Data Zone
Country/territory: Guam (to USA)
IBA criteria met: A1, A2 (2007)
For more information about IBA criteria, please click here
Area: 147 ha
| IBA conservation status | |||
|---|---|---|---|
| Year of assessment (most recent) | State (condition) | Pressure (threat) | Response (action) |
| 2014 | favourable | high | high |
| For more information about IBA monitoring, please click here | |||
Site description (2007 baseline)
The caves are sinkholes in limestone substrate, with multiple entrances (USFWS, 1992). Surrounding areas are forested and access to the caves is difficult. The caves, on land owned by the US Navy, has been established as part of a “No Disturbance” area and are managed under a Integrated Natural Resources Management Plan and in cooperation with the Guam National Wildife Refuge. Guam Swiftlets nest on the ceilings of the caves.
Key biodiversity
The Guam Comprehensive Wildlife Conservation Strategy (GDAWR, 2005) reported over 500 Guam Swiftlets in three small colonies in three caves in the center of Guam (Mahlac, Fachi, and Maemong (Firebreak 3) Caves). The majority of birds are located in the Mahlac Cave on the Naval Ordnance Annex in Southern Guam, although some individuals may use the caves interchangeably, and all three are located in the same areas. The caves are part of the Navy portion of the Guam National Refuge Overlay Refuge and as such are managed through cooperative agreements between the USFWS and the US Navy (USFWS, 2007), and in accordance with the Navy’s Integrated Natural Resources Management Plan mandated under the Sikes Act. The caves are located in forested area that is not readily accessible, on land owned by the US Navy. The US Navy has established Mahlac cave as a “No Disturbance” area (USFWS, 2004b) and initiated snake trapping in 2001. A survey conducted in 2000 estimated a population of 700-800 swiftlets at Mahlac Cave and far fewer birds at the other caves (DAWR, 2000). Recent sightings indicate that the population may be increasing (G. Grimm, pers. comm.). Although Mahlac Cave is the only cave to have confirmed use by swiftlets, there are reports that the swiftlets may be using all three caves interchangeably. Thus, all three caves (Mahlac, Fachi, and Maemong) are proposed as a single IBA.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Mahlac Caves (Guam (to USA)). Downloaded from
https://datazone.birdlife.org/site/factsheet/mahlac-caves-iba-guam-(to-usa) on 23/11/2024.