Rail Release
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Reintroduction of Guam Rails to the wild is proceeding through several
stages. Rails are bred in several zoos (see Captive Breeding). The first
releases were made on Rota which has habitat very similar to the Rail's
native home, and an absence of brown treesnakes. Following experience with
this, Rails were released in a large fenced area on Northwest Field, where
snakes were excluded. Now a new project will release them to the wild, in a
"safe harbor" on Talofofo Golf Club, where snakes populations are low and
under control.
The captive management of the Guam rail calls for the establishment of more than one subpopulation. This has been accomplished by dispersing the captive rails into two primary captive populations on Guam and in U.S. zoos (see Captive Breeding). However, captive breeding is only a means toward the goal of reintroducing the Guam rail to part of its historical range on Guam. Additionally, it was important to establish an experimental wild population on snake-free Rota, not only to serve as a third genetic reservoir to prevent genetic drift and inbreeding, but also to ensure the maintenance of behavioral adaptations for the wild. Reintroductions of captive produced animals are less likely to succeed than translocations of wild-caught animals because of behavioral deficits. Experience gained in releasing Guam rails on Rota provided valuable information for subsequent steps toward reintroducing the rail to the wild on Guam.
In 1987, a cooperative agreement was signed between the Government of Guam, CNMI, and the U.S. Fish and Wildlife Service (USFWS) outlining the responsibilities of each entity for the introduction. An environmental assessment was prepared for the USFWS covering the introduction of the Guam rail to Rota. After a permit to establish an “experimental population” of Guam rails on Rota was issued, 22 rails were released at a site on the Sabana on Rota in December 1989 and January 1990. All but 1 rail were released with radio transmitters attached in order to monitor their dispersal, mortality and possible breeding success. The site proved to be unsatisfactory probably due to the presence of dense grassland habitat. Of the 22 released birds, the whereabouts of 9 were unknown as their radios failed, 4 were killed by vehicles, 2 were killed by cats, 2 apparently died of starvation, 1 died of poisoning, and 4 died of unknown causes.
In February 1991, 33 rails were released at the forest edge in I Chenchon Park near the Bird Sanctuary overlook. This release appeared to be more successful than previous ones. Releases were discontinued until the spring of 1995 due to the low production of rails at captive breeding facilities. In FY00 high production allowed relaease of 117 birds in January, August and September 2000.
The release site was moved further inside the forest beginning in 1995, to the east from the 1991 release site. Currently, 384 rails have been released on Rota including: 21 (12/89); 33 (2/91); 15 (3/95); 30 (8/95); 15 (9/95); 15 (4/96); 19 (4/97); 19 (6/98); 50 (2/99); 50 (8/99) and 117 during FY00. [more in FY01?]
One important observation about the birds that has come from these releases is that they seem to prefer scrub habitats along the forest edge rather than the interior. All FY99 and FY00 nests were found in coconut groves with an understory of Pennisitum , and cattle fields of grasses and vines. All but 2 rails detected in the April survey were in open habitat. The Gampapa area was then selected as the new release site composed of forest, edge habitat and open fields. This information was also put to use in selecting the Talofofo Golf Course for the Safe Harbor Project (see below).
Detailed report (FY00).
Current brown treesnake control methods can reduce or eradicate snakes from large-scale areas using traps and barriers. Area 50 is a 24-hectare plot of mixed forest on Anderson Air Force Base. It is surrounded by old runway tarmacs and enclosed by a 2 m tall chain link fence and set aside for the purpose of environmental recovery activities to include: 1) the removal of bropwn treesnakes, feral pigs (Sus scrofa), and Guam deer (Cervus mariannus); and 2) the recovery of several native species including the Guam rail, Mariana crow (Corvus kubaryi), Micronesian kingfisher (Halcyon cinnamomina), and the Fire tree (Serianthes nelsonii).
Sixteen Guam rails (8 males, 8 females) were released in Area 50 on 16 November 1998. Rails survived an average of 198 days, although 5 (31%) rails were still known to be alive at the end of the reporting period (318 days). Seven birds (44%) were found dead, 2 birds had their radios fail before the end of the fiscal year, while 2 birds dropped their radios. A total of 4 females and 5 males nested during the reporting period producing 17 nests (mean clutch size of 2.94 eggs, range = 1-4) and successfully hatching 42 of 50 eggs (84%).
When Guam rails were initially released into Area 50, birds were seen pacing along the edge of the fence on several occasions, as if they were still confined in their holding cages at the DAWR breeding facility. It was this sort of behavior that led to the death of one bird seven days after its release, suggesting the bird never adapted to the wild. However, after several weeks, most birds seemed to settle down and establish territories. The perimeter fence was successful in controlling the dispersal of the rails, as no birds were known to have escaped during the study. This facilitated the pairing up of rails and the establishment of territories. Most birds appeared to settle within 100 m of the fence, mostly in the south, west, and east corners, in areas of secondary forest and low scrubby vegetation. Snake capture rates remained at maintenance levels (0.0 – 0.5 captures/100 trap nights) throughout the study and no mortality of rails or eggs was attributed to snake predation.
During FY00 playback surveys, using recorded rail territorial calls, conducted in February and March 2000 detected 10 rails in Area 50. Work continues to trap feral cats and monitor lizards inside Area 50 and to determine the size of the rail population at present.
Details of set up (FY99 report). Current status (FY00)
Safe Harbor Project
The Safe Harbor Project will begin this year (FY03). The golf course provides a mixture of grassy areas with a few stands of trees. Forest edge seems to be the preferred habitat for rails, and there is not a large population of snakes in that area. The snake population will be further reduced by trapping....
