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Longevity and survival of the Endangered Seychelles Magpie Robin Copsychus sechellarum

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The Seychelles Magpie Robin Copsychus sechellarum was once one of the most threatened birds in the world, but was downgraded from Critically Endangered to Endangered after a long-term recovery programme was success- fully implemented. Comprehensive long-term monitoring of this species was conducted on the islands of Cousin and Cousine over an 18-year period. We report here on the species longevity and annual survival at these two sites. The oldest recorded individual was a male who died on Cousine Island on 28 September 2000 at just under 16 years old. This individual was recorded to have hatched on Frégate Island on 3 January 1985, before being translocated to Cousine Island in 1995. Mean annual survival rates over an 18-year period were 81.6% on Cousin and 77.9% on Cousine islands. A decrease in annual survival was noted with increasing population size on both islands (Cousin: t = −3.09, p < 0.05; Cousine: t = −2.71, p < 0.05), which is a likely consequence of increased territory disputes and competition for food.
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Journal of African Ornithology
ISSN: 0030-6525 (Print) 1727-947X (Online) Journal homepage: http://www.tandfonline.com/loi/tost20
Longevity and survival of the Endangered
Seychelles Magpie Robin Copsychus sechellarum
Julie Gane & April Burt
To cite this article: Julie Gane & April Burt (2016) Longevity and survival of the Endangered
Seychelles Magpie Robin Copsychus sechellarum, Ostrich, 87:1, 81-83
To link to this article: http://dx.doi.org/10.2989/00306525.2015.1134694
Published online: 17 Feb 2016.
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Ostrich 2016, 87(1): 81–83
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ISSN 0030–6525 EISSN 1727-947X
http://dx.doi.org/10.2989/00306525.2015.1134694
Ostrich is co-published by NISC (Pty) Ltd and Taylor & Francis
Short Note
Longevity and survival of the Endangered Seychelles Magpie Robin
Copsychus sechellarum
Julie Gane1* and April Burt2
1 Cousine Island, PO Box 977, Victoria, Mahé, Seychelles
2 Nature Seychelles, Roche Caiman, Mahé, Seychelles
* Corresponding author, email: julie_gane@yahoo.ca
The Seychelles Magpie Robin Copsychus sechellarum was once one of the most threatened birds in the world, but
was downgraded from Critically Endangered to Endangered after a long-term recovery programme was success-
fully implemented. Comprehensive long-term monitoring of this species was conducted on the islands of Cousin
and Cousine over an 18-year period. We report here on the species longevity and annual survival at these two sites.
The oldest recorded individual was a male who died on Cousine Island on 28 September 2000 at just under 16 years
old. This individual was recorded to have hatched on Frégate Island on 3 January 1985, before being translocated
to Cousine Island in 1995. Mean annual survival rates over an 18-year period were 81.6% on Cousin and 77.9% on
Cousine islands. A decrease in annual survival was noted with increasing population size on both islands (Cousin:
t = −3.09, p < 0.05; Cousine: t = −2.71, p < 0.05), which is a likely consequence of increased territory disputes and
competition for food.
Keywords: annual survival, Copsychus sechellarum, Cousin Island, Cousine Island, longevity, Seychelles Magpie Robin
The Seychelles Magpie Robin Copsychus sechellarum
(SMR) is endemic to the Seychelles Archipelago in
the Indian Ocean (López-Sepulcre et al. 2008). It is a
passerine bird that forms small social groups comprised
of a dominant pair and up to eight subordinate individuals
(López-Sepulcre et al. 2008). Each social group defends a
common territory on which they rely for their nesting sites,
foraging areas and water provisions (McCulloch 1996;
López-Sepulcre et al. 2008). Each territory varies in quality
and size causing individuals and social groups to compete
for and extend existing territories into higher quality habitat
areas (López-Sepulcre et al. 2010). Habitat loss and
predator introduction occurred after human settlement in
1770 and were responsible for the dramatic decrease in
population numbers, consequently resulting in the extinction
of the species from seven of only eight originally occupied
islands (Komdeur 1996). In 1990 a total of 23 individuals
remained on Frégate Island (201 ha) alone. This prompted
BirdLife International and the Royal Society for the
Protection of Birds to initiate a recovery programme in 1990
(Norris and McCulloch 2003; López-Sepulcre et al. 2008),
which was later taken over by Nature Seychelles in 1998.
