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, 193 RAS projects were active in 2021 and of these 191 were able to run. While most of the RAS analysis could be undertaken, there were several species that we were unable to produce trends for, either because no projects ran last year, some ran but with effort much reduced from normal, or because not enough active projects ran to produce comparable data.

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.

Summary results

The summary table of active and historical RAS projects shows, for each species, how many projects ran in 2021 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 2021

Species Number of projects contributing to the survival trend Number of projects active in 2021 Number of projects new in 2021 Survival Trend Quality
Mute Swan 4 5 1 Moderate
Greylag Goose 1 0 0 Uncertain
Eider 5 2 0 Uncertain
Fulmar 0 1 0 -
Manx Shearwater 2 0 0 Good
Storm Petrel 5 2 0 Good
Shag 4 2 0 Uncertain
Avocet 1 1 1 Uncertain
Ringed Plover 1 0 0 Good
Little Ringed Plover 1 1 0 Uncertain
Common Sandpiper 3 2 0 Moderate
Puffin 2 2 0 Good
Razorbill 4 3 0 Good
Guillemot 3 2 0 Good
Common Tern 1 1 0 Moderate
Arctic Tern 1 1 0 Moderate
Kittiwake 7 8 2 Good
Black-headed Gull 2 0 0 Moderate
Herring Gull 1 1 0 Moderate
Great Black-backed Gull 1 1 0 Moderate
Lesser Black-backed Gull 3 1 0 Moderate
Woodpigeon 1 1 0 Uncertain
Collared Dove 2 2 0 Uncertain
Barn Owl 4 4 0 Good
Little Owl 1 1 0 Good
Tawny Owl 1 1 0 Moderate
Swift 3 0 0 Uncertain
Peregrine 1 1 0 Moderate
Jackdaw 5 4 0 Good
Rook 0 1 0 -
Blue Tit 2 1 0 Uncertain
Great Tit 4 2 0 Moderate
Willow Tit 0 1 1 -
Marsh Tit 2 4 0 Uncertain
Bearded Tit 4 2 0 Moderate
Sand Martin 23 10 2 Good
Swallow 8 3 0 Good
House Martin 6 1 0 Moderate
Wood Warbler 2 1 0 Uncertain
Willow Warbler 3 1 0 Moderate
Blackcap 1 0 0 Uncertain
Garden Warbler 1 1 0 Uncertain
Whitethroat 1 2 1 Moderate
Sedge Warbler 1 3 1 Moderate
Reed Warbler 10 9 2 Good
Starling 16 21 2 Good
Dipper 8 6 0 Good
Blackbird 3 0 0 Moderate
Robin 2 2 0 Moderate
Nightingale 2 2 0 Moderate
Pied Flycatcher 29 19 1 Good
Redstart 0 1 0 -
Whinchat 1 1 0 Moderate
Stonechat 3 2 0 Moderate
Wheatear 5 3 0 Moderate
Dunnock 2 1 0 Uncertain
House Sparrow 18 20 5 Good
Tree Sparrow 4 4 1 Uncertain
Tree Pipit 2 3 0 Moderate
Chaffinch 3 1 0 Good
Hawfinch 3 3 0 Moderate
Bullfinch 5 2 0 Moderate
Greenfinch 1 0 0 Moderate
Linnet 2 2 0 Good
Twite 2 2 0 Good
Siskin 8 5 0 Moderate
Reed Bunting 1 1 0 Uncertain
Total 258 193 20

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 2013-2020 - - 68 - - 68
Greylag Goose 2003–2015 - - 79 - - 48
Eider 1998–2021 86 - - 40 - -
Manx Shearwater 1994–2015 - - 92 - - 19
Storm Petrel 1998–2021 - - 78 - - 21
Shag 1998–2021 81 79 - 30 33 -
Avocet 2012-2021 - - 81 - - 80
Ringed Plover 2000–2009 73 62 - 88 91 -
Little Ringed Plover 2000–2021 54 71 - 40 42 -
Common Sandpiper 1977–2021 67 64 - 62 64 -
Puffin 2008–2021 - - 91 - - 12
Razorbill 1981–2021 - - 89 - - 16
Guillemot 1981–2021 - - 81 - - 23
Arctic Tern 2013-2021 - - 84 - - 77
Kittiwake 2000–2021 - - 83 - - 29
Herring Gull 2012-2021 - - 89 - - 57
Great Black-backed Gull 2015-2021 - - 87 - - 50
Black–headed Gull 2009–2017 - - 73 - - 49
Lesser Black–backed Gull 2003–2021 - - 82 - - 42
Woodpigeon 2012–2021 - - 62 - - 41
Collared Dove 2012–2021 51 52 - 27 - -
Barn Owl 1997–2021 68 67 - 46 29 -
Little Owl 2006–2021 72 - - 78 - -
Tawny Owl 2006–2020 82 77 - 62 59 -
Swift 2002–2019 - - 74 - - 23
Peregrine 2004–2021 86 86 - 78 72 -
Jackdaw 2006–2021 83 74 - 40 36 -
Blue Tit 2001–2021 63 47 - 34 52 -
Great Tit 1999–2021 60 56 - 45 34 -
Marsh Tit 2003–2021 - - 54 - - 79
Bearded Tit 2002–2021 31 10 - 33 31 -
Sand Martin 1990–2021 30 34 - 39 33 -
Swallow 1998–2021 38 41 - 70 52 -
House Martin 1994–2021 32 30 - 34 51 -
Wood Warbler 2003–2021 24 33 - 55 52 -
Willow Warbler 1994–2019 47 48 - 41 56 -
Blackcap 2013–2018 30 38 - 16 16 -
Garden Warbler 2011–2021 28 50 - 40 37 -
Whitethroat 2015-2021 41 50 - 38 12 -
Sedge warbler 2014-2021 21 40 - 63 32 -
Reed Warbler 1981–2021 49 47 - 25 32 -
Starling 2005–2021 51 52 - 44 42 -
Dipper 2002–2021 52 48 - 68 64 -
Blackbird 1998–2019 52 58 - 57 58 -
Robin 1974–2021 38 45 - 45 44 -
Nightingale 2011–2021 44 51 - 36 59 -
Pied Flycatcher 1980–2021 41 43 - 64 53 -
Whinchat 2011–2021 27 43 - 76 83 -
Stonechat 2002–2021 22 27 - 72 87 -
Wheatear 1998–2021 52 53 - 62 63 -
Dunnock 1998–2021 39 38 - 72 59 -
House Sparrow 2003–2021 43 46 - 56 59 -
Tree Sparrow 2007–2021 34 24 - 30 16 -
Tree Pipit 2011–2021 - - 48 - - 58
Chaffinch 1998–2015 63 68 - 36 38 -
Hawfinch 2011–2021 66 67 - 34 42 -
Bullfinch 1999–2021 37 39 - 43 49 -
Greenfinch 1999–2012 39 35 - 36 38 -
Linnet 2003–2021 27 34 - 51 49 -
Twite 2007–2021 35 36 - 69 70 -
Siskin 2004–2021 27 24 - 12 16 -
Reed Bunting 2014-2021 35 42 - 56 61 -
Yellowhammer 2007–2017 - - - - - -

Species specific results

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

Arctic Tern

One project contributes to the national trend and is considered to be Moderate. The trend fluctuates over the short period of time that this trend has been calculated but it seems to be stable. The narrow confidence limits show that the project is getting a good number of re-sightings from the use of colour rings however these are very wide for 2019 due to the site being abandoned in 2020 by the terns.
Arctic Tern RAS trend 2013-2021

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