bluuebunny/crossref_metadata_2025 huggingface dataset:
The Feeding Behaviour of Domestic Chicks as a Function of Rate of Pecking By a Surrogate Companion
Authors: Tolman C.W.
Published: April 2008

The feeding behaviour of chicks was observed in the presence of a model hen that was made to peck at rates of 30, 60, 120, and 240 per min. under two conditions of presentation: with the beak striking the floor to make a tapping sound and with the beak failing to strike the floor for silent pecking. Tapping sounds were also presented at the four rates while the model remained notionless. Under the silent pecking conditions, the number of food pecks emitted by the subjects was found to increase with the rate of pecking by the model. The addition of the tapping sound enhanced this effect, particularly at the two higher rates. The tapping sounds alone had no apparent effect upon the feeding behaviour of the chicks. It was concluded that the pecking movements of companions can be important in controlling the feeding behaviour of chicks. The tapping sound was tentatively interpreted as a general motivator.
The Lutong of Kuala Selangor
Authors: Bernstein Irwin S.
Published: April 2008

A field study of the Lutong, (Presbytis cristatus) was conducted in Malaya. Lutong troops were observed for more than 1000 hours and were found to be markedly territorial. Only one control male lives in each troop and he actively defends the territory against incursions by other lutong males. Each troop moves slowly through its territory feeding and resting and comes into frequent visual contact with adjacent troops. Each troop is a well organized social unit but only the control males show consistent hostility to one another when troops meet. Grooming, play, sexual responses, maternal behavior and agonistic episodes are described as well as travel, feeding and diurnal patterns. These patterns appear similar to those reported in other Presbytis species, but contrast markedly with macaque and baboon reports. Differences in behavior between species of Presbytis do not exceed differences reported in the same species by different observers in different areas.
Reproductive Behavior in the Passifloraceae and Some of Its Pollinators in Central America
Authors: Janzen Daniel H.
Published: April 2008

The movements of the styles (and consequently stigmas) of flowers of Central American Passifloraceae is described. The timing of this behavior is closely associated with the timing of flower visitors and pollinators; the result is that the first pollinators to arrive visit many flowers and can contact only anthers. Later, the styles bend over and these same insects place a mixture of pollen from many flowers on the stigmas, rather than a coat of pollen from the same flower as would have been the case had the styles been bent over from the time of flower opening. The flowers pollinated by hummingbirds (flying all day) are much slower to turn down their stigmas than are the species pollinated by early morning bees with a short flight period. It is postulated that the selective forces that have led to the timing and movements of the styles and stigmas are those positive advantages generally associated with out-crossing in plants.
Maternal Behavior in the Rat: an Investigation and Quantification of Nest Building
Authors: Denenberg Victor H. , Taylor Rhoda E. , Zarrow M.X.
Published: April 2008

A technique has been developed to quantify nest building in rats. Small wooden dowels are provided as nest material. Rats shred the dowels, and the degree of nest building is determined by the amount shredded daily. Pregnant females show a marked increase in dowel shredding at or just prior to the time of parturition; shredding falls precipitously after parturition. Males and nonpregnant females show no such pattern over an equivalent period of time; their dowel shredding, in fact, decreases over time. A series of experiments were carried out involving hormone manipulations of pregnant and nonpregnant females. The only significant finding was that progesterone reduced the percentage of females which shredded dowels and also delayed the time of onset of this behavior. When nonpregnant females and males were exposed to cool ambient temperatures, dowel shredding increased markedly. On the other hand, exposing females to a warm temperature blocked dowel shredding behavior. Some similarities and differences between these findings and findings for the rabbit and mouse are discussed.
Measures of the Aggression of Parental Male Three-Spined Sticklebacks
Authors: Wootton R.J.
Published: April 2008

