Selection and Dropping of Whelks By Northwestern Crows

Behaviour ◽  
1978 ◽  
Vol 67 (1-2) ◽  
pp. 134-147 ◽  
Author(s):  
Reto Zach
Keyword(s):  
Site Selection ◽  
Intertidal Zone ◽  
Prey Selection ◽  
Hard Substrate ◽  
Safe Sites ◽  
Corvus Caurinus ◽  
The Mean ◽  
Final Selection

AbstractPrey selection, dropping behaviour and dropping site selection was investigated in Northwestern crows (Corvus caurinus) feeding on whelks (Thais lamellosa). Crows selected only the largest whelks available in the intertidal zone. Although equally palatable, smaller whelks were ignored. Crows assessed size of whelks first by sight and then by weight. Thus, some were picked up with the bill and laid down again before a final selection was made. Rejects were longer and heavier than available whelks and shorter and lighter than selected ones. Usually, crows carried and dropped only one whelk at a time. While dropping, crows typically flew almost vertically up, released the whelk and then dove after it. The mean number of drops required to break a whelk was 4.36. Crows dropped whelks until they could obtain most or all of the soft parts. Usually crows did not give up dropping a whelk until it broke. The mean height of drop was 5.23 m. Crows had a tendency to increase height of drop over successive attempts. During most flights, crows lost some height before releasing a whelk. Presumably, this allowed them to watch whelks fall and bounce. All whelks were dropped onto rock. None were released over water or grass. Crows had specific dropping sites. This was because they selected hard substrate and safe sites for dropping. On dropping sites whelks were unlikely to bounce into water. Results were compared with those of other studies of dropping behaviour in gulls and hawks. Dropping behaviour in crows seems to be much more adaptable than in gulls.

scholarly journals Pre-selection of apple seedlings for partial powdery mildew (Podosphaera leucotricha Ell. et Ev. /Salm./) resistance

2011 ◽  
Vol 50 (No. 2) ◽  
pp. 65-69 ◽  
Author(s):  
J. Blažek
Keyword(s):  
Powdery Mildew ◽  
First Year ◽  
Podosphaera Leucotricha ◽  
Green House ◽  
Healthy State ◽  
The Mean ◽  
Resistant Genotypes ◽  
Different Levels ◽  
Final Selection ◽  
Selection Of

Incidences of powdery mildew were repeatedly evaluated for two years on 1 420 young seedlings of 20 progenies (of different levels of mildew susceptibility) in a green house, and then for 10 years on 642 seedlings in an orchard. Part of the seedlings in the orchard were pre-selected for the characteristic and others not. Except for the first scoring done in the first year, there was no correlation between mildew incidence on individual seedlings in the green house and their mean performance in the orchard. The seedlings with scores above 6 (resistant or tolerant) at the first stage of evaluation in the green house, however, yielded four times more desirable seedlings after final selection in the orchard than the mean of the total. The progenies that had a better healthy state as a whole yielded more partially resistant genotypes than those with low mean scores. Therefore, the progenies that most rapidly develop infestation on the whole lot should be discarded, whereas those that retain a healthy state longer should be subjected to individual selection according to the previous item.

NEST PROVISIONING IN THE MUD-DAUBER WASP SCELIPHRON LAETUM (F. SMITH): BODY MASS AND TAXA SPECIFIC PREY SELECTION

Behaviour ◽  
1999 ◽  
Vol 136 (2) ◽  
pp. 147-159 ◽  
Author(s):  
Matthew Jebb ◽  
Mark Elgar
Keyword(s):  
Field Experiment ◽  
Papua New Guinea ◽  
Body Mass ◽  
Prey Selection ◽  
Larval Instar ◽  
New Guinea ◽  
Spider Species ◽  
Volumetric Capacity ◽  
The Mean ◽  
Nest Provisioning

