Wintering grounds under protection: population stability and conservation of migrating waders at Europa Island, western Indian Ocean

Geographical variation in measurements and colouration among populations and subspecies of White‐tailed Tropicbirds Phaethon lepturus, including birds from Europa Island (southern Mozambique Channel] was examined worldwide. Two groups were distinguished: the ‘large subspecies’(lepturus and fulvus from the Indian Ocean, catesbyi from the western Atlantic Ocean) and the ‘small subspecies’(ascensionis from the central and eastern Atlantic Ocean, dorotheae from the Pacific Ocean, and the birds from Europa Island). No clinal variation was found in the Indian Ocean, the birds from Europa Island being the only ‘small’ ones. This population also had a high frequency of golden morphs, a feature that does not exist elsewhere in the western Indian Ocean. These results indicate that Europa's population is isolated from all nearby colonies in the Indian Ocean, and does not belong to any of the two previously known subspecies of the area. It also differs from the birds of the two small subspecies by the frequency of the colour morphs and the distribution. Consequently, we propose to treat this population as a previously undescribed subspecies, endemic to Europa Island, for which we propose the name Phaethon lepturus europae. Geographical isolation of Europa Island and oceanic conditions in the Mozambique Channel are discussed to explain the isolation of this population.

Tropical seabirds have evolved a wide range of breeding regimes to fit with their local environment. The western Indian Ocean shows various oceanic situations, providing opportunities to link variations in breeding phenology with variations of the environment. The breeding seasons of seabirds at Europa Island (Mozambique Channel, western Indian Ocean) are analysed. Three oceanic, tuna‐associated species (the sooty tern Sterna fuscata, the red‐footed booby Sula sula, and Audubon's shearwater Puffinus lherminieri) breed during austral winter (June–October), whereas the red‐tailed tropicbird Phaethon rubricauda breeds during austral summer (November–April). During winter, sea‐surface temperatures are the lowest, subtropical waters are the closest to the island, and long‐line catches of tunas are important. Thermal fronts occur during winter, in relation to the northward shift of subtropical waters. This is known to be favourable to tunas, and I suggest that the winter breeding of sooty terns, red‐footed boobies and Audubon's shearwaters is because of an increase in the abundance of tunas. Geographic variations in the breeding phenology of sooty terns in the western Indian Ocean largely support the hypothesis that sooty terns take advantage of cool subtropical waters, when those waters are within their foraging range. The red‐tailed tropicbird is a solitary forager, not associated with tunas. During the chick‐rearing period, 40% of the mass of food brought to the chicks consists of dolphin‐fishes Coryphaena spp. Those warm water, surface dwelling fishes are known to migrate in relation to sea‐surface temperatures. Seasonal changes in the occurrence or vulnerability of dolphin‐fish in the Mozambique Channel may have favoured a summer breeding regime in red‐tailed tropicbirds at Europa Island. Further studies of the marine life of seabirds are needed to test these hypotheses and to learn more about the foraging ecology of tropical seabirds.

The pantropical red-footed booby Sula sula is one of the most polymorphic seabirds. In the Indian Ocean most extant colonies hold white morph adults except on Europa Island (southern Mozambique Channel), where adults are of the white-tailed brown morph and on Tromelin Island (western Indian Ocean), where one-third of the birds are of the white-tailed brown morph and two-thirds are of the white morph. On Tromelin, the morph ratio has remained constant over the last 40 years. An extinct colony (Glorieuses Islands, northern Mozambique Channel) once supported a white-tailed brown morph population. These results suggest that the colonies of the western Indian ocean do not constitute one great gene pool where exchanges occur, but are isolated at various degree from each other. Particularly, the population of Europa is the only current population of the Indian Ocean constituted almost entirely of white-tailed brown morph, suggesting that it is isolated from other nearby colonies. Possible causes of isolation are discussed in the light of oceanic features of the Mozambique Channel. Although further studies are needed to understand the adaptive significance of plumage coloration in red-footed boobies, I suggest that white-tailed brown morph at Europa may act as a defensive camouflage against kleptoparasitism by great frigatebirds Fregata minor and brown skuas Catharacta antarctica.

