THE PELAGIC DISTRIBUTION OF SEA-BIRDS IN THE WESTERN INDIAN OCEAN

The present paper summarises observations made during the International Indian Ocean Expedition on board the R.R.S.' Discovery, from August to November 1963 and from February to September 1964 in the Indian Ocean north of 20° S and west of 70° E. In 1963 work was carried out in the Somali Basin. In 1964 a series of transects were made over the ocean, the main purpose of which was to investigate the system of equatorial currents and the changes in the sea associated with the onset of the Southwest Monsoon in May. The Tropical Indian Ocean is briefly described. Except for local concentrations, the surface layers are poor in nutrient salts and plankton. There is a seasonal reversal of winds and surface currents in the Arabian Sea, but seasonal changes become less marked further south. Previous ornithological observations in the western Indian Ocean are mostly confined to the Arabian Sea or to the island groups. Thus, existing information on the pelagic range of pantropical species is incomplete. Observations made on each transect across the Indian Ocean in 1964 are summarised and compared with oceanographic data collected at the same time. General conclusions are not possible on the basis of so little information, though there appeared to be some relationship between the distribution of certain species and wind or current belts. The only marked discontinuity recorded was a concentration of Puffinus pacificus and Gygis alba at the northern edge of the Equatorial Counter-current at 58° E in March. Observations made on transects that were repeated before and after the onset of the Southwest Monsoon suggested that Sterna fuscata concentrates in the equatorial region as the monsoon develops. In general, both plankton and sea-birds were more abundant at 58° E than at 67¹/₄° E. An analysis of the presence or absence of sea-birds during each observation period, which lasted an average of one hour, established the difference between pelagic species and those largely restricted to within 50 miles of their breeding stations. There was no evidence of any correlation with zooplankton abundance, though birds of all species taken together were commonest where flying-fish were most abundant and S. fuscata appeared to be commonest in cool-water areas with strong winds, i.e. the Trade-wind belts. It was not possible to sample the food organisms of sea-birds quantitatively. Sea-bird observations in the Indian Ocean more than 200 miles from the continental coasts are summarized and compared with previous observations. The little information collected in the Indian Ocean agrees with previous work in the Pacific Ocean, where sea-birds are commonest in areas of convergence, and not where local upwelling and an associated concentration of plankton occur, such as on the equator. This may be due to the fact that populations of organisms on which sea-birds feed develop or concentrate a considerable time after upwelling of nutrient-rich water occurs. Since few sea-birds were seen feeding, it seems likely that available food is scarce and that much time is required to locate areas where it is abundant. Finally, evidence is presented to indicate how some sea-bird species may avoid or reduce competition by feeding at different distances offshore, or in different geographical areas.     

SEA-BIRDS AT LAGOS AND IN THE GULF OF GUINEA

Regular observations of sea-birds were made in the vicinity of Lagos, southwest Nigeria, between October 1967 and June 1971. Records in the Gulf of Guinea were obtained in April 1969 and, together with others from Ghana and Sierra Leone, were used to complement this study. While few large populations of sea-birds are supported, the diversity of species occurring at Lagos and over offshore deep water was great. The occurrence of nine species of sea-bird new to Nigeria was established or confirmed; most of these were also new to West Africa southeast of Gambia. Details are given of fluctuations in numbers these and a further 16 species.
All coastal habitats at Lagos supported a large population of immature Black Terns, and groups of immatures made up a high proportion of observations of other Palaearctic terns and of Royal Terns, which breed only in northwest Africa. In contrast, the Lesser Black-backed Gulls and Damara Terns reaching Lagos (from breeding grounds almost two continents apart) were mainly adults; both these species are amongst those showing a current increase in numbers. A pronounced spring passage was observed among species including Royal and Sandwich Terns, but adult movements in autumn were not elucidated. The occurrence of the European race of the Little Tern in southwest Nigeria was confirmed, it is at least a regular spring migrant. The frequency of vagrants in January and February was linked to local climate as much to general distribution. Brief comment is also given on immature plumages, and the growing exploitation and pollution of coastal waters.     

