Definitions

The species accounts use the following definitions to describe the local status. 

Status                             Level of abundance                                                                                      Population counts 

Very rare                        Five or fewer records in the Avon area                                                                                                                         Rare                                Less than annual, several years may pass between sightings                                                                                  Very scarce                   Less than annual, typically recorded every two or three years                                                                               Scarce                           Very small numbers recorded virtually every year                                   1 – 10                                                      Uncommon                   Low numbers recorded every year                                                             11 – 100                                                  Fairly common             Occurs in reasonable numbers in suitable habitat                                  101 – 1000                                       Common                       Occurs regularly in good numbers in most suitable habitats                1001 – 10000                                     Abundant                      Large numbers occur in all suitable habitats                                           10000+ 

Resident – This applies to a population which is largely sedentary and occurs throughout the year. It may be augmented by passage migrants and/or winter or summer visitors. 

Summer visitor – This applies to a species that occurs during the late spring and/or summer after having migrated from its wintering areas. 

Winter visitor – This applies to a species that occurs during the winter months after having migrated from its breeding areas. These include species that do not occur during the summer (for example Fieldfare), or that already have a separate resident population (for example Starling). 

Passage migrant – This applies to a species that appears on spring and/or autumn migration to or from its breeding/wintering ranges. Some have protracted spring and autumn passage periods that can appear to ‘overlap' in mid-summer (in most cases this is likely to involve immature birds or failed breeders). 

Introduced – This applies to a species with a self-supporting population derived from escapes from captivity or deliberately released individuals (BOU Group C). 

Storm/Wind-blown visitor – This is used mainly for seabirds that typically occur after having been blown up the Bristol Channel (and often from much further away) as a result of strong winds. 

Irruptive – This applies to a species occurring only irregularly often in big numbers (mainly Waxwing). 

Local rarity – a species, or subspecies for which supporting notes are required to be assessed by the Recorder’s Committee. See this link for a list of species

National rarity – a species or subspecies for which supporting notes are required and assessed by the British Birds Rarity Committee (BBRC). See this link for list of species.

The following site abbreviations have been used. 

ASW Avonmouth Sewage Works 

BG Barrow Gurney Reservoirs 

BL Blagdon Lake 

Cl-Y Severn shore and its environs between the western outskirts of Clevedon and the mouth of the R. Yeo (sometimes called Clevedon Bay), including Blake’s and other pools and the tidal part of the R. Yeo 

CVL Chew Valley Lake 

OPS Oldbury-on-Severn Nuclear Power Station lagoons and their surrounding areas 

PWD Portbury Wharf and Dock, including Portbury Wharf NR, St George’s Wharf with Chapel Pill, the Royal Portbury Dock area and the bank of the R. Avon north of the Avon Bridge 

RPD Royal Portbury Dock 

Severnside Severn shore and its environs, including Pilning Wetlands, between Aust and Chittening Warths inclusive 

SGW St George’s Wharf, which is now part of Portbury Wharf. Some older records marked as this site were in Royal Portbury Dock

Weston STW Weston-s-Mare Sewage Treatment Works and its surrounding areas