The pantropical red‐footed booby Sula sula is one of the most polymorphic seabirds. In the Indian Ocean most extant colonies hold white morph adults except on Europa Island (southern Mozambique Channel), where adults are of the white‐tailed brown morph and on Tromelin Island (western Indian Ocean), where one‐third of the birds are of the white‐tailed brown morph and two‐thirds are of the white morph. On Tromelin, the morph ratio has remained constant over the last 40 years. An extinct colony (Glorieuses Islands, northern Mozambique Channel) once supported a white‐tailed brown morph population. These results suggest that the colonies of the western Indian ocean do not constitute one great gene pool where exchanges occur, but are isolated at various degree from each other. Particularly, the population of Europa is the only current population of the Indian Ocean constituted almost entirely of white‐tailed brown morph, suggesting that it is isolated from other nearby colonies. Possible causes of isolation are discussed in the light of oceanic features of the Mozambique Channel. Although further studies are needed to understand the adaptive significance of plumage coloration in red‐footed boobies, I suggest that white‐tailed brown morph at Europa may act as a defensive camouflage against kleptoparasitism by great frigatebirds Fregata minor and brown skuas Catharacta antarctica.

The western Indian Ocean holds five subspecies of the pantropical Audubon's Shearwater (Puffinus lherminieri), but none was known to breed in the Mozambique Channel. Here, I describe a newly discovered population of Audubon's Shearwaters on Europa Island, southern Mozambique Channel. Comparison of geographic variation of morphometric characters showed that the birds of this population belong to the P. l. bailloni subspecies, previously thought to be endemic to the Mascarenes Islands. They were distinct from the three subspecies of the Comoro, Aldabra, and Seychelles group, suggesting that few successful exchanges of individuals occur between north of the Mozambique Channel and Europa Island. This biogeographic pattern is similar to that of two phylogenetically independent pelagic species from Europa Island. This suggests that a common cause related to geographic isolation and oceanic conditions in the Mozambique Channel may explain the apparent isolation of these three seabird populations from Europa Island.

The western Indian Ocean holds five subspecies of the pantropical Audubon's Shearwater (Puffinus lherminieri), but none was known to breed in the Mozambique Channel. Here, I describe a newly discovered population of Audubon's Shearwaters on Europa Island, southern Mozambique Channel. Comparison of geographic variation of morphometric characters showed that the birds of this population belong to the P. l. bailloni subspecies, previously thought to be endemic to the Mascarenes Islands. They were distinct from the three subspecies of the Comoro, Aldabra, and Seychelles group, suggesting that few successful exchanges of individuals occur between north of the Mozambique Channel and Europa Island. This biogeographic pattern is similar to that of two phylogenetically independent pelagic species from Europa Island. This suggests that a common cause related to geographic isolation and oceanic conditions in the Mozambique Channel may explain the apparent isolation of these three seabird populations from Europa Island.