SEABIRDS OF THE SENEGAL UPWELLING AND ADJACENT WATERS

Seabird distributions were observed off Senegal during the upwelling season there, in February-March 1976, and are interpreted against an oceanographic background. Gannets Sula bassana , Pomarine Skuas Stercorarius pomarinus , Great Skuas Catharacta skua , Lesser Black-backed Gulls Larus fuscus , Black-headed Gulls L. ridibundus , Sandwich Terns Sterna sandvicensis and Royal Terns S. maxima were the dominant species on the shelf and slope adjacent to the inshore upwelling zone. Grey Phalaropes Phalaropus fulicarius were the only seabirds associated with an oceanic 'front' farther offshore; it is suggested that this and similar boundary zones are important feeding areas during the pelagic phase of this species' annual cycle.
Leach's Storm-Petrels Oceanodroma leucorhoa were seen east to 20W, but the predominant storm-petrel of the waters between 23W and the continental slope was the Madeiran O. castro. It is suggested that the hatching period of Madeiran Storm-Petrels on the Cape Verde Islands is timed to take advantage of the arrival there of young fish in the surface waters, spawned off the African coast and drifted offshore. However Madeiran Storm-Petrels make no direct use of the coastal upwelling; nor do Little Shearwaters Puffinus assimilis or White-faced Storm-Petrels Pelagodroma marina , the other winter-breeding Cape Verdes seabirds, which probably feed close to the Islands.
The Senegal upwelling is underexploited by seabirds, in contrast to comparable upwelling systems elsewhere. It is suggested that this is due to the seasonal timing of the upwelling, the scarcity of secure nest-sites for breeding seabirds, and the competing attractions of the Benguela upwelling in the South Atlantic.     

THE BREEDING SEASONS OF AFRICAN BIRDS—2. SEA BIRDS.

1. All the available data, largely unpublished, are assembled for sea-birds breeding in African waters, about 36° N.-36° S.
2. An ill-defined breeding season by any species at any station is exceptional.
3. North of the Equator practically all sea-birds breed in spring or summer.
4. South of the Equator there is much more variation. Round the Cape there is a good deal of mid-winter breeding, mainly in stations affected by the warm Agulhas current.
5. On the east coast most of the breeding takes place in the period June–August from the Gulf of Suez (27° N.) to the mouth of the Zambesi (19° S.) and beyond, i.e. in the hottest months north of the Equator and the coolest months south of it.     

FIRST FOSSIL EVIDENCE FOR THE PRIMITIVE ANGIOSPERM FAMILY LACTORIDACEAE

Pollen of the primitive angiosperm family Lactoridaceae has been recovered from Turonian-Campanian (Upper Cretaceous) sediments from eleven boreholes off the southwest coast of southern Africa. This is the first report of the Lactoridaceae in the fossil record. The one extant species of the Lactoridaceae is confined to the Juan Fernandez Islands located off the coast of Chile. The occurrence of lactoridaceous pollen in Cretaceous deposits of southern Africa suggest that this primitive angiosperm family may have been more widespread in the Southern hemisphere during the Cretaceous.     

SEA-BIRD OBSERVATIONS OFF SOMALIA

The oceanography of the coastal waters of eastern Somalia was investigated by R.R.S. ‘Discovery’ during August and September 1964. The oceanographic findings are briefly described. Although upwelling was in progress north of 8^oN, plankton, sea-birds and other signs of a high rate of organic production were notably scarce. Previous knowledge of the marine ornithology of the Somali coast is poor and some unpublished notes ot ine late M. E. W. North are given in full. In 1964 both the warm Somali current and the upwelling area between Ras Mabber and Cape Guardafui supported few sea-birds, though they were largely different species. The only area with abundant sea-birds was at the boundary between the cool upwelled water and the warm water spreading from the Gulf of Aden. It is suggested that the former may sink before the final stages of the ecological succession are reached, so that food for sea-birds is scarce. Summaries of the distributions of each species are given and these are compared with previous observations.     

