Manx Shearwater Puffinus puffinus
Status; International importance;
Population
estimates; Distribution; Annual abundance/
productivity; Phenology/diet/survival
Description
The following was adapted
from original text by Stephen F. Newton, Kate Thompson and P. Ian
Mitchell in
Seabird Populations of Britain and Ireland (with
permission from A&C Black, London).
Manx shearwaters spend most of the year at sea returning to land
only to breed. They nest in burrows and under boulders, and come
ashore only under the hours darkness in order to evade predators
such as great skuas and great black-backed gulls. They breed
exclusively on islands, usually free of rats that depredate eggs,
chicks and adults. Manx shearwaters were believed to have been
exterminated from their eponymous colony on the Calf of Man by the
introduction of rats from a wrecked ship in the late
18th Century. More recently rats and cats were
responsible for the extirpation of Manx shearwaters from Canna
(Lochaber). Those few colonies that occur on islands with rats are
generally small and limited in distribution. The exception is on
Rum (Lochaber), where the largest single colony in the world
coexists with rats, though there is evidence that
deleterious impacts are occurring. Coexistence has been allowed by
shearwaters nesting on the slopes of the island's mountains at
altitudes of more than 450m -higher than rats normally occur,
though milder winters in recent years may be increasing the
habitable range of rats into the shearwaters' range.
Most of the estimated world population of c.340,000 – 410,000
pairs of Manx shearwaters breed in Britain and Ireland. Of the UK
population, 40% breed on Rum, and 50% in Pembrokeshire on
the adjacent islands of Skomer, Skokholm and Middleholm.
Conservation status
Manx shearwater is currently identified as a conservation
priority in the following:
Amber listed in Birds
of Conservation Concern 3 (2009 update)
(further information on Conservation Designations for UK Taxa)
Amber listed in
Birds of Conservation Concern in Ireland 2 (2007
update)
International importance
* AOS = Apparently Occupied
Sites
The UK
population figure (rounded to the nearest hundred) was derived from
data in Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E.
(eds.) 2004. Seabird Populations of Britain and Ireland. Poyser, London. This was also
the source of figures for the Biogeographic and World
populations.
UK population estimates and change 1969-2002 (census data)
Manx shearwaters' nocturnal and subterranean habits have caused
problems for surveyors in the past. Hence, Operation Seafarer and
the SCR Census' estimates of 175,000-300,000 pairs and
250,000-300,000 pairs respectively were based solely on order of
magnitude estimates and should not be compared to the
estimate of Seabird 2000 which represents the first
accurate baseline estimate of the number of Manx shearwaters
breeding in the UK. Surveyors used 'tape playback'
which involved playing calls of Manx shearwaters to elicit a
response from adults occupying burrows during the day.
Unfortunately not all adults present at a colony will respond to
the taped calls, thus counts of responses will
underestimate numbers so have to be adjusted by a
response rate measured at the colony. Some colonies were also
surveyed by counting burrow entrances that had visible signs of
use, though this method is difficult or impossible to use in
colonies that are shared with other burrowers, i.e. rabbits and
Atlantic puffins, or where burrow entrances are obscured, i.e.
under boulders or in thick vegetation.
The main gaps in coverage in the UK were in the northern Isles,
where only relict populations remain, Bearasay (Western Isles),
Eigg and Muck (Lochaber) and the Sanda Islands (Argyll & Bute).
However, the combined population of all these islands is thought to
be no more than 1,000 apparently occupied burrows.
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| UK Population estimate (AOS)* |
N/a |
N/a |
299,678 |
| % change since previous census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
For census results for individual countries and Ireland, the
Channel Islands and the Isle of Man see under relevant
sections below.
Distribution/abundance
The Seabird
2000 census provides the most comprehensive recent
assessment of the distribution and abundance of breeding seabirds.
Numbers of Manx shearwater found in different regions, and a
map showing where colonies are found and how large they are is
provided in the Seabird 2000 Manx shearwater
results page (PDF, 1.0 mb).
