Components of breeding productivity in a marine bird community: key factors and concordance

1990 ◽  
Vol 68 (8) ◽  
pp. 1680-1690 ◽  
Author(s):  
Scott A. Hatch ◽  
Martha A. Hatch
Keyword(s):  
Annual Variation ◽  
Size Variation ◽  
Bird Community ◽  
Gulf Of Alaska ◽  
Similar Species ◽  
Marine Bird ◽  
Proximate Cause ◽  
Avian Predators ◽  
Food Shortages ◽  
Key Factor

We estimated components of annual breeding productivity for eight species of marine birds on the Semidi Islands in the western Gulf of Alaska. Mortality of eggs and young, caused primarily by avian predators, accounted for most of the annual variation in productivity. Failure to produce eggs, clutch size variation, and the hatchability of eggs were generally less important. The stage of breeding at which annual productivity was most strongly regulated differed among species. In murres, chick-rearing success accounted for the largest share of annual variation in overall productivity, whereas incubation success was the key factor in fulmars, kittiwakes, and puffins. Although avian predators were the dominant proximate cause of egg and chick losses in some species, food supply seemed ultimately responsible for variation in all the major components of productivity. Concordance of productivity among species was low for the marine bird community as a whole, but selected pairs of species exhibited a greater tendency for high and low productivities to occur in the same years. Compared with the same or similar species outside Alaska, Semidi Islands birds were in one of three categories: (i) species whose productivity was about the same as reported from other areas (fulmars and gulls), (ii) species with comparatively low productivity (murres, puffins, kittiwakes), and (iii) species with similar mean productivity but greater annual variation (cormorants). These patterns suggest that specialized consumers of forage fish experienced food shortages at the Semidi Islands and that surface feeders were more severely affected than divers.

scholarly journals Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity

2009 ◽  
Vol 27 (5) ◽  
pp. 1909-1914 ◽  
Author(s):  
A. Yoshida
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Geomagnetic Activity ◽  
Physical Meaning ◽  
Solar Wind Velocity ◽  
Annual Variation ◽  
Geomagnetic Disturbance ◽  
Data Sets ◽  
Key Factor ◽  
Solar Wind Parameters

Abstract. Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity is investigated based on the three-hourly am index and solar wind parameters. When the z component of the interplanetary magnetic field (IMF) in geocentric solar magnetospheric (GSM) coordinates is southward, am indices are well correlated with BsVx2, where Bs is the southward component of the IMF and Vx is the solar wind velocity in the sun-earth direction. The am-BsVx2 relationship, however, depends on the range of Vx2: the am in higher ranges of Vx2 tends to be larger than am in lower ranges of Vx2 for the same value of BsVx2 for both equinoctial and solstitial epochs. Using the data sets of the same Vx2 range, it is shown that distribution of points in the am-BsVx2 diagram at the solstitial epochs overlaps with that at the equinoctial epochs and the average am values in each BsVx2 bin in solstitial epochs are closely consistent with those in equinoctial epochs, if Vx2 for each point at solstices are reduced to Vx2sin2 (Ψ) where Ψ is the geomagnetic colatitude of the sub-solar point. Further, it is shown that monthly averages of the am index in the long period is well correlated with the values of sin2(ψ) for the middle day of each month. These findings indicate that the factor that contributes to the generation of geomagnetic disturbance is not the velocity of the solar wind, but the component of the solar wind velocity perpendicular to the dipole axis of the geomagnetic field. The magnitude of the perpendicular velocity component varies semi-annually even if the solar wind velocity remains constant, which is considered to be the long-missed key factor causing the equinoctial effect.

