Vigilance Patterns of Bald Eagles Feeding in Groups

The Auk ◽  
1986 ◽  
Vol 103 (2) ◽  
pp. 263-272 ◽  
Author(s):  
Susan K. Knight ◽  
Richard L. Knight
Keyword(s):  
Group Size ◽  
Human Activity ◽  
Small Groups ◽  
Haliaeetus Leucocephalus ◽  
Potential Danger ◽  
Predator Detection ◽  
Bald Eagles ◽  
Additional Function ◽  
Scanning Time ◽  
Large Groups

Abstract Patterns of vigilant behavior of wintering Bald Eagles (Haliaeetus leucocephalus) feeding on spawned salmon were examined in 1983-1984 on the Nooksack River in northwestern Washington. Vigilance in feeding birds has, in general, been attributed to predator detection; however, we proposed an additional function of vigilance in socially feeding birds that are vulnerable to food robbery and possible injury by conspecifics. We tested predictions of two nonexclusive hypotheses: (1) eagles look up while feeding to detect danger from humans, and (2) eagles look up while feeding to detect pirating attempts or avoid injury by conspecifics. Results suggest that the function of vigilance varies, depending on the size of the feeding group. Vigilance patterns of eagles feeding in small groups (1-4 eagles) and medium groups (5-7 eagles0 are consistent with hypothesis 1, whereas those of eagles feeding in large groups (8-14 eagles) are consistent with hypothesis 2. Eagles in small groups were more vigilant (measured as scanning time and rate of head raising) when feeding near potential danger (riverbank cover) than when far from danger. Adult eagles feeding in areas of intense human activity were more vigilant than immatures feeding at the same site and were more vigilant than both adults and immatures feeding at secluded sites. Vigilance declined as group size increased from 1 to 4 eagles, and increased as group size ranged from 8 to 14 eagles. Feeding eagles that were looking up at the time of a pirating attempt were more successful in keeping their food than eagles with their heads down. In feeding areas where human activity was minimal, eagles formed larger groups than at more disturbed sites.

scholarly journals Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay

2014 ◽  
Vol 281 (1789) ◽  
pp. 20140184 ◽  
Author(s):  
Stefan Fischer ◽  
Markus Zöttl ◽  
Frank Groenewoud ◽  
Barbara Taborsky
Keyword(s):  
Group Size ◽  
Small Groups ◽  
Cooperative Breeding ◽  
Breeding Systems ◽  
Idle Period ◽  
Cognitive Constraints ◽  
Size Dependent ◽  
Cooperatively Breeding ◽  
Group Members ◽  
Large Groups

In cooperative breeding systems, dominant breeders sometimes tolerate unrelated individuals even if they inflict costs on the dominants. According to the ‘pay-to-stay’ hypothesis, (i) subordinates can outweigh these costs by providing help and (ii) dominants should be able to enforce help by punishing subordinates that provide insufficient help. This requires that dominants can monitor helping and can recognize group members individually. In a field experiment, we tested whether cooperatively breeding cichlid Neolamprologus pulcher subordinates increase their help after a forced ‘idle’ period, how other group members respond to a previously idle helper, and how helper behaviour and group responses depend on group size. Previously idle helpers increased their submissiveness and received more aggression than control helpers, suggesting that punishment occurred to enforce help. Subordinates in small groups increased their help more than those in large groups, despite receiving less aggression. When subordinates were temporarily removed, dominants in small groups were more likely to evict returning subordinates. Our results suggest that only in small groups do helpers face a latent threat of punishment by breeders as predicted by the pay-to-stay hypothesis. In large groups, cognitive constraints may prevent breeders from tracking the behaviour of a large number of helpers.

scholarly journals The Impact of Group Size on Decision Effectiveness

2020 ◽  
Vol 3 (2) ◽  
pp. 108
Author(s):  
Juliana Osmani
Keyword(s):  
Group Size ◽  
Small Groups ◽  
Quantitative Research ◽  
Banking Institutions ◽  
High Level ◽  
The Impact ◽  
Large Groups ◽  
The Relationship ◽  
Individual Commitment

The relationship between organization and environment, based on the need to gather information and find resources, is increasingly characterized by a high level of uncertainty. Uncertainty means that managers do not have enough information and time to anticipate changes and make good decisions. More and more managers make decisions about new problems or situations. The level of risk increases, as well as the degree of complexity that the decision maker has to face. Under these conditions, organizations are moving towards the use of groups. The main purpose of the current research is to identify what are the most important benefits and limits of the group referring to its size, taking into analysis the banking institutions. For the current study is adopted the quantitative research and for the data collection is used the questionnaire. A total of 344 questionnaire are distributed. 80 percent of the participants agree that group size affects the quality of the decisions made and most of them prefer small groups. Also, most of them believe that within large groups are more conflicts, the relationships between members are more formal, the attention and individual commitment are lower than in small groups, the consensus is difficult, decisions can be made only through a voting process and there are no delays in decision-making, but coordination problems are not necessarily higher than within small groups.