Nature Seychelles set up and facilitated a local stakeholder
group, the Seychelles Magpie Robin Recovery Team
(SMART), to assist in decision-making and management.
BirdLife International successfully translocated individ-
uals from Frégate Island to the islands of Cousin in 1994
and Cousine in 1995. Nature Seychelles led the transloca-
tions to Aride in 2002 and Denis in 2008 (López-Sepulcre
et al. 2008; Gerlach and Le Maitre 2009). Due to the
conservation efforts to increase the overall population, the
International Union for the Conservation of Nature changed
the status of the SMR from Critically Endangered to
Endangered in 2005 (López-Sepulcre et al. 2009). Despite
this conservation success little is known about the longevity
and annual survival of this species. Individual SMRs are
believed to be long-lived (Komdeur 1996), but no analysis
of long-term data has been undertaken.
For this study we considered data from the islands of
Cousin (04°33′14″ S, 55°66′31″ E) (27 ha) and Cousine
(04°21′41″ S, 55°38′51″ E) (26 ha), for which reliable and
consistent data have been collected for 18 years. Cousin
and Cousine support an average of 49 and 32 individual
SMRs, respectively. Since translocation to both islands
the SMR populations have been monitored closely on
a daily (sightings), weekly (behavior and breeding) and
monthly (movement) basis. All chicks were ringed prior
to or shortly after fledging. Each individual wears a metal
South African Bird Ringing Unit (SAFRING) and an island-
specific colour ring, allowing for early identification of birds
that have migrated from another island. The second leg
holds two colour rings, the combination of which is unique
to that individual allowing for ease of population monitoring.
Individuals were identified from several metres away by
sight or by further using binoculars. Each individual bird
was located and recorded at least once monthly but in
most cases weekly, providing rigorous mark and ‘recapture’
data. A summary of activity was made and individuals that
were not seen during that particular month were noted as
missing; if they disappeared for three consecutive months
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Gane and Burt
82
they were assumed dead and removed from the island
population list. This assumption of death was valid due to
there being no record of missing individuals re-emerging
once removed from the respective islands population list.
Since 1994 there have been a total of seven confirmed
inter-island movements/migrations, six of which involved
movement either to or from Cousine or Cousin. The
nature of the monitoring of SMR on each island makes it
extremely unlikely that a migrated bird would go unnoticed
and therefore these figures can be considered robust and
hence migration of birds can be considered a negligible
factor when calculating annual survival. All breeding
attempts were monitored and all individuals have recorded
life histories from hatching to death. Longevity results were
taken from when the individuals hatched to when they died
or went missing (assumed dead), or if they were still living
the age is accurate until June 2014. Annual survival was
calculated using the same method as Watson et al. (1992)
as the percentage of marked adult birds present in year Y
and detected in Y + 1 (juveniles added after one year).
For each year Y there was replenishment of the number of
marked birds.
Since translocation to present, a total of 201 individuals
have resided on Cousin and 143 individuals on Cousine.
Longevity was determined using this data set of 344
individuals over an 18-year period. A total of 11 (3.2%)
individuals from both Cousin and Cousine surpassed a
10-year survival period. The oldest recorded individual was
a male who died on Cousine Island on 28 September 2000
at just under 16 years old. This individual was recorded to
have hatched on Frégate Island on 3 January 1985 and
was translocated to Cousine Island in 1995. The mean
age at death on both islands is 3 (SD 2.6) years old, with
no significant difference between the sexes (two-sample
t-test: t = −1.257, df = 46, p = 0.947). Annual survival
rates over this 18-year period were recorded as 81.6%
on Cousin and 77.9% on Cousine (Figure 1). Both islands
showed a significant relationship in annual survivorship with
population increase (linear regression; Cousin b = −0.348,
t = −3.09, p < 0.05, df = 18; Cousine: b = −0.639, t = −2.71,
p < 0.05, df = 17). No significant difference was found in
annual survival between the islands overall (two-sample
t-test: t = 0.869, df = 17, p = 0.397).