Annual variation in common eider egg size: effects of temperature, clutch size, laying date, and laying sequence

1995 ◽  
Vol 73 (9) ◽  
pp. 1579-1587 ◽  
Author(s):  
Gregory J. Robertson
Keyword(s):  
Clutch Size ◽  
Egg Size ◽  
Annual Variation ◽  
Size Variation ◽  
Egg Laying ◽  
Laying Date ◽  
Somateria Mollissima ◽  
Ambient Temperatures ◽  
Common Eiders ◽  
N 93

Annual variation in volumes of eggs laid by common eiders (Somateria mollissima sedentaria) nesting at La Pérouse Bay, Manitoba (58°43′N, 93°27′W), was studied over 3 years (1991–1993). Temperatures during the egg-laying period were higher in 1991 than in 1992 and 1993. However, the eiders began nesting in 1993 at the same time as in 1991, whereas in 1992 the eiders began laying approximately 2 weeks later. Eiders laid significantly smaller clutches in 1992 than in the other 2 years. Egg size did not correlate with clutch size or laying date in any year. However, eiders laid smaller eggs in 1992 and 1993 than in 1991. In five egg clutches, the pattern of intraclutch egg-size variation was different among years. The last laid eggs of five egg clutches were disproportionately smaller in 1992 and 1993 (cold years) than those laid in 1991. Minimum daily temperatures before the egg-laying period (during rapid yolk development) were positively correlated with egg size. However, this effect was not significant when year and egg sequence were controlled for. Egg-size variation was correlated with the overall ambient temperatures during the laying period, whereas annual clutch-size variation was correlated with laying date, suggesting that the proximate mechanisms affecting clutch and egg size are different.

The trophic organization of the marine bird community in the Bering Sea

1993 ◽  
Vol 1 (4) ◽  
pp. 311-335 ◽  
Author(s):  
David C. Schneider ◽  
Viacheslav P. Shuntov
Keyword(s):  
Bering Sea ◽  
Bird Community ◽  
Marine Bird ◽  
The Bering Sea

scholarly journals Phylogenomic Variation at the Population-Species Interface and Assessment of Gigantism in a Model Wolf Spider Genus (Lycosidae, Schizocosa)

2021 ◽  
Vol 5 (5) ◽  
Author(s):  
James Starrett ◽  
Ashley Bui ◽  
Rowan McGinley ◽  
Eileen A Hebets ◽  
Jason E Bond
Keyword(s):  
Body Size ◽  
Size Variation ◽  
Wolf Spider ◽  
Similar Species ◽  
Machine Learning Approach ◽  
Population Structuring ◽  
Phylogenetic Framework ◽  
Genetic Clustering ◽  
Close Relatives ◽  
And Behavior

Abstract Animal body size has important evolutionary implications. The wolf spider genus Schizocosa Chamberlin, 1904 has developed as a model for studies on courtship, with visual and vibratory signals receiving attention; however, body size has never been carefully evaluated. Although species of Schizocosa can be distinguished from their close relatives by differences in genitalic structures, male ornamentation, and behavior, some species are morphologically similar, making diagnosis, and identification difficult. Evaluation of species boundaries using genetic data across Schizocosa is limited. The similar species S. maxima Dondale & Redner, 1978 and S. mccooki (Montgomery, 1904) are separated predominantly on the basis of size differences, with S. maxima being larger. We evaluate the evolution of size in these two Schizocosa species distributed in western North America, where gigantism of S. maxima is hypothesized to occur, particularly in California. We sampled subgenomic data (RADseq) and inferred the phylogeny of S. mccooki, S. maxima, and relatives. We apply a variational autoencoder machine learning approach to visualize population structuring within widespread S. mccooki and evaluate size within the context of a comparative phylogenetic framework to test the hypotheses related to genetic clustering of populations and gigantism. Our data show S. mccooki populations are not genealogically exclusive with respect to S. maxima. Likewise, S. maxima individuals are not recovered as a lineage and do not form an isolated genetic cluster, suggesting that the observed differences in size cannot be used to accurately delimit species. The cause of gigantism in S. maxima remains unexplained, but provides a framework for future studies of size variation and speciation.