THE SEA-BIRDS OF GOUGH ISLAND

Between November 1955 and May 1956 continuous observations were made on the sea-birds of Gough Island. These have been augmented by further occasional observations during seven subsequent years, and are compared with all previous published records for the island.
A check-list of 30 species of sea-birds has been compiled and substantiated, as far as possible, by a series of skins of 20 species.
Nearly 900 sea-birds cf 20 species were caught and measured, considerably more than at any previous time there; in the case of eight species, these are analysed in detail and some are compared with those from other populations.
The relative status of each species was estimated, together with total breeding populations where possible. In same cases the distribution of nests was mapped.
A detailed sound and photographic record, of 14 and 16 species respectively, was made.
Numbers of Wandering Albatrosses Diomedea exulans dabbenena and skuas Catharacta skua hamiltoni were ringed and colour-marked respectively to enable a more detailed study to be made of them.
General observations were made on the nesting seasons, breeding behaviour and moult of various species which are treated systematically.     

Thermocline Regulated Seasonal Evolution of Surface Chlorophyll in the Gulf of Aden

The Gulf of Aden, although subject to seasonally reversing monsoonal winds, has been previously reported as an oligotrophic basin during summer, with elevated chlorophyll concentrations only occurring during winter due to convective mixing. However, the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data reveal that the Gulf of Aden also exhibits a prominent summer chlorophyll bloom and sustains elevated chlorophyll concentrations throughout the fall, and is a biophysical province distinct from the adjacent Arabian Sea. Climatological hydrographic data suggest that the thermocline, hence the nutricline, in the entire gulf is markedly shoaled by the southwest monsoon during summer and fall. Under this condition, cyclonic eddies in the gulf can effectively pump deep nutrients to the surface layer and lead to the chlorophyll bloom in late summer, and, after the transition to the northeast monsoon in fall, coastal upwelling driven by the northeasterly winds produces a pronounced increase in surface chlorophyll concentrations along the Somali coast.     

Zoogeography of the coral reef fishes of the Socotra Archipelago

Fish communities and habitats were studied at the Socotra archipelago (Gulf of Aden, ≈12°N 54°E). Extensive and unexpected hermatypic coral communities were recorded, at the centre of a 2200 km gap in knowledge of species and habitat distributions which coincides with a change from a western Indian Ocean coral reef fauna to an Arabian one. The fish assemblage associated with the Socotra archipelago corals is predominantly south Arabian. An east African influence, minimal on the mainland coasts of Arabia, is more evident here, and results in previously unrecorded sympatry between Arabian endemic species and their Indian Ocean sister taxa. A study of distributions of Chaetodontidae (butterflyfishes) in the north-western Indian Ocean reveals a number of distinct patterns, with a trend for species replacement along a track from the northern Red Sea to the Indian Ocean. A major feature of the reef fish zoogeography of the region is found to be a distinct south Arabian area, characterized by a 'pseudo-high latitude effect' which results from seasonal cold water upwelling along the Arabian sea coasts of Yemen and Oman and the Indian Ocean coast of Somalia. This south Arabian feature is consistent across a wide range of fish families. It is most pronounced in Oman and Yemen, and although it is the dominant influence at Socotra it is slightly 'diluted' here by the east African influence. The south Arabian area wholly or partly accounts for most of the major marine zoogeographic features around Arabia, and is the principal feature fragmenting Arabian coastal fish assemblages, and separating them from those of the wider Indo-west Pacific.     