AbstractThe mud dauber wasp Sceliphron laetum (F. Smith) lays a single egg in a mud chamber that is provisioned almost exclusively with orb-weaving spiders. In Madang, Papua New Guinea, the wasps provision their chambers with between three and nine spiders that weigh between 0.01 and 0.28 g and are from at least twelve species. The number of spiders placed in each chamber is negatively correlated with the mean mass of each spider. A field experiment revealed that females cease provisioning after capturing a certain mass of spiders, rather than simply filling each chamber to its volumetric capacity. Furthermore, the wasps select different spider species according to the provisioning sequence. In general, wasps avoid provisioning the early larval instar with species of Gasteracantha, perhaps because the newly emerged wasp larvae cannot penetrate the hard integuments of these spiders.

Prey selection by sparrowhawks, Accipiter nisus : relative predation risk for breeding passerine birds in relation to their size, ecology and behaviour

1996 ◽  
Vol 351 (1347) ◽  
pp. 1559-1577 ◽  
Keyword(s):  
Body Size ◽  
Relative Density ◽  
Predation Risk ◽  
Prey Species ◽  
Prey Selection ◽  
Common Belief ◽  
Passerine Birds ◽  
Accipiter Nisus ◽  
The Mean ◽  
Nest Height

Predation is a fundamental ecological process, but there are few studies of predation risk for adult, breeding birds. In this study, we quantified Relative Predation Risk (RPR) for 46 species of passerine birds preyed on by sparrowhawks during the breeding season in south-western Sweden. The sparrowhawk is a major predator of smaller birds in Eurasian forests and woodland. Near nesting hawk pairs, prey abundance was estimated by line transects. From prey remains at hawk nests, we estimated the frequency of prey species in the diet of hawks. For each hawk pair, RPR values for different prey species were calculated. The mean RPR for each prey species, based on hawk pairs as sample units, indicated degree of overrepresentation (positive RPR) or underrepresentation (negative RPR) of the prey in the diet. Prey species with a high positive RPR nested mainly near human habitations (villages or towns), at forest edges and in farmland. However, there were marked seasonal changes in RPR. Forest birds, such as the goldcrest and wren, had the highest RPR in April. Later, the hawks seemed to hunt mainly in the habitats mentioned above, where prey were more abundant or easier to catch, resulting in increasing RPR for the house sparrow, yellowhammer, greenfinch and other species. RPR values were analysed in relation to prey body size (mass) and relative density, as well as prey foraging height and nest height (categorized from the literature). In addition, the mean perch height and mean exposure of prey species were quantified in the field. Most predation was due to the smaller male hawks, providing food for their mates and young, RPR increased with prey body size up to a mass of about 40 g, then declined with increasing body size (larger prey being more difficult to catch), RPR decreased with increasing relative density of prey species. Nest height was not correlated with RPR, but foraging height seems to be an important factor: RPR decreased with increasing foraging height. A similar result was found for mean perch height, when larger prey (over 40 g) and singing individuals were excluded from the field data. RPR increased with mean exposure of prey species when larger prey and singing birds were excluded; a combination of perch height and exposure improved the correlation with RPR. Singing birds were generally perched high in the vegetation and may not suffer high predation risk, contrary to common belief. The results of this study are discussed in relation to temporal and geographical variation in RPR and antipredator adaptations in passerine birds.

scholarly journals Can a repository site be safer than safe? – Criteria and methods for a safety-oriented comparison of repository sites

2021 ◽  
Vol 1 ◽  
pp. 41-42
Author(s):  
Martin Navarro ◽  
Ingo Kock ◽  
Gerd Frieling ◽  
Thomas Beuth
Keyword(s):  
Site Selection ◽  
Selection Procedure ◽  
Evaluation Methods ◽  
Safety Concept ◽  
Joint Project ◽  
Safety Requirements ◽  
Operational Criteria ◽  
Host Rocks ◽  
Final Selection ◽  
Selection Phase