An
interactive map is available on the NBN Gateway, where you can
filter to display only the Seabird 2000 data. For more
recent, but less comprehensive, coverage view the distribution on
the NBN with all available contributing datasets
The locations sampled during the annual
Seabird Monitoring Programme provide some information on
distribution and are accessible via the Seabird Monitoring Programme
online database.
Annual abundance and productivity by geographical
area
Breeding abundance
The first comprehensive estimates of population size of Manx
shearwater were obtained during the Seabird 2000 Census, when
300,000 pairs was estimated. Over 90% of the UK population is found
on the islands of Rum in Scotland and on Skomer/Skokholm in Wales.
Due to the logistical difficulty in monitoring this nocturnal and
burrow-nesting species, little information exists as to population
trends.
Productivity
Few Manx shearwater colonies are monitored
for productivity. At the colonies monitored, the
mean value between 1986-2010 was 0.69 chicks per breeding
pair; there is no statistically significant annual variation within
the sample. There is some evidence that predation of nests/chicks
by brown rats Rattus norvegicus on
Rum may affect productivity there; this is the
subject of ongoing investigation.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
126,545 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
The first comprehensive estimates of population size of Manx
shearwater in Scotland were obtained during the Seabird 2000
Census, when 126,545 pairs was estimated. By far the majority
of these (approximately 120,000 pairs) were found on Rum with a
further 4,803 pairs on the islands of St. Kilda which was the next
largest colony. The only other colony to hold over one thousand
pairs was the Treshnish Isles (1,283 pairs). Due to the
logistical difficulty in monitoring this nocturnal and
burrow-nesting species, little information exists as to population
trends.
Productivity
Productivity data have been collected in most
years from colonies on Rum and Canna and in some years
from Sanda. Analysis showed no statistically significant
variation over time with productivity
averaging approximately 0.70 chicks fledged per pair per
year. There is some evidence that predation of nests/chicks by
brown rats Rattus norvegicus on
Rum may affect productivity there; this has been
the subject of ongoing investigation in recent years.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
367 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
Relatively few Manx shearwaters nest in England,
the estimate obtained during Seabird
2000 totalling 367 AOS. Most of these were spread around
the Isles of Scilly (201 AOS) with Lundy holding the only other
colony (166 AOS, though a later re-assessment put the figure at 297
AOS). Recently, eradication of rats from Lundy has benefitted
Manx shearwaters; a whole island survey in 2008 estimated
1,081 AOS1. A
re-survey of the Isles of Scilly in 2006 found 171 AOS, a slight
decline from Seabird 2000.
Productivity
No systematic data on the productivity of Manx shearwaters
in England have been collected as part of the SMP.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
168,133 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
Together with Scotland, Wales holds over 90% of the UK
population of Manx shearwaters. The first comprehensive estimates
of the population size were obtained during the Seabird 2000
Census, when 101,800 pairs were estimated on Skomer, 46,200
pairs on Skokholm and a maximum of 16,183 pairs on Bardsey. Smaller
colonies of 1,000-3,000 pairs were recorded on Middleholm and
Ramsey. Due to the logistical difficulty in monitoring this
nocturnal and burrow-nesting species, little information exists as
to population trends.
Productivity
Figure 2: Trend
in breeding productivity (no. of chicks fledged per pair)
of Manx shearwater in Wales, 1986-2010. Based on SMP data; view
the methods
of analysis (PDF 158 kb).
Productivity data have been collected on Skomer (since
1991) and Bardsey (since 1996). Overall, productivity has generally
been high but variable since 1995 but was very low on Skomer
from 1991 to 1994.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
4,633 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
As for the other countries the first comprehensive
estimates of population size of Manx shearwater in Northern Ireland
were obtained during the Seabird 2000 census. Only two
colonies are known, both in the Copeland Islands; Big Copeland was
estimated to hold 1,766 pairs with a further 2,867 pairs on nearby
Lighthouse Island. Due to the logistical difficulty in
monitoring this nocturnal and burrow-nesting species, little
information exists as to population trends.