Phytogeography of upwelling areas in the Arabian Sea

Aim The identification of the marine plant communities of two islands from different upwelling areas of the Arabian Sea, with a similar diversity in biotopes. A comparison of the species composition of these macroalgal communities and their biogeographical affinities within the Indian Ocean should give insight into the biogeographical position of the Arabian Sea within the larger Indian Ocean. The incorporation of environmental parameters in the analysis is instructive in understanding their importance in shaping the diverse marine assemblages of the Arabian Sea. Location Arabian Sea: (1) the Socotra Archipelago (Yemen; 12.47° N, 53.87° E) in the Somali upwelling area, (2) Masirah Island (Oman; 20.42° N, 58.79° E) in the upwelling area of the southern Arabian Peninsula. Methods The marine flora of different biotopes around both islands were examined by means of qualitative assessments. Ordination analysis [detrended correspondence analysis (DCA)] was used to identify the different plant communities and to correlate these with environmental parameters. The species composition of the identified communities were compared (tripartite similarity index) and their biogeographical affinity with nations bordering the Indian Ocean was determined. Indicator species analyses were performed to identify the characteristic species of the different plant communities and their biotopes. Results The DCA analysis shows a clustering of sites (plant communities) corresponding with their geographical position, linked in turn to the prevailing environmental conditions of the different coastal areas. The combined interpretation of the ordination, similarity and biogeographical analyses results in the aggregation of similar plant communities of both upwelling areas into four biotopes. Main conclusions The north coast communities of Socotra and the west coast communities of Masirah can be grouped into three biotopes related to the degree of exposure (to upwelling) and sedimentation. These biotopes are typified by indicator species, characteristic for specific substrata, and have a high biogeographical affinity with the East African coast. The plant communities of Socotra's south coast and Masirah's east coast constitute a fourth biotope, being diverse and species rich, typified by a large proportion of red macroalgae including the characteristic species of the unique Arabian Sea flora. This biotope has a pronounced biogeographical affinity with distant regions (disjunctly distributed taxa) as South Africa's East Coast and Western Australia. Within the different biotopes, the communities of Masirah are more divergent from an East African flora in comparison to Socotra, the latter being a stepping stone between the East African and Arabian Sea flora.     

NOTES ON THE BIRDS OF EASTER ISLAND

Information on the occurrence and breeding status of sea-birds at Easter Island has long been scanty and incomplete. In order to obtain accurate information and in particular to investigate reports of a supposed breeding site of a "brown-plumaged petrel", we spent three weeks on the island, including 12 days camping out on the uninhabited, waterless islet of Motu-Nui.
The petrel proved to be the Christmas Island Shearwater Puffinus nativitatis , whose breeding range is thus extended by nearly 2,000 miles. Ten other species of sea-birds were definitely identified and specimens, photographs and breeding records were obtained for most of them. It is shown that the bird species frequenting Easter Island are, like the human inhabitants, predominantly of Polynesian origin—in fact the American continents are not represented at all.
The paper opens with a brief outline of present-day conditions on the main island, and concludes with an account of the "bird-cult" rituals which are known to have been a feature of life in Easter Island for centuries.     

Breeding seasons of sea-birds in the Galapagos Islands

The sea-birds breeding in the Galapagos Islands show a diversity of breeding cycles. Some species have rigidly fixed annual breeding while others breed throughout the year but have peaks of breeding at less than annual intervals. The eight species which have non-annual breeding are probably breeding as often as possible with the interval between the end of a breeding attempt and the start of the next being the time needed to moult the wing and tail feathers. Only one species is definitely known to breed and moult at the same time.
Although there are well marked seasonal fluctuations in the sea temperature, regular sampling failed to demonstrate any regular fluctuations in the surface plankton. The available evidence suggests that food for some sea-birds is erratic and unpredictable. Some non-annual breeding species have their breeding synchronized by severe food shortages which delay breeding, presumably because females cannot find enough food to form eggs, until conditions improve.
Timing of the breeding season in annual breeders is less easily explained but some species may be feeding well away from the islands in areas where there is a regular fluctuation in the food supply. Most of the annual breeders have prolonged breeding seasons and in two species breeding is out of phase on different islands. Perhaps species are influenced by some weak annual variation in food supply which makes it disadvantageous to breed in a few months of the year.     

