Glossary

Aberrant
Abnormal or atypical; unlike most of its species. Examples of aberrant plumage could be an albino Blackbird or a melanistic (all black) Robin. A Treecreeper that spent most of its time feeding on the ground away from trees would be an example of aberrant behaviour.

Aflatoxin
A naturally occurring poison found on a variety of foodstuffs including peanuts. Aflatoxin is impossible to detect with the naked eye and is ten times more lethal than cyanide or strychnine. In mild doses death is thought to take hours or days, and may result from secondary causes such as damage to the immune system. CJ WildBird Foods quarantine all consignments of peanuts until an independent laboratory report confirms that there are no detectable traces of aflatoxin in samples taken from that batch.

Alarm call
As the name suggests, one of a series of calls designed to warn other birds of danger or summon help. Most bird species have distinctive alarms calls for different threats, such as a ground predator, aerial predator or roosting bird of prey. The aerial predator call is usually very "thin" and high pitched, making it difficult for the Sparrowhawk or whatever to locate the alarming bird whilst still warning other birds in the area.

Birder
What most birdwatchers prefer to be called. See twitcher.

Brood
The collective term for the young birds of a breeding attempt. Can refer to the young birds in a nest, a group of dependent young that have fledged, or to the number of breeding attempts, as in "Blue Tits are single-brooded but Great Tits occasionally attempt two broods in a year." See also brooding.

Brooding
When an adult bird gently sits on nestlings to keep them warm or dry, this is referred to as brooding. On unhatched eggs the same process is called incubation.

BTO
The British Trust for Ornithology is a partnership of birdwatchers and professional ornithologists which has been working to provide important information on Britain's birds and their habitats for over 70 years. Their research forms a sound basis for conservation and features prominently in practically any survey that makes the news.

Call
Any sound made by a bird's voice which isn't song. Alarm calls or "contact calls", used to keep a flock together, are typical examples.

Clutch
The eggs laid by a female for one nesting attempt. If a bird's normal clutch size is five and that nest is destroyed, she will normally lay five eggs in the replacement nest. For most garden birds, incubation does not start until the clutch is completed.

Corvid
A member of the crow family. Birders will often refer to a mixed flock of Carrion Crows, Rooks and Jackdaws as a corvid flock.

Dawn chorus
The daily peak of bird song, at its best in broadleaved woodland in May.

Displaying
A behaviour that signals some sort of message. Typical displays include territorial displays (where the message is often simply "keep out"), courtship displays, aggressive displays aimed at displacing a potential rival, and song flights. Wildfowl often display very obviously during the winter months as their courtship reaches a peak at this time.

Feeding station
Any area where food is deliberately provided for birds or other wildlife.

Feral
Species which exist as a self-sustaining population but which were originally introduced to an area deliberately or accidentally. Canada Geese and Ring-necked Parakeets are examples of a feral species. The descendants of wild Rock Doves which inhabit our towns and cities, often interbreeding with racing pigeons, are also referred to as Feral Pigeons.

Fledgling
Literally a young bird on the point of, or after, leaving the nest. Not to be confused with fledging, which is the act of leaving the nest. The term refers only to birds which develop in the nest, as opposed to those birds such as wildfowl which leave the nest shortly after hatching.

Hirundine
A member of the swallow and martin family. When flocks of House Martins, Sand Martins and Swallows hawk over water they are often referred to simply as flocks of hirundines.

Incubation
When an adult bird gently sits on unhatched eggs to keep them warm or dry, this is referred to as incubation. On nestlings the same process is called brooding.

Irruptive
A species which migrates to an area irregularly - only during exceptional conditions, such as adverse weather or lack of food. Irruptive species which we may see in our gardens include Bramblings, Waxwings or Crossbills. Strictly speaking, irruptions are distinct from migrations as they are not a regular movement.

Jizz
Allegedly a corruption of the wartime aircraft recognition acronym GISS, meaning "general impression of size and shape". If you identify a medium-sized bird of prey that is hovering by the side of a motorway as a Kestrel without taking in the details of the bird's plumage, you've identified it on its "jizz".

Juvenile/immature
A juvenile bird is one which still has its fledgling plumage, such as a young Robin which is yet to replace its speckled plumage with adult red breast feathers. Technically, immature can mean the same as juvenile, but it usually refers to a sub-adult plumage, as seen in birds such as gulls or larger birds of prey which take two or more years to attain full adult plumage.