The proximate effects of food supply on intraclutch egg-size variation in American kestrels

1996 ◽  
Vol 74 (1) ◽  
pp. 118-124 ◽  
Author(s):  
Karen L. Wiebe ◽  
Gary R. Bortolotti
Keyword(s):  
Food Supply ◽  
Egg Size ◽  
Size Variation ◽  
Food Supplementation ◽  
Laying Order ◽  
American Kestrels ◽  
Good Body Condition ◽  
Adaptive Explanation ◽  
Food Shortages

Egg size can be an important determinant of offspring survival in birds. We measured eggs from 275 clutches of wild American kestrels (Falco sparverius) to study the degree of intraclutch variability in egg size. We also performed two food-supplementation experiments to investigate the proximate role of food supply during laying in determining egg size. Females with relatively abundant food and those in good body condition did not lay eggs that were more uniform in size than those laid by control females. This result is contrary to hypotheses that propose an adaptive explanation for intraclutch egg-size variation and also to ideas of energy depletion during laying. Patterns of egg size versus laying order were different between years, suggesting that females did not adaptively manipulate laying order and egg size within a clutch. The food-supplementation experiments showed that laying female kestrels probably depend on both stored energy reserves and on daily energy surpluses to form eggs. It appears that slight intraclutch variations in egg size occur in response to short-term food shortages during laying, but that these variations are probably nonadaptive. This is in marked contrast to interclutch (among females) variation in egg size, which we have shown varies significantly with food supply.

Size Variation of Neocalanus plumchrus and Neocalanus flemingeri in a 20-yr Sample Series from the Gulf of Alaska

1992 ◽  
Vol 49 (2) ◽  
pp. 389-399 ◽  
Author(s):  
Charles B. Miller ◽  
John Fulton ◽  
Bruce W. Frost
Keyword(s):  
Geographic Variation ◽  
Size Variation ◽  
Gulf Of Alaska ◽  
Growth Conditions ◽  
Prosome Length ◽  
New Production ◽  
Resting Stages ◽  
Sample Series ◽  
Neocalanus Plumchrus ◽  
Range Of Variation

Prosome length of the resting stages of Neocalanus plumchrus and Neocalanus flemingeri varied significantly, but modestly, among years at Station P in the Gulf of Alaska. The range of variation over 20 yr was small relative to the known geographic variation. Among-year length variations were significantly greater than within-year variations, implying similarity of year-to-year variation in growth conditions over an indeterminate, subregional scale. The two species tended to vary in the same fashion both among and within years, despite the offset of about 1 mo in their developmental schedules. Length of N. plumchrus was negatively correlated with Emerson's (1987. J. Geophys. Res. (Oceans) 92(C6): 6535–6544) estimates of May–August new production at Station P from 1969 to 1978.

scholarly journals Variation of glucocorticoid metabolite levels is associated with survival demands in immature and reproductive demands in adult wild black capuchins (Sapajus nigritus)

2016 ◽  
Vol 9 (2) ◽  
pp. 20-29 ◽  
Author(s):  
Caio M. Moreira ◽  
Lucas Peternelli Dos Santos ◽  
Maria Bernardete Cordeiro Sousa ◽  
Patrícia Izar
Keyword(s):  
Allostatic Load ◽  
Annual Variation ◽  
Adult Males ◽  
Cumulative Energy ◽  
Fecal Glucocorticoid Metabolites ◽  
Adult Females ◽  
Animal Survival ◽  
Energy Mobilization ◽  
Food Shortages ◽  
Survival And Reproduction

According to the concept of allostasis and its association with energy mobilization, glucocorticoids (GCs) should parallel cumulative energy expenditure for animal survival and reproduction. Therefore, it is expected that seasonal food shortages might lead to increased levels of GCs. We tested this hypothesis by analyzing the intra-annual variation of fecal glucocorticoid metabolites (GCM) in 14 wild black capuchin monkeys (Sapajus nigritus) living in a social group in the Brazilian Atlantic Forest. We analyzed the association between GCM and social and environmental variables for the three age/sex classes (adult males, adult females and immatures [juveniles and infants]). Decreased fruit intake during the dry season increased the GCM levels of both immatures and adult males. Although fruit shortage influenced the allostasis of adult males, the variation in their GCM levels was more impacted by the breeding season. GCM levels of adult females varied during the late stage of pregnancy. These results suggest fruit consumption as the main source of allostatic load for immature animals, while reproductive costs had greater effect on adults. 

