RAS results

Dipper is a RAS priority species. There are currently seven 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, 191 RAS projects were active in 2018. 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 2018 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 2018

Species

Number of projects contributing to the survival trend

Number of projects active in 2018

Number of projects new in 2018

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

0

Moderate

Puffin

2

2

0

Good

Razorbill

4

3

0

Good

Guillemot

3

3

0

Good

Common Tern

0

1

0

-

Arctic Tern

1

1

0

Moderate

Kittiwake

6

4

0

Good

Black-headed Gull

2

0

0

Moderate

Lesser Black-backed Gull

2

2

0

Moderate

Woodpigeon

1

1

0

Uncertain

Collared Dove

2

2

0

Uncertain

Barn Owl

3

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

4

0

Good

Rook

0

1

0

-

Blue Tit

2

1

0

Uncertain

Great Tit

4

2

1

Moderate

Coal Tit

0

1

0

-

Willow Tit

0

0

0

-

Marsh Tit

1

4

1

Uncertain

Bearded Tit

3

3

0

Moderate

Sand Martin

22

13

1

Good

Swallow

8

3

0

Good

House Martin

6

2

0

Moderate

Wood Warbler

3

1

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

9

10

1

Good

Starling

11

17

3

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

Uncertain

Pied Flycatcher

27

23

1

Good

Redstart

0

2

0

-

Whinchat

1

1

0

Moderate

Stonechat

2

2

0

Moderate

Wheatear

4

2

0

Moderate

Dunnock

2

1

0

Uncertain

House Sparrow

16

18

3

Good

Tree Sparrow

4

5

0

Uncertain

Tree Pipit

2

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

Moderate

Twite

2

2

0

Good

Siskin

7

7

0

Moderate

Reed Bunting

0

1

0

-

Total

227

200

11

Mean survival and re-encounter rates by species

Survival

Re–encounter

Species

Duration of project

M

F

Single sex

M

F

Single sex

Mute Swan

2013–2018

56

62

-

52

73

-

Greylag Goose

2003–2015

-

-

79

-

-

48

Eider

1998–2018

-

-

87

-

-

40

Manx Shearwater

1994–2015

-

-

92

-

-

19

Storm Petrel

1998–2018

-

-

79

-

-

21

Shag

1998–2018

84

87

-

34

31

-

Ringed Plover

2000–2009

62

73

-

91

88

-

Little Ringed Plover

2000–2018

73

56

-

40

36

-

Common Sandpiper

1977–2018

60

63

-

66

68

-

Puffin

2008–2018

-

-

92

-

-

12

Razorbill

1981–2018

-

-

89

-

-

16

Guillemot

1981–2018

-

-

81

-

-

26

Arctic Tern

2013–2018

-

-

86

-

-

83

Kittiwake

2000–2018

-

-

81

-

-

49

Black–headed Gull

2009–2017

-

-

73

-

-

49

Lesser Black–backed Gull

2003–2018

-

-

73

-

-

46

Woodpigeon

2012–2018

-

-

59

-

-

37

Collared Dove

2012–2018

44

61

-

33

24

-

Barn Owl

1997–2018

68

70

-

23

41

-

Little Owl

2006–2018

-

-

74

-

-

78

Tawny Owl

2006–2018

78

83

-

61

63

-

Swift

2002–2018

-

-

81

-

-

14

Peregrine

2004–2018

86

84

-

71

80

-

Jackdaw

2006–2018

66

75

-

39

41

-

Blue Tit

2001–2018

49

62

-

22

67

-

Great Tit

1999–2018

55

60

-

36

45

-

Marsh Tit

2003–2013

66

71

-

35

45

-

Bearded Tit

2002–2018

42

32

-

29

31

-

Sand Martin

1990–2018

38

34

-

31

38

-

Swallow

1998–2018

41

39

-

53

69

-

House Martin

1994–2018

29

31

-

50

35

-

Wood Warbler

2003–2018

28

19

-

69

73

-

Willow Warbler

1994–2018

47

46

-

59

45

-

Blackcap

2013–2018

38

30

-

16

17

-

Garden Warbler

2011–2018

47

23

-

43

42

-

Whitethroat

1991–2009

34

29

-

57

36

-

Reed Warbler

1981–2018

47

48

-

32

25

-

Starling

2005–2018

53

52

-

34

39

-

Dipper

2002–2018

50

53

-

62

67

-

Blackbird

1998–2018

58

53

-

57

56

-

Robin

1974–2018

47

40

-

45

46

-

Nightingale

2011–2018

50

48

-

70

34

-

Pied Flycatcher

1980–2018

42

40

-

53

64

-

Whinchat

2011–2018

41

32

-

84

65

-

Stonechat

2002–2018

29

22

-

85

68

-

Wheatear

1998–2018

54

53

-

65

61

-

Dunnock

1998–2018

38

40

-

59

71

-

House Sparrow

2003–2018

45

43

-

59

58

-

Tree Sparrow

2007–2018

26

37

-

16

28

-

Tree Pipit

2011–2018

-

-

47

-

-

58

Chaffinch

1998–2015

68

63

-

38

36

-

Hawfinch

2011–2018

68

63

-

32

25

-

Bullfinch

1999–2018

40

38

-

59

53

-

Greenfinch

1999–2012

35

39

-

36

38

-

Linnet

2003–2018

35

29

-

49

48

-

Twite

2007–2018

36

33

-

69

74

-

Siskin

2004–2018

22

29

-

18

13

-

Reed Bunting

2014–2018

60

62

-

52

26

-

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 between 2017 and 2018 shows the survival rate to be 100%, this is unlikely to be a genuine figure due to the size of the error bars around the mean. The previous year's decline may be a result of a botulism outbreak in the colony during the summer of 2016. The mean survival rate remains relatively high, at 86%. The use of colour marks on the birds has also resulted in a high re-encounter rate for the individuals in this study population.


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