Migration
A regular seasonal movement of all or part of a bird population. More familiar in the context of summer migrants heading to Africa, but the Pied Wagtails that breed on moors and winter in the coastal lowlands are also migrants.

Moulting
The process by which old feathers are dropped and replaced. Many garden birds start moulting at the end of the breeding season and tend to be much less obvious during this period as their reduced ability to fly makes them vulnerable to predators. Wildfowl typically drop all of their flight feathers at once and form large "moulting flocks" on open water.

Nestling
A young bird in the nest. Nestlings remain as such until they fledge.

On the wing
Normally taken to mean "in flight".

Overwintering
As the name suggests, the act of spending the winter in a place. Typical overwintering species are many of the wildfowl that flock to the UK's coasts, winter visitors such as Brambling and Waxwing and, of course, the winter thrushes.

Passage
A bird "on passage" or passing through an area. Typical examples would be Ospreys that spend a few days at an English lake before moving on, or Wheatears seen on short grass in lowland areas during March and April. A passage bird neither breeds nor overwinters, and is often referred to as a passage migrant.

Passerine
The birds which are usually referred to as songbirds. Most typical garden or parkland visitors are passerines, exceptions being raptors such as Tawny Owl and Sparrowhawk, wildfowl such as Mallard, or "near-passerines" like Swifts and woodpeckers.

Preening
Feathers are essential to birds, being used for flight, warmth, waterproofing, streamlining and display or camouflage. Preening is the act of maintaining feathers by keeping them in order with repeated stroking movements of the bill or feet. At the same time oil from the preen gland at the upper base of the tail is often applied to the plumage, although some birds such as herons use a dry powder instead.

Raptor
A bird of prey such as a Kestrel, Sparrowhawk, Buzzard or Tawny Owl.

Resident
A species which is present throughout the year. The other categories are summer migrants/breeders, overwintering species or passage migrants.

Ringing
Placing a metal ring, marked with a unique number and contact address, on a bird's leg so that the bird can be identified if it is recaptured or found at a later date. Combinations of coloured rings can allow birds to be identified in the field without capture. The information gained from ringing allows for bird populations to be monitored to a degree that would be impossible if the birds could not be identified as individuals. In the UK and Ireland ringing is administered by the BTO. To report a ringed bird click here.

Roosting
In simple terms another word for sleeping. Some birds roost discretely amongst vegetation or, particularly during cold weather, in nest boxes, while others form large communal roosts. Hundreds or even thousands of Pied Wagtails and Starlings will sometimes roost in town centres or reedbeds, forming an amazing spectacle. Nocturnal birds such as owls roost during the day.

Song
A noise made by a bird to defend a territory and/or to attract a mate. Song can vary from the very complex utterances of a Nightingale to the two-tone song of the Chiffchaff. Some birds, such as Robins, use song to defend territory throughout the year. These are examples of vocal song, but some birds use instrumental song where an object is used to produce the sound. The best known example of this to UK birdwatchers is the "drumming" sound made by a Great Spotted Woodpecker repeatedly striking a hollow tree branch with its bill.

Territory
An area used for one or more purposes by a bird or colony of birds. Breeding territories can range from hundreds of acres in the case of birds like Golden Eagles, while for colonial nesters such as House Sparrows or manyof our sea birds, it may extend no further than the confines of the nest. Pied Wagtails which are seen vigorously chasing off other wagtails are defending a feeding territory.

Twitchers
One of the many sub-divisions of birdwatchers. Twitching is the pursuit of rare or unusual birds and is so named because of the fevered excitement of a participant as they arrive at a "twitch" site after what may have been a long, tension-filled journey. Twitchers specialise in this aspect of the hobby, but many ordinary birdwatchers or "birders" will twitch a rarity that happens to visit their area.

Wader
One of a group of long-legged birds usually associated with marshland, mudflats or shallow water, such as Curlew, Common Sandpiper or Avocet. The exception to this rule is the Woodcock, which still requires soft ground in which to probe for food with its long bill, but nests in woodland.

Wildfowl
A collective term for geese and ducks.

Winter thrushes
The collective term for the Fieldfares and Redwings which spend the winter in the UK but breed further north (although both Fieldfare and Redwing do have tiny UK breeding populations). These birds are members of the thrush family along with Song Thrush, Mistle Thrush and Blackbird.

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