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Preliminary assessment of the release of captive-bred Gran Canaria Blue Chaffinches Fringilla teydea polatzeki as a reinforcement population

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Capsule: The endangered Gran Canaria Blue Chaffinch Fringilla teydea polatzeki has been bred in captivity with the aim of reinforcing wild populations. We released and monitored 26 males and 15 females between 2010 and 2012. Survival and reproductive success were similar between the reinforced population and a stable reference population, suggesting that the process could be useful for the conservation of the species.
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Preliminary assessment of the release of captive-
bred Gran Canaria Blue Chaffinches Fringilla
teydea polatzeki as a reinforcement population
Alejandro Delgado, Pascual Calabuig, Víctor Suárez, Domingo Trujillo & M.
Mercedez Suárez-Rancel
To cite this article: Alejandro Delgado, Pascual Calabuig, Víctor Suárez, Domingo Trujillo & M.
Mercedez Suárez-Rancel (2016): Preliminary assessment of the release of captive-bred Gran
Canaria Blue Chaffinches Fringilla teydea polatzeki as a reinforcement population, Bird Study,
DOI: 10.1080/00063657.2016.1239694
To link to this article: http://dx.doi.org/10.1080/00063657.2016.1239694
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SHORT REPORT
Preliminary assessment of the release of captive-bred Gran Canaria Blue
Chaffinches Fringilla teydea polatzeki as a reinforcement population
Alejandro Delgado
a
, Pascual Calabuig
a
, Víctor Suárez
a
, Domingo Trujillo
a
and M. Mercedez Suárez-Rancel
b
a
Wildlife Recovery Center Tafira, Las Palmas de Gran Canaria, Canary Islands, Spain;
b
Departamento de Matemáticas, Estadística e Investigación
Operativa, Facultad de Matemáticas, Universidad de La Laguna, Santa Cruz de Tenerife, Canary Islands, Spain
ABSTRACT
Capsule: The endangered Gran Canaria Blue Chaffinch Fringilla teydea polatzeki has been bred in
captivity with the aim of reinforcing wild populations. We released and monitored 26 males and
15 females between 2010 and 2012. Survival and reproductive success were similar between the
reinforced population and a stable reference population, suggesting that the process could be
useful for the conservation of the species.
ARTICLE HISTORY
Received 3 April 2016
Accepted 15 September 2016
It is widely accepted that breeding animals in captivity
for reintroduction is an important management tool
for recovering endangered species but there have been
frequent calls for increased monitoring of
reintroductions (Maunder 1992, Kleiman et al. 1994,
Hein 1997, Seddon 1999, Fischer & Lindenmayer 2000)
and for critical evaluation of programmes (Sarrazin &
Barbault 1996, Armstrong et al. 2002). For example,
reintroduced captive-bred birds often experience high
post-release mortality and the survival of reintroduced
captive-bred birds is dependent on the release
strategies employed (Bernardo et al. 2011).
The success of a reintroduction is partly dependent on
the translocation procedure and whether a hardor soft
release strategy is used (Scott & Carpenter 1987).
Soft release involves a animals being held on-site prior
to a delayed release and can also include the provision
of supplementary food or other resources after
release (Richardson et al. 2013). According to the
International Union for Conservation of Nature (IUCN
2013), animals may be held for some period at the
release site to allow them to become accustomed to
local conditions or enhance social group cohesion;
such procedures are most likely to be useful with
captive-bred animals. The propensity of reintroduced
birds to move during the immediate post-release
period will in part depend on soft release protocols,
specifically the timing and number of release cohorts,
supplementary feeding and the proximity of the soft
release enclosure to freshwater sources. Captive-bred
birds will be unfamiliar with the release site and this
will also influence home-range establishment and site
fidelity (Bernardo et al. 2011).
TheBlueChaffinchFringilla teydea is a specialist
passerine of thick upland Canary Island Pine Pinus
canariensis forest on Tenerife and Gran Canaria (Canary
Islands). One subspecies exists in each of these islands,
although some authors have recently suggested that these
represent two distinct species: the Gran Canaria Blue
Chaffinch Fringilla polatzeki and the Tenerife Blue
Chaffinch F. teydea (Sangster et al. 2015, Lifjeld et al.
2016). The reclassification of Gran Canaria Blue
Chaffinch as a single-island endemic species would make
it Europes rarest passerine species. Its population is very
limited because the extent of pine forest on Gran Canaria
is small and highly fragmented, that is why the Red Book
of Birds in Spain termed the Gran Canaria subspecies as
Critically Endangered (Madroño et al. 2004). A
conservation strategy was initially implemented by the
Canary Island Government in 1991, followed by the
approval of a recovery plan in 2005. This plan includes,
among other activities, the formation of at least one other
population by reintroduction (Suárez et al. 2012).
The overall goal of the captive breeding programme
was to decrease the risk of extinction of the Gran
Canaria Blue Chaffinch by establishing a self-sustaining
wild population in other pine forests. This paper
reports a preliminary assessment of the three-year
programme of captive-bred releases and provides
information for future management actions for
conservation and reintroduction of this and other
passerine species.
© 2016 British Trust for Ornithology
CONTACT Alejandro Delgado adelgadogento@gmail.com Wildlife Recovery Center Tafira, Vivero Forestal, Cabildo de Gran Canaria, 35017, Las Palmas
de Gran Canaria, Canary Islands, Spain Supplemental data for this article can be accessed here: http://dx.doi.org/10.1080/00063657.2016.1239694.
