Calculation of flows and disaggregation of accumulated values

Some important economic flow variables, notably consumption and investment, have only been observed annually in Iceland. We have developed methods to estimate the flow by spline functions or Fourier series. Aggregated values over shorter intervals can be obtained by integration of the flows. A method to obtain quarterly values from annual observations by estimating a quarterly time series model from the observed values is also presented. The source code of Fortran programs and examples of input files are included. Access to the NAG subroutines is necessary to use the programs directly.

Statistical considerations in the analysis of catch-at-age observations

. Statistical considerations in the analysis of catch-at-age observations. -J. Cons. int. Explor. Mer, 43: 83-90. Fishing mortality rates are described by a model encompassing common simplifying assumptions, including separable age and year effects, constant mortality rate above the age of full recruitment, and proportionality to a given fishing effort. Each of these assumptions can be tested against a more general specification. Because of the great difference in the catch numbers for different ages, transformations are necessary to stabilize variances, and care must be exercised so that large departures from normality do not invalidate inferences from the least-squares analysis

Migration Patterns of Tundra Birds: Tracking Radar Observations along the Northeast Passage

Bird migration was recorded by tracking radar and visual observations at 15 study sites, situated between 50°E and 170°E along the Northeast Passage, during a ship-based expedition in July and August 1994. A total of 1087 radar tracks (average duration 220 s) of bird flocks on postbreeding migration were recorded. Migration was dominated by waders and to a certain degree also skuas (especially pomarine skua Stercorarius pomarinus). Terns, gulls, ducks, and geese were also among the migrants tracked by radar. The radar data revealed a major migratory divide at about 100°E (Taymyr Peninsula), with mainly eastbound migration to the east of this divide, and mainly westbound migration to the west of it. The main stream of eastbound migration was directed toward the sector 90-120° and that of westbound migration toward the sector 240-270°; these directions are broadly in parallel with the coasts of the Arctic Ocean east and west of the Taymyr Peninsula, respectively. There was also important ENE migration, which provided strong indications of long-distance flights along orthodrome-like routes directly between Siberia and North America, across vast expanses of the Arctic Ocean pack ice. Analysis of flight directions in relation to wind indicated complete compensation for wind drift. Mean flight altitude was 1.3 km, and the birds regularly travelled at high altitudes above 3 km (9% of the tracks) up to a maximum height of 4.8 km. They preferred to migrate on occasions and at altitudes with following winds; such conditions provided an average gain in speed of 4.6 m/s. There were also recurrent cases of birds migrating in tailwinds of gale force, between 18 and 24 m/s. The birds' airspeed varied between 8 and 22 m/s, with a mean of 14 m/s. Airspeed was significantly correlated with altitude, wind, and vertical speed and seemed to be intermediate between the speeds for minimum power and maximum range predicted by aerodynamic theory.Durant une expédition ayant pour base un navire, réalisée en juillet et août 1994, on a enregistré la migration des oiseaux à l'aide d'un radar de poursuite et d'observations visuelles dans 15 zones d'étude situées entre 50 et 170° de longit. E., le long du passage du Nord-Ouest. On a enregistré un total de 1087 poursuites radar (d'une durée moyenne de 220 s) de volées d'oiseaux en migration après la nidification. La migration était dominée par les échassiers et, à un certain degré également, par les labbes (en particulier le labbe pomarin Stercorarius pomarinus). Les sternes, goélands, canards et oies étaient aussi au nombre des migrants suivis au radar. Les données de radar révèlent une scission migratoire majeure à environ 100° de longit. E. (presqu'île de Taïmyr), avec surtout une migration vers l'est, à l'est de cette division, et une migration vers l'ouest, à l'ouest de cette division. Le courant principal de la migration en direction de l'est était dirigé vers le secteur allant de 90 à 120° et celui de la migration en direction de l'ouest, vers le secteur allant de 240 à 270°; ces directions sont en gros parallèles aux rivages de l'océan Arctique à l'est et à l'ouest de la presqu'île de Taïmyr respectivement. Il y avait aussi une importante migration E.-N.-E., qui offrait une indication assez précise de vols de longue distance suivant un tracé ressemblant à la ligne orthodromique directe entre la Sibérie et l'Amérique du Nord, au travers de vastes étendues de la banquise de l'océan Arctique. L'analyse des directions de vol par rapport aux vents révèle une compensation totale pour la dérive due au vent. L'altitude moyenne de vol était de 1,3 km, et les oiseaux voyageaient régulièrement à altitude élevée, allant de 3 km (pour 9 p. cent des poursuites) à une hauteur maximale de 4,8 km. Les oiseaux préféraient parfois effectuer leur migration à haute altitude avec des vents arrière, de telles conditions offrant un gain de vitesse moyen de 4,6 m/s. On a observé des cas répétés d'oiseaux qui migraient avec un vent arrière soufflant en tempête, entre 18 et 24 m/s. La vitesse relative des oiseaux variait entre 8 et 22 m/s, avec une moyenne de 14 m/s. Cette vitesse relative était corrélée fortement avec l'altitude, le vent et la vitesse verticale, et semblait être intermédiaire entre les vitesses prédites par la théorie aérodynamique pour la puissance minimale et la portée maximale

