This document discusses developing conservation strategies for the chough population on Islay, Scotland. It summarizes that (1) providing nest sites near good feeding areas helped increase the chough population in the 1980s. (2) Dung insects are an important food source for choughs, but avermectin treatments used to control parasites in livestock can negatively impact invertebrate communities and chough populations. (3) High nestling mortality and low post-fledging survival have been major bottlenecks, with a focus on improving survival in sand dune and silage aftermath feeding areas through more diverse sward structures.

1. Chough stuff: developing
chough conservation
strategies
Davy McCracken
Senior Agricultural Ecologist
Ayrshire Branch of Scottish Wildlife Trust
Evening Meeting, SAC Auchincruive, 15 March 2011

2. Chough stuff: developing
chough conservation
strategies
Scottish
Chough
Study
Group
Eric, Sue & Caitlin Bignal Pat Monaghan & Maria Bogdanova Jane Reid

3. Chough: distribution

4. Chough: distribution

5. Islay: mixture of land types
Land types on Islay
A: Upland heath,
moorland and bog
H: Coastal sedge B: Rocky coastal
grassland and moorland, heath
permanent pasture and grassland
G: Sandy coastal C: Broken moorland
ISLAY rushy fields and rough
pasture and machair
pasture
F: Small farms and D: Blanket bogs,
crofts and moorland lowland moorland
edge and rough pasture
E: Rotational pastures
and mixed farmland
mosaics

6. Islay: variety of bird species

7. Islay: variety of bird species
Annex 1 birds on Islay
LAND-TYPE
A B C D E F G H
W-Fronted Goose
Golden Eagle
Barnacle Goose
Hen Harrier
Corncrake
Merlin
Peregrine
Red-Throated Diver
Golden Plover
Chough
NESTING SUMMER WINTER

8. Chough on Islay: annual no.
of breeding pairs
90
Number of breeding pairs
80
70
60
50
40
30
20
1980 1985 1990 1995 2000 2005
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9. Detailed understanding through,
e.g., students and Earthwatch
9

10. Colour-ringing has been crucial
for detailed understanding

11. Colour-ringing has been crucial
for detailed understanding

12. Chough annual cycle
12

13. Major factors affecting chough
on Islay
(1) Nest site availability
(2) ‘Suitable’ feeding areas
13

14. Chough on Islay: increase in
1980s
90
Number of breeding pairs
80
70
60
50
40
30
20
1980 1985 1990 1995 2000 2005
14

15. Provision of nest sites in
good feeding areas
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16. Chough diet on Islay
Chough Diet on Islay
J F M A M J J A S O N D
SOIL Tipulidae
Bibionidae
Lepidoptera larvae
DUNG Diptera larvae
Coleptera adults
Coleoptera larvae
SURFACE-ACTIVE
VEG Cereals
Gagea
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17. Dung insects important
LIVESTOCK DUNG
•Waves of invasion
•Diptera (flies)
•Coleoptera (beetles)
•Nematodes & mites
•Earthworms & soil inverts
•Valuable resource
IMPACT OF AVERMECTINS
•Invertebrates in dung
•Knock-on effects
•Invertebrate communities?
• Chough & other birds? 17

18. Dung insects important
DAMAGE LIMITATION STRATEGY
•Livestock need treatment
•Assess potential/real risk
•What is being used?
•When and how often is treatment applied?
•Ecology of wildlife of concern?
•Manipulate
•Method of application of treatment?
•Timing of treatments?
•Dung invertebrates need dung!!
18

19. Leatherjackets in grassland:
annual mean number per field

20. Chough on Islay: annual no.
of breeding pairs
Assessed
by full
90 census
Number of breeding pairs
80 Predicted
from
population
70 dynamics
model
60
50
40
30
20
1980 1985 1990 1995 2000 2005

21. Major factors affecting chough
on Islay
(3) Bottlenecks to recruitment
- high nestling mortality
- post-fledging survival
21

22. Focus on post-fledging survival
• Observe the colour-ringed choughs
• Follow their movements
• Collect data on their feeding habits
22

23. Focus on post-fledging survival
Movement from
nest sites to sub-
adult flock areas
Map removed from slide before making
presentation more widely available
23

24. Focus on post-fledging survival
Highlighted
importance of sand
dune systems
- 90% of foraging
observations between
April 06 and March 08
24

25. Focus on post-fledging survival
Silage aftermaths
also important
- 10% of
observations
between June 06
and August 08 (but
concentrated in June –
August period)
25

26. Focus on post-fledging survival
More diverse sward and structure
Increased forb and seed resource
Increased invertebrate resource
Increased soil accessibility
26

27. Chough on Islay: annual first
year survival probability
Marked
differences in
survival since
2007 – last four
years, i.e.
including 2010
cohort, has
been c. 10% or
less

28. Chough on Islay: annual first
year survival probability
Major
differences in
July –
September
period in 2007-
2010. Large
proportion of
mortality
occurring
during that
period

29. Chough on Islay: annual first
year survival probability
First year survival probability of each years young:
Solid line = based on re-sightings of colour-ringed birds post-fledging Not simply a
Dashed line = predictions based on weather and leatherjacket abundance
food
abundance
issue.
Predictions not
reflecting
reality since
2007– could
grassland
grazing &/or
cutting regimes
be preventing
access to
insect prey at
key times?

30. What does the future hold?
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31. Further information
Refereed papers: 6 in Journal of Animal Ecology and 1 in Journal of
Applied Ecology to-date
Chough – the story
http://efncp.org/hnv-showcases/scottish-hebrides/chough/facts/
Developing conservation strategies for the
chough in Scotland
http://www.knowledgescotland.org/briefings.php?id=148
British Wildlife, 1997, vol. 8,
issue 6, pages 373-383
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