BIRD STUDY, 2016
http://dx.doi.org/10.1080/00063657.2016.1239694
The research was carried out in the only two pine forest
regions on the island of Gran Canaria where the Blue
Chaffinch breeds. The first of these was the pine forest
at the Inagua Nature Reserve (3920 ha, 27°57N 15°
42W). The population here is the islands largest, with
121339 birds, and has a stable population trend
(Rodríguez & Moreno 2008). Carrascal & Seoane (2008)
estimated the population size at 122 individuals after a
fire devastated part of this pine forest in 2007. Inagua
pine forest is used here as the reference population for
comparison in the analysis. The second pine forest
under study, Cumbre (1800 ha, 27°57N 15°35W), is on
the summit of the island. This forest was clear-felled in
the mid-nineteenth century and repopulated in the
1950s and 1960s. There are no historical data on the
presence of the Blue Chaffinch at this location because
when the species was discovered on Gran Canaria in
1905 this area was classified as non-forested land. It is
poorly connected by vegetation cover and separated by
about 4.5 km from the upper pine forest at its most
narrow section (Figure 1). This second Blue Chaffinch
population was discovered by Víctor Suárez in 2008,
when colour-ringed birds from Inagua were observed in
Cumbre pine forest and found to be breeding.
Following the initial discovery, sightings were scarce in
Cumbre forest: two adults were located in 2009 and
three in 2010, two of these managing to successfully
fledge two young. Cumbre forest is located in the centre
of the island, is connected with other pine forests and,
following what seems to be a natural colonization of the
site, it was chosen as a highly suitable area to release
captive-bred birds.
Sixteen Gran Canaria Blue Chaffinches were wild-
caught in Inagua Nature Reserve and are currently
used in the captive breeding programme run since
2005 (see Garcia-del-Rey et al. 2013 for more detail of
the captive breeding stock). A total of 41 Blue
Chaffinches (11 in 2010, 13 in 2011 and 17 in 2012),
26 males and 15 females were reared in captivity, and
released between 15 August and 15 October, 518
weeks after hatching to limit the period in captivity.
Birds were liberated through soft release techniques,
remained 14 days in groups of no more than seven in
an acclimatization cage located at the release site. All
the birds wore a combination of colour rings to allow
individual identification at a distance. These facilities
were similar to the pre-release cages at the breeding
centre and birds were held in similar groups in both
aviaries. These installations were watched by day to
monitor bird condition and kept opened up to three
months after liberation, so that individuals could use
feeders that were placed inside. Furthermore, six
artificial feeders were placed in the area surrounding
the release cages. Feeders were suspended from
branches in dense vegetation and held P. canariensis
seeds with a mixture of other seeds. Supplementary
Figure 1. Map of Gran Canaria island showing the sites of the Blue Chaffinch populations at Inagua (circle) and Cumbre (triangle), where
captive-bred birds were released. The extent of pine forest is marked in grey.
2A. DELGADO ET AL.
food was supplied throughout the winter until March.
Additionally, mealworms (larvae of Tenebrio molitor)
were provided during the holding period and for the
first three weeks after liberation.
Translocation success can be determined during two
phases: establishment and longer-term persistence
(Armstrong et al. 1999). We assessed the success of the
translocation programme based on two criteria: (1)
short-term criteria: survival of the captive-bred birds
through the first winter, by comparing the apparent
survival five months after liberation of released and
wild birds in the same periods and (2) long-term
criteria: annual survival of adults, by comparing the
apparent survival after a ten-month period for adults
in the reinforced and reference populations. We also
compared population trends and reproductive success
between the reference and reinforced populations.
Between 16 and 41 fledglings and adults were captured
by mist net and individually colour-ringed at the two sites
each year. Two to three people carried out the fieldwork in
the reference population from March to mid-October
20062011. We looked over almost the entire area of
pine forests on foot and by car to find, and individually
identify, marked birds. A large fire in 2007 affected of
the reference population (Carrascal & Seoane 2008),
consequently our database covers periods before and
two years after this fire, when a significant recovery of
the vegetation cover had taken place.
One or two people recorded field data in the
reinforced population between 2008 and 2013 in the
same way as at the reference site. Intensive monitoring
in the small pine area allowed researchers to follow the
entire population. Additionally, nests were locating and
monitoring every 45 days in order to determine the
number of chicks that fledged. Given the limited
number of chaffinchs in the Cumbre pine forest, the
whole adult population and all fledglings produced
each year (201013) could be ringed and identified in
this new population.
We analysed survival using the live recaptures
CormackJollySeber model in MARK 8.1 (White &
Burnham 1999) with two encounter occasions and four
groups: juveniles released into reinforced population,
juveniles of reference population, adults of reinforced
population and adults of reference population
(Supplementary Appendix 1). The data set is not
extensive enough to enable the analysis of time or finer
age classes in the survival analysis. Released individuals
were considered to have survived their first winter if
they were resighted in the two months after 15 March
in the year following hatching (for the winters of 2010
11, 201112 and 201213). We compared survival
against similarly collected data from the reference
population but in different winters (200607, 201011).
Annual survival of adults was assessed between 15 April
and 15 June each year, during 200911 in the reference
population and 201113 in the reinforced population.
Reproductive success was monitored in the reinforced
population for comparison against similar data collected
by Rodríguez & Moreno (2008) in the reference
population during 19942004 (but excluding 2003).
Reproductive success parameters were: nest success
(nests that fledged at least one young), production of a
second clutch (second broods and replacements) and
nest productivity (number of offspring per successful
nest). Statistical analyses were performed using R
program (R Core Team 2014).
