Abstract

            The Abbott’s booby is an Endangered, long-lived seabird listed on the IUCN Red List of Threatened Species in 2019, with only known extant breeding colonies located on Christmas Island in the Indian Ocean (National Recovery Plan, 2004). The species only breeds on a tiny island with breeding limited habitat, making this seabird species particularly vulnerable (Papasula abbotti, 2019). The quality of nesting habitat continues to decline (Papasula abbotti, 2019). Current and potential future threats include climate change effects of Southern Oscillation from El Niño, extreme weather events, wind turbulence, increasing sea surface temperature, mining and forest clearing of nesting habitat, and die-back of forested nesting habitat due to ecological impacts of introduced exotic species like the Yellow crazy ant. The conservation objectives and strategies laid out in the Australian Abbott’s Booby National Recovery Plan of 2004 are important steps necessary for supporting population and nesting habitat recovery, but many of the objectives in the recovery plan are still unrealized actions or are activities still in their infancy. Christmas Island needs to be included in Australia’s National Representative System of Marine Protected Areas and current species distribution and abundance need to be surveyed to develop successful conservation management planning and policies.

(Montgomery, 2017).

Introduction

            The Abbott’s booby is a seabird species listed as Endangered in The International Union for Conservation of Nature and Natural Resources’ IUCN Red List of Threatened Species 2019 Assessment, conducted by BirdLife International and published by the IUCN (Papasula abbotti, 2019). The Abbott’s booby seabird species is scientifically named Papasula abbotti and taxonomically classified within the Family of Sulidae (Papasula abbotti, 2019). The physical appearance of females includes pink dark-tipped bills while their male counterparts have grey dark-tipped bills (Papasula abbotti, 2019). The booby has black and white feathers with white heads and mostly black wings with black tails and blue-grey feet (Papasula abbotti, 2019).

            The boobies prey on fish and squid from the open ocean (Papasula abbotti, 2019). Their rainforest breeding grounds are placed along the tall plateau forest of the northern coast and upper terrace forest along the west and center of the island at elevations between 160 and 260 meters (Papasula abbotti, 2019; (National Recovery Plan, 2004).

            The species lives an average of 40 years, can only lay one egg per breeding cycle, only breed once every two years, and cannot reproduce until they are at least eight years old (Papasula abbotti, 2019). If a parental pair is reproductively successful, they will nest only once within that two year period and their breeding cycle will last between fifteen and eighteen months (Papasula abbotti, 2019). A successful breeding pair can only successfully fledge one chick within a two year period while an unsuccessful pair will attempt breeding the next year or take one or more rest years before trying to breed again (Papasula abbotti, 2019). The booby population cannot recover quickly after population decline, “due to generally long generation times and low fecundity” (Morris-Pocock et al., 2012).

Distribution of Species

            By the early 1900’s, the range of Abbott’s booby individuals globally is known to have acutely diminished (National Recovery Plan, 2004). The only known breeding colony is located on Christmas Island, though the species, “formerly bred on many islands in the Indian and Pacific Oceans” (National Recovery Plan, 2004). Their known breeding distribution is represented in Figure 1 and their resident species distribution is represented in Figure 2. Within Indonesia in the Indian Ocean, the Territory of Christmas Island belongs to the Commonwealth of Australia, located 960 miles northwest of Australia and 224 miles south of Jakarta (Sturchler, 2017). Figure 3 shows locations of booby nesting sites mostly mapped in 1991.

            At sea, their distribution is largely unknown, although the species is known to regularly make long trips far away from its nesting colony when foraging (Papasula abbotti, 2019; National Recovery Plan, 2004). “It was previously thought that cold water upwellings south of Java could be important feeding areas for breeding boobies, however tracking studies showed that chick-rearing adults forage relatively close to Christmas Island, on average about 60 km off the island, and show no association with oceanographic features” (Papasula abbotti, 2019). Breeding adults are believed to forage northeast of the island in open ocean, near Java, Sumatra, the Kai and Aru Islands, Irian Jaya, and Tayandu (National Recovery Plan, 2004). The species may range up to 4,000 km west of their nesting grounds, “as far as the Chagos Archipelago” (National Recovery Plan, 2004). In the 1990’s there were a few sightings of individuals, “in the Bandha Sea south of Moluccas,” that, “may indicate a more extensive foraging range,” than earlier thought (National Recovery Plan, 2004).