Evolution and adaptations of Galapagos sea-birds

With two endemic genera, 26% endemism at the specific, and 58% endemism at the subspecific level, the Galapagos sea-bird fauna is more highly endemic than that of any other archipelago. Of the four most distinct, hence probably oldest, endemics, three are probably of north Pacific origin and the fourth may be. The next most distinct group is of Humboldt Current origin, and the remainder, which are very little differentiated, are of Pacific or Caribbean origin. Special adaptations to Galapagos conditions include the loss of flight by a cormorant and the evolution of nocturnal habits by a gull, the latter probably as a result of kleptoparasitism or nest-predation by frigatebirds. As a group the Galapagos sea-birds show varied adaptive responses to the relatively ascasonal and highly unpredictable marine environment. Opportunistic and non-annual breeding regimes predominate. Unlike the Galapagos land-birds, the study of Galapagos sea-birds has thrown light not on speciation processes but on the consequences of natural selection acting on breeding ecology and associated behaviour.     

DISTRIBUTION AND DISPERSAL OF CENTRAL PACIFIC LESSER FRIGATEBIRDS ‘FREGATA ARZEL*

During the period from March 1963 to July 1965 the Pacific Ocean Biological Survey Program made an extensive study of the islands of the Central Pacific in the area bounded by 10°N.,180° W., 10° S. and 150° W. In the course of this study much new information was obtained on the distribution and dispersal of the Lesser Frigatebird. We have found that Lesser Frigatebirds are an abundant and widely distributed breeding bird in the Central Pacific, although only once previously reported breeding. Most of the young Lesser Frigatebirds from the Phoenix Islands travel to the Solomon Islands, Bismarck Archipelago, New Guinea, or the Philippines. A few travel farther north to the Ryukyu Islands, Japan, Taiwan, and Siberia, and a few also move to areas southwest and southeast of the Phoenix Islands. Most of the dispersal to these latter areas apparently occurs earlier than the dispersal to the Solomons. The dispersal pattern may be dependent in part on the surface wind pattern.     

SUMMER RECORDS FROM WEST-SPITSBERGEN, 1964

An expedition studying geese spent six weeks in the summer of 1964 on the west coast of West-Spitsbergen, Svalbard. The topography of the area is described. Observations were made on 28 species of birds and details of numbers and distribution are given for each. Counts were made over a period of a week of the numbers of Common Eider Somateria mollissima which began nesting in a small colony as the snow cleared from the ground. Weights and measurements were taken of Purple Sandpipers Calidris maritima and Glaucous Gulls Larus hyperboreus. One species new to Svalbard was seen, a Black-headed Gull Larus ridibundus. Previously unrecorded breeding sites of Pink-footed Geese Anser brachyrhynchus, and Barnacle Geese Branta leucopsis were found, and it is concluded that the further spread of the Barnacle Goose is probable. New sea-bird colonies were also located.     

THE BIRDS OF THE SANTA ELENA PENINSULA, S.W. ECUADOR

A systematic account is given of the birds of the Santa Elena peninsula in S.W. Ecuador, based on three years observations (1954-7) and a collection of 425 skins. The status of individual species is decribed and the different elements of the avifauna discussed, viz. the Equatorial arid fauna, Nearctic migrants, sea-birds, and other wide-ranging forms and waterfowl. Seasonal movements of species of the Equatorial arid fauna are indicated in greater detail than has been previously known. The effect of a recently constructed reservoir on the bird life is mentioned. More detailed knowledge of the occurrence of species from the cold Humboldt current is provided. Several additions to the Ecuadorian list are given, and some birds recorded which were hitherto unknown or very rarely recorded from the west coast of S. America. Various matters of taxonomy affecting races of birds along the whole west coast of S. America are discussed.     