In total, 35 of the 41 Gran Canaria Blue Chaffinches
were successfully released into the reinforced
population (7 in 2010, 11 in 2011 and 17 in 2012).
Another six birds were released at another date, hence
are not included in this analysis. Also excluded from the
analysis are six birds killed as a result of attacks by
Eurasian Sparrowhawks Accipiter nisus while feeding in
the release cages (2 in 2010, 4 in 2011). All of them died
due to injuries caused by blows against the walls of the
cage while trying to escape the predator. As these birds
died in the cage, they were excluded from the survival
analysis. Additionally, in one case, we detected wounds
caused by a plastic ring in the tibiotarsus articulation
after release. This bird was captured and released after
removing the colour markers on that leg.
Of the 35 individuals successfully released, 21 were
detected after winter. In the same period, 46 juveniles
were marked in the reference population, 24 of which
survived the first winter. At the reinforced population
site, 27 adults were observed and 11 of them were
subsequently detected on the following year. At the
reference site, 51 adults were detected and 23 of them
were subsequently relocated the following year.
Winter survival probability was 0.774 (95% confidence
intervals (CI) = 0.6530.862) for released birds in the
reinforced population and 0.722 (95% CI = 0.6120.811)
for wild birds in the reference population. Annual
survival of adults was 0.638 (95% CI = 0.4840.768) in
the reinforced population and 0.671 (95% CI = 0.563
0.764) in the reference population.
We have reproductive success data on 24 out of the 28
monitored nests produced within the reinforced
population after the first release (10 in 2011, 9 in 2012
and 9 in 2013; excludes nests abandoned before
incubation). At least one chick was fledged from 79% of
the nests and 41% of the breeding females attempted a
second clutch (Table 1). In 46% of the nests, a single
chick fledged and 54% fledged two, giving a productivity
of 1.52 chicks (n= 24, sd = 0.51) per successful nest.
BIRD STUDY 3
There were no significant differences between the
percentage of successful breeders in the reinforced
population and the reference population (χ
2
= 0.31,
df = 1, P= 0.58). Furthermore, the number of fledglings
produced per successful nest did not differ between the
two populations (t= 0.37, df = 29.26, P= 0.71).
All adults displayed breeding behaviour in the
reinforced population and there was an increase in the
number of adults and fledglings following releases.
Despite the lack of increase in adults in 2013, the
number of fledglings increased slightly from 2012
(Figure 2).
According to our assessment criteria, we consider the
release of captive-bred Gran Canaria Blue Chaffinch, as a
reinforcement to the Cumbre population, to be a success.
The birds released had similar survival prospects, during
the first winter, as those of young wild birds in the
reference population. Likewise, adults at Cumbre had
similar annual survival rates as those observed in the
reference area at Inagua pine forest over the same
period. We also found that the reproductive success
measures of both populations did not differ
significantly and there was an increase in the adult
population and offspring production following releases
of captive-bred birds.
Nevertheless, during the time the birds were held in
the acclimatization cage or fed in the enclosure after
release, six Blue Chaffinches died because of injuries
caused by impacts against the mesh of the cage when
trying to escape a predator attack. Occasionally, the
supervising staff observed birds of prey in the area of
the cages and on two occasions they witnessed the
attack on the chaffinches acclimatizing inside. In order
to prevent attacks by predators we recommend
protecting the cage and reducing slightly the holding
period. A reduction in the number of days of the
acclimatization period would logically lower the
chances of a Eurasian Sparrowhawk attack but it also
could put at risk the birdsacclimatization success. As
regards the latter, some authors indicate that a 614-
day holding period is enough for captive-bred
passerine translocation (Kuehler et al. 2000, Gálvez
2012, Lagios et al. 2014).
Stacey & Taper (1992) highlight the importance of
immigration to the persistence of small populations.
The movement of Blue Chaffinches from one pine
forest to another occurs, but individuals probably have
to cross a deforested area. Therefore, we emphasize the
need to connect both forests, by creating an ecological
corridor through pine reforestation, in order to
facilitate their movement between populations.
We recommend further monitoring of population size
and reproductive success in the reinforced population, to
create a longer data series which would allow us to
monitor survival rates and generate estimates of
population growth rate. Population viability analysis is an
inexact science (Thomas 1990,Reedet al. 2003, Flather
et al. 2011), but it could be considered a valid and
sufficiently accurate tool for managing endangered
species (Boyce 1992,Brooket al. 2000). Brook &
Kikkawa (1998) conducted a population viability analysis
with parameters estimated from relatively short (5 years)
periods of data collection and produced very different
predictions of extinction risk compared with population
viability analysis based on more comprehensive
ecological data spanning 1525 years. As a guideline,
population analyses provide information about the
minimum number of birds that this population needs to
remain viable. The information obtained will be
important to design conservation strategies for the species.
Acknowledgements
We are grateful to David Shea for translating the first draft of
this paper and Andy Paterson for helpful comments. Ringing
and translocation permission was obtained from
Table 1. Comparison of survival and reproductive success of Blue
Chaffinch populations at Cumbre (reinforced) and Inagua
(reference), Gran Canaria.
Parameters
Reference
population
Reinforced
population
First-winter survival 0.72 (95% CI 0.61
0.81)
0.77 (95% CI 0.65
0.86)
Adult annual survival 0.67 (95% CI 0.56
0.76)
0.64 (95% CI 0.48
0.77)
Nests fledging at least one
young
70.80%
a
79.17%
Females produced a second
clutch
33.00%
a
41.18%
Offspring per successful nest
(±sd)
1.47 0.50)
a
1.52 0.51)
a
Data obtained from Rodríguez & Moreno (2008).
