Starlings (Tommy Holden)
It’s maybe something you’ve not thought much about, but where do garden birds go at night? During long, cold winter nights they need not only to keep warm, but also to keep out of reach of a range of predators such as cats, owls, rodents and stoats or weasels.
The habits of roosting birds are diverse. Sparrows, Wrens and Chaffinches seem to vanish at dusk. They secrete themselves away in dense foliage, cracks or crevices, and avoid drawing attention to their whereabouts.
It’s a juggling act: trying to find enough shelter to keep warm and conserve energy, without increasing the risk of attack. Too close to the trunk and there could be danger from a rat or stoat, too far out on a limb means vulnerable to a sharp-eyed owl. The branch acts as an intruder alarm; a motion sensor providing a split-second warning of danger.
Ivy is one of the UK’s few native evergreen plants. Much maligned it is often accused of strangling trees. However, it should be celebrated and valued for the pivotal role it plays in providing wildlife with food and shelter.
The nest box that was used earlier to raise a brood of youngsters might now provide a snug bed for the night for a single Blue or Great Tit. They really do seem to prefer their own company at night, but for Wrens it is definitely a case of the more the merrier. The record number found roosting in a single nest box stands at 62. If you turned your nest-box camera off at the end of summer, it is worth switching it on again. You never know who might be using it as a winter residence.
Crows, swallows, swifts and starlings aren’t closely related, but they share some incredible communal roosting behaviours. For social or safety reasons or for warmth, some species choose to sleep together—sometimes in very large numbers. The spectacle of these flocks gathering at dusk is really something, whether the murmuration of Starlings, the rowdy evening antics of Rooks and Crows or the skeins of geese and gulls heading for the safety of a local waterbody.
To cope with this perilous situation, birds have developed a range of abilities, such as sleeping with one eye open. The eyes of most birds (unlike humans) send information to only one side of the brain, so unihemispheric slow-wave sleep allows birds to have one hemisphere of their brain in a deep sleep whilst the other remains awake and alert.
Most garden birds are Passerines, perching birds, which manage to stay put while they’re asleep, having developed “flexor tendons” in their legs that involuntarily clasp shut when they squat on a perch. The tendons won’t relax until the bird straightens its leg to leave.
If you find the lives of our garden birds to be of interest and would like to join in and count the feathered occupants of your garden, have a look at the BTO Garden BirdWatch website (www.bto.org/gbw). If you know of an organisation not a million miles from York which would like a talk on garden birds call: Mike Gray 07596 366342 or firstname.lastname@example.org