Chlorophyll <Emphasis Type="Italic">a</Emphasis> as a measure of seasonal coupling between phytoplankton and the monsoon periods in the Gulf of Oman

We present data from a long time-series study to describe the factors that control phytoplankton population densities and biomass in the coastal waters of Oman. Surface temperature, salinity, nutrients, dissolved oxygen, chlorophyll a (Chl a), and phytoplankton and zooplankton abundance of sea water were measured as far as possible from February 2004 through February 2006, at two stations along the southern coast of the Gulf of Oman. The highest concentrations of Chl a (3 mg m⁻³) were recorded during the southwest monsoon (SWM) when upwelling is active along the coast of Oman. However, results from our study reveal that the timing and the amplitude of the seasonal peak of Chl a exhibited interannual variability, which might be attributed to interannual differences in the seasonal cycles of nutrients caused either by coastal upwelling or by cyclonic eddy activity. Monthly variability of SST and concentrations of dissolved nitrate, nitrite, phosphate, and silicate together explained about 90% of the seasonal changes of Chl a in the coastal ecosystem of the Gulf of Oman. Phytoplankton communities of the coastal waters of Oman were dominated by diatoms for most part of the year, but for a short period in summer, dinoflagellates were dominant.     

Spatio-Temporal Variability of Copepod Abundance along the 20°S Monitoring Transect in the Northern Benguela Upwelling System from 2005 to 2011

Long-term data sets are essential to understand climate-induced variability in marine ecosystems. This study provides the first comprehensive analysis of longer-term temporal and spatial variations in zooplankton abundance and copepod community structure in the northern Benguela upwelling system from 2005 to 2011. Samples were collected from the upper 200 m along a transect at 20°S perpendicular to the coast of Namibia to 70 nm offshore. Based on seasonal and interannual trends in surface temperature and salinity, three distinct time periods were discernible with stronger upwelling in spring and extensive warm-water intrusions in late summer, thus, high temperature amplitudes, in the years 2005/06 and 2010/11, and less intensive upwelling followed by weaker warm-water intrusions from 2008/09 to 2009/10. Zooplankton abundance reflected these changes with higher numbers in 2005/06 and 2010/11. In contrast, zooplankton density was lower in 2008/09 and 2009/10, when temperature gradients from spring to late summer were less pronounced. Spatially, copepod abundance tended to be highest between 30 and 60 nautical miles off the coast, coinciding with the shelf break and continental slope. The dominant larger calanoid copepods were Calanoides carinatus, Metridia lucens and Nannocalanus minor. On all three scales studied, i.e. spatially from the coast to offshore waters as well as temporally, both seasonally and interannually, maximum zooplankton abundance was not coupled to the coldest temperature regime, and hence strongest upwelling intensity. Pronounced temperature amplitudes, and therefore strong gradients within a year, were apparently important and resulted in higher zooplankton abundance.     

THE BREEDING SEASON IN S.W. ECUADOR

The breeding season on the Santa Elena peninsula in S.W. Ecuador is described on the basis of 1761 nests found in the four years 1955 to 1958. The environment and climate are outlined—a cool, dry season from about May to November and a warm, variable wet season from December to April, when alone rain may fall. It is shown that each year the general breeding season is closely correlated with the rainfall. The peak of breeding varies from year to year by at least a month and its length from about six weeks to three and a half months.
Although all species for which there are enough data, are stimulated to breed after important falls of rain, most of those species of small land-birds which are completely resident, attempt to nest before the rain and often continue for some time afterwards. Some specific differences, between seed- and insect-eating finches, seem to be adaptations to food supply and the availability of nest sites and building material. Such evidence as there is suggests that raptors, waders and waterfowl also nest in the wet season (often late), rather than in the dry season. (Unfortunately herons and sea-birds do not nest in the area.)
Annual differences in the amount of breeding by the same species are thought not to be entirely due to differences in weather between years.
It is suggested that the late (August-September) breeding in the Galápagos Islands described by Lack (1950) and the apparent dry-season nesting of raptors, waders and waterfowl there might be found to be linked with variable or abnormally wet weather, if records of rainfall from the islands were available.