Sharks have declined worldwide and remote sanctuaries are becoming crucial for shark conservation. The southwest Indian Ocean is a hotspot of both terrestrial and marine biodiversity mostly impacted by anthropogenic damage. Sharks were observed during surveys performed from April to June 2013 in the virtually pristine coral reefs around Europa Island, a remote Marine Protected Area located in the southern Mozambique Channel. Observation events comprised 67 1-hour scientific dives between 5 – 35m depth and 7 snorkeling inspections, as well as 4 dinghy-based observations in the shallow lagoon. In a period of 24 days, 475 sharks were tallied. Carcharhinus galapagensis was most encountered and contributed 20% of the abundance during diving, followed by C. albimarginatus (10%). Both species were more abundant between 11-14h, and on the exposed sides of the island. Numbers of Sphyrna lewini were highest with 370 individuals windward and leeward, mostly schooling. S. lewini aggregations in the area are hypothesized to be attracted to the seamount archipelago offering favorable conditions for deep incursions and of which Europa Island forms part. C. amblyrhynchos, Galeocerdo cuvier and S. mokarran were uncommon, while there was an additional observation of Rhincodon typus. The lagoon of Europa was a nursery ground for C. melanopterus where it was the only species present. A total of 8 species was recorded, contributing to the shark diversity of 15 species reported from Europa since 1952 in the scientific and gray literature. Overall, with the occurrence of several species of apex predators in addition to that of R. typus, large schools of S. lewini, fair numbers of reef sharks and a nursery of C. melanopterus, Europa’s sharks constitute a significant reservoir of biodiversity, which contributes to preserve the functioning of the ecosystem. Our observations highlight the relevance of Europa Island for shark conservation and the need for shark-targeted management in the EEZ of both Europa and Bassas da India.

The western Indian Ocean holds five subspecies of the pantropical Audubon's Shearwater (Puffinus lherminieri), but none was known to breed in the Mozambique Channel. Here, I describe a newly discovered population of Audubon's Shearwaters on Europa Island, southern Mozambique Channel. Comparison of geographic variation of morphometric characters showed that the birds of this population belong to the P. l. bailloni subspecies, previously thought to be endemic to the Mascarenes Islands. They were distinct from the three subspecies of the Comoro, Aldabra, and Seychelles group, suggesting that few successful exchanges of individuals occur between north of the Mozambique Channel and Europa Island. This biogeographic pattern is similar to that of two phylogenetically independent pelagic species from Europa Island. This suggests that a common cause related to geographic isolation and oceanic conditions in the Mozambique Channel may explain the apparent isolation of these three seabird populations from Europa Island.

We studied the relationships between the habitat use of migratory shorebirds and the spatial distributions of the Southwestern Atlantic Fiddler Crab Uca uruguayensis, polychaetes, sediment characteristics and tidal levels in the Río de La Plata estuary, Argentina, where U. uruguayensis is one of the most important intertidal species. Crabs have a well‐defined patchy distribution that is segregated spatially from that of polychaetes. Crab density on the surface varied across the tidal cycle, reaching maximum values during low tide. Polychaete density decreased with depth but showed no change through the tidal cycle; however, given that sediment penetrability did change during the same period, their availability to probing shorebirds is expected to change. Habitat use by shorebirds followed the spatial distribution of prey; shorebirds that foraged on polychaetes (White‐rumped Sandpiper Calidris fuscicollis, Two‐banded Plover Charadrius falklandicus and Hudsonian Godwit Limosa haemastica) focused their attention on the areas with the highest densities of polychaetes, whereas species that preyed mostly on crabs (Ruddy Turnstone Arenaria interpres, Whimbrel Numenius phaeopus and Grey Plover Pluvialis squatarola) predominantly used areas with crabs. This segregation occurred particularly during low tide, a period in which polychaetes became fully available. Results show that the spatial and temporal heterogeneity of mudflats in relation to the types and availability of prey has a strong effect on shorebird habitat use.

The tidal flats of the Bragantinian Peninsula in the tropical part of Brazil harbour wintering and migratory nearctic shorebirds in very high densities, whereas the benthic food supply is very low. In 2001 and 2002 a study was conducted on the habitat choice and distribution of shorebirds to investigate the formation of niches and the spatial distribution under the constraint of a limited food supply. We showed that shorebird densities were not correlated with a range of abiotic variables or with prey density within sites, but that between sites birds tended to select sites with peak prey densities. Two foraging guilds were differentiated: Whimbrel Numenius phaeopus, Willet Tringa semipalmata and Short-billed Dowitcher Limnodromus griseus preferred to forage in the water or on wet sand at the water's edge; while Red Knot Calidris canutus, Grey Plover Pluvialis squatarola, Ruddy Turnstone Arenaria interpres, Semipalmated Sandpiper Calidris pusilla and Semipalmated Plover Charadrius semipalmatus, were found predominantly on dry substrate. Although the birds showed species-specific preferences for characteristics defining microhabitats, niches were broadly overlapping. The results of our study suggest that, in case of a very low food supply, individuals might not be able to react to competition by niche segregation but might be forced to feed in a broad range of available niches.