Abstract. In the course of the German site selection procedure, repository potential sites will be rejected if it becomes apparent that they will probably not meet the regulatory safety requirements (EndlSichAnfV). It is therefore likely that the remaining sites of the final selection phase (which is specified by paragraph 19 of the StandAG) will meet the safety requirements and are therefore capable of being approved. Under these circumstances, finding the site with the highest possible level of safety (as required by the StandAG) calls for a further differentiation of safety above the level of safety that is prescribed by the safety requirements. Based on this differentiation, operational criteria have to be developed for a safety-oriented comparison of repository sites and systems; however, finding suitable criteria is not a trivial task if the repository systems that are available for selection make use of different host rocks and therefore differ with respect to the internal structure and safety concept. Between 2007 and 2010, criteria and associated evaluation methods for a safety-oriented comparison of approvable repository sites were developed by project 3607R02589 of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) within the joint project VerSi. The robustness of the repository system was proposed as a central criterion for site comparison. In the years to follow, criteria and evaluation methods were tested and refined by BfE/BMU projects 05504/2 and 4719E03250, which finally showed a substantial need for further research and development. The presentation outlines the results of these three projects and discusses the questions that are still open.

scholarly journals Population- and individual-level prey selection by a solitary predator as determined with two estimates of prey availability

2016 ◽  
Vol 94 (4) ◽  
pp. 275-282 ◽  
Author(s):  
L. Mark Elbroch ◽  
Patrick E. Lendrum ◽  
Hugh Robinson ◽  
Howard B. Quigley
Keyword(s):  
Prey Species ◽  
Puma Concolor ◽  
Prey Availability ◽  
Prey Selection ◽  
Population Level ◽  
Simple Calculation ◽  
Individual Level ◽  
Dietary Niche ◽  
Two Measures ◽  
The Mean

Prey selection is exhibited by predator populations that kill a prey species disproportionate to its availability, or alternatively, individual predators that select prey disproportionate to the mean selection exhibited by their populations. Prey selection is a simple calculation when one can determine prey availability; however, measuring prey availability is challenging. We compared population- and individual-level prey selection as determined with two measures of prey availability for five ungulate species killed by pumas (Puma concolor (L., 1771)) in the Southern Yellowstone Ecosystem, USA: (1) annual prey counts and (2) total prey killed by marked pumas. We also tested whether individual pumas in the population exhibited a narrower dietary niche breadth compared with their population as a whole. The two methods yielded different estimates of prey availability and highlighted the need to consciously match prey availability estimates with appropriate ecological questions. Prey counts may have overestimated elk (Cervus canadensis (Erxleben, 1777)) abundance and underestimated deer abundance, whereas predation data may have better captured the influence of prey size on puma-specific prey vulnerability and availability. Prey counts were the more appropriate metric for analyzing population-level prey selection or differences in interspecific foraging, whereas total prey killed was the more appropriate metric for intraspecific comparisons.

scholarly journals Selection for protection from insolation results in the visual isolation of Yellow-eyed Penguin Megadyptes antipodes nests

2014 ◽  
Vol 25 (2) ◽  
pp. 192-206 ◽  
Author(s):  
RYAN D. CLARK ◽  
RENAUD MATHIEU ◽  
PHILIP J. SEDDON
Keyword(s):  
Site Selection ◽  
Habitat Restoration ◽  
Nest Site ◽  
Nest Site Selection ◽  
Logistic Regression Models ◽  
Habitat Features ◽  
Nest Sites ◽  
Rare And Endangered ◽  
The Mean ◽  
Selection For

