice known roller-feeding , birds @ of flock continually fly front feeding opportunities best. larger flock, nearer individuals 1 while foraging. flocks feed in 1 place time, , return previous foraged sites.

there 3 types of foraging behaviour observed in common starling. probing involves bird plunging beak ground randomly , repetitively until insect has been found, , accompanied bill gaping bird opens beak in soil enlarge hole. behaviour, first described konrad lorenz , given german term zirkeln, used create , widen holes in plastic garbage bags. takes time young common starlings perfect technique, , because of diet of young birds contain fewer insects. hawking capture of flying insects directly air, , lunging less common technique of striking forward catch moving invertebrate on ground. earthworms caught pulling soil. common starlings have periods without access food, or have reduction in hours of light available feeding, compensate increasing body mass deposition of fat.

nesting

a parent feeding chick in nest in tree hole in england

unpaired males find suitable cavity , begin build nests in order attract single females, decorating nest ornaments such flowers , fresh green material, female later disassembles upon accepting him mate. amount of green material not important, long present, presence of herbs in decorative material appears significant in attracting mate. scent of plants such yarrow acts olfactory attractant females.

the males sing throughout of construction , more when female approaches nest. following copulation, male , female continue build nest. nests may in type of hole, common locations include inside hollowed trees, buildings, tree stumps , man-made nest-boxes. s. v. zetlandicus typically breeds in crevices , holes in cliffs, habitat used nominate form. nests typically made out of straw, dry grass , twigs inner lining made of feathers, wool , soft leaves. construction takes 4 or 5 days , may continue through incubation.

common starlings both monogamous , polygamous; although broods brought 1 male , 1 female, pair may have helper. pairs may part of colony, in case several other nests may occupy same or nearby trees. males may mate second female while first still on nest. reproductive success of bird poorer in second nest in primary nest , better when male remains monogamous.

breeding

five eggs in nest



eggs, collection museum wiesbaden, germany



chicks waiting fed @ entrance of nest made in gap in wall in galway, ireland

breeding takes place during spring , summer. following copulation, female lays eggs on daily basis on period of several days. if egg lost during time, lay replace it. there 4 or 5 eggs ovoid in shape , pale blue or white, , commonly have glossy appearance. colour of eggs seems have evolved through relatively visibility of blue @ low light levels. egg size 26.5–34.5 mm (1.04–1.36 in) in length , 20.0–22.5 mm (0.79–0.89 in) in maximum diameter.

incubation lasts thirteen days, although last egg laid may take 24 hours longer first hatch. both parents share responsibility of brooding eggs, female spends more time incubating them male, , parent @ night when male returns communal roost. young born blind , naked. develop light fluffy down within 7 days of hatching , can see within 9 days. once chicks able regulate body temperature, 6 days after hatching, adults largely cease removing droppings nest. prior that, fouling wet both chicks plumage , nest material, thereby reducing effectiveness insulation , increasing risk of chilling hatchlings. nestlings remain in nest 3 weeks, fed continuously both parents. fledglings continue fed parents 1 or 2 weeks. pair can raise 3 broods per year, reusing , relining same nest, although 2 broods typical, or 1 north of 48°n. within 2 months, juveniles have moulted , gained first basic plumage. acquire adult plumage following year. other passerines, nest kept clean , chicks faecal sacs removed adults.

intraspecific brood parasites common in common starling nests. female floaters (unpaired females during breeding season) present in colonies lay eggs in pair s nest. fledglings have been reported invade own or neighbouring nests , evict new brood. common starling nests have 48% 79% rate of successful fledging, although 20% of nestlings survive breeding age; adult survival rate closer 60%. average life span 2–3 years, longevity record of 22 yr 11 m.