Rail releases on Rota
The captive management of the Guam rail calls for the establishment of more than one subpopulation. This has been accomplished by dispersing the captive rails into two primary captive populations on Guam and in U.S. zoos (see Captive Breeding). However, captive breeding is only a means toward the goal of reintroducing the Guam rail to part of its historical range on Guam. Additionally, it was important to establish an experimental wild population on snake-free Rota, not only to serve as a third genetic reservoir to prevent genetic drift and inbreeding, but also to ensure the maintenance of behavioral adaptations for the wild. Reintroductions of captive produced animals are less likely to succeed than translocations of wild-caught animals because of behavioral deficits. Experience gained in releasing Guam rails on Rota provided valuable information for subsequent steps toward reintroducing the rail to the wild on Guam.
In 1987, a cooperative agreement was signed between the Government of Guam, CNMI, and the U.S. Fish and Wildlife Service (USFWS) outlining the responsibilities of each entity for the introduction. An environmental assessment was prepared for the USFWS covering the introduction of the Guam rail to Rota. After a permit to establish an “experimental population” of Guam rails on Rota was issued, 22 rails were released at a site on the Sabana on Rota in December 1989 and January 1990. All but 1 rail were released with radio transmitters attached in order to monitor their dispersal, mortality and possible breeding success. The site proved to be unsatisfactory probably due to the presence of dense grassland habitat. Of the 22 released birds, the whereabouts of 9 were unknown as their radios failed, 4 were killed by vehicles, 2 were killed by cats, 2 apparently died of starvation, 1 died of poisoning, and 4 died of unknown causes.
In February 1991, 33 rails were released at the forest edge in I Chenchon Park near the Bird Sanctuary overlook. This release appeared to be more successful than previous ones. Releases were discontinued until the spring of 1995 due to the low production of rails at captive breeding facilities. In FY00 high production allowed relaease of 117 birds in January, August and September 2000.
The release site was moved further inside the forest beginning in 1995, to the east from the 1991 release site. Currently, 384 rails have been released on Rota including: 21 (12/89); 33 (2/91); 15 (3/95); 30 (8/95); 15 (9/95); 15 (4/96); 19 (4/97); 19 (6/98); 50 (2/99); 50 (8/99) and 117 during FY00. [more in FY01?]
One important observation about the birds that has come from these releases is that they seem to prefer scrub habitats along the forest edge rather than the interior. All FY99 and FY00 nests were found in coconut groves with an understory of Pennisitum , and cattle fields of grasses and vines. All but 2 rails detected in the April survey were in open habitat. The Gampapa area was then selected as the new release site composed of forest, edge habitat and open fields. This information was also put to use in selecting the Talofofo Golf Course for the Safe Harbor Project (see below).
Detailed report (FY00).
Rail releases on Northwest Field (Area 50)
Current brown treesnake control methods can reduce or eradicate snakes from large-scale areas using traps and barriers. Area 50 is a 24-hectare plot of mixed forest on Anderson Air Force Base. It is surrounded by old runway tarmacs and enclosed by a 2 m tall chain link fence and set aside for the purpose of environmental recovery activities to include: 1) the removal of bropwn treesnakes, feral pigs (Sus scrofa), and Guam deer (Cervus mariannus); and 2) the recovery of several native species including the Guam rail, Mariana crow (Corvus kubaryi), Micronesian kingfisher (Halcyon cinnamomina), and the Fire tree (Serianthes nelsonii).
Sixteen Guam rails (8 males, 8 females) were released in Area 50 on 16 November 1998. Rails survived an average of 198 days, although 5 (31%) rails were still known to be alive at the end of the reporting period (318 days). Seven birds (44%) were found dead, 2 birds had their radios fail before the end of the fiscal year, while 2 birds dropped their radios. A total of 4 females and 5 males nested during the reporting period producing 17 nests (mean clutch size of 2.94 eggs, range = 1-4) and successfully hatching 42 of 50 eggs (84%).
When Guam rails were initially released into Area 50, birds were seen pacing along the edge of the fence on several occasions, as if they were still confined in their holding cages at the DAWR breeding facility. It was this sort of behavior that led to the death of one bird seven days after its release, suggesting the bird never adapted to the wild. However, after several weeks, most birds seemed to settle down and establish territories. The perimeter fence was successful in controlling the dispersal of the rails, as no birds were known to have escaped during the study. This facilitated the pairing up of rails and the establishment of territories. Most birds appeared to settle within 100 m of the fence, mostly in the south, west, and east corners, in areas of secondary forest and low scrubby vegetation. Snake capture rates remained at maintenance levels (0.0 – 0.5 captures/100 trap nights) throughout the study and no mortality of rails or eggs was attributed to snake predation.
During FY00 playback surveys, using recorded rail territorial calls, conducted in February and March 2000 detected 10 rails in Area 50. Work continues to trap feral cats and monitor lizards inside Area 50 and to determine the size of the rail population at present.
Details of set up (FY99 report). Current status (FY00)
Safe Harbor Project
The Safe Harbor Project will begin this year (FY03). The golf course provides a mixture of grassy areas with a few stands of trees. Forest edge seems to be the preferred habitat for rails, and there is not a large population of snakes in that area. The snake population will be further reduced by trapping....
Guam Comprehensive Wildlife Conservation Strategy, 9/27/2005
