Seabird

Abstract

Prey resources in oligotrophic tropical marine environments are often scattered and unpredictable. Tracking studies of tropical seabirds can provide critical information about ocean habitat affinities, prey choice and the utilisation of surrounding areas, which can be useful for conservation managers. Foraging studies of Red-billed Tropicbird populations in the Caribbean are scarce but increasing. We sought to expand on this by tracking chick-rearing adults using GPS devices and subsequently linking these tracking data to remotely-sensed environmental variables. We related our spatial data to opportunistic sampling of regurgitates in a globally significant nesting colony on Saba, Caribbean Netherlands. Diet samples were dominated by flying fish (Exocoetidae; numerical frequency: 70.73%), but prey items from the squid family (Loliginidae; 9.76%) and the families of flying gurnards (Dactylopteridae; 2.44%) and the rayfinned fish (Carangidae; 2.44%) were also identified, although we were unable to identify 14.63% of samples due to digestion. An additional goal of our study was to compare the foraging ecology of Tropicbirds on Saba with those nesting on St. Eustatius, located circa 25 km south-east. As expected, Tropicbirds nesting on Saba exhibited diurnal foraging patterns, travelling a maximum distance from the colony of 553.7 km, with an average trip length of 117.2 ± 144.6 km (±SD). Adults foraged in shallower, cooler waters with higher chlorophyll a concentrations and higher Exocoetidae species richness compared to travelling points. Despite the proximity of Saba and St. Eustatius, this is contrary to what was found for Tropicbirds nesting on St. Eustatius, where adults foraged in deeper waters with a low Exocoetidae species richness. However, Tropicbirds from Saba and St. Eustatius did exhibit some similarities in their foraging behaviour; specifically, foraging adults traversed multiple exclusive economic zones and marine protected areas, reinforcing our recommendation for nature managers in the Caribbean to create a transboundary network in order to effectively protect and conserve this species.

Investigating the foraging patterns of tropical seabirds can provide important information about their ocean habitat affinities as well as prey choice. Foraging studies of Red-billed Tropicbird Phaethon aethereus populations in the Caribbean are lacking. We sought to rectify this by opportunistically sampling regurgitates at nest sites on the island of St. Eustatius, Lesser Antilles, and by linking the GPS tracks of foraging adults to remotely sensed environmental variables. Diet samples were dominated by Exocoetidae (59.5%) and Belonidae (14.9%), although we were unable to identify 25.5% of samples due to digestion. Tropicbirds nesting on St. Eustatius exhibited diurnal foraging patterns, foraged in deeper waters with higher chlorophyll concentration, and consumed fewer Exocoetidae species compared to travelling behaviour. The maximum distance travelled from the colony was 953.7 km, with an average trip length of 176.8 (± 249.8) km. The biologged birds crossed multiple exclusive economic zones and marine protected areas, and on that basis, we suggest that efforts to protect and conserve this species may require transboundary collaboration throughout the wider Caribbean.

Investigating the foraging patterns of tropical seabirds can provide important information about their ocean habitat affinities as well as prey choice. Foraging studies of Red-billed Tropicbird Phaethon aethereus populations in the Caribbean are lacking. We sought to rectify this by opportunistically sampling regurgitates at nest sites on the island of St. Eustatius, Lesser Antilles, and by linking the GPS tracks of foraging adults to remotely sensed environmental variables. Diet samples were dominated by Exocoetidae (59.5%) and Belonidae (14.9%), although we were unable to identify 25.5% of samples due to digestion. Tropicbirds nesting on St. Eustatius exhibited diurnal foraging patterns, foraged in deeper waters with higher chlorophyll concentration, and consumed fewer Exocoetidae species compared to travelling behaviour. The maximum distance travelled from the colony was 953.7 km, with an average trip length of 176.8 (± 249.8) km. The biologged birds crossed multiple exclusive economic zones and marine protected areas, and on that basis, we suggest that efforts to protect and conserve this species may require transboundary collaboration throughout the wider Caribbean.

Even though there are very many scattered seabird sighting records for the pelagic waters of the wider Caribbean Sea, only few studies bring these data together to generate a more comprehensive understanding of seabird use of the offshore areas of the region. The same is the case for the Dutch Caribbean EEZ which amounts to about 92 thousand km2 of the Caribbean Sea. As a consequence, information on seabird use of offshore waters has been identified as a key knowledge gap and research priority for both EEZ conservation and management purposes (Jongman et al. 2010, Meesters et al. 2010) and in support of a Bonaire-Curacao UNESCO World Heritage nomination that has been a Bonaire government ambition since 2003 (Debrot et al. 2017).  
 