SummaryThe concealed and widely dispersed nests of the rare and endangered Yellow-eyed Penguin Megadyptes antipodes, or “hoiho”, have been considered to reflect an essential requirement for the visual isolation of nest sites from conspecifics. However, this may be a consequence of selection for habitat features that provide protection from insolation, thereby minimising the risk of heat stress. To help improve the understanding of hoiho nesting requirements and the effectiveness of habitat restoration, we aimed to determine whether visual isolation from conspecifics or protection from insolation is the primary driver of hoiho nest site selection. We compared the mean maximum distance of visibility and the mean percentage insolation cover of active nests with randomly sampled unused sites in flax Phormium tenax and Hebe elliptica coastal scrub at Boulder Beach, and in coastal forest at Hinahina Cove, New Zealand, 2006–2007. Results of univariate tests and the evaluation of logistic regression models suggested that the amount of insolation cover was more important than visibility for hoiho nest site selection, particularly in flax and scrub. In addition, Spearman's correlations indicated that decreasing insolation cover significantly increased the visibility of nests in the forest habitat, and had a similar effect on inter-nest distance in flax. We infer that hoiho nest site selection and distribution are influenced primarily by the location and density of micro-habitat features (particularly within 1 m of the ground) that provide optimal protection from insolation, possibly along with other important features such as a firm backing structure. Strong selection for these features results in the typical but non-essential visual isolation of nest sites from conspecifics. Restoration of nesting habitats with a relatively high density and diversity of vegetation and solid structures within 1 m of the ground may eventually provide an optimal availability and quality of suitable nest sites.

scholarly journals Primary production of the benthic microflora living on intertidal flats in the Santos estuarine system (24ºS, 46ºW), São Paulo, Brazil

1983 ◽  
Vol 32 (2) ◽  
pp. 177-186 ◽  
Author(s):  
Eduinetty Ceci Pereira Moreira de Sousa
Keyword(s):  
Primary Production ◽  
Intertidal Zone ◽  
Mean Value ◽  
Estuarine System ◽  
Total Production ◽  
Tropical Estuary ◽  
Southern Coast ◽  
Dark Fixation ◽  
The Mean ◽  
One Year

Estimates of primary produetion of benthic microflora were carried out in the Santos tropical estuary, on the southern coast of Brazil (24ºS, 46ºW). The samples were obtained seasonally over a one-year period. Six stations with different environ mental conditions were chosen. The samples, which consisted of the upper 2 mm of the sediment, were collected in the intertidal zone, according to Grøntved's (1960) methodology. The mean annual value of primary production was 45 mgC/m²/h, ranging from 1. 0 to 301.0 mgC/m²/h. The highest values were observed at the more sheltered stations, which contained the highest amount of organic material and, the highest input of polluted material. The epipsammic algae contributed with 40% of the total production while the epipelic ones contributed with 60%. The mean value for dark fixation of14C was 63%

Single-row plots for agronomic evaluation of flax (Linum usitatissimum L.) lines

1992 ◽  
Vol 72 (4) ◽  
pp. 997-1000
Author(s):  
G. N. Atlin ◽  
E. O. Kenaschuk ◽  
D. J. Lockwood
Keyword(s):  
Site Selection ◽  
Linum Usitatissimum ◽  
Breeding Lines ◽  
Single Row ◽  
Plot Size ◽  
Linum Usitatissimum L ◽  
Agronomic Evaluation ◽  
Maturity Date ◽  
The Mean ◽  
Highly Correlated

The usefulness of short, single-row plots for preliminary agronomic evaluation of flax (Linum usitatissimum L.) breeding materials was assessed by comparing 25 cultivars and breeding lines in 1.5-m rows and in conventional multiple-row plots at four western Canadian locations. Line means over locations for plant height, maturity date, and grain yield were highly correlated in the two plot sizes. Heritability of yield (the reference unit was the mean of a line in four, four-replicate trials) was 0.66 for the single-row plots and 0.70 for the multiple-row plots. Two-site selection in 1.5-m single rows was predicted to give greater gains than single-site selection in multiple-row plots.Key words: Linum usitatissimum, plot size, heritability, genotypic correlation, predictred gains

scholarly journals Diet, prey selection, and activity of Asian golden cats and leopard cats in northern Laos