            The seabird is now regionally extinct in both Mauritius and the Seychelles, but in the past few years an individual was sighted on Rota Island within the Northern Mariana Islands (Papasula abbotti, 2019). Little is known about why the individual seabird was so far away from the rest of its kind, but it is thought to be a vagrant (Papasula abbotti, 2019).

Abundance of Species

            The first official breeding population estimate of the Abbott’s booby was made in 1967, when Christmas Island was the only active breeding area left for the species, and was determined somewhere between 2,300 and 2,000 seabird pairs (National Recovery Plan, 2004).

            In 1983, the breeding population on Christmas Island was approximated as 1,900 pairs and 400 breeding booby pairs were lost due to forest clearance for phosphate mining between 1970 and 1983 (National Recovery Plan, 2004). In 1991, the most recent breeding population survey reported 2,500 breeding booby pairs (National Recovery Plan, 2004). The difference in pairs between the two most recent breeding population estimates of 1983 and 1991 is misleading. This was, “due to discovery of further nesting areas on the northern side of the island, and also among the southern and southwestern areas of distribution,” and, “was not thought to indicate an increase in population size” (National Recovery Plan, 2004).In 1997, the total species population was estimated at 2,500 active pairs (Papasula abbotti, 2019). In 2002, a survey counting 1,500 active nest sites was recorded by helicopter, but was never verified via ground survey (Papasula abbotti, 2019). It is believed that between 1991 and 2002 the breeding population of the Abbott’s booby was generally stable (Papasula abbotti, 2019).

            In 2000, the IUCN listed the Abbott’s booby as Critically Endangered (National Recovery Plan, 2004). An estimated 30% to 49% decline in species population occurred between 1929 and 2019 and reflects the disappearance of the Abbott’s booby from the geographic locations of Mauritius and the Seychelles in the Pacific and Indian Oceans (Papasula abbotti, 2019). The current population trend of the Abbott’s booby is considered stable, although the species population has not been properly surveyed since 1991 (Papasula abbotti, 2019).

Threats

            The Abbott’s booby is currently listed on the IUCN Red List as an Endangered species and faces many threats, like most other seabirds, from environmental effects of climate change like Southern Oscillation from El Niño, extreme weather events, and cyclones that can destroy nesting sites with chicks (Papasula abbotti, 2019). Also, increased sea surface temperature in the ocean leads to decreased ocean productivity, threatening the species by disrupting prey availability, foraging trip duration, prey composition, and dive depths (Papasula abbotti, 2019).

            In the past, mining has been a serious threat for the species. Phosphate mining commenced on the northwestern portion of the island in 1970 destroying booby chicks, parents, and nests by clearing trees within booby breeding habitat (National Recovery Plan, 2004). Between 1965 and 1987 the phosphate extraction industry destroyed an estimated one-third of the total nesting habitat of the Abbott’s booby (Papasula abbotti, 2019; Reville et al., 1990). Mining stopped in 1987, but in more recent years, “significant patches of mature secondary forest were cleared for mining,” and, “some trees in nesting areas have degenerated, but the extent of this is unquantified” (National Recovery Plan, 2004; Papasula abbotti, 2019). A mining lease between Australia and the Phosphate Resources Limited went into effect in 1998 and has stayed that way for over 20 years. The Mining Lease, “covers the re-mining of old stockpiles and in-situ mining of previously mined areas. The lease includes areas surrounded by, but not within, the National Park” (National Recovery Plan, 2004). It was suspended briefly in 1999 and was reinstated and renegotiated in 2002 (National Recovery Plan, 2004).

            Permission to build a new mine using 250 hectares of rainforest habitat on Christmas Island was initially denied in 2007, but has since been appealed and is a potential future threat to Abbott’s booby nesting grounds (Papasula abbotti, 2019). Also related to mining, introduced exotic plants to the island have colonized in old mining locations as potential invaders of currently degraded habitat (Papasula abbotti, 2019). Less breeding habitat could increase booby breeding pairs choosing to skip breeding season without enough safe nesting habitat. With less breeding in a season, species population stability will be at risk.

            Wind turbulence can also cause adult mortality and reduce fledgling success, so forest clearing causing wind turbulence may be a threat to fledgling success and reproductive success (Papasula abbotti, 2019). Nesting areas on Christmas Island within 300 m northwest of manmade tree clearings showed significantly less breeding success compared to nesting areas with less canopy movement from, “increased exposure to the south-east tradewinds” (Reville et al., 1990). Helicopter wind turbulence is also a potential threat for the species.

