RAS results

RAS results

RAS aims to generate annual survival rate estimates for adult birds, focusing primarily on species not encountered in large numbers during standard mist netting activities such as CES.

In total, 188 RAS projects were active in 2023. Data from historical projects and active projects that have been running successfully for five or more years are included in the analyses of the national results presented here.

The RAS analyses generate two parameters: survival rates and re-encounter rates. The survival rates indicate the proportion of birds that survive and return to the site to breed each year, while the re-encounter rates provide a measure of the probability of a bird’s presence being detected should it have survived and returned; the higher the re-encounter rate, the more precise the survival estimate.

The table and graphs below present the mean re-encounter rates, survival rates and survival trends for all species for which we have sufficient data to produce a trend. For more information about the RAS results, please see the Explanatory Notes pages.


Summary results

The summary table of active and historical RAS projects shows, for each species, how many projects ran in 2023 and how many projects contributed to each trend. It is apparent from these data that some species, e.g. Pied Flycatcher, House Sparrow, lend themselves well to RAS and uptake has been very high.  Priority species for future RAS recruitment are those for which established studies are producing reliable survival trends but currently only at a few sites; these include Barn Owl, Dipper, Mute Swan, Starling, Swallow and Tree Sparrow.

The other table below summarises the mean survival and re-encounter rates by species. Re-encounter rates may be heavily influenced by methodology and several general patterns are apparent:

  • Species that are caught on or near nests/nestboxes, such as Dipper, Barn Owl and Pied Flycatcher, tend to exhibit higher re-encounter rates for females as they spend more time incubating and brooding the contents than the males do.
  • Species caught using tape lures, e.g. Willow Warbler, Sedge Warbler, tend to exhibit higher re-encounter rates for males.
  • Colony nesters, such as seabirds and Sand Martins, tend to have lower re-encounter rates as it is much harder to systematically target individual birds. 

While not summarised in this table, re-encounter rates are also generally higher in studies using colour rings, e.g. Bearded Tit, Kittiwake, Shag and Wood Warbler, but this is obviously dependent on resighting effort.

Summary of active and historical RAS projects in 2023

SpeciesNumber of projects contributing to the survival trendNumber of projects active in 2023Number of projects new in 2023Survival Trend Quality
Mute Swan460Good
Eider520Uncertain
Swift310Uncertain
Rock Dove010-
Woodpigeon110Uncertain
Collared Dove210Uncertain
Ringed Plover111Good
Little Ringed Plover100Uncertain
Common Sandpiper310Moderate
Kittiwake870Good
Great Black-backed Gull110Moderate
Herring Gull110Moderate
Lesser Black-backed Gull310Moderate
Little Tern110Uncertain
Common Tern110Uncertain
Arctic Tern110Moderate
Guillemot540Good
Razorbill430Good
Puffin220Good
Storm Petrel520Moderate
Fulmar010-
Shag431Uncertain
Barn Owl440Good
Little Owl110Moderate
Tawny Owl110Moderate
Peregrine110Moderate
Chough110Good
Jackdaw550Good
Rook120Uncertain
Marsh Tit440Uncertain
Blue Tit220Uncertain
Great Tit420Moderate
Bearded Tit310Moderate
Sand Martin2380Good
Swallow810Good
House Martin610Moderate
Wood Warbler210Uncertain
Sedge Warbler320Moderate
Reed Warbler1191Good
Garden Warbler100Uncertain
Whitethroat210Moderate
Starling18242Good
Robin220Moderate
Nightingale210Moderate
Pied Flycatcher30200Good
Whinchat100Moderate
Stonechat331Moderate
Wheatear630Moderate
Dipper860Good
Tree Sparrow430Uncertain
House Sparrow20161Good
Dunnock210Uncertain
Tree Pipit230Moderate
Hawfinch330Moderate
Bullfinch520Moderate
Twite200Good
Linnet233Moderate
Siskin880Moderate
Reed Bunting110Moderate
Total25818810 

Mean survival and re-encounter rates by species

SpeciesDuration of projectSurvivalRe-encounter    
  FMSingle sexFMSingle sex
Mute Swan2013-2023--66--58
Eider1998–202386--40--
Woodpigeon2012–2023--60--53
Collared Dove2012–20235747-2624-
Little Ringed Plover2000–20215471-4042-
Common Sandpiper1977–20236764-6363-
Kittiwake2000–2023--83--30
Great Black-backed Gull2015-2023--86--55
Herring Gull2012-2023--88--59
Lesser Black–backed Gull2003–2023--83--43
Little Tern2017-2023--94--73
Common Tern2016-2023--69--46
Arctic Tern2013-2023--84--74
Guillemot1981–2023--82--29
Razorbill1981–2023--88--17
Puffin2008–2023--93--12
Storm Petrel1998–2023--79--21
Shag1998–20238786-3030-
Barn Owl1997–20236767-4628-
Little Owl2006–202372--77--
Tawny Owl2006–20238275-5958-
Peregrine2004–20238584-7974-
Chough2018–20239079 8175 
Jackdaw2006–20238071-4739-
Rook2017–2023--79--70
Marsh Tit2003–2023--46---
Blue Tit2001–20236255-3347-
Great Tit1999–20235956-4535-
Bearded Tit2002–20233042-3730-
Sand Martin1990–20233034-3933-
Swallow1998–20233741-7152-
House Martin1994–20233229-3451-
Wood Warbler2003–20232333-5552-
Sedge warbler2014-20232538-4350-
Reed Warbler1981–20234745-2734-
Garden Warbler2011–20222748-4439-
Whitethroat2015-20234137-3536-
Starling2005–20235052-4542-
Robin1974–20234044-4445-
Nightingale2011–20234655-3454-
Pied Flycatcher1980–20234143-6553-
Whinchat2011–20222942-7283-
Stonechat2002–20232430-6478-
Wheatear1998–20235252-6266-
Dipper2002–20235250-6863-
Tree Sparrow2007–20233327-3014-
House Sparrow2003–20234245-5757-
Dunnock1998–20234038-6858-
Tree Pipit2011–2023--47--59
Hawfinch2011–20236768-3239-
Bullfinch1999–20233840-5257-
Twite2007–20223435-6971-
Linnet2003–20232734-5149-
Siskin2004–20233634-1215-
Reed Bunting2014-20234246-5566-

Species specific results

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