Figure 2. Population size and sources of Blue Chaffinches in the
reinforced population at Cumbre. Number of birds released
successfully (columns), adult numbers prior to the years
release (circles) and fledglings produced (diamonds) during
each of the years of study.
4A. DELGADO ET AL.
Viceconsejeria de Medio Ambiente of Gobierno de Canarias
(Canary Islands government).
Funding
Funding was provided by Consejeria de Medio Ambiente y
Emergencias from Cabildo Insular de Gran Canaria (Gran
Canaria government).
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BIRD STUDY 5
... It inhabits mature pine forests, where nests are placed in tall trees; breeding success is very low for a Fringillidae, with only ca. 1.5 fledglings per successful nesting attempt, and 1.4 clutches per breeding season (Rodríguez & Moreno, 2008;Delgado et al., 2016). The estimated population size of the Gran Canaria blue chaffinch (guessed at around 300 birds with no recent estimation in its whole area of distribution, BirdLifeInternational, 2016a) lies within the left tail of the distribution of minimum viable population (MVP) estimates for many species, far away from the average MVP of 3,750 individuals for birds (Brook,Traill & Bradshaw, 2006;Traill, Bradshaw & Brook, 2007). ...
... Although the topic merits an exhaustive census program, this assessment should be considered as a first approximation to the population estimation in Inagua. Another 38 blue chaffinches can be added to those low numbers (minimum estimation;Rodríguez, 2016), given the recently established small population located at higher altitudes in La Cumbre (20.7 km 2 ; from a captive breeding and translocation program;Delgado et al., 2016;Rodríguez, 2016). Therefore, with ∼320 individuals in 58.3 km 2 of pine forests during the breeding season, the Gran Canaria blue chaffinch is the passerine with the lowest population size in the Western Palearctic (average density: 5.5 birds/km 2 ). ...
... threshold is not a true biological limit as the data of the recently established small population in La Cumbre demonstrates. The species is able to dwell at higher altitudes in this area (Delgado et al., 2016), and has shown a formidable increase in the number of breeding pairs from two in 2010 to 16 in 2016 (Rodríguez, 2016). Therefore, the altitudinal range of Gran Canaria probably imposes, per se, restrictions to the distribution of the blue chaffinch, assuming that F. teydea and F. polatzeki share similar abiotic environmental preferences as sibling species. ...
Article
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Background Understanding constraints to the distribution of threatened species may help to ascertain whether there are other suitable sectors for reducing the risks associated with species that are recorded in only one protected locality, and to inform about the suitability of other areas for reintroduction or translocation programs. Methods We studied the Gran Canaria blue chaffinch ( Fringilla polatzeki ), a habitat specialist endemic of the Canary Islands restricted to the pine forest of Inagua, the only area where the species has been naturally present as a regular breeder in the last 25 years. A suitability distribution model using occurrences with demographic relevance (i.e., nest locations of successful breeding attempts analysed using boosted classification trees) was built considering orographic, climatic and habitat structure predictors. By means of a standardized survey program we monitored the yearly abundance of the species in 100 sectors since the declaration of Inagua as a Strict Nature Reserve in 1994. Results The variables with the highest relative importance in blue chaffinch habitat preferences were pine height, tree cover, altitude, and rainfall during the driest trimester (July–September). The observed local abundance of the blue chaffinch in Inagua (survey data) was significantly correlated with habitat suitability derived from modelling the location of successful nesting attempts (using linear and quantile regressions). The outcomes of the habitat suitability model were used to quantify the suitability of other natural, historic, pine forests of Gran Canaria. Tamadaba is the forest with most suitable woodland patches for the species. We estimated a population size of 195–430 blue chaffinches in Inagua since 2011 (95% CI), the smallest population size of a woodland passerine in the Western Palearctic. Discussion Habitat suitability obtained from modelling the location of successful breeding attempts is a good surrogate of the observed local abundance during the reproductive season. The outcomes of these models can be used for the identification of potential areas for the reintroduction of the species in other suitable pine forests and to inform forest management practices.
... The protection offered by Inagua did not protect the species against a devastating wildfire in July 2007, which reduced its population density by half (Moreno et al. 2018). By 2008, some individuals had moved naturally from Inagua and were recorded in the nearby pine forests of La Cumbre (located c.3 km away), beginning shortly after a successful captive breeding programme that has released birds in that area since 2010 (Delgado et al. 2016). The captive breeding programme was reinforced by a new translocation programme from 2015 to 2019, using wild juvenile individuals from the source population of Inagua (LIFEþPINZÓ N 2019). ...
... One breeding pair of Blue Chaffinch naturally established in La Cumbre in 2008, and a translocation programme began in 2010, first releasing birds from captive breeding and then from translocations of juveniles from the core population of Inagua. For more details on the Blue Chaffinch and environmental characteristics of La Cumbre pine forest see Delgado et al. (2016). See Figure 1 for the location of the two study areas in Gran Canaria and the Canary archipelago. ...