            An invasive species called the Yellow Crazy Ant was introduced to Christmas Island in the 1990’s and has changed island ecology by increasing red crab mortality and damaging trees (Papasula abbotti, 2019). The yellow crazy ant’s introduction may be causing or worsening die-back of forest within a small area of booby nesting habitat, but the ant is not a critical threat to Abbott’s booby survival (Papasula abbotti, 2019).

Methods of Conservation

            The Australian Government Initiative National Recovery Plan for the Abbott’s Booby that was originally written in 1999 created eight recovery objectives for seabird conservation. These objectives include (1) protecting, restoring, and enhancing breeding habitat, (2) Managing threats to ecosystem function posed by crazy ants in infested areas, (3) ensuring construction and operation activities of the Immigration Center do not impede habitat recovery, (4) ensuring construction and operation of the Asia Pacific Space Center doesn’t hinder habitat recovery, (5) identifying foraging habitat for both adults and juveniles as well as creating management responses to identified threats, (6) creating a population monitoring program, (7) designing a model for wind turbulence to guide and evaluate tree clearance policies near recovering habitat, (8) to assess fisheries impacts on the species, and to (9) edit this recovery plan when necessary (National Recovery Plan, 2004).

            Australia’s Department of Environment and Heritage put this recovery plan in motion and have worked with Parks Australia North (PAN) to implement the Christmas Island Rainforest Rehabilitation Program (National Recovery Plan, 2004). PAN continues to implement weed management strategies for helping with recovery of tree die-back at breeding habitat and are working to map critical breeding habitat (National Recovery Plan, 2004). PAN is also responsible for controlling the Yellow crazy ant population and using satellite telemetry to determine at-sea distribution of boobies to confirm foraging range and potential overlapping of threats like fishing and hunting (National Recovery Plan, 2004). Identifying critical feeding habitat to the survival of booby adults and juveniles is important for developing successful management planning.

Recommendations

            The abundance of the Abbott’s booby species is currently unknown and has not been properly surveyed since 1991. Without knowing the total species population, conservationists cannot truly know whether the population is stable, increasing, or decreasing. This seabird species is very much under-studied and much more research needs to be done before appropriate conservation strategies can be designed properly. It is necessary via future research to quantify current species abundance, current foraging trip durations during breeding season, as well as the approximate number of booby pairs successfully fledging chicks and the approximate number of booby pairs skipping breeding season each year. This research is vital developing successful management planning and policy.

            PAN should continue to map current foraging locations and work to identify prey availability as well as prey species being consumed by Abbott’s booby individuals and also the prey species being fed to booby chicks. Tagging should be utilized on as many nesting adults and fledglings / juveniles as possible from each of the nesting locations on Christmas Island.

            Creating a citizen science program to monitor the species will get local Christmas Islanders interested and involved in research and conservation of the Abbott’s booby seabird. For the success of the program, it’s critical to have, “multiple coordinating institutions and diverse partnerships involved in management; accessibility of the resource; and the strong presence of at least one characteristic indicating social or cultural importance” (Chase & Levine, 2016). The National Recovery Plan from 1999 stated that they would work to use various agencies to create a cost=effective monitoring program for the Abbott’s booby to, “detect changes in population with high precision,” but I cannot find any current information or proof of existence of this program (National Recovery Plan, 2004). Population monitoring is extremely important and a monitoring program still needs to be created and managed by PAN and other Australian environmental agencies to keep track of species abundance.

            Christmas Island is governed by Australia but is not currently included in Australia’s National Representative System of Marine Protected Areas (NRSMPA) (Hobbs, 2014). Starting an Australian citizen grassroots campaign lobbying for MPA status for Christmas Island as well as filing of a citizen law suit against the Australian government could hopefully lead to the NRSMPA including Christmas Island as a Marine Protected Area. This is an important conservation effort to conserve fish communities and safeguard Abbott’s booby prey availability.

            The currently pending appeal of a proposed and denied new phosphate mine from 2007 is still a potential threat to the Abbott’s booby (Papasula abbotti, 2019). Protests should be held to show public support for prevention of new mining and conservation of Abbott’s booby endangered nesting habitat.

Figures

Figure 1. Abbott’s Booby Resident Range Distribution Map (Papasula abbotti, 2019).

Figure 2. Abbott’s Booby Breeding Range Distribution Map (Papasula abbotti, 2019).

Figure 3. Known Abbott’s Booby Nest Sites In Relation To The Distribution Of The Booby’s Rainforest Habitat (National Recovery Plan, 2004).

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