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, 200 RAS projects were active in 2020 however due to the COVID pandemic, only 147 RAS projects were able to run. While most of the RAS analysis could be undertaken, there were 15 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. 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 2020 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 2020

Species

Number of projects contributing to the survival trend

Number of projects active in 2020

Number of projects new in 2020

Survival Trend Quality

Mute Swan

4

5

1

Moderate

Greylag Goose

1

0

0

Uncertain

Eider

5

2

0

Uncertain

Fulmar

0

1

1

-

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

2

2

0

Good

Razorbill

4

3

0

Good

Guillemot

3

4

1

Good

Common Tern

0

1

0

-

Arctic Tern

1

1

0

Moderate

Kittiwake

6

7

1

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

1

0

Uncertain

Kestrel

0

0

0

-

Peregrine

1

1

0

Moderate

Jackdaw

4

4

0

Good

Rook

0

2

1

-

Blue Tit

2

1

0

Uncertain

Great Tit

4

2

0

Moderate

Coal Tit

0

0

0

-

Willow Tit

0

0

0

-

Marsh Tit

1

4

0

Uncertain

Bearded Tit

3

3

0

Moderate

Sand Martin

23

10

1

Good

Swallow

8

4

0

Good

House Martin

6

2

0

Moderate

Wood Warbler

2

1

0

Uncertain

Willow Warbler

3

0

0

Moderate

Blackcap

1

0

0

Uncertain

Garden Warbler

1

1

0

Uncertain

Whitethroat

1

1

0

Moderate

Sedge Warbler

1

2

0

Moderate

Reed Warbler

10

8

0

Good

Starling

14

19

2

Good

Dipper

7

7

0

Good

Blackbird

3

2

0

Moderate

Spotted Flycatcher

0

0

0

-

Robin

2

2

0

Moderate

Nightingale

2

2

0

Moderate

Pied Flycatcher

28

20

0

Good

Redstart

0

1

0

-

Whinchat

1

1

0

Moderate

Stonechat

2

2

0

Moderate

Wheatear

4

4

1

Moderate

Dunnock

2

1

0

Uncertain

House Sparrow

17

18

1

Good

Tree Sparrow

4

4

0

Uncertain

Tree Pipit

2

3

0

Moderate

Chaffinch

3

1

0

Good

Hawfinch

2

3

0

Moderate

Bullfinch

5

2

0

Moderate

Greenfinch

1

0

0

Moderate

Linnet

2

3

0

Good

Twite

2

2

0

Good

Siskin

8

6

0

Moderate

Reed Bunting

1

1

0

Uncertain

Total

251

201

15

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 1998–2019 - - 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 1977–2020 66 64 - 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 2012-2020 - - 91 - - 56
Great Black-backed Gull 2015-2020 - - 90 - - 50
Black–headed Gull 2009–2017 - - 73 - - 49
Lesser Black–backed Gull 2003–2020 - - 83 - - 41
Woodpigeon 2012–2020 - - 61 - - 36
Collared Dove 2012–2020 54 52 - 22 16 -
Barn Owl 1997–2020 69 68 - 46 28 -
Little Owl 2006–2020 72 - - - - 79
Tawny Owl 2006–2020 82 77 - 62 59 -
Swift 2002–2019 - - 74 - - 23
Peregrine 2004–2020 85 86 - 82 74 -
Jackdaw 2006–2020 80 71 - 37 35 -
Blue Tit 2001–2020 56 52 - 67 22 -
Great Tit 1999–2020 60 56 - 45 35 -
Marsh Tit 2003–2013 71 66 - 45 35 -
Bearded Tit 2002–2020 31 42 - 33 30 -
Sand Martin 1990–2020 33 37 - 39 33 -
Swallow 1998–2020 38 42 - 70 52 -
House Martin 1994–2020 31 30 - 35 51 -
Wood Warbler 2003–2020 22 34 - 64 51 -
Willow Warbler 1994–2019 47 48 - 41 56 -
Blackcap 2013–2018 30 38 - 16 16 -
Garden Warbler 2011–2019 21 46 - 44 43 -
Whitethroat 2015-2020 46 6 - 46 100 -
Sedge warbler 2014-2020 22 41 - 100 41 -
Reed Warbler 1981–2020 48 47 - 26 33 -
Starling 2005–2020 52 53 - 42 38 -
Dipper 2002–2019 52 51 - 67 61 -
Blackbird 1998–2019 52 58 - 57 58 -
Robin 1974–2020 38 45 - 47 47 -
Nightingale 2011–2020 45 52 - 36 63 -
Pied Flycatcher 1980–2020 41 43 - 65 54 -
Whinchat 2011–2020 29 43 - 76 82 -
Stonechat 2002–2020 22 27 - 73 87 -
Wheatear 1998–2019 52 54 - 63 65 -
Dunnock 1998–2020 40 38 - 72 61 -
House Sparrow 2003–2020 43 47 - 63 63 -
Tree Sparrow 2007–2020 35 24 - 29 16 -
Tree Pipit 2011–2020 - - 48 - - 58
Chaffinch 1998–2015 63 68 - 36 38 -
Hawfinch 2011–2019 63 68 - 30 36 -
Bullfinch 1999–2020 38 40 - 53 59 -
Greenfinch 1999–2012 39 35 - 36 38 -
Linnet 2003–2020 28 34 - 50 48 -
Twite 2007–2019 33 35 - 71 71 -
Siskin 2004–2020 35 33 - 12 16 -
Reed Bunting 2014-2020 39 49 - 39 55 -
Yellowhammer 2007–2017 - - - - - -

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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