Rethinking reintroduction as a valuable integral conservation tool:

the case of an island pigeon Javier Romero1,3*, Marta López-Darias1, Mariano Hernández2, Gonzalo Albaladejo2, Alejandro Suárez-Pérez, Manuel Nogales1, Francisco J. Sosa4 & Aurelio Martín2

1Island Ecology and Evolution Research Group, Spanish National Research Council (IPNA-CSIC), La Laguna, Tenerife, Spain; 2University of La Laguna (ULL), La Laguna, Tenerife, Spain; 3PhD student from the University of La Laguna (ULL), La Laguna, Tenerife, Spain; 4Cabildo de Gran Canaria (Island Governmet), Spain. *Correspondence author: javier.romero.rguez@gmail.com

BackgroundBackgroundBackground

Over the last few decades, the reintroduction of species with primary conservation purposes has been increasingly used as a conservation approach to reverse species extinction1. Also,

rewilding initiatives involving the reintroduction of species to restore an ecosystem functioning are starting to be carried out worldwide2. However, despite the development of reintro-

duction biology as an applied science3-5, other key aspects of this conservation tool (i.e. ‘flagship to restore ecosystems’, ’sustainable economic resource’ or ‘catalyst for environmental

awareness’) have not yet been highlighted. Here, we show an example of reintroduction of a pigeon that, despite not itself being critically threatened, has contributed significantly to

mobilize restoration efforts of an ecosystem that had become functionally extinct at island level. In addition, this project has acted as a social and economic driver of an insular region

traditionally located outside the focus of environmental education and business attention.

The reintroduction of The reintroduction of The reintroduction of Columba junoniae Columba junoniae Columba junoniae on Gran Canaria islandon Gran Canaria islandon Gran Canaria island………

۞ Columba junoniae is one of the two endemic pigeons in the Canary Islands, listed as

‘Near Threatened’ by the IUCN and as ‘Vulnerable’ by the Spanish Goverment.

۞ Although it was consumed by Prehispanic inhabitants, this pigeon probably became

extinct on Gran Canaria after the Spanish conquest (1478 CE) due to forest devasta-

tion, predation by introduced rats and hunting.

۞ In 2006 the Island Government and the University of La Laguna started its reintroduc-

tion, performing a captive breeding programme.

۞ Cross-fostering with barbary Doves (Streptopelia

risoria) was the chosen option (Fig. 1) following

the example of the pink pigeon on Mauritius

(Nesoenas mayeri). To that end, C. junoniae eggs

and chicks were collected from La Palma island,

which is the captive breeding programme base.

ReferencesReferencesReferences 1IUCN (2013); 2Seddon et al. (2014) Science 345, 406-412; 3Seddon et al. (2007) Conserv. Biol. 21, 303-312; 4Armstrong & Seddon (2008) Trends Ecol.

Evol. 23, 20-25; 5Taylor et al. (2017) Trends Ecol. Evol. 32, 873-880; 6Walker (2007) Oryx 41, 289-299; 7Corlett (2017) Glob. Ecol. Conserv. 11, 1-22.

AcknowledgementsAcknowledgementsAcknowledgements

We are specially grateful to the LIFE + Rabiche team: partners, colleagues and volunteers. We are also thankful to the ‘Cabildo de La Palma’ for the kindness of

its staff and for selflessly providing assistance and facilities on La Palma during the egg and chick collection fieldwork period. This project was funded by the

European Union and the 'Cabildo de Gran Canaria'.

… and its impact beyond this species recovery … and its impact beyond this species recovery … and its impact beyond this species recovery

۞ Since 2012, 289 pigeons had been 'soft-released' into the wild (Fig. 2), with a wide genetic

diversity (He = 0.59 ± 0.049; ± SE) in comparison with natural populations. Reintroduced

birds have been rearing chicks in the wild since 2013, and the current proportion of wild-

born pigeons has already overtaken the reintroduced ones. Survival is estimated at around

35%.

Social benefitsSocial benefits

۞ Gran Canaria’s social context before the project

→ 843,000 people (69,000 in the project area). → Deficient environmental awareness and high unemployment rate (≈ 30%).

۞ Contributions of the project

→ $515,000 invested as wages in local employment. → 16,700 inhabitants reached through environmental

awareness campaigns (Fig. 5). → 26 % increase in rural tourism lodging occupation.

CONCLUSIONCONCLUSIONCONCLUSION

Reintroductions must be considered as an integral conservation tool, beyond the recovery of threatened or locally extinct species. This successful reintroduction example from Gran Canaria can be extrapolated to hundreds of oceanic islands around the world, where pigeons are widely distributed and threatened6, and where similar projects can bring natural, social and economic richness. Due to the frequent absence of large-sized animals on oceanic islands, pigeons can act as flagship/umbrella/key species when it co-mes to implementing integral conservation projects, building up ecological interactions essential for forest ecosystem functioning7. We encourage this tool as a keystone to develop the ‘new global conservation agenda’.

Potential

Actual

Fig. 5. Informative brochure of the project edited with the main results obtained *Left+. People involved in the environmental awareness actions of the project *Right+.

Fig. 1. Columba junoniae chick with its Streptopelia risoria adoptive

parents.

Habitat restorationHabitat restoration

۞ The European laurel forest is:

→ a highly biodiverse cloud forest exclusive to the Maca-ronesian archipelagos, relict from Tertiary Period.

→ a UE priority habitat, key for ecosystem services (e.g. water reserves), which had almost disappeared on Gran Canaria: 1% of its original distribution remained (Fig. 3).

۞ This project has resulted in:

→ 175,000 trees planted of native species

(↑ 206% in laurel forest cover).

→ 320 ha of degraded land restored.

Ecosystem functionsEcosystem functions

۞ Columba junoniae as seed disperser

→ Gran Canaria’s frugivore assemblages, as an oceanic island, are relatively simple and down-sized. → Pigeons are the largest seed dispersers.

۞ Restoring a key lost function

→ Pigeons are essential for largest-fruit seed dispersal (SD) of native structural species (Fig. 4).

→ Recovery of long-distance SD across forest fragments (70 km max. movement).

ø 23 mm

ø 12 mm

ø 7 mm

ø 16 mm

ø 10 mm

ø 7 mm

ø 15 mm

ø 11 mm

ø 8 mm 18 g / ø 8 mm

400 g / ø 25 mm

100 g / ø 13 mm

20 g / ø 8 mm

Fig. 4. Frugivore-plant network in the laurel forest. The largest-fruited plants depend entirely on Columba junoniae due to gape-width / fruit diameter restrictions.

289 pigeons released

62 group liberations

mean = 5 birds/liberation

Sex ratio (M : F) = 1 : 1.24

Fig. 2. Follow-up of Columba junoniae soft-releases over time *Left+. Opening moment of the

acclimatization aviary *Right+.

Fig. 3. Gran Canaria’s laurel forest area (ha): potential cover (inner circle) and actual cover (outer circle).