scholarly journals Pareto meets Olson – A Note on Pareto-optimality and Group Size in Linear Public Goods Games

ORDO ◽  
2012 ◽  
Vol 63 (1) ◽  
Author(s):  
Michael Pickhardt
Keyword(s):  
Public Goods ◽  
Group Size ◽  
Small Groups ◽  
Pareto Optimality ◽  
Pareto Optimal ◽  
Public Goods Games ◽  
Optimal Allocations ◽  
Large Groups ◽  
The Relationship ◽  
Pareto Optimal Allocations

SummaryIn this paper I examine the relationship between Pareto-optimality and group size in linear public goods games or experiments. In particular, I use the standard setting of homogeneous linear public goods experiments and apply a recently developed tool to identify all Pareto-optimal allocations in such settings. It turns out that under any conceivable circumstances, ceteris paribus, small groups have a higher Pareto-ratio (Pareto-optimal allocations over total allocations) than large groups. Hence, if Pareto-optimality of an allocation is a property that makes such allocations acceptable and maintainable, small groups will find is easier to provide Pareto-optimal amounts of a public good than large groups. This is a novel reasoning for Mancur Olson′s claim, in particular, with respect to what he has termed inclusive goods and inclusive groups.

scholarly journals The effects of group size and subtherapeutic antibiotic alternatives on growth performance and morbidity of nursery pigs: a model for feed additive evaluation1

2018 ◽  
Vol 2 (3) ◽  
pp. 298-310 ◽  
Author(s):  
Kristin M Olsen ◽  
Nicholas K Gabler ◽  
Chris J Rademacher ◽  
Kent J Schwartz ◽  
Wesley P Schweer ◽  
...  
Keyword(s):  
Health Status ◽  
Growth Performance ◽  
Group Size ◽  
Small Groups ◽  
Block Design ◽  
Feed Additive ◽  
Experimental Unit ◽  
Careful Study ◽  
Dietary Treatments ◽  
Large Groups

Abstract The objectives of this experiment were to evaluate the effects of alternatives to antibiotic growth promoters (AGP), two group sizes, and their interaction on nursery pig performance to serve as a model for future AGP alternative studies. A 41-d experiment was conducted in a commercial wean-to-finish barn; 1,300 piglets weaned at 21 d of age (weaned 2 or 4 d prior to experiment; 6.14 ± 0.18 kg BW; PIC 1050 sows and multiple sire lines) were blocked by sire, sex, and weaning date, then assigned to eight treatments: four dietary treatments each evaluated across two group sizes. The four dietary treatments were: negative control (NC), positive control (PC; NC + in-feed antibiotics), zinc oxide plus a dietary acidifier (blend of fumaric, citric, lactic, and phosphoric acid) (ZA; NC + ZnO + acid), and a Bacillus-based direct-fed-microbial (DFM) plus resistant potato starch (RS) (DR; NC + DFM + RS). The two group sizes were 31 or 11 pigs/pen; floor space was modified so area/pig was equal between the group sizes (0.42 m2/pig). There were 7 pens/diet with 11 pigs/pen and 8 pens/diet with 31 pigs/pen. Data were analyzed as a randomized complete block design with pen as the experimental unit. Diagnostic assessment of oral fluids, serum, and tissue samples was used to characterize health status. Pigs experienced natural challenges of acute diarrhea and septicemia in week 1 and porcine reproductive and respiratory syndrome virus (PRRSV) in weeks 4–6. There was a significant interaction between diet and group size for ADG (P = 0.012). PC increased ADG in large and small groups (P < 0.05) and ZA increased ADG only in large groups (P < 0.05). Small groups had improved ADG compared to large groups when fed NC or DR diets (P < 0.05). Similarly, PC increased ADFI (P < 0.05). Compared to NC, ZA improved ADFI in large groups only (P < 0.05; diet × group size: P = 0.015). Pigs fed PC had greater G:F than NC (P < 0.05), and small groups had greater G:F than large groups (P < 0.05). There was no effect of ZA or DR on G:F. Pigs fed PC required fewer individual medical treatments than NC and pigs fed ZA were intermediate (P = 0.024). More pigs were removed from large than small groups (P = 0.049), and there was no effect of diet on removals (P > 0.10). In conclusion, careful study design, protocol implementation, sample collection, and recording of important information allowed us to characterize the health status of this group of pigs and determine treatment effects on growth performance and morbidity.