In this project we followed up on these information needs by compiling many older but as-yet unpublished seabird records around the Dutch Caribbean islands, the eastern Caribbean as well as many poorly accessible seabird records for the waters off the coasts of Colombia and Venezuela. The most important additions of previously unavailable or new records for the eastern Caribbean were as follows: 1824 records by Poppe (1974), 627 by Halewijn (1972), 443 recent records by M. de Boer and J. Saulino (2014) all principally for the waters of the Dutch Caribbean, 547 records from Casler and Lira (1979) and Casler and Pirela (2004) for the northwestern sector of Venezuela and 249 records by Naranjo (1979) and Estela et al. (2004) for the Caribbean coast of Colombia. These were subsequently merged with several smaller and larger sources of seabird sighting records to yield a current total compilation of 150,372 sighting records with either exact or approximate position determinations. 
 
The database provides temporal and positional occurrence information for 65 nominate species and 13 larger familial or generic species groups in the Caribbean basin. As such, it provides a major new opportunity for the WUR to study and publish on various aspects of seabird distribution in the coming years. The potential topics include: 1) the community composition of the pelagic seabirds of the Caribbean in comparison with the community structure of other pelagic seabird communities, 2) how different habitat features (such as upwelling areas, proximity of nesting and/or roosting areas) are used by different species, 3) the identification of temporal trends in seabird species distribution and abundance, 4) identification of areas deserving conservation and management priority, either around seabird colonies or at the high seas. 

We present the first confirmed evidence of plastic ingestion by a Red-billed Tropicbird on the Caribbean Netherlands island of St. Eustatius, which supports a regionally important nesting population. With our observations, all species of tropicbird have now been documented ingesting marine plastic pollution.

Marine spatial planning(MSP) has become an important tool to balance the needs of commercial,economical and recreational users of the marine environment with the protection of marine biodiversity. BirdLife International advocate the designation of marine Important BirdAreas (IBAs) as a key tool to improve the protection and sustainable management of the oceans, including the designation of Marine Protected Areas, which can feed into MSP processes.This study presents the results of three years of seabird tracking from the UK Overseas Territory of Anguilla,where marine resources are currently relatively unexploited and MSP is in its infancy.The core foraging areas of 1326 foraging trips from 238 individuals, representing five species (brown booby Sula leucogaster, masked booby Sula dactylatra, sooty tern Onychoprionfuscatus, magnificent frigate bird Fregata magnificens and red-billed tropic bird Phaethon aethereus) breeding on three of Anguilla's off shore cays were used to calculate the hotspot foraging areas for each study species.These high activity areas were then compared with fishing activity within Anguilla's Exclusive Economic zone and to proposed coastal developments.Two marine IBAs were identified within Anguilla's waters: the first to be defined, using seabird tracking data,in the Caribbea nregion. Whilst the level of fishing activity and associated seabird by-catch is hard to quantify, the core foraging areas  f seabirds breeding in Anguilla were observed to overlap with areas known for high fishing activity. These findings highlight the need to work both nationally and across territorial boundaries to
implement appropriate marine spatial planning.

Destruction of nests and predation by introduced species are among the main factors responsible for seabird declines.The red-billed tropicbird (Phaethon aethereus) is a tropical, colonially nesting seabird whose distribution in Brazil is restricted to a small, isolated breeding colony located within Abrolhos National Park. This represents the southernmost population of the species in the western Atlantic, and is among the most southerly in its global distribution. Despite its isolation, the population on Abrolhos is threatened by egg predation by two invasive rat species: the house rat (Rattus rattus) and brown rat (Rattus norvegicus). In this study we conduct a population viability analysis of P. aethereus in Abrolhos to estimate the potential long term impacts of the rats. Our results indicate that egg and chick predation by rats has the potential to quickly drive the Abrolhos tropicbird population into serious decline. Reducing this threat may require the urgent implementation of a rat control program. 

