Changing prey size preferences in the annual cycle of Retusa obtusa (Montagu) (Opisthobranchia) feeding on Hydrobia ulvae (Pennant) (Prosobranchia)

1990 ◽  
Vol 141 (2-3) ◽  
pp. 145-158 ◽  
Author(s):  
A.J. Berry ◽  
D.R. Thomson
Keyword(s):  
Annual Cycle ◽  
Prey Size ◽  
Hydrobia Ulvae

Intertidal activity, breeding and the floating habit of Hydrobia ulvae in the Ythan estuary

1971 ◽  
Vol 51 (2) ◽  
pp. 423-437 ◽  
Author(s):  
A. Anderson
Keyword(s):  
Annual Cycle ◽  
Breeding Success ◽  
Food Item ◽  
Ecological Studies ◽  
Time Data ◽  
Hydrobia Ulvae ◽  
Sampling Programme ◽  
One Year ◽  
Index Of Abundance ◽  
Tringa Totanus

INTRODUCTIONEcological studies of Eider Somateria mollisima, Shelduck Tadorna tadorna, Redshank Tringa totanus [Aves], and Flounder Platichythys flesus [Osteichthys], in the estuary of the River Ythan, Aberdeenshire, have entailed investigations of their food requirements, and there is evidence to suggest that Hydrobia ulvae [Gastopoda], as a numerous food item common to all, may in some instances have influenced their breeding success and numbers in some years. In order to get an index of abundance of Hydrobia, the Ythan population has been sampled four times a year since May 1963. The full results of this sampling programme are being published separately. At the same time data on the annual cycle of Hydrobia were collected from one area (transect number 3, Fig. 1), on the assumption that breeding onset and intensity would be the same in other parts of the estuary in any one year.

Birds in the Dark: Complementary and Partial Information

2017 ◽  
Author(s):  
Graham R. Martin
Keyword(s):  
Annual Cycle ◽  
Colour Vision ◽  
Partial Information ◽  
Night Time ◽  
Light Levels ◽  
Night Feeding ◽  
Nocturnal Species ◽  
Length Changes

Night-time poses exacting problems for vision, resolution inevitably falls and colour vision is not possible as light levels decrease to those of natural night time. Furthermore, light levels are highly variable depending upon whether there is moonlight, and night length changes dramatically in the annual cycle according to latitude. Few birds exploit the resources available at night. Those that do rely upon information received from vision complemented by information from other senses (hearing, olfaction, and touch), and upon highly specialized and restricted behaviours. However, many birds occasionally exploit night-time, e.g. during migration, arriving and departing from nests, and occasional night feeding. Some seabirds dive to such depths that they experience night-time light levels when foraging. Truly nocturnal species such as owls, kiwi, and oilbirds are highly sedentary, and this is essential to allow them to interpret correctly the partial information that is available to them.

scholarly journals Yearly evolution of Euro-Atlantic weather regimes and of their sub-seasonal predictability

2021 ◽  
Author(s):  
Nicola Cortesi ◽  
Verónica Torralba ◽  
Llorenó Lledó ◽  
Andrea Manrique-Suñén ◽  
Nube Gonzalez-Reviriego ◽  
...  
Keyword(s):  
Annual Cycle ◽  
Winter Season ◽  
Skill Score ◽  
Seasonal Forecast ◽  
Forecast Skill ◽  
Seasonal Forecasts ◽  
Sea Level Pressure ◽  
Weather Regimes ◽  
Start Dates ◽  
Weekly Frequency

AbstractIt is often assumed that weather regimes adequately characterize atmospheric circulation variability. However, regime classifications spanning many months and with a low number of regimes may not satisfy this assumption. The first aim of this study is to test such hypothesis for the Euro-Atlantic region. The second one is to extend the assessment of sub-seasonal forecast skill in predicting the frequencies of occurrence of the regimes beyond the winter season. Two regime classifications of four regimes each were obtained from sea level pressure anomalies clustered from October to March and from April to September respectively. Their spatial patterns were compared with those representing the annual cycle. Results highlight that the two regime classifications are able to reproduce most part of the patterns of the annual cycle, except during the transition weeks between the two periods, when patterns of the annual cycle resembling Atlantic Low regime are not also observed in any of the two classifications. Forecast skill of Atlantic Low was found to be similar to that of NAO+, the regime replacing Atlantic Low in the two classifications. Thus, although clustering yearly circulation data in two periods of 6 months each introduces a few deviations from the annual cycle of the regime patterns, it does not negatively affect sub-seasonal forecast skill. Beyond the winter season and the first ten forecast days, sub-seasonal forecasts of ECMWF are still able to achieve weekly frequency correlations of r = 0.5 for some regimes and start dates, including summer ones. ECMWF forecasts beat climatological forecasts in case of long-lasting regime events, and when measured by the fair continuous ranked probability skill score, but not when measured by the Brier skill score. Thus, more efforts have to be done yet in order to achieve minimum skill necessary to develop forecast products based on weather regimes outside winter season.

scholarly journals Prey Size Decline as a Unifying Ecological Selecting Agent in Pleistocene Human Evolution

Quaternary ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 7
Author(s):  
Miki Ben-Dor ◽  
Ran Barkai
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Stone Tool ◽  
Foraging Efficiency ◽  
Energetic Cost ◽  
Large Prey ◽  
Biomass Density ◽  
Cultural Changes ◽  
Progressive Decline ◽  
Brain Expansion

We hypothesize that megafauna extinctions throughout the Pleistocene, that led to a progressive decline in large prey availability, were a primary selecting agent in key evolutionary and cultural changes in human prehistory. The Pleistocene human past is characterized by a series of transformations that include the evolution of new physiological traits and the adoption, assimilation, and replacement of cultural and behavioral patterns. Some changes, such as brain expansion, use of fire, developments in stone-tool technologies, or the scale of resource intensification, were uncharacteristically progressive. We previously hypothesized that humans specialized in acquiring large prey because of their higher foraging efficiency, high biomass density, higher fat content, and the use of less complex tools for their acquisition. Here, we argue that the need to mitigate the additional energetic cost of acquiring progressively smaller prey may have been an ecological selecting agent in fundamental adaptive modes demonstrated in the Paleolithic archaeological record. We describe several potential associations between prey size decline and specific evolutionary and cultural changes that might have been driven by the need to adapt to increased energetic demands while hunting and processing smaller and smaller game.

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