endothermic

Barn owl Tyto alba peering out from barn rafters

Swallow Hirundo rustica sketch in flight

Black Casqued Hornbill Ceratogymna atrata

Black headed gull Chroicocephalus ridibundus with winter and summer head plumage

Black redstart Phoenicurus ochruros view from behind, head slightly cocked

Blackbird Turdus merula

Blue-tit Parus caeruleus male on a branch

Blue tit Parus caeruleus, Coal tit, Long tailed tit, and great tits in a Scots pine tree with cowslip and snakeshead fritillary growing underneath

Blue tit Parus caeruleus adult feeding chicks inside a bird box

Blue tit Parus caeruleus visiting a bird box

Bohemian Waxwing Bombycilla garrulus perched on a twig of rowan with orange berries

Bullfinch Pyrrhula pyrrhula male

Buzzard Buteo buteo at rest on a branch

Canada goose Branta canadensis

Hand holding a duck egg and a candle to see whether or not the egg is viable as egg becomes translucent

Chaffinch Fringilla coelebs male in amongst grasses

Coal tit Periparus ater perched on a twig covered with lichen including Usnea species