scholarly journals Dynamics of muskox groups in northeastern Alaska

Rangifer ◽  
1993 ◽  
Vol 13 (3) ◽  
pp. 83 ◽  
Author(s):  
P. E. Reynolds
Keyword(s):  
Group Size ◽  
Small Groups ◽  
Social System ◽  
Early Winter ◽  
Food Acquisition ◽  
Ovibos Moschatus ◽  
Large Groups

Group size and stability was studied in a population of re-established muskoxen (Ovibos moschatus) in northeastern Alaska by re-locating radio-collared animals. Mixed-sex groups (cows, calves, sub-adults and often adult bulls) ranged in size from 2-118 with a mean of 19.2. Almost 60 % of all mixed-sex groups contained 5¬19 individuals. Solitary cows were seen infrequently. Adult bulls were observed in mixed-sex groups, in bull groups or alone. Bull groups averaged 3.9 and ranged in size from 2 to 12. Thirty percent of all adult bulls seen outside mixed-sex groups were solitary animals. Mixed-sex groups were significantly smaller in summer/ rut Quly-September) than in midwinter Qanuary-March), spring/calving (April-June) and early winter (October-November). Mean group size was 12.2 in August compared with 23.6 in February. In August, during the rut, numbers of small groups (2-14) increased, while numbers of medium-sized (15-29) and large groups (> 29) decreased. Bull groups were significantly larger in spring/calving than during other seasons. The ratio of single bulls to bull groups was less than 0.30 in winter, increased in June, and reached a maximum during the rut in August when more than 2 single bulls were seen for every bull group. Group size and individuals within a group changed frequently. This fluid social system provides a balance between protection from predators, efficient food acquisition and the formation of harems during the rut.

scholarly journals A 60-Kilodalton Protein Component of the Counting Factor Complex Regulates Group Size in Dictyostelium discoideum

2006 ◽  
Vol 5 (9) ◽  
pp. 1532-1538 ◽  
Author(s):  
Debra A. Brock ◽  
Wouter N. van Egmond ◽  
Yousif Shamoo ◽  
R. Diane Hatton ◽  
Richard H. Gomer
Keyword(s):  
Acid Phosphatase ◽  
Phosphatase Activity ◽  
Dictyostelium Discoideum ◽  
Group Size ◽  
Small Groups ◽  
Acid Phosphatase Activity ◽  
Low Levels ◽  
Fourth Component ◽  
Protein Components ◽  
Large Groups

ABSTRACT Much remains to be understood about how a group of cells or a tissue senses and regulates its size. Dictyostelium discoideum cells sense and regulate the size of groups and fruiting bodies using a secreted 450-kDa complex of proteins called counting factor (CF). Low levels of CF result in large groups, and high levels of CF result in small groups. We previously found three components of CF (D. A. Brock and R. H. Gomer, Genes Dev. 13:1960-1969, 1999; D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, R. Ammann, and R. H. Gomer, Development 129:3657-3668, 2002; and D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, W. Jang, R. Ammann, and R. H. Gomer, Eukaryot. Cell 2:788-797, 2003). We describe here a fourth component, CF60. CF60 has similarity to acid phosphatases, although it has very little, if any, acid phosphatase activity. CF60 is secreted by starving cells and is lost from the 450-kDa CF when a different CF component, CF50, is absent. Although we were unable to obtain cells lacking CF60, decreasing CF60 levels by antisense resulted in large groups, and overexpressing CF60 resulted in small groups. When added to wild-type cells, conditioned starvation medium from CF60 overexpressor cells as well as recombinant CF60 caused the formation of small groups. The ability of recombinant CF60 to decrease group size did not require the presence of the CF component CF45-1 or countin but did require the presence of CF50. Recombinant CF60 does not have acid phosphatase activity, indicating that the CF60 bioactivity is not due to a phosphatase activity. Together, the data suggest that CF60 is a component of CF, and thus this secreted signal has four different protein components.

scholarly journals The Association between Sensitivity, Group Size and Satisfaction

2020 ◽  
Author(s):  
Kamarul Zaman Ahmad
Keyword(s):  
Group Size ◽  
Small Groups ◽  
Statistical Tests ◽  
Shop Floor ◽  
Manufacturing Plant ◽  
Hierarchical Multiple Regression ◽  
Interaction Terms ◽  
Worker Satisfaction ◽  
Large Groups ◽  
The Relationship

Previous research have looked at the relationship between sensitivity and satisfaction, and between group size and satisfaction. However there appears to be no reported studies that have investigated the interacting effects of group size on the relationship between sensitivity and satisfaction. Data from 257 shop floor workers in a light manufacturing plant in the U.K were collected and analysed. Group size was significantly negatively related to satisfaction with co-workers. Statistical tests of hierarchical multiple regression were used to determine the significance of the interaction terms (sensitivity x group size) on pay and co-worker satisfaction. Support for both hypotheses were obtained. Results suggested that group size significantly moderated the relationship between sensitivity and pay satisfaction, and the relationship between sensitivity and co-worker satisfaction. Linear regression plots showed that the relationship between sensitivity and satisfaction (pay and co-worker) were negative in large groups but positive in small groups.  

