RAS results

Dipper. Photograph by Ruth Walker

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, 195 RAS projects were active in 2017. 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 2017 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 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 2017

Species

Number of projects contributing to the survival trend

Number of projects active in 2017

Number of projects new in 2017

Survival Trend Quality

Mute Swan

1

4

0

Moderate

Greylag Goose

1

0

0

Uncertain

Eider

4

2

0

Uncertain

Manx Shearwater

2

0

0

Good

Storm Petrel

5

3

0

Good

Shag

3

2

0

Uncertain

Sparrowhawk

0

0

0

-

Ringed Plover

1

0

0

Good

Little Ringed Plover

1

1

0

Uncertain

Common Sandpiper

3

2

1

Moderate

Puffin

2

2

0

Good

Razorbill

4

3

0

Good

Guillemot

3

3

1

Good

Common Tern

0

1

0

-

Arctic Tern

1

1

0

Moderate

Kittiwake

6

4

0

Good

Black-headed Gull

2

1

0

Moderate

Lesser Black-backed Gull

2

2

0

Moderate

Woodpigeon

1

1

0

Uncertain

Collared Dove

2

2

0

Uncertain

Barn Owl

2

4

0

Good

Little Owl

1

1

0

Good

Tawny Owl

1

1

0

Moderate

Swift

2

2

0

Uncertain

Kestrel

0

0

0

-

Peregrine

1

1

0

Moderate

Jackdaw

3

3

1

Good

Rook

0

1

1

-

Blue Tit

2

1

0

Moderate

Great Tit

4

1

0

Good

Coal Tit

0

1

1

-

Willow Tit

0

0

0

-

Marsh Tit

1

3

1

Uncertain

Bearded Tit

3

3

0

Moderate

Sand Martin

22

11

0

Good

Swallow

7

5

0

Good

House Martin

6

2

0

Moderate

Wood Warbler

3

2

0

Uncertain

Willow Warbler

3

1

0

Moderate

Blackcap

1

1

0

Uncertain

Garden Warbler

1

1

0

Uncertain

Whitethroat

2

1

0

Moderate

Sedge Warbler

2

2

0

Moderate

Reed Warbler

7

9

0

Good

Starling

9

15

2

Good

Dipper

7

8

0

Good

Blackbird

3

2

0

Moderate

Spotted Flycatcher

0

0

0

-

Robin

2

2

0

Moderate

Nightingale

2

2

0

Uncertain

Pied Flycatcher

26

20

0

Good

Redstart

0

2

0

-

Whinchat

1

1

0

Moderate

Stonechat

2

2

0

Moderate

Wheatear

4

3

0

Moderate

Dunnock

2

1

0

Uncertain

House Sparrow

14

16

1

Good

Tree Sparrow

1

6

0

Uncertain

Tree Pipit

2

3

0

Moderate

Chaffinch

3

0

0

Good

Hawfinch

2

3

1

Moderate

Bullfinch

5

4

0

Moderate

Greenfinch

1

0

0

Moderate

Linnet

2

3

0

Moderate

Twite

2

2

0

Good

Siskin

7

6

1

Moderate

Reed Bunting

0

1

0

-

Total

215

195

11

.Mean survival and re-encounter rates by species

Mean survival rate (%)

Mean re–encounter rate (%)

Species

Duration of project

M

F

Single sex

M

F

Single sex

Mute Swan

2013–2017

56

62

52

73

-

Greylag Goose

2003–2015

-

-

79

-

-

48

Eider

1998–2017

-

-

86

-

-

40

Manx Shearwater

1994–2015

-

-

92

-

-

19

Storm Petrel

1998–2017

-

-

78

-

-

21

Shag

1998–2017

79

81

-

33

32

-

Ringed Plover

2000–2009

62

73

-

91

88

-

Little Ringed Plover

2000–2017

72

56

-

40

35

-

Common Sandpiper

1977–2017

61

63

-

66

68

-

Puffin

2008–2017

-

-

92

-

-

11

Razorbill

1981–2017

-

-

90

-

-

16

Guillemot

1981–2017

-

-

80

-

-

26

Arctic Tern

2013­–2017

-

-

93

-

-

91

Kittiwake

2000–2017

-

-

82

-

-

48

Black–headed Gull

2009–2016

-

-

73

-

-

49

Lesser Black–backed Gull

2003–2017

-

-

73

-

-

46

Woodpigeon

2012–2017

-

-

-

-

Collared Dove

2012–2017

-

-

-

-

Barn Owl

1997–2017

64

66

-

29

47

-

Little Owl

2006–2017

-

-

74

-

-

80

Tawny Owl

2006–2017

77

82

-

62

63

-

Swift

2002–2017

-

-

81

-

-

14

Peregrine

2004–2017

87

84

-

71

83

-

Jackdaw

2006–2017

66

75

-

38

40

-

Blue Tit

2001–2017

43

58

-

47

75

-

Great Tit

1999–2017

55

60

-

36

45

-

Marsh Tit

2003–2013

66

71

-

35

45

-

Bearded Tit

2002–2017

41

29

-

32

32

-

Sand Martin

1990–2017

38

34

-

31

38

-

Swallow

1998–2017

42

39

-

50

68

-

House Martin

1994–2017

29

31

-

48

40

-

Wood Warbler

2003–2017

28

19

-

70

72

-

Willow Warbler

1994–2017

46

45

-

64

50

-

Blackcap

2013–2017

19

33

-

31

16

-

Garden Warbler

2011–2017

45

16

-

49

-

-

Whitethroat

1991–2009

34

29

-

57

36

-

Reed Warbler

1981–2017

46

49

-

29

23

-

Starling

2005–2017

53

50

-

25

29

-

Dipper

2002–2017

51

54

-

52

54

-

Blackbird

1998–2017

58

53

-

57

55

-

Robin

1974–2017

48

40

-

42

44

-

Nightingale

2011–2017

52

51

-

71

30

-

Pied Flycatcher

1980–2017

43

40

-

54

66

-

Whinchat

2011–2017

42

20

-

85

100

-

Stonechat

2002–2017

28

23

-

85

64

-

Wheatear

1998–2017

54

52

-

65

62

-

Dunnock

1998–2017

39

40

-

59

70

-

House Sparrow

2003–2017

44

42

-

44

42

-

Tree Sparrow

2007–2017

-

-

36

-

-

26

Tree Pipit

2011–2017

-

-

44

-

-

59

Chaffinch

1998–2015

68

63

-

38

36

-

Hawfinch

2011–2017

65

61

-

33

27

-

Bullfinch

1999–2017

41

38

-

59

53

-

Greenfinch

1999–2012

35

39

-

36

38

-

Linnet

2003–2017

35

29

-

50

50

-

Twite

2007–2017

35

30

-

69

84

-

Siskin

2004–2017

23

29

-

24

39

-

Species specific results

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

Black-headed Gull

One historical and one current project contribute to the national trend; the quality of the trend is considered to be 'moderate'. Although the studies have only been running for a few years, the trend shows a long-term decline (2009-16) in survival. The mean survival rate for Black-headed Gull is 73%.