Article
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The Gran Canaria Blue Chaffinch Fringilla polatzeki is a threatened, endemic, forest‐dwelling bird species of the Canary Islands, whose core population at the end of the 20th century was restricted to the pine forests of Inagua Nature Reserve (38 km ² ). A translocation programme released birds from a breeding centre into the nearby (<3 km) pine forests of La Cumbre in the years following 2010. From 2015 to 2019 the La Cumbre population was reinforced by translocation of wild juveniles from the source population of Inagua. We estimate the population size, the spatial variation of abundance, and recent temporal changes in density of the species in Inagua and La Cumbre by means of line transects, distance sampling, and habitat suitability modelling using random forests. The average density of the Blue Chaffinch in Inagua Nature Reserve was 10.2 birds/km ² in spring 2019, with a population estimated at 362 birds (95% CI: 257–489). The most important variables affecting the distribution of the Blue Chaffinch in Inagua were the amount of precipitation during the summer (July–September), the solar radiation in June, and the northern position in the reserve, highlighting the importance of abiotic factors related to thermal and hydric stress during the breeding season. The density was considerably lower in the translocated population inhabiting 21 km ² of pine forests in La Cumbre (3.3 birds/km ² ), with an estimate of 68 Blue Chaffinches (35–141) breeding freely in the wild. The translocation programme successfully contributed to the establishment of a second viable nucleus, accounting for 16% of the total population within a time span of 10 years. This result reinforces the role of translocations in preventing extinctions of endangered species with very low population sizes restricted to only one isolated area.
... The Gran Canaria blue chaffinch (Fringilla polatzeki, Canary Islands) is a rare, threatened species that occupies an island-habitat within the island of Gran Canaria (Martín and Lorenzo, 2001 for the probable status of the species since the beginning of the 20 th century). Currently split from F. teydea according to genetic, morphological and behavioural data (Pestano et al., 2000;Lifjeld et al., 2016;Sangster et al., 2016), it is mainly restricted to the Strict Nature Reserve of Inagua-Ojeda-Pajonales (Inagua, hereafter; 39.2 km 2 ; Moreno and Rodríguez, 2007), although a few pairs have recently established elsewhere as a result of a translocation program (Delgado et al., 2016). The Gran Canaria blue chaffinch is a habitat specialist of the mature Canarian pine forests (Pinus canariensis), likely as a consequence of past competition with other Fringilla species and niche displacement (Illera et al., 2016). ...
... Breeding success is low for a Fringillidae, with only ca. 1.5 fledglings per successful nesting attempt, and 1.4 clutches per breeding season (Rodríguez and Moreno, 2008;Delgado et al., 2016). The estimated population size (with a previous educated guess at around 300 birds, BirdLife International, 2016) lies within the left tail of the distribution of minimum viable population (MVP) estimates for many species, far from the average MVP of 3,750 individuals for birds (Brook et al., 2006;Traill et al., 2007). ...
Article
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Evidence regarding population trends of endangered species in special protection areas and their recovery ability from catastrophic disturbances is scarce. We assessed the population trend of the Gran Canaria blue chaffinch (Fringilla polatzeki), a habitat specialist endemic to the pine forest of Inagua in the Canary Islands, following a devastating wildfire in July 2007. Using a standardized census program that accounts for detectability, we have monitored the population trend of the species since Inagua was declared a Strict Nature Reserve in 1994. The breeding population density of the blue chaffinch remained stable in Inagua from the beginning of the monitoring program in 1994 until the year before the wildfire. However, in spring 2008, the population density decreased by half with respect to density in the preceding years. Since 2008, the population has gradually increased, reaching its highest recorded density in 2016 (15.8 birds/km2).This represents an average annual increase of 23.7%, indicating impressive resilience to catastrophic events. The creation of Inagua as a strict nature reserve did not therefore increase the global population or protect the blue chaffinch against a demographic crisis but probably prevented a deepening of the demographic crisis or further declines. Except for the two years immediately after the severe wildfire of 2007, the population density of the blue chaffinch in Inagua has remained relatively stable at around 9–16 birds/km2, the lowest recorded abundance for a small woodland passerine in the Western Palearctic.
... Therefore, this site was chosen to develop a reinforcement programme (population augmentation), starting with birds bred in captivity and subsequently translocating individuals captured in Inagua as a source population (LIFE + PINZÓN 2019). Preliminary analyses give a positive assessment of the program, which started with birds bred in captivity and recorded survival and reproductive success values similar to those of natural populations (Delgado et al. 2016). Subsequently, Illera et al. (2023) found that the reinforced population at La Cumbre, from juvenile individuals from captive breeding and captured from the source population of Inagua, seemed to be viable in the short term, considering the similar values of biometric measurements, reproductive success, body condition, genetic diversity, and inbreeding of wild-born birds in both populations. ...
Article
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The Gran Canaria Blue Chaffinch is the rarest forest passerine in the western Palaearctic with a population reduced to a single locality, Inagua, in the west of the island. After a forest fire, some birds were established in another location and a reinforcement programme was launched with the aim of consolidating this new population. Between 2010 and 2019, 194 Blue Chaffinches were released in the pine forest of La Cumbre, in the centre of the island and at a higher altitude than the previous one. Birds of two origins were used for this action: captive-bred birds were released using “soft” release methods, and wild-caught birds from the Inagua source population were released using “hard” release methods. Survival of radio-tagged birds (20–42 days of battery life) was high and similar between the two groups. Wild-caught birds occupied 12–15 times more surface area than captive-bred birds that remained close to supplementary feeding sites. All translocated birds displayed breeding behaviour in the following breeding season, although the rate of contribution to the new population was significantly lower for wild-caught birds (21% compared to 54% for captive-bred birds). This disparity can be partly attributed to nearly one-fifth of the wild-caught birds returning to Inagua. We conclude that the establishment phase of the Blue Chaffinch reinforced program in Gran Canaria has been successful. To retain wild-caught birds and deter their return to the source population, we recommend employing methods akin to the soft-release techniques utilized for captive-bred birds. Ongoing monitoring of the enhanced population, collecting data on survival and breeding success, will enable the evaluation of the long-term success of the translocation program.
... La tasa de re-avistamiento ha sido una medida de la contribución de los ejemplares liberados a la población de La Cumbre. Delgado et al. (2016) valoran positivamente las liberaciones de pinzones azules realizadas los primeros años y recomiendan protección de las jaulas frente a los ataques de gavilanes y un tiempo de aclimatación de 6-14 días. ...
... Objetivo: Estimar la densidad y el tamaño de la población del pinzón azul de Gran Canaria ("pinzul") en La Cumbre (Gran Canaria), zona de reciente establecimiento de la especie, primeramente de manera natural y luego favorecida mediante la suelta de animales provenientes de cría en cautividad en Tafira y de traslocación desde Inagua (Delgado et al. 2016). Se pone el énfasis en el uso de la misma metodología ya establecida en Inagua desde 1994. ...
Technical Report
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Estimar la densidad y el tamaño de la población del pinzón azul de Gran Canaria (“pinzul”) en La Cumbre (Gran Canaria).
Article
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Determining the effectiveness of conservation actions is a priority in conservation biology, especially in island ecosystems which can host large numbers of endemic and often threatened species. In this study, we have brought together a genetic, body condition and breeding success assessment with the aim of evaluating the viability of a newly founded population of the endangered Gran Canaria blue chaffinch (Fringilla polatzeki), the forest passerine species with the most restricted distribution in the Western Palearctic. The species occurs exclusively in the Canary pine forests (Pinus canariensis) of the island of Gran Canaria, with the Inagua nature reserve harbouring the highest number individuals. In 2010, a translocation program was initiated within the same island in the nearby pine forests of La Cumbre with the goal of establishing a viable breeding population. Genetic results revealed that La Cumbre shows genetic parameters (diversity, inbreeding, and relatedness) similar to the core source of Inagua, which contrasts with the reduced genetic diversity expected due to the small size of the newly founded population. The biometric and body condition results (wing and tarsus length, body mass, and length asymmetry of the tail feathers), together with the breeding success (nest survival and number of fledglings per successful breeding attempt), were also similar in both populations. Overall, these findings suggest that the translocation program has been successful and provide insights on the effectiveness of the actions performed. Our evaluation also delivers future avenues for the conservation planning in other upland forest endangered avian species inhabiting island ecosystems, especially those threatened by the effects of global warming.
Preprint
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Background . Understanding constraints to the distribution of threatened species may help to ascertain whether there are other suitable sectors for reducing the risks associated with species that are recorded in only one protected locality, and to inform about the suitability of other areas for reintroduction or translocation programs. Methods . We studied the Gran Canaria blue chaffinch ( Fringilla polatzeki ), a habitat specialist endemic of the Canary Islands restricted to the pine forest of Inagua, the only area where the species has been naturally present as a regular breeder in the last 25 years. A suitability distribution model using occurrences with demographic relevance (i.e., nest locations of successful breeding attempts analysed using boosted classification trees) was built considering orographic, climatic and habitat structure predictors. By means of a standardized survey program we monitored the yearly abundance of the species in 100 sectors since the declaration of Inagua as a Strict Nature Reserve in 1994. Results . The variables with the highest relative importance in blue chaffinch habitat preferences were pine height, tree cover, altitude, and rainfall during the driest trimester (July-September). The observed local abundance of the blue chaffinch in Inagua (survey data) was significantly correlated with habitat suitability derived from modelling the location of successful nesting attempts (using linear and quantile regressions). The outcomes of the habitat suitability model were used to quantify the suitability of other natural, historic, pine forests of Gran Canaria. Tamadaba is the forest with most suitable woodland patches for the species. We estimated a population size of 195-430 blue chaffinches in Inagua since 2011 (95% CI), the smallest population size of a woodland passerine in the Western Palearctic. Discussion . Habitat suitability obtained from modelling the location of successful breeding attempts is a good surrogate of the observed local abundance during the reproductive season. The outcomes of these models can be used for the identification of potential areas for the reintroduction of the species in other suitable pine forests and to inform forest management practices.
Preprint
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Background . Understanding constraints to the distribution of threatened species may help to ascertain whether there are other suitable sectors for reducing the risks associated with species that are recorded in only one protected locality, and to inform about the suitability of other areas for reintroduction or translocation programs. Methods . We studied the Gran Canaria blue chaffinch ( Fringilla polatzeki ), a habitat specialist endemic of the Canary Islands restricted to the pine forest of Inagua, the only area where the species has been naturally present as a regular breeder in the last 25 years. A suitability distribution model using occurrences with demographic relevance (i.e., nest locations of successful breeding attempts analysed using boosted classification trees) was built considering orographic, climatic and habitat structure predictors. By means of a standardized survey program we monitored the yearly abundance of the species in 100 sectors since the declaration of Inagua as a Strict Nature Reserve in 1994. Results . The variables with the highest relative importance in blue chaffinch habitat preferences were pine height, tree cover, altitude, and rainfall during the driest trimester (July-September). The observed local abundance of the blue chaffinch in Inagua (survey data) was significantly correlated with habitat suitability derived from modelling the location of successful nesting attempts (using linear and quantile regressions). The outcomes of the habitat suitability model were used to quantify the suitability of other natural, historic, pine forests of Gran Canaria. Tamadaba is the forest with most suitable woodland patches for the species. We estimated a population size of 195-430 blue chaffinches in Inagua since 2011 (95% CI), the smallest population size of a woodland passerine in the Western Palearctic. Discussion . Habitat suitability obtained from modelling the location of successful breeding attempts is a good surrogate of the observed local abundance during the reproductive season. The outcomes of these models can be used for the identification of potential areas for the reintroduction of the species in other suitable pine forests and to inform forest management practices.
Technical Report
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OBJETIVO: Estimar el tamaño de la población, la densidad media, y el cambio temporal reciente de los efectivos del pinzón azul de Gran Canaria en el entorno de los pinares de La Cumbre (Gran Canaria). Inferir si la población establecida como consecuencia del programa de translocación ha sido viable independientemente de la liberación de ejemplares provenientes del centro de cría de Tafira y de la población salvaje en la Reserva Natural Integral de Inagua, Ojeda y Pajonales.
Article
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Background One of the biggest challenges in avian taxonomy is the delimitation of allopatric species because their reproductive incompatibility cannot be directly studied in the wild. Instead, reproductive incompatibility has to be inferred from multiple, divergent character sets that indicate a low likelihood of allopatric populations amalgamating upon secondary contact. A set of quantitative criteria for species delimitation has been developed for avian taxonomy. ResultsHere, we report a broad multi-trait comparison of the two insular subspecies of the Blue Chaffinch Fringilla teydea, endemic to the pine forests of Tenerife (ssp. teydea) and Gran Canaria (ssp. polatzeki) in the Canary Islands. We found that the two taxa were reciprocally monophyletic in their whole mitogenomes and two Z chromosome introns. The genetic distance in mitogenomes indicates around 1 Mya of allopatric evolution. There were diagnostic differences in body morphometrics, song and plumage reflectance spectra, whose combined divergence score (=11) exceeds the threshold level (=7) set for species delimitation by Tobias et al. (Ibis 152:724–746, 2010). Moreover, we found a marked divergence in sperm lengths with little range overlap. Relatively long sperm with low intra- and intermale CV compared to other passerines suggest a mating system with high levels of sperm competition (extrapair paternity) in these taxa. Conclusion The large and diagnostic divergences in multiple functional traits qualify for species rank, i.e., Tenerife Blue Chaffinch (Fringilla teydea) and Gran Canaria Blue Chaffinch (Fringilla polatzeki). We encourage a wider use of sperm traits in avian taxonomy because sperm divergences might signal reproductive incompatibility at the postcopulatory prezygotic stage, especially in species with sperm competition.
Technical Report
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El Pinzón azul es una especie muy escasa en Inagua, Ojeda y Pajonales, donde alcanza una densidad media de 3,51 pinzones / km2. El grueso de la población se localiza en esta zona en el sector norte, y en el sur por encima de los 1.150 m de altitud, que cubren el 45% de toda la superficie de los pinares analizados y acogen el 73% de todos los efectivos de la especie. La distribución del Pinzón azul en Inagua, Ojeda y Pajonales no se ve afectada por la del Pico picapinos (i.e., ausencia de patrón excluyente). El Pinzón azul no fue detectado en Tamadaba, en donde, de existir, tendría una densidad inferior a 0,36 pinzones / km2. El esfuerzo de muestreo realizado para el seguimiento poblacional del Pinzón azul en Inagua, Ojeda y Pajonales ha sido suficiente a lo largo de todos estos años, incluso en escenarios de abundancia tan bajos como los registrados en 2008 y 1994. No se han encontrado diferencias significativas en la detectabilidad de la especie entre observadores-años. La distancia eficaz de censo media del Pinzón azul en esta región fuertemente montañosa y abarrancada ha sido de unos 82 m (rango 65 – 110 m al 90% de confianza). Se recomienda seguir utilizando la red de sendas empleadas desde 1994 para efectuar el seguimiento de los efectivos de la especie. La red fija de transectos utilizada desde 1994 sobre-estima considerablemente la densidad y el tamaño de población de la especie en todo Inagua, Ojeda y Pajonales (por un factor que en 2008 sería x1,49). Esto es debido a la gran heterogeneidad espacial del reparto de la abundancia de la especie dentro de esta zona. Se recomienda cautela dando crédito a las estimas previas del tamaño de población del Pinzón azul. El tamaño de población en los 34,85 km2 de Inagua, Ojeda y Pajonales es muy pequeño, estimándose en unos 122 individuos (intervalo de confianza al 90%: 75 – 176 pinzones). El Pinzón azul ha disminuido significativamente su abundancia desde 2004 a 2008 en la zona sobre la que se han establecido los transectos control, con una magnitud relativa del descenso muy notable y preocupante (promedio del -49%). La estima de abundancia en 2008 es consistentemente la más baja registrada para la especie en Inagua, Ojeda y Pajonales desde 1994, siendo al menos un 35% inferior que la menor observada previamente. El Pinzón azul no ha manifestado cambios significativos en su abundancia relativa en Inagua, Ojeda y Pajonales desde 1994, año en que se crea la figura de Reserva Integral, hasta 2004, ni siquiera en el periodo de cambios más acusados en su abundancia relativa (1998-2002). Globalmente, el Pinzón azul ha aumentado su abundancia un 3,4% por año desde 1994 a 2004, aunque tal magnitud de cambio es indistinguible de lo que podría esperarse por puro azar. De seguir utilizando el esfuerzo de muestreo efectuado hasta la fecha (22,9 km de transectos realizados una sola vez al año) sólo serían detectables disminuciones significativas a p<0,1 superiores al 29,2% e incrementos superiores al 40,4% entre dos años consecutivos. Se recomienda repetir 3-4 veces al año el censo del Pizón azul sobre la red fija de transectos iniciada en 1994 para seguir sus efectivos poblacionales. La distribución del Pinzón azul en Mayo de 2008 en Inagua, Ojeda y Pajonales fue un fenómeno fácilmente explicable y altamente predecible y coherente, aunque la ausencia de la especie se predijo más fácilmente (92% de clasificaciones correctas) que su presencia (57%). Las características ambientales y geográficas que maximizan la probabilidad de adecuación del territorio para la especie son:a localización en el tercio occidental de la reserva, en áreas con cobertura de pinos superior al 24% (y en zonas situadas a más de 1.345 m s.n.m. en el resto de la reserva). La intensidad de quema del pinar en Mayo-Junio de 2008, derivada del incendio de Julio de 2007, ha afectado en muy escasa medida a su distribución actual en la reserva. Es altamente probable que la filopatría sea un importante determinante de la distribución actual de la especie en Inagua, Ojeda y Pajonales. El área de distribución preferente del Pinzón azul en Inagua, Ojeda y Pajonales tiene una elevada carga térmica durante el verano. Durante una alta proporción del tiempo del día la temperatura está por encima de lo que suele ser la temperatura crítica máxima en pequeñas aves forestales (unos 35 ºC). Estos resultados muestran el carácter tórrido de Inagua, Ojeda y Pajonales en verano, a pesar de ser un ambiente forestal y tener una elevada altitud. El Pinzón azul es mucho más frecuente en los pinares de Tenerife que en los de Gran Canaria (las frecuencias de aparición son de 49% y 23%, respectivamente). La distribución del Pinzón azul en Tenerife puede describirse con precisión (80% de clasificación correcta) con un modelo que la asocia positivamente con la altura y cobertura del arbolado (a partir de 16,5 m y 33% de cobertura), la altitud sobre el nivel del mar (por encima de 1590 m) y el índice de vegetación (valor de NDVI entre 146 y 192). Los pinares estudiados en Gran Canaria (Tamadaba y reserva integral de Inagua) tienen unas características en general poco favorables para el Pinzón azul, si atendemos a las preferencias de hábitat de la subespecie tinerfeña teydea. Las áreas más adecuadas serían aquellas a más de 1206 m de altitud, con un índice NDVI mayor de 141, con una altura media de los pinos superior a 16,9 m, una cobertura de arbolado mayor del 24%, y una cobertura del matorral superior al 10%. Las localidades más adecuadas en Tamadaba serían aquellas localizadas a más de 1116 m de altitud, con un índice NDVI mayor de 168, con una altura media de los pinos superior a 15 m, una cobertura de arbolado mayor del 35% y una cobertura del matorral superior al 9%. A estas zonas se les debería conferir el máximo estatus de protección.
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High post-release survival, low dispersal and the recruitment of captive-reared individuals into the wild population are critical to the success of any reintroduction programme. Reintroducing a migratory species poses an additional challenge as success also depends on the return of captive-reared individuals to breeding grounds in subsequent years. We investigated the effects of seven husbandry and management factors on the return rate of captive-reared eastern loggerhead shrikes Lanius ludovicianus migrans and documented the recruitment of returning individuals. During 2004–2010, 564 juveniles were released in Ontario, Canada, as part of a field propagation and release programme and there were 27 confirmed sightings of returning birds during 2005–2011. Returning birds were significantly more likely to have been released in large groups of juveniles (9–10 birds) at 5.5 weeks post-fledging from the Carden field propagation site. Comparisons of the number of young fledged and survival to 2 weeks post-fledging revealed similar results for pairs comprising one captive-reared and one wild-reared individual and pairs comprising two wild individuals. These results highlight the contribution of captive-reared shrikes to the recovery of the wild population and the importance of monitoring outcomes and evaluating techniques.
Article
The conservation of endangered taxa often critically depends on accurate taxonomic designations. The status of the Gran Canaria population of the Blue Chaffinch Fringilla t. polatzeki has not been reevaluated since the early 1900s when this taxon was described as a subspecies and combined with the much more common Tenerife Blue Chaffinch F. t. teydea in a single species. We show that multiple diagnostic differences in plumage, songs, calls and morphometrics distinguish F. t. polatzeki from F. t. teydea. Preliminary playback experiments suggest that F. t. polatzeki is able to discriminate between songs of both taxa. Along with previously reported differences in mitochondrial DNA, these findings show that the blue chaffinches on Gran Canaria and Tenerife represent two distinctive species: F. polatzeki and F. teydea. Gran Canaria Blue Chaffinch is Europe’s rarest passerine species and should be classified as Critically Endangered. Its long-term survival in the wild currently depends on a very small (<20 km2) area in southwest Gran Canaria. Reclassification of Gran Canaria Blue Chaffinch as a species increases the urgency of ongoing conservation efforts. Our study underscores the critical importance of taxonomic clarification of threatened taxa that are currently classified as ‘subspecies’.
Chapter
The recent surge of interest in the use of reintroduction, especially of captive-bred animals, as a conservation tool, has resulted in two recent reviews of the subject (Jones, 1990; Gipps, 1991) and the formation of a Re-introduction Specialist Group (RSG) of the Species Survival Commission (SSC) of the World Conservation Union (IUCN) and a Reintroduction Advisory Group (RAG) for the American Association of Zoological Parks and Aquariums (AAZPA).