Replenishing the Soil: Food, Fertiliser and Soil Science in Occupied Japan (1945–52)

2020 ◽  
Author(s):  
Christopher M. Aldous
Keyword(s):  
Food Supply ◽  
Agricultural Chemicals ◽  
Mining Operations ◽  
Allied Occupation ◽  
Early Twenty ◽  
The Us ◽  
Food Shortages ◽  
Key Factor ◽  
Food Imports ◽  
The Many

Environmental scientists and activists in the early twenty-first century have identified productive, healthy soils as a key factor in feeding a rapidly increasing global population and mitigating climate change. This article argues that serious food shortages in Japan following its defeat in 1945 caused the fertility of its soils to become a pressing issue for the Allied Occupation (1945–52) and one seen as central to the success of democratisation. The prospect of famine in the cities in 1946 and 1947 and associated political unrest justified urgent imports of food from the US, causing much resentment among its allies, who questioned the seriousness of the food supply crisis in Japan. The Occupation’s Natural Resources Section worked to reduce Japan’s dependence on food imports by surveying Japan’s soils and recommending their rapid augmentation with chemical fertilisers, the manufacture of which had practically ceased during the war. The US imported nitrogenous fertiliser to supplement inadequate domestic output and provided phosphate ore (for superphosphate fertiliser) from Florida, in addition to encouraging Japanese mining operations on Angaur Island, formerly part of the Japanese empire. The latter generated conflicts with the natives of the island, the local US naval command and the Australian government. Such tensions demonstrate the many and varied facets of the ‘fertiliser problem’, which was seen as pivotal to food supply and economic recovery. Major imports of agricultural commodities from the US after 1952 reflected its Cold War alliance with Japan. Likewise, significant transfers of technology contributed to a steep increase in the use of agricultural chemicals, causing the fertiliser problem to become a pressing environmental one by the 1990s.

scholarly journals Structure and variability of the marine-bird community in the northeastern Chukchi Sea

2013 ◽  
Vol 67 ◽  
pp. 96-115 ◽  
Author(s):  
Adrian E. Gall ◽  
Robert H. Day ◽  
Thomas J. Weingartner
Keyword(s):  
Chukchi Sea ◽  
Bird Community ◽  
Marine Bird

Body size and sex ratio in emergent stonefly nymphs (Isogenoides olivaceus: Perlodidae): variation between cohorts and populations

1994 ◽  
Vol 72 (8) ◽  
pp. 1371-1375 ◽  
Author(s):  
Roger J. Haro ◽  
Kay Edley ◽  
Michael J. Wiley
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Annual Variation ◽  
Sexual Size Dimorphism ◽  
Population Regulation ◽  
Size Variation ◽  
Size Distributions ◽  
Ecological Significance ◽  
Male Size ◽  
Animal Size

The ecological significance of pattern in animal-size distribution has been receiving increased scrutiny in studies of population regulation and individual energetics. However, few studies have assessed differences in size variation between sequential generations or adjacent populations. Annual variation in body size and sex ratio of emergent perlodid stonefly nymphs, Isogenoides olivaceus (Frison) (Plecoptera: Perlodidae), were examined in populations from two Michigan mesic groundwater rivers. Final nymphal body size was estimated from sex-specific length to mass regression relationships using exuviae collected from each site. Sexual size dimorphism accounted for much of the intraspecific size variation within both populations and cohorts: females were larger ([Formula: see text]) than males ([Formula: see text]). Males showed less size variation than females; unlike those for females, size distributions for males were significantly skewed. Secondary sex ratios were female biased in both populations and all cohorts and ranged between 59.1 and 72.8%. Female sex bias increased with relative male size in both populations.

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