The soft coral fauna (Octocorallia: Alcyonacea) on reefs around Europa Island (Western Indian Ocean) were surveyed in 2016. The species richness was rather low for a protected, relatively pristine environment in the region. While certain ‘fugitive’ alcyonacean species were noticeably abundant, other soft corals were rare or absent. Since Europa Island is remote and isolated, connectivity was thus investigated with other alcyonacean communities in the Mozambique Channel by particle transport modelling. This revealed that, while the north-west coast of Madagascar appears well-connected with the northern Mozambique coast, the most likely source of soft coral recruits at Europa Island would be the Tulear region further south in Madagascar.

Testes from 47 adult (4-20 years) stallions obtained in November-January (non-breeding season) and 41 adult stallions obtained in May-July (breeding season) were perfused with glutaraldehyde, placed in osmium and embedded in Epon 812. Percentage Leydig cell cytoplasm or nuclei in the testis was determined by point counting of 0.5 micron sections under bright-field microscopy. Testes from 6 randomly selected horses per season were processed for electron microscopy. The volume (ml) of SER/testis was calculated from the % SER in the cytoplasm % Leydig cell cytoplasm, and parenchymal volume. Number of Leydig cells was calculated from the % nuclei, parenchymal volume, histological correction factor, and volume of single nucleus. Intratesticular testosterone content was determined from the contralateral testis by radioimmunoassay. The volume of SER/g and testosterone/g tended to be higher in the breeding than non-breeding season. Leydig cell number/g, volume of SER/testis, testosterone/testis, and Leydig cell number/testis were significantly greater in the breeding than in the non-breeding season. Volume of SER/testis and testosterone/testis were related significantly to the cell number/testis, and SER/testis was related (P less than 0.05) to testosterone/testis. These results emphasize the importance of seasonal changes in the number of Leydig cells on the amount of SER available to produce testosterone and on testosterone content/testis in the stallion.

