Status and Abundance Definitions in The Birds of Shropshire 2019
Each species has been allocated to at least one of the categories in Table 2. The table includes a code for each definition, which has been used as part of the ‘Shropshire Status’ definition in the Shropshire List summary table in Appendix 6 of Birds of Shrophire..
Table 2. Status Definitions
| Status | Code | Definition |
| Resident | R | Breeds and present all year |
| Summer Visitor | S | Mainly occurs as a breeding visitor in summer |
| Winter Visitor | W | Mainly occurs as a visitor throughout the winter |
| Visitor | V | Can appear at any time during the year, with no obvious pattern as to when it occurs |
| Passage Migrant | P | Mainly passes through in the spring and/or autumn; this category is only used when it is the predominant status |
| Vagrant | Va | A very rare bird well outside its usual range |
| Naturalised | N | Introduced deliberately or accidentally by man and now breeds in the wild |
| Irruptive | I | Occurs sporadically, or in very variable numbers, in response to severe food shortages within its home range |
| No Modern Record | NMR | A species that has only occurred before 1 January 1950 |
| Has Bred | HB | Species that have bred before 2008, either regularly or infrequently, but no longer breed; they may have another status now |
| Breeding Species | BS | Species that breed in low numbers and not always annually. This includes those that are predominantly winter visitors or passage migrants, where the breeding population is considerably lower; and those that have bred for the first time since 2008, but have not yet become established as a regular breeding species |
Each species has also been allocated an abundance score based on the definitions below.
‘Resident’ species may have seasonal, sometimes substantial, movements of individuals in and out of the County, and, particularly in the case of species that breed in the uplands, may occupy different areas and habitats in the winter. Many ‘Summer’ and ‘Winter Visitors’ pass through in larger numbers as they arrive or depart; in neither case do the status definitions cover these movements, and they usually refer to the predominant status unless there is a significant discrepancy between the two, in which case both are mentioned (e.g. a scarce summer visitor but common passage migrant). In other cases, the ‘Resident’ population is largely stable, but there is a significant influx of ‘Winter Visitors’, and they determine the primary status. Occasional ‘out of season’ records have been discounted, but may be referred to in the account. Some passage migrants are still present into the winter season, but have usually departed by mid-November, and others occasionally pass through during the winter period; in neither case are they considered to be winter visitors. Occasionally, some regular visitors are also irruptive and arrive in very large numbers. The ‘Has Bred’ category makes no distinction between previous occasional or regular breeding. Two species, Cormorant and Cetti’s Warbler, appear to be resident, but breeding has yet to be proven and they are defined as ‘Non-breeding Residents’.
The definitions in Table 2 have been used in conjunction with the status category to give some indication of the abundance of an individual species. Where a population is supplemented by releases this is also noted in the heading to the account, and denoted by the code ‘SR’ in the Shropshire List summary table in Appendix 6 of Birds of Shropshire. This table also incorporates the code in Table 2 as part of the definition of the ‘Shropshire Status’.
Table 3. Abundance Definitions
| Abundance | Code | Definition |
| Residents and Summer Visitors (ie breeding species) | ||
| Very rare | 1 | Less than annual |
| Rare | 2 | Annual and up to 10 Breeding Pairs |
| Scarce | 3 | 11–100 Breeding Pairs |
| Uncommon | 4 | 101–1,500 Breeding Pairs |
| Fairly Common | 5 | 1,501–3,500 Breeding Pairs |
| Common | 6 | 3,501–15,000 Breeding Pairs |
| Very Common | 7 | Over 15,000 Breeding Pairs |
| Winter Visitors, Passage Migrants and Rarities | ||
| Very Rare | 1 | Less than annual |
| Rare | 2 | Annual or nearly annual and up to 20 individuals each year |
| Scarce | 3 | 21–200 individuals each year |
| Uncommon | 4 | Found in 10–24% of tetrads (2007–13) |
| Fairly Common | 5 | Found in 25–39% of tetrads (2007–13) |
| Common | 6 | Found in 40–89% of tetrads (2007–13) |
| Very Common | 7 | Found in 90–100% of tetrads (2007–13) |
Table 4: Population trends since 2014