Abstract: Invasive rats are some of the largest contributors to seabird extinction and endangerment world- wide. We conducted a meta-analysis of studies on seabird–rat interactions to examine which seabird phyloge- netic, morphological, behavioral, and life history characteristics affect their susceptibility to invasive rats and to identify which rat species have had the largest impact on seabird mortality. We examined 94 manuscripts that demonstrated rat effects on seabirds. All studies combined resulted in 115 independent rat–seabird in- teractions on 61 islands or island chains with 75 species of seabirds in 10 families affected. Seabirds in the family Hydrobatidae and other small, burrow-nesting seabirds were most affected by invasive rats. Laridae and other large, ground-nesting seabirds were the least vulnerable to rats. Of the 3 species of invasive rats, Rattus rattus had the largest mean impact on seabirds followed by R. norvegicus and R. exulans; nevertheless, these differences were not statistically significant. Our findings should help managers and conservation prac- titioners prioritize selection of islands for rat eradication based on seabird life history traits, develop testable hypotheses for seabird response to rat eradication, provide justification for rat eradication campaigns, and identify suitable levels of response and prevention measures to rat invasion. Assessment of the effects of rats on seabirds can be improved by data derived from additional experimental studies, with emphasis on understudied seabird families such as Sulidae, Phalacrocoracidae, Spheniscidae, Fregatidae, Pelecanoididae, Phaethontidae, and Diomedeidae and evaluation of rat impacts in tropical regions. 

Environmental Protection In the Caribbean (EPIC) carried out breeding seabird research in the Lesser Antilles between February and June 2009, to determine the abundance and distribution of breeding seabirds within the archipelago. The research spans two years, with the study continuing in January to July 2010. This allows each island to be surveyed both in the winter (February‐mid April) and summer (May‐ July) breeding seasons.

The basis for the project was the limited existing data on breeding seabird populations in the Lesser Antilles. Many islands had never been systematically surveyed, had incomplete data sets or only anecdotal accounts. Research was, therefore, undertaken in the following islands: St. Maarten, Saba, St. Eustatius, St. Kitts, Nevis, Montserrat, Antigua, Barbuda, St. Lucia, St. Vincent and the Grenadines, Grenada and the Grenadines. It is intended that breeding surveys will be completed in Sombrero, north of Anguilla in 2010 (they were not undertaken this year due to inclement weather). Similarly, it is planned that Dominica will be included in 2010. It was not surveyed in 2009 due to the perception that data was extant, which was later confirmed incorrect. Anguilla, St. Barthelemy, Guadeloupe, Marie‐Galante, Martinique and Barbados have complete seabird data and were not surveyed by the team. Existing data from these latter islands will be incorporated into the Atlas.

The research will form the Seabird Breeding Atlas of the Lesser Antilles. A hard copy will be given to all participating countries in the study area, generally to the government. The data will inform the Society for the Conservation and Study of Caribbean Birds (SCSCB) Waterbird Conservation Plan and will be available to the public on the web at the West Indies GIS and OBIS/SEAMAP. The study involved an ongoing literature review of breeding seabird records within existing papers, books and articles, as well as gathering information held in libraries and bird group archives. Anecdotal information from fishermen and other interest groups was also noted. This was particularly interesting in the case of the nocturnal Audubon’s Shearwater, when locations were suggested for historic colonies that were otherwise hard to locate within the time frame of the study. Information on egg poaching and other threats to seabirds was also forthcoming as well as anecdotal trends in seabird numbers.

The field work included collecting data on the number of breeding seabirds and threats to their populations on every island within the study area. Consistent methods were used and documented to allow repeat surveys in the future.

Outreach included presentations and meetings with governments and interest groups, education at schools, and media campaigns. A permit to undertake the non‐obtrusive research was obtained in every participating country. Katharine Lowrie (Project Manager), David Lowrie (Captain and Surveyor) and Megan Friesen (Research Assistant) undertook the research.

Abstract:

The UK has sovereignty over 16 Overseas Territories, which hold some of the world’s great seabird colonies and collectively support more endemic and globally threatened bird species than the whole of mainland Europe. Invasive alien mammalian predators have spread throughout most of the Territories, primarily since European expansion in the 16th century. Here we review and synthesize the scale of their impacts, historical and current, actions to reduce and reverse these impacts, and priorities for conservation. Mammalian predators have caused a catastrophic wave of extinctions and reductions in seabird colony size that mark the UKOTs as a major centre of global extinction. Mammal-induced declines of threatened endemics and seabird colonies continue, with four Critically Endangered endemics on Gough Island (Tristan da Cunha), St Helena and Montserrat directly threatened by invasive alien House Mice Mus musculus, Feral Cats Felis catus and rats Rattus spp. Action to reduce these threats and restore islands has been modest in comparison with other developed countries, although some notable successes have occurred and a large number of ambitious eradication and conservation plans are in preparation. Priority islands for conservation action against mammalian predators include Gough (which according to one published prioritization scheme is the highest-ranked island in the world for mammal eradication), St Helena and Montserrat, but also on Tris- tan da Cunha, Pitcairn and the Falkland Islands. Technical, financial and political will is required to push forward and fund the eradication of invasive mammalian predators on these islands, which would significantly reduce extinction risk for a number of globally threatened species.