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, 197 RAS projects were active in 2015. 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 2015 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 2015

Species

Number of projects contributing to the survival trend

Number of projects active in 2015

Number of projects new in 2015

Survival Trend Quality

Mute Swan

0

3

2

Greylag Goose

1

1

Uncertain

Eider

4

1

Uncertain

Manx Shearwater

2

1

Good

Storm Petrel

5

3

Good

Shag

3

2

1

Uncertain

Sparrowhawk

0

0

Moorhen

0

1

Little Ringed Plover

1

1

Uncertain

Ringed Plover

1

0

Good

Dunlin

1

0

Uncertain

Common Sandpiper

2

2

Moderate

Puffin

2

2

Moderate

Razorbill

4

3

Good

Guillemot

3

2

Good

Arctic Tern

0

1

Kittiwake

3

3

Moderate

Black-headed Gull

2

2

Moderate

Lesser Black-backed Gull

2

2

Good

Woodpigeon

0

1

Collared Dove

0

2

1

Barn Owl

2

4

1

Good

Little Owl

1

1

Good

Tawny Owl

1

1

Moderate

Swift

2

2

Uncertain

Kestrel

0

0

Chough

0

0

Jackdaw

3

4

1

Good

Blue Tit

1

2

Moderate

Great Tit

4

3

Good

Willow Tit

0

0

Marsh Tit

1

1

Uncertain

Bearded Tit

3

3

Moderate

Sand Martin

20

15

2

Good

Swallow

7

5

Good

House Martin

5

3

1

Good

Wood Warbler

2

2

Uncertain

Willow Warbler

2

1

Good

Blackcap

0

1

Whitethroat

2

0

Moderate

Sedge Warbler

2

2

Moderate

Reed Warbler

7

8

Good

Starling

6

11

2

Good

Dipper

7

8

1

Good

Blackbird

3

2

Good

Spotted Flycatcher

0

0

Robin

2

2

Moderate

Nightingale

0

2

Pied Flycatcher

25

23

2

Good

Redstart

0

2

1

Whinchat

1

1

Moderate

Stonechat

2

1

Good

Wheatear

2

3

Moderate

Dunnock

2

1

Uncertain

House Sparrow

12

20

4

Good

Tree Sparrow

1

6

2

Uncertain

Tree Pipit

0

3

Chaffinch

3

2

Good

Hawfinch

1

2

Uncertain

Bullfinch

5

4

Good

Greenfinch

1

0

Moderate

Linnet

1

2

1

Moderate

Twite

1

2

1

Good

Siskin

6

6

1

Uncertain

Yellowhammer

2

2

Uncertain

Reed Bunting

0

1

.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

Greylag Goose

2003-2015

-

-

79

-

-

48

Eider

1998-2015

-

-

87

-

-

40

Manx Shearwater

1994-2015

-

-

92

-

-

19

Storm Petrel

1998-2015

-

-

79

-

-

21

Shag

1998-2015

78

79

-

35

31

-

Little Ringed Plover

2000-2015

59

43

-

54

37

-

Ringed Plover

2000-2009

62

73

-

91

88

-

Dunlin

1998-2006

-

-

71

-

-

18

Common Sandpiper

1977-2015

59

61

-

72

73

-

Puffin

2008-2015

-

-

90

-

-

34

Razorbill

1981-2015

-

-

92

-

-

15

Guillemot

1981-2015

-

-

80

-

-

26

Kittiwake

2000-2015

-

-

74

-

-

29

Black-headed Gull

2009-2015

-

-

69

-

-

48

Lesser Black-backed Gull

2003-2015

-

-

73

-

-

49

Barn Owl

1997-2015

66

66

-

29

48

-

Little Owl

2006-2015

-

-

76

-

-

83

Tawny Owl

2006-2015

78

82

65

65

Swift

2002-2015

-

-

83

-

-

14

Jackdaw

2006-2015

69

79

-

31

35

-

Blue Tit

2001-2015

-

-

57

-

-

51

Great Tit

1999-2015

55

59

-

34

47

-

Marsh Tit

2003-2013

66

71

-

35

45

-

Bearded Tit

2002-2015

46

33

-

29

31

-

Sand Martin

1990-2015

38

33

-

28

35

-

Swallow

1998-2015

42

39

-

51

68

-

House Martin

1994-2015

29

30

-

50

36

-

Wood Warbler

2003-2015

34

25

-

55

61

-

Willow Warbler

1994-2012

50

49

-

63

38

-

Whitethroat

1991-2009

34

29

-

57

36

-

Sedge Warbler

1996-2015

32

33

-

66

36

-

Reed Warbler

1981-2015

46

48

-

29

23

-

Starling

2005-2015

57

58

-

23

24

-

Dipper

2002-2015

50

51

-

62

70

-

Blackbird

1998-2015

59

54

-

57

54

-

Robin

1974-2015

51

42

-

42

43

-

Pied Flycatcher

1980-2015

43

40

-

54

67

-

Whinchat

1998-2004

54

39

-

55

69

-

Stonechat

2002-2015

26

19

-

87

83

-

Wheatear

1998-2015

50

48

-

48

42

-

Dunnock

1998-2015

38

37

-

59

72

-

House Sparrow

2003-2015

42

40

-

50

51

-

Tree Sparrow

2007-2015

-

-

42

-

-

23

Chaffinch

1998-2015

68

63

-

38

36

-

Hawfinch

2011-2015

68

80

-

36

32

-

Bullfinch

1999-2015

42

42

-

48

39

-

Greenfinch

1999-2012

35

39

-

36

38

-

Linnet

2003-2015

28

22

-

38

36

-

Twite

2007-2015

32

27

-

56

81

-

Siskin

2004-2015

20

30

-

20

14

-

Yellowhammer

2007-2015

24

9

-

59

53

-

Species specific results

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

Black-headed Gull

Two current projects contribute to the national trend; the quality of the trend is considered to be 'moderate'. These studies have only been running for a few years, but the survival trend appears to be relatively stable. The mean survival rate for Black-headed Gull is 69%.