Diurnal dwarf geckos of the genus Lygodactylus are distributed in tropical and subtropical regions and live in highly diverse habitats. The genus currently comprises 79 species and several candidates for new species or subspecies. Most of these taxa occur in Sub-Saharan Africa and Madagascar, with only two described species in South America. Although the main center of diversity of Lygodactylus currently is Africa, the genus probably has a Malagasy origin, followed by two or three independent transoceanic dispersal events between Madagascar and Africa and one trans-Atlantic dispersal from Africa to South America. A few species colonised islands in the Western Indian Ocean belonging to the Zanzibar Archipelago and to the Îles Éparses. Here we examined L. grotei pakenhami from Pemba Island, L. insularis from Juan de Nova, and L. verticillatus from Europa Island to clarify their taxonomic status and their origin. Concerning L. grotei pakenhami and L. insularis, preceding studies pointed to a relation to species of the African L. capensis group. In contrast, L. verticillatus on Europa Island is considered to be conspecific with Malagasy populations. Therefore, we conducted a phylogenetic study of the African L. capensis group and the Malagasy L. verticillatus group, and examined color pattern, selected morphological characters and two mitochondrial markers (ND2 for African and 16S rRNA for Malagasy Lygodactylus). Lygodactylus grotei pakenhami from Pemba and L. grotei from mainland Africa cannot be distinguished by their scalation, but their reciprocal monophyly suggested by mitochondrial DNA, conspicuously different coloration (both in adults and hatchlings) and their high genetic distances (16.3% in ND2) support the hypothesis that these taxa represent two distinct species. Consequently, we elevate L. grotei pakenhami to species level, as Lygodactylus pakenhami Loveridge, 1941. Lygodactylus pakenhami is endemic to Pemba Island which was possibly separated from the African mainland during the late Miocene or Early Pliocene (6 million years ago). The simplest explanation for the existence of L. pakenhami on Pemba is vicariance. A recent, human-mediated transportation is excluded, as the molecular data clearly indicate a longer period of isolation. Lygodactylus insularis has been supposed to be related to the taxa 'capensis' or 'grotei'. However, it is impossible to discern the relationship of L. insularis, L. capensis and L. grotei by means of scalation or coloration alone. Our molecular phylogenetic analyses reveal that L. insularis is embedded within the L. capensis group, clearly indicating its African origin. The single gene (ND2) as well as the multigene analyses fully support a closer common origin of L. insularis and L. capensis than of L. insularis and L. grotei. However, the position of L. insularis within the clade formed by L. insularis, L. nyaneka, L. capensis sensu stricto and six L. aff. capensis groups is not clearly resolved. Lygodactylus insularis is endemic on Juan de Nova Island, an old low elevation atoll. That all L. insularis mitochondrial sequences are very similar to each other and together form a monophyletic lineage is in agreement with the hypothesis of a single dispersal event to the island. For the L. verticillatus population from Europa Island our mitochondrial data suggest close relationships to conspecific samples from the coastal regions of south-western Madagascar. As we found no relevant morphological or genetic differences between the insular and the Malagasy populations of L. verticillatus, and no remarkable genetic variation within the monophyletic lineage on Europa, we suggest a single, very recent dispersal event, perhaps human-mediated. Although the genus Lygodactylus colonised Africa, islands in the Gulf of Guinea, South America and some islands in the Western Indian Ocean, it seems-compared to other lizard genera-to be only moderately successful in transoceanic long-distance dispersal.

Three species of the pagurid hermit crab genus Pagurixus Melin, 1939, are reported from Europa Island in the MozambiqueStrait, western Indian Ocean: P. haigae Komai & Osawa, 2007, P. annulus n. sp., and P. europa n. sp. Pagurixushaigae is recorded from the western Indian Ocean for the first time. Pagurixus annulus n. sp. and P. europa n. sp. arereferred to the P. boninensis (Melin, 1939) species group and P. anceps (Forest, 1954) group, respectively. Diagnosticcharacters of these two new species are discussed.

A census was carried out using the method of transects along stretches of coast of the Province of Trapani in order to estimate the wintering population of Common Sandpiper and Ruddy Turnstone. Although the International Waterbird Census (IWC) provides accurate estimation of wintering waders in Italy, the number of wintering individuals of Common Sandpiper Actitis hypoleucos and Ruddy Turnstone Arenaria interpres are strongly underestimated. The reason for this underestimation lies in the type of habitat they are used to populate along with the solitary life habits of the Common Sandpiper. To address this issue, we inspected 46.9 km of coastline where we recorded to 92 Ruddy Turnstones and 56 Common Sandpipers. For both species, the sites (coast) where bird-sightings occurred were marked with georeferenced data and classified as harbour area, sandy, rocky (including vermetid reefs) and posidonia banquettes. For each species, the IKA (Index of Abundance per Kilometer) was calculated, both global index and relative to each type of coast. As for the Common Sandpiper we observed 87 individuals, between transects and spot observations in the province of Trapani, which is the 22% of the whole wintering population estimated in Italy. Notably, even greater is the importance of our observations of the Ruddy Turnstone, which accounting for up to 154 individuals corresponds to the 71% of the whole Italian wintering population. Projection of these data to the entire Italian coast allows estimating a wintering population in Italy much larger than that reported so far, especially for the Common Sandpiper, which uses not only the sea cost but also inland wetlands and rivers as suitable wintering habitats for wintering.