Providing evidence to improve practice

Action: Translocate songbirds Bird Conservation

Key messages

  • Nine studies from across the world, including a review of 31 translocation attempts in New Zealand found that translocations led to the establishment of songbird populations. The review found that 79% and 100% of translocation programmes for saddlebacks Philesturnus carunculatus and New Zealand robins Petroica australis, respectively, were successful in establishing populations. Eight of the studies were from islands, mostly following predator removal.
  • Three studies from Zimbabwe, New Zealand and the USA report on three translocation programmes that failed to establish populations.
  • A methodological paper found that the nesting success of saddlebacks decreased as the latitudinal difference between source area and release site increased.

 

Supporting evidence from individual studies

1 

A before-and-after study in Zimbabwe from 1975 to 1977 (Grobler 1979) surveyed the populations of yellow-billed oxpeckers Buphagus africanus and red-billed oxpeckers B. erythrorhyncus in Rhodes Matopos National Park (an area within the former range of both species), following the translocation of 47 yellow-billed and 12 red-billed oxpeckers in 1975. Sightings of B. africanus rose from 1975 (3.9 sightings/month) to 1977 (13.7 sightings/month). B. erythrorhyncus did not appear to establish in the park, with a single pair seen in the release area in 1977. Translocation mortalities occurred only for those birds released more than 30 hours after capture.

 

2 

A before-and-after study from September 1988 to January 1993 in the Seychelles (Komdeur 1997) found that all 29 Seychelles warblers Acrocephalus sechellensis translocated from Cousin Island to each of Aride Island (in September 1988) and Cousine Island (in June 1990) were alive in 1991 and that populations had grown from before translocations to 210 on Aride Island and 53 on Cousine Island. A further census on Aride Island in January 1993 estimated a population of 239 warblers. Prior to translocation, potential introduction sites were identified according to food availability, the absence of feral cats Felis catus and black rats Rattus rattus, and a sustained commitment to conservation management from the land owners. Translocation was in well-ventilated cardboard cages (15 × 15 × 20 cm) with a stick trellis 1 cm above the floor of each box allowing birds to perch, and the entire process of capture, translocation and release took on average little more than three hours, with no mortalities.

 

3 

A site comparison study on three islands offshore from South Island, New Zealand, in April-June 2001 (Hooson & Jamieson 2004), found that the nesting success of translocated saddlebacks Philesturnus carunculatus declined with increasing difference in latitude from the source population. All birds originally came from Big South Cape island, being translocated to the study islands and others when rats invaded Big South Cape in 1964. Birds on Ulva Island (60 km north of Big South Cape) had 73% nesting success (11 pairs), compared with 32% (16 pairs) for Breaksea Island (190 km north) and 19% success (14 pairs) for Motuara Island (810 km north). Success was calculated using the Mayfield method and differences were largely due to higher egg fertility and hatching success. The authors note that differences in habitat (due to latitude) were unlikely to be the only reason for varying reproductive success, as Breaksea, Ulva and Big South Cape are all similar in habitat, but Breaksea had significantly lower reproductive success.

 

4 

A before-and-after study on Mokoia Island (135 ha) in Lake Rotorua, North Island, New Zealand (Armstrong et al. 2005), found that a population of saddlebacks Philesturnus carunculatus (referred to as North Island saddlebacks P. rufusater) reintroduced onto the island increased from the 36 birds released in April 1992 to 217 birds in September 1996. The population fell following the attempted eradication of mice but recovered to 200 by September 1997. Reproductive output declined over time as the population grew. Before birds were released, brown rats Rattus norvegicus were eradicated from the island.

 

5 

A replicated study (Taylor et al. 2005) covering a range of time periods assessed the success or failure of 31 translocation attempts of saddlebacks Philesturnus carunculatus (24 attempted translocations) and New Zealand robins Petroica australis (six attempted) into separate offshore islands around New Zealand, found that both species established successful populations from small founder populations. The average founder population size of robins and saddlebacks was 31 and 34 respectively (ranging from 5-188 individuals). Only five of 24 saddleback populations went extinct or quasi-extinct (population decreased by > 50% after 3 years), while none of the 6 robin populations failed. Predation caused 80% of translocation failure. In total, five populations established from fewer than 15 individuals survived and grew. Populations were categorised as extinct if surveys subsequent to translocation failed to record any birds.

 

6 

A before-and-after study from May 2004 to September 2005 (Richardson et al. 2006) investigated the translocation of 58 adult Seychelles warblers Acrocephalus sechellensis in May and June 2004 from Cousin Island to Denis Island, Seychelles. The introduced population grew to 75 individuals by August 2005. Twenty-seven female and 31 male warblers were captured a month before the onset of the breeding season (the time of peak bird weight and condition) and were translocated within 24 hours. Denis Island, which was not part of the warbler’s historic range, was selected as the site for introduction as a predator-free island with suitable habitat and food availability. Of the 35 breeding territories vacated on Cousin Island because of the warbler translocations, all but three were occupied within an average of 5.4 days, with the source population rebounding to its pre-translocation level by September 2005.