Watson et al. (1992) reported on the low reproductive
rate for this species with an average 1.1 chicks per pair
annually and reproductive maturity being reached by
12–14 months. In addition, only the dominant pair in each
territory breed. With populations fully saturated on Cousin
and Cousine there are 10–11 and 7–9 territories, respec-
tively, and therefore population recruitment is restricted to
and dependent on 10–11 and 7–9 breeding pairs, respec-
tively. The long lifespan that is here recorded is a likely
benefit to population survival and growth of this species;
by having the same dominant breeder for several years
the number of disputes within territorial groups is likely
reduced. There also appears to be an increase in reproduc-
tive output with age once a breeding pair is established
(unpublished data), which would suggest that there is
an optimum breeding age, though further study here
is required. Longevity of the SMR is of further interest
considering its endangered status and its recent history
involving several translocations. By understanding the
lifespan we are better able to make conservation manage-
ment plans for this species, such as improving output by
removing unproductive, older dominant individuals to
alternative territories or by ensuring the successful translo-
cation and establishment of a population by selecting the
most favourable individuals according to life stage. All
applications of management are aimed at improving the
conservation status from Endangered to Threatened. The
thorough data collected on this species on both Cousin
and Cousine since translocation has provided long-term
insight into the species annual survival. Both islands
demonstrate similar levels of annual survival with no signifi-
cant difference found overall (t = 0.869, df = 17, p = 0.397).
Most notably, an overall decrease in annual survival
overtime on both islands was linked to population increase.
It has been reported that aggressive defense of territorial
Figure 1: Significant linear regression of Seychelles Magpie Robin annual survival and population size with associated R2 values for Cousin
and Cousine Islands, Seychelles
R
² = 0.3601
R
² = 0.3529
10
20
30
40
50
60
70
80
90
100
10 20 30 40
Cousin
Cousine
Linear (Cousin)
Linear (Cousine)
ANNUAL SURVIVAL (%)
POPULATION SIZE
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Ostrich 2016, 87(1): 81–83
83
boundaries operate as a limiting factor within populations
of this species (Watson et al. 1992), likewise density-
dependent effects on reproduction can also be caused by
competition for food as recorded for the Seychelles Warbler
Acrocephalus sechellensis (Brouwer et al. 2009). It is likely
that both increased territory disputes and competition for
food are limiting factors for this species’ population growth,
particularly given its geographic constraints.
Acknowledgements We would like to thank all personnel who
have contributed to SMR data collection over the years. The data
used for this report were taken from the SMART databases for both
Islands; the monitoring of this species has been the combined effort
of many personnel over the years. We would also like to thank
Drs Lorinda Hart, Mark Brown and Nirmal Shah for their expertise
and guidance in producing this paper. Thanks to Nature Seychelles
and Cousine Island management for financially supporting our
work. We would also like to thank the three anonymous reviewers
for recommendations to improve this manuscript.
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populations of an endangered bird, the Seychelles Magpie
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Received 18 October 2014, revised 9 March 2015, accepted 21 March 2015
Associate Editor: Richard Sherley
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... Critical habitat requirements for the Magpie-robin are specifically bare earth and leaf litter occurring under mature shady woodland (Watson et al. 1992 ). Magpie-robins form small social groups comprised of a dominant pair and a number of subordinates, varying from one to eight and living to a maximum of 15 years (Gane and Burt 2016 ). Each social group defends a common territory that they rely on for nesting sites, foraging areas and water (López-Sepulcre et al. 2008, McCulloch 1996. ...
... In general a minimum of one migrant per generation is sufficient to minimise the loss of polymorphism and heterozygosity within subpopulations while allowing for divergence in allele frequencies among subpopulations (Mills and Allendorf 1996 ). With the average lifespan of Magpie-robin being 2.6 years old, and longest lived 15 years old (Gane and Burt 2016 ), it is likely that the Cousin/Cousine Magpie-robins could be considered one population, based on inter-island movements, whereas Frégate, Aride and Denis are isolated populations. Further studies are required to investigate this. ...
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