This study compared three methods used to measure aggression in the male three-spined stickleback by using them to measure changes in behaviour over the twelve days following the fertilization of eggs. These methods have been used in various studies without the certainty that they measure the same behavioural phenomena. In addition a number of different, possible measures of aggression were taken in the hope that this would show whether a unitary drive concept of aggression was realistic. The methods consisted of recording the behaviour of experimental males in one of three situations: (i) a tube containing another male was visible for five minutes, (ii) another male was visible through a glass partition at all times, (iii) a fish-shaped wax model was visible for two minutes. Each method showed that in the twelve days after the fertilization of eggs, there was a U-shaped trend in the frequency of biting, frequency of charging and in the rate of biting per minute of time spent oriented towards the test stimulus. In Method (i), the total oriented time took up about 70% of a test period, was not correlated with frequency of biting and did not show a U-shaped trend. In Method (ii) and (iii) the total oriented time formed an average less than 50% of a test period, was correlated with frequency of biting and did follow a U-shaped trend over the 12 days. In both Method (iii) and especially Method (ii) fanning was an important component of the test period, notably in the middle of the 12 day period. There were no comparable trends in either spine-raising or threatening. The agreement between Methods (i) and (ii) was very close for the frequency and rate measures but not for the duration measures. Only one model, that painted red ventrally and silver dorsally, showed a significant degree of agreement with Methods (i) and (ii). The measure rate of biting per minute of oriented time, which is independent of both the length of the test period and the total oriented time, showed a very high level of agreement in comparisons between the three methods. Allowing for the differences inherent in the methods it was concluded that there probably was a common causal factor for the changes in aggression seen over the parental period and measured in the three different test methods. The literature and personal observations suggest that these changes are paralleled by changes in territorial size over the parental period. Behaviour such as spine-raising and threatening did not show similar changes and so may not be affected by the same factor or factors.
Reproductive Behavior and Its Relation To Territoriality in Cal Op Ter Yx Ma Cula Ta (Beauvois) (Odonata: Calopterygidae)
Authors: Waage Jonathan K.
Published: April 2008

Pair-forming, courtship, mating, and post-copulatory behaviors are described for populations of Calopteryx maculata in the central and northeastern United States. Two pair forming displays were noted: (1) a display of the male's wings and abdomen (the cross display) at an oviposition site in his territory to an approaching female; and (2) a hovering courtship flight before a perching female. Similar displays are performed by C. aequabilis, C. splendens, and C. virgo, although intra- and interspecific variations occur in the cross display and its position in the pair-forming sequence. Both displays present the species and sex-specific color patterns of the male's wings and abdomen to the female early in pair formation. Pair formation differs in the three types of male-female encounters observed: (1) female flies into the male's territory; (2) male discovers an ovipositing female; and (3) male discovers a female on shore. The first type involves only territorial males and is the only one in which the cross display is performed. The other encounters involve both territorial and nonterritorial males. Courtship flight is present in the pair-forming sequences of all three encounter types. The cross display identifies a particular male with an oviposition site in his territory. This makes it possible for females to choose among males on the basis of the suitability of these oviposition sites. Females mating with territorial males benefit from reduced interference from other males during oviposition. The selective advantages of territoriality for a Calopteryx male are: (1) an increase in his mating frequency by the exclusive occupation of an oviposition area attractive to females ; and (2) an increase in the number of eggs he fertilizes by protecting mated females during their oviposition. It is likely that territorial behavior in Calopteryx functions primarily in obtaining and selecting mates and secondarily in reducing interference with pair formation and oviposition. Sexual selection among males for attracting mates and lessening sperm competition may have been an important factor in the evolution of territorial behavior in Calopteryx.
Thermoregulatory Behavior of Eared Seals
Authors: Gentry Roger L.
Published: April 2008

1. Thermoregulatory behavior was studied in the Steller sea lion and in the South Australian fur seal during their respective reproductive seasons. Data were gathered using a temperature-sampling technique. 2. The rest postures used by animals of both species were closely correlated with solar radiation (as indicated by rock temperatures). At low temperatures both species used postures that concealed the flippers, thus exposing a minimum of surface area to the air. In addition, sea lions huddled against one another at low temperatures, but fur seals did not. 3. No quantitative species differences existed in behavioral responses to low (10°C) rock temperatures. At intermediate temperatures both species progressively exposed their flippers to the air. At high temperatures (30°C and above) both species resorted to the water for cooling. Female sea lions became wet at temperatures 5°C lower than did fur seals. 4. Fur seal males without direct access to water temporarily abandoned their territories and went to sea at a mean rock temperature of 33°C (approximate solar radiation level between 0.666 and 1.073 cal./cm2/min.). 5. Mass movements of females from dry areas across the rookery to the water were temperature-dependent in both species. 6. The behavior of sea lion pups showed less of a direct correlation with temperatures than for their mothers. 7. The social consequences of thermoregulatory behavior were, 1) increased frