a b s t r a c tMarine 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 Bird Areas (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 Onychoprion fuscatus, magnificent frigatebird Fregata magnificens and red-billed tropicbird Phaethon aethereus) breeding on three of Anguilla's offshore 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 Caribbean region. Whilst the level of fishing activity and associated seabird by-catch is hard to quantify, the core foraging areas of 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.

The Caribbean Island of Anguilla in the northeastern Lesser Antilles is home to one of the last populations of the Critically Endangered Lesser Antillean iguana Iguana delicatissima. This population is highly threatened primarily because of hybridisation with non-native Iguana iguana. This study assesses the degree of hybridisation between Anguilla's Iguana species firstly using morphological characteristics and then genetic analysis to validate the genetic integrity of morphologically identified I. delicatissima. We also examined the genetic diversity of Anguilla's I. delicatissima population, and that of a population on the nearby island of Îlet Fourchue, St Barthélemy. Forty-five iguanas were captured in Anguilla and 10 in St Barthélemy, and sequences from 3 nuclear and 1 mtDNA genes were obtained for each. Of the 45 iguanas captured in Anguilla, 22 were morphologically identified as I. delicatissima, 12 as I. iguana and the remainder were identified as hybrids. Morphological assignments were all confirmed by genetic analyses except for one I. iguana and one hybrid individual. These two individuals appeared likely to have originated following ancestral hybridisation events several generations ago. A significant paucity of genetic diversity was found within Anguillan and St Barthélemy I. delicatissima populations, with a single haplotype being identified for each of the three nuclear genes and the mtDNA sequence. This study highlights the urgency for immediate action to conserve Anguilla's remnant I. delicatissima population. Protection from hybridisation will require translocation to I. iguana-free offshore cays, with supplementary individuals being sourced from neighbouring islands to enhance the genetic diversity of the population.

SummarySeabird populations breeding in the UK Overseas Territories remain relatively understudied compared to UK seabird populations, despite their international importance. Here we present results from one of the first seabird tracking studies in the Caribbean region, of Brown Boobies Sula leucogaster breeding on the Important Bird Area (IBA) of Dog Island, Anguilla. Birds were tracked for 5–7 days during the chick-rearing period using GPS data loggers. We assess how representative the at-sea areas of use (utilisation distributions) identified from our sample of 16 birds are likely to be of those of the whole breeding colony, and examined the effect that grid cell size used in the ‘time-in-area’ analytical approach has on these predictions. We also assess the effectiveness of the BirdLife International’s seaward extension approach to marine IBA designation, where terrestrial IBAs are buffered a set distance using existing information on the foraging radii of the same or similar breeding species. Foraging trips were 125.3 ± 54.4 (SD) km long and lasted for 5.6 ± 1.95 hrs on average. Birds travelled into the waters of four neighbouring territories; Saint Martin, Saba, Saint Eustatius and Saint Barthelemy. Our models suggest that many more individuals would need to be tracked to fully identify important at-sea areas for this colony, although this depends on the scale that important areas are defined. Whilst a smaller grid cell size may be necessary for assessing fine-scale habitat use, a larger grid cell size may be more appropriate for marine spatial planning processes. Although the BirdLife Seaward extension approach using maximum foraging distance recorded from Brown Boobies at a Mexican colony predicted a smaller foraging area than that used by Dog Island birds this approach still incorporated at least 99% of their 50% UD, 98% of their 75% UD and 86% of the 95% UD.

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The archetypal foraging behaviour of tropical seabirds is generally accepted to differ from that of their temperate and polar breeding counterparts, with the former exhibiting less predictable foraging behaviour associated with the less predictable prey of the tropical marine environment. Similarly, temperate and polar species have predictable, annual breeding seasons, enabling them to profit during periods of the year when prey availability is highest, while tropical seabird species exhibit considerable variability in their breeding strategies. Until now, the reasons for such variation in breeding strategies between tropical seabirds are yet to be investigated. We hypothesise that while some tropical species breed asynchronously in response to unpredictable fluctuations in prey availability, others adopt a seasonal breeding strategy for the same reasons that temperate and polar species do. Consequently, the predictability of seabird foraging behaviour in the tropics may be related to breeding strategy, with populations that breed seasonally exhibiting more predictable foraging behaviour than those that breed aseasonally. To test these predictions, we used GPS tracking to examine the foraging behaviour of two closely related tropical seabird species that colonise the same island yet exhibit markedly different breeding strategies: the asynchronously breeding brown booby Sula leucogaster and the seasonal breeding masked booby Sula dactylatra. We obtained tracks for 251 birds over five years. We found that brown boobies forage less predictably than masked boobies, indicated by larger core foraging areas, lower levels of foraging area overlap between individuals and exhibit more variability between breeding periods. Our results challenge the view that the foraging behaviour of tropical seabirds is always less predictable than that of seabirds breeding in temperate and polar regions and highlight the considerable variability in the breeding and foraging strategies adopted by tropical seabirds which demand further exploration.