Rapid changes in the size of different functional organ and muscle groups during refueling in a long-distance migrating shorebird

The adaptive value of size changes in different organ and muscle groups was studied in red knots (Calidris canutus islandica) in relation to their migration. Birds were sampled on five occasions: at arrival in Iceland in May 1994, two times during subsequent refueling, at departure toward, and on return from, the high arctic breeding grounds. During their 24-d stopover in May, body mass increased from 144.3 to 214.5 g. Mass gains were lowest over the first week (0.85 g/d, only fat-free tissue deposited). Over the subsequent 10 d, average mass increased by 5.0 g/d (fat contributing 78%), and over the last week before takeoff, it increased by 2.0 g/d (fat contributing over 100% because of loss of lean components). There were no sex differences in body and fat mass gains. Over the first interval, lean masses of heart, stomach, and liver increased. During the middle 10 d, sizes of leg muscle, intestine, liver, and kidneys increased. Stomach mass decreased over the same interval. In the last interval before takeoff, the stomach atrophied further and the intestine, leg muscles, and liver became smaller too, but pectoral muscles and heart increased in size. Sizes of "exercise organs" such as pectoral muscle and heart were best correlated with body mass, whereas sizes of organs used during foraging (leg muscles) and nutrient extraction (intestine, liver) were best correlated with rate of mass gain. Kidneys changed little before takeoff, which suggests that they are needed as much during flight as during refueling

Ross's Gulls in the Central Arctic Ocean

The central Arctic Ocean is difficult to access, the result, the bird fauna of the area, with its potential input from all around the circumpolar perimeter, is still only little known. The present paper contributes observations on the distsribution of Ross's gull (Rhodosethia rosea) made during the Arctic Ocean 96 expedition from mid-July to mid-September 1996, from the Swedish icebreaker Oden. Ross's gull was the most common bird in the central parts of the Arctic Ocean, with a grand total at least 131 individuals seen up to 87 30 N. Its absence further north was judged as due to an early freeze-up. A marked concentration was noted at the shelf-break north of Franz Josef Land in late July. Most Ross's gulls were observed as single birds or two together, but some small flocks were seen, the largest consisting of 10 birds. Most birds were adults, the proportion of immature (second-year) birds being no more than 10-15%.Vu qu'il est difficile d'accéder à la partie centrale de l'océan Arctique, la faune aviaire de la région ainsi que l'apport à celle-ci venant de tout le périmètre circumpolaire sont relativement peu connus. Cet article présente des observations sur la distribution de la mouette rosée (Rhodostethia rosea) faites de la mi-juillet à la mi-septembre 1996 dans le cadre de l'expédition Océan Arctique 96 réalisée par le brise-glace suédois Oden. La mouette rosée était l'oiseau le plus répandu dans les régions centrales de l'océan Arctique, avec un total global d'au moins 131 individus observés jusqu'à 87° 30' de latit. N. On a interprété son absence plus au nord comme étant la conséquence d'un engel précoce. On a remarqué une forte concentration à la rupture de pente au nord de l'archipel François-Joseph à la fin juillet. La plupart des mouettes rosées ont été observées en solitaires ou en paires, mais on a aussi vu quelques petites volées dont la plus importante comptait 10 oiseaux. La plupart des mouettes étaient des adultes, la proportion des oiseaux immatures (dans leur deuxième année) ne représentant pas plus de 10 à 15 p. cent

Aspects of pre-migratory feeding ecology of sanderling (Calidris alba pallas) at Teesmouth, NE England

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Ross's Gulls in the Central Arctic Ocean

ABSTRACT. The central Arctic Ocean is difficult to access. As a result, the bird fauna of the area, with its potential input from all around the circumpolar perimeter, is still only little known. The present paper contributes observations on the distribution of Ross’s gull (Rhodostethia rosea) made during the Arctic Ocean 96 expedition from mid-July to mid-September 1996, from the Swedish icebreaker Oden. Ross’s gull was the most common bird in the central parts of the Arctic Ocean, with a grand total of at least 131 individuals seen up to 87˚30'N. Its absence further north was judged as due to an early freeze-up. A marked concentration was noted at the shelf-break north of Franz Josef Land in late July. Most Ross’s gulls were observed as single birds or two together, but some small flocks were seen, the largest consisting of 10 birds. Most birds were adults, the proportion of immature (second-year) birds being no more than 10 –15%

Migration Along Orthodromic Sun Compass Routes by Arctic Birds

Flight directions of birds migrating at high geographic and magnetic latitudes can be used to test bird orientation by celestial or geomagnetic compass systems under polar conditions. Migration patterns of arctic shorebirds, revealed by tracking radar studies during an icebreaker expedition along the Northwest Passage in 1999, support predicted sun compass trajectories but cannot be reconciled with orientation along either geographic or magnetic loxodromes (rhumb lines). Sun compass routes are similar to orthodromes (great circle routes) at high latitudes, showing changing geographic courses as the birds traverse longitudes and their internal clock gets out of phase with local time. These routes bring the shorebirds from high arctic Canada to the east coast of North America, from which they make transoceanic flights to South America. The observations are also consistent with a migration link between Siberia and the Beaufort Sea region by way of sun compass routes across the Arctic Ocean