2020 ◽  
Vol 101 (5) ◽  
pp. 1267-1278
Author(s):  
Jan F Kamler ◽  
Xaysavanh Inthapanya ◽  
Akchousanh Rasphone ◽  
Anita Bousa ◽  
Chanthavy Vongkhamheng ◽  
...  
Keyword(s):  
Prey Selection ◽  
Activity Patterns ◽  
Potential Predator ◽  
Important Prey ◽  
Murid Rodents ◽  
Dietary Niche ◽  
The Mean ◽  
Leopard Cat ◽  
Prionailurus Bengalensis ◽  
Felid Species

Abstract The Asian golden cat (Catopuma temminckii) occurs in small, declining, and highly fragmented populations throughout Southeast Asia, whereas the smaller leopard cat (Prionailurus bengalensis) is common and widespread. In contrast to leopard cats, little is known about the ecology of Asian golden cats, and resource partitioning between these species has not been studied. We used DNA-confirmed scats, camera-trap data, and prey surveys, to determine the diet, prey selection, and activity, of Asian golden cats and leopard cats in a protected area in northern Laos. The two felids had different diets: Asian golden cats consumed mostly ungulates (35% biomass consumed), murid rodents (23%), and carnivores (15%), whereas leopard cats consumed mostly murid rodents (79%). Asian golden cats were not random in their consumption of ungulates, because muntjac (Muntiacus spp.) were selectively consumed over larger ungulates, indicating muntjac were preyed upon rather than scavenged. Dietary overlap between the two felid species was moderate (R0 = 0.60), and the dietary niche breadth of Asian golden cats (B = 8.44) was nearly twice as high as that of leopard cats (4.54). The mean (± SD) scat diameter was greater for Asian golden cats (2.1 ± 0.3 cm) than leopard cats (1.8 ± 0.2 cm), although diameters of leopard cat scats were considerably larger than previously assumed for this species. The felid species differed in their activity patterns, because Asian golden cats were diurnal, whereas leopard cats were nocturnal, although they did not differ in their use of elevation, suggesting there was no habitat segregation. Overall, leopard cats appeared to coexist with Asian golden cats, a potential predator and competitor, by exhibiting dietary and temporal partitioning. Our results showed that muntjac were important prey of Asian golden cats, suggesting the management of muntjac might be important for conserving populations of Asian golden cats.

Population structure and secondary production of Heteromastus filiformis (Polychaeta: Capitellidae) in the Loire estuary, France

2002 ◽  
Vol 82 (3) ◽  
pp. 395-402 ◽  
Author(s):  
Patrick Gillet ◽  
Eric Gorman
Keyword(s):  
Secondary Production ◽  
Intertidal Zone ◽  
Life Time ◽  
Sediment Layer ◽  
Fresh Weight ◽  
Annual Variations ◽  
Annual Biomass ◽  
The Mean ◽  
Recruitment Period ◽  
Heteromastus Filiformis

A survey was carried out from April 1998 to June 2000 to study the structure and the secondary production of the population of Heteromastus filiformis in the Loire estuary. Each month, samples were collected in the intertidal zone of Mindin harbour. The length of the thorax (L12) was correlated with the fresh weight (FW) with the relation FW=1·49848 L12–3·62804 (r=0·92). In 1999, the mean density was 2184 ind m−2 with a minimum of 1104 ind m−2 in December and a maximum of 3328 ind m−2 in March. The mean annual biomass was 15·4 g m−2 with a minimum of 2·6 g m−2 in December and a maximum of 28·2 g m−2 in March. Most of the histograms of size–frequency are unimodal and could be considered a single cohort except in May and November/December 1999. The abundance and biomass of the population of H. filiformis decreased during summer and winter which are mortality periods and increase during spring and autumn which are recruitment periods for the population. The life time for a cohort was from six to nine months depending on the recruitment period and on the inter-annual variations. The secondary production was estimated by the method of Crisp (1971). The annual secondary production in 1999 was P=104·3 g m−2 with B¯=15·4 g m−2 and P:B¯=6·8. The quantity of sediment reworked by H. filiformis is about 116 l m−2 y−1 or 65 kg m−2 y−1 which is approximately a deep-sediment layer of 12 cm transported to the surface annually.

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