scholarly journals Ecological interactions and habitat modification in nesting Common Murres, Uria aalge

1996 ◽  
Vol 6 (3) ◽  
pp. 261-269 ◽  
Author(s):  
Julia K. Parrish ◽  
Robert T. Paine
Keyword(s):  
Reproductive Output ◽  
Habitat Modification ◽  
Haliaeetus Leucocephalus ◽  
Uria Aalge ◽  
Ecological Interactions ◽  
Bald Eagles ◽  
Predator Removal ◽  
Common Murre ◽  
Corvus Caurinus ◽  
Common Murres

SummarySeabird populations suffer from a variety of natural and human-induced sources of mortality and loss of lifetime reproductive output. On the outer coast of Washington State, Common Murre Uria aalge populations have been in decline for approximately the last decade and are currently reproductively active only at Tatoosh Island. These murres nest in two basic habitat types: crevices (25% of the population) and larger cliff-top subcolonies (75%). Murres in cliff-top subcolonies have suffered dramatic reductions in reproductive success in recent years relative to conspecifics nesting in the crevices, primarily due to egg predation by Glaucous-winged Gulls Larus glaucescens and Northwestern Crows Corvus caurinus, facilitated by the presence of Bald Eagles Haliaeetus leucocephalus. Because predator removal is not feasible and creation of additional crevice habitat is difficult, expensive and potentially ineffective, we have designed a temporary habitat modification (the “silk forest”) which replaces the natural vegetation cover and modifies the interaction between murres and eagles. Within the test subcolony, murres nesting under and immediately adjacent to the silk forest produced nearly twice as many eggs per square metre as their conspecifics nesting in adjacent exposed-ground areas.

scholarly journals Climate-mediated cooperation promotes niche expansion in burying beetles

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Syuan-Jyun Sun ◽  
Dustin R Rubenstein ◽  
Bo-Fei Chen ◽  
Shih-Fan Chan ◽  
Jian-Nan Liu ◽  
...  
Keyword(s):  
Climate Change ◽  
Small Groups ◽  
Social Insects ◽  
Breeding Success ◽  
Cooperative Groups ◽  
Burying Beetles ◽  
Ecological Consequences ◽  
Social Species ◽  
The Earth ◽  
Large Groups

The ability to form cooperative societies may explain why humans and social insects have come to dominate the earth. Here we examine the ecological consequences of cooperation by quantifying the fitness of cooperative (large groups) and non-cooperative (small groups) phenotypes in burying beetles (Nicrophorus nepalensis) along an elevational and temperature gradient. We experimentally created large and small groups along the gradient and manipulated interspecific competition with flies by heating carcasses. We show that cooperative groups performed as thermal generalists with similarly high breeding success at all temperatures and elevations, whereas non-cooperative groups performed as thermal specialists with higher breeding success only at intermediate temperatures and elevations. Studying the ecological consequences of cooperation may not only help us to understand why so many species of social insects have conquered the earth, but also to determine how climate change will affect the success of these and other social species, including our own.

scholarly journals Development of Herbarium Book as Biology Instructional Media in Plant Morphology Subject for Biology Education Undergraduate Students, University of Pasir Pangaraian

2020 ◽  
Vol 4 (1) ◽  
pp. 10-19
Author(s):  
Dahlia Dahlia
Keyword(s):  
Undergraduate Students ◽  
Small Groups ◽  
Leaf Morphology ◽  
Biology Education ◽  
Plant Morphology ◽  
Average Score ◽  
Study Program ◽  
Individual Assessment ◽  
Large Groups

The development of instructional especially media of a herbarium book is an innovation that aims to assist students in searching directly the object of leaf morphology studies. This development research starts from the needs analysis stage which is used to gather information, planning in media making, media design, media making, after that product validation by a team of media experts and material experts, then testing individual products, small groups and large groups. The subject of this product testing were students of the Biology Education Study Program at Pasir Pengaraian University. The results of the validation by the material experts showed that the quality of learning media using the herbarium book on leaf morphology material was included in the "very feasible" criteria, with an average score of 86.46%. The results of validation by media experts are included in the "very feasible" criteria, with an average score of 88.54%. Individual assessment obtained the criteria of "very feasible", with an average score of 84.16%. Judgement from small groups obtained a percentage of eligibility of 81.45% with very feasible criteria, and judgement from large groups of 83.95% with "very feasible" criteria. The results of the development of herbarium book media are very decent.

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