Productivity
No systematic data on the productivity of Manx shearwaters in
Northern Ireland have been collected as part of the SMP.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
32,545 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
During Seabird 2000, 32,545 pairs of Manx shearwater were
recorded in the Republic of Ireland although several small
colonies each probably holding a few hundred pairs were not
surveyed. The main concentration of colonies were in the south-west
on the offshore islands of County Kerry several of which each
held between 2,000-10,000 pairs. In County Galway, Cruagh held
3,286 pairs with small numbers on a couple of other islands. A
few small colonies were recorded in counties Wexford and
Dublin. Due to the logistical difficulty in monitoring this
nocturnal and burrow-nesting species, little information exists as
to population trends.
Productivity
No systematic data on the productivity of Manx shearwaters in
the Republic of Ireland have been collected as part of the SMP.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
37,178 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
The first comprehensive estimates of population size of Manx
shearwater for Ireland were obtained during the Seabird 2000
Census, when 37,178 pairs was estimated. The majority of these
(approximately 33,000 pairs) were found in the Republic of Ireland
where many colonies exist on offshore islands. In contrast, only
two colonies are known in Northern Ireland, both in the Copeland
Islands. Due to the logistical difficulty in monitoring this
nocturnal and burrow-nesting species, little information exists as
to population trends.
Productivity
No systematic data on productivity have been collected as
part of the SMP.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
34 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
The population of Manx shearwaters on the Isle of Man is small
and confined to the Calf of Man; during Seabird 2000 only 34
AOS were recorded. Recent data suggest that the population has
increased; in 2005 tape playback obtained responses from
104 burrows and 91 burrows were found to be occupied in 2010.
These figures suggest a population of around 200
pairs.
Productivity
No systematic data on the productivity of Manx shearwaters on
the Isle of Man have been collected as part of the SMP.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AOS*) |
N/a |
N/a |
10 |
| % change since previous
census |
N/a |
N/a |
N/a |
* AOS = Apparently Occupied Sites
Breeding Abundance
The known population of Manx shearwaters on the Channel Islands
is small at only 10 AOS. These were split evenly between
Jethou and Little Sark. There has been no assessment of the
population since Seabird 2000.
Productivity
No systematic data on the productivity of Manx shearwaters on
the Channel Islands have been collected as part of the SMP.
UK phenology, diet, survival rate
Phenology
No systematic data on phenology (timing of life-cycle events)
have been collected as part of the SMP.
Diet
No data on diet have been collected as part of the SMP.
Survival rate
Figure 1 shows no discernible trend in adult survival rate at
Skomer, the only colony at which survival is monitored in the
UK.
Figure 1. Estimated adult survival rate of Manx
shearwaters on Skomer, Pembrokeshire, 1979-2009.
References
1 Brown, A., Price, D., Slader,
P., Booker, H., Lock, L. & Deveney, D. (2011).
Seabirds on Lundy: their current status, recent history and
prospects for the restoration of a once important bird area.
British Birds 104: 139-158.
Partners
Data have been provided to the SMP by the generous contributions
of its partners, other organisations and volunteers throughout
Britain and Ireland. Partners to the SMP are: BirdWatch Ireland;
The British Trust for Ornithology; Centre for Ecology and
Hydrology; Countryside Council for Wales; Department of
Agriculture, Fisheries and Forestry (Isle of Man); Department of
Environment, Heritage and Local Government (Republic of Ireland);
States of Guernsey Government; JNCC; Manx Birdlife; Manx National
Heritage; The National Trust; National Trust for Scotland; Natural
England; Northern Ireland Environment Agency; The Royal Society for
the Protection of Birds; Scottish Natural Heritage; Seabird Group;
Shetland Oil Terminal Environmental Advisory Group; Scottish
Wildlife Trust. More about the SMP partners >>
Image of Manx shearwater appears courtesy of
Ian Rendall ©, is subject to international copyright law and may
not be reproduced in any form whatsoever.