RAS results

Dipper is a RAS priority species. There are currently eight active Dipper projects. 

RAS aims to generate annual survival rate estimates for adult birds, focussing primarily on species not encountered in large numbers during standard mist netting activities such as CES. In total, 192 RAS projects were active in 2019. 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 2019 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 2019

Species Number of projects contributing to the survival trend Number of projects active in 2019 Number of projects new in 2019 Survival Trend Quality
Mute Swan 4 4 0 Moderate
Greylag Goose 1 0 0 Uncertain
Eider 5 2 0 Uncertain
Manx Shearwater 2 0 0 Good
Storm Petrel 5 2 0 Good
Shag 4 2 0 Uncertain
Sparrowhawk 0 0 0 -
Ringed Plover 1 0 0 Good
Little Ringed Plover 1 1 0 Uncertain
Common Sandpiper 3 2 0 Moderate
Puffin 3 2 0 Good
Razorbill 4 3 0 Good
Guillemot 4 3 0 Good
Common Tern 0 1 0 -
Arctic Tern 1 1 0 Moderate
Kittiwake 6 6 2 Good
Black-headed Gull 2 0 0 Moderate
Herring Gull 1 1 1 Moderate
Great Black-backed Gull 1 1 1 Moderate
Lesser Black-backed Gull 3 1 1 Moderate
Woodpigeon 1 1 0 Uncertain
Collared Dove 2 2 0 Uncertain
Moorhen 0 1 1 -
Barn Owl 4 4 0 Good
Little Owl 1 1 0 Good
Tawny Owl 1 1 0 Moderate
Swift 3 1 0 Uncertain
Kestrel 0 0 0 -
Peregrine 1 1 0 Moderate
Jackdaw 4 4 0 Good
Rook 0 1 0 -
Blue Tit 2 1 0 Uncertain
Great Tit 5 2 1 Moderate
Coal Tit 0 0 0 -
Willow Tit 0 0 0 -
Marsh Tit 2 4 0 Uncertain
Bearded Tit 3 3 0 Moderate
Sand Martin 22 8 1 Good
Swallow 8 4 0 Good
House Martin 6 2 0 Moderate
Wood Warbler 3 1 0 Uncertain
Willow Warbler 4 1 0 Moderate
Blackcap 1 0 0 Uncertain
Garden Warbler 1 1 0 Uncertain
Whitethroat 1 1 0 Moderate
Sedge Warbler 2 2 0 Moderate
Reed Warbler 9 10 0 Good
Starling 13 17 3 Good
Dipper 7 7 1 Good
Blackbird 3 2 0 Moderate
Spotted Flycatcher 0 0 0 -
Robin 2 2 0 Moderate
Nightingale 2 2 0 Moderate
Pied Flycatcher 30 22 0 Good
Redstart 0 1 0 -
Whinchat 2 1 0 Moderate
Stonechat 2 2 0 Moderate
Wheatear 4 3 1 Moderate
Dunnock 2 1 0 Uncertain
House Sparrow 17 17 2 Good
Tree Sparrow 4 4 1 Uncertain
Tree Pipit 3 3 0 Moderate
Chaffinch 3 1 0 Good
Hawfinch 2 3 0 Moderate
Bullfinch 5 3 0 Moderate
Greenfinch 1 0 0 Moderate
Linnet 2 3 0 Good
Twite 2 2 0 Good
Siskin 7 6 0 Moderate
Reed Bunting 1 1 0 Uncertain
Total 251 192 16

Mean survival and re-encounter rates by species

Survival Re–encounter
Species Duration of project F M Single sex F M Single sex
Mute Swan 2013-2019 75 70 - 72 67 -
Greylag Goose 2003–2015 - - 79 - - 48
Eider 1998–2019 - - 87 - - 40
Manx Shearwater 1994–2015 - - 92 - - 19
Storm Petrel 1998–2019 - - 79 - - 21
Shag 1998–2019 89 86 - 31 33 -
Ringed Plover 2000–2009 73 62 - 88 91 -
Little Ringed Plover 2000–2019 55 72 - 39 41 -
Common Sandpiper 1977–2019 66 63 - 63 63 -
Puffin 2008–2019 - - 92 - - 13
Razorbill 1981–2019 - - 89 - - 16
Guillemot 1981–2019 - - 82 - - 26
Arctic Tern 2013-2019 - - 88 - - 77
Kittiwake 2000–2019 - - 82 - - 30
Herring Gull 2012-2019 - - 88 - - 54
Breat Black-backed Gull 2015-2019 - - 87 - - 53
Black–headed Gull 2009–2017 - - 73 - - 49
Lesser Black–backed Gull 2003–2019 - - 83 - - 40
Woodpigeon 2012–2019 - - 63 - - 32
Collared Dove 2012–2019 58 47 - 19 21 -
Barn Owl 1997–2019 69 68 - 47 28 -
Little Owl 2006–2019 73 - - - - 79
Tawny Owl 2006–2019 82 77 - 63 61 -
Swift 2002–2019 - - 74 - - 23
Peregrine 2004–2019 85 86 - 82 74 -
Jackdaw 2006–2019 81 74 - 38 37 -
Blue Tit 2001–2019 60 50 - 67 23 -
Great Tit 1999–2019 60 56 - 45 35 -
Marsh Tit 2003–2013 71 66 - 45 35 -
Bearded Tit 2002–2019 32 42 - 32 30 -
Sand Martin 1990–2018 34 38 - 38 31 -
Swallow 1998–2019 38 41 - 69 53 -
House Martin 1994–2019 32 30 - 35 51 -
Wood Warbler 2003–2019 20 28 - 73 70 -
Willow Warbler 1994–2019 47 48 - 41 56 -
Blackcap 2013–2018 30 38 - 16 16 -
Garden Warbler 2011–2019 21 46 - 44 43 -
Whitethroat 1991–2009 43 5 - 62 100 -
Sedge warbler 1996–2015 33 32 - 36 66 -
Reed Warbler 1981–2019 48 46 - 25 31 -
Starling 2005–2019 52 53 - 43 38 -
Dipper 2002–2019 52 51 - 67 61 -
Blackbird 1998–2019 52 58 - 57 58 -
Robin 1974–2019 39 46 - 47 46 -
Nightingale 2011–2019 44 53 - 36 63 -
Pied Flycatcher 1980–2018 40 42 - 64 53 -
Whinchat 2011–2019 28 40 - 71 89 -
Stonechat 2002–2019 22 27 - 72 86 -
Wheatear 1998–2019 52 54 - 63 65 -
Dunnock 1998–2019 40 38 - 72 60 -
House Sparrow 2003–2019 43 46 - 58 59 -
Tree Sparrow 2007–2019 35 24 - 29 17 -
Tree Pipit 2011–2019 - - 44 - - 60
Chaffinch 1998–2015 63 68 - 36 38 -
Hawfinch 2011–2019 63 68 - 30 36 -
Bullfinch 1999–2019 38 40 - 52 59 -
Greenfinch 1999–2012 39 35 - 38 36 -
Linnet 2003–2019 28 35 - 50 48 -
Twite 2007–2019 33 35 - 71 71 -
Siskin 2004–2019 26 23 - 13 18 -
Reed Bunting 2014-2019 50 59 - 29 48 -

Species specific results

Select a species from the drop-down list and click on the graph to enlarge.

Arctic Tern

One current project contributes to the national trend; the quality of the trend is considered to be ‘Moderate’. Although the trend fluctuates over the short period of time that this project has been running, it appears to show a slight decline in the survival rate for this population. The apparent decline in survival between 2016 and 2017 may be a result of a botulism outbreak in the colony during the summer of 2016; however, the cause of the decline between 2018 and 2019 is less clear. The relatively high re-encounter rate for this project (77%) suggests this project generates a good number of resighting, which is likely to be due to the use of colour rings project. The mean survival rate remains high, at 88%.


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