 

7 

A before-and-after study in the Cook Islands (Richardson et al. 2006) translocated 30 Rarotonga monarchs Pomarea dimidiata (one to two years old) from Rarotonga Island to Atiu Island between August 2001 and August 2003. In June 2004 the monarch population was at least 15 birds, with breeding occurring in 2002 and 2003. Atiu Island was selected as the area for introduction based on the local community’s commitment to conservation, the island’s size (greater than 500ha), the apparent absence of black rats Rattus rattus, and the presence of suitable areas of habitat. Translocated birds were screened for blood-borne parasites before release, with the risk of infection from other species on Atiu considered low. Birds were translocated in 50 cm x 30 cm x 30 cm plywood boxes, each with a dwelling perch and ventilation holes, within 18 hours of capture.

 

8 

A before-and-after study from February 2003 to December 2005 investigated the reintroduction of 32 rifleman Acanthisitta chloris to Ulva Island, New Zealand in February 2003 (Leech et al. 2007) and found that at least 20 birds survived and bred by November 2003, and offspring were observed breeding in the second year. The 58 rifleman were captured on Codfish Island and kept in 14 x 4.5 x 2 m aviaries for up to four days before release. Of these, 26 died in captivity and transport, including 14 deaths while in the aviaries. Transport mortality was highest when birds were kept in transfer boxes for long periods of time (6-8 hours), or when transfer boxes were in close proximity and birds attempted to attack one other.

 

9 

A before-and-after study in New Zealand (Taylor & Jamieson 2007) investigated the translocation of 46 saddlebacks Philesturnus carunculatus from Breaksea Island to Erin Island in September 2003 and April 2004 and found that no birds survived until June 2006. Birds carried for an hour before ringing had higher mortality in the first two weeks (20/22 individuals dying) than birds caught within 20 m of the banding hut (9/25 dying). Male saddlebacks with low body condition scores and females with ectoparasites (e.g. ticks, fleas) were most likely to die within 11 days of release. A measure of inbreeding and the total time held in captivity were not good predictors of initial saddleback mortality. Birds were kept in a 2 x 4 × 7 m aviary for up to five days before translocation.

 

10 

A before-and-after study on Cousin Island, Seychelles (Lopez-Sepulcre et al. 2008), found that the population of Seychelles magpie-robins Copsychus sechellarum increased from five individuals, translocated from Frégate Island in 1994-5, to 46 individuals in 2006, before declining to 31 birds in 2007. Two males and two females were originally moved, plus a replacement female following the death of one of the original females in early 1995. The birds were kept in individual holding aviaries for two days before translocation. Cousin Island was identified as a suitable introduction site based on its status as a nature reserve, the absence of invasive predators, and the availability of large areas of native forest and food resources.

 

11 

A before-and-after study on Motuihe Island, New Zealand (Parker & Laurence 2008), found that survival of 20 saddlebacks Philesturnus carunculatus (formely North Island saddlebacks P. rufusater) translocated from Matangi Island in August 2005, was 70% for the first year, with at least 11 chicks fledged. The reintroduction was one part of a management project for Motuihe Island, including the eradication of brown rats Rattus norvegicus, house mice Mus musculus, European rabbits Oryctolagus cuniculus and feral cats Felis catus between 1997 and 2002. Extensive planting of native vegetation also took place from 2003-8. Birds were housed for 1-3 days in an aviary (8 x 5 x 3.5 m) before transport, with no mortalities during captivity and transport. This study is also discussed in ‘Provide artificial nesting sites’.

 

12 

A before-and-after study in Florida, USA, reintroduced 47 brown-headed nuthatches Sitta pusilla and 62 eastern bluebirds Sialia sialis to Long Pine Key, Everglades National Park, between December 1997 and April 2001 (Lloyd et al. 2009). Although 16 eastern bluebirds and 21 nuthatches failed to establish territories and presumably died shortly after release, population growth was initially observed in both species after the translocations were completed. By 2007, however, the populations of both species were either stable or declining, and only at approximately 10% of their predicted carrying-capacity (200 breeding pairs of each species). Nuthatches and bluebirds were captured at either Big Cypress National Preserve or Naples, Florida, transported and then kept in aviaries at the release site for up to three weeks before reintroduction.

 

Referenced papers

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2017) Bird Conservation. Pages 95-244 in: W.J. Sutherland, L.V. Dicks, N. Ockendon & R.K. Smith (eds) What Works in Conservation 2017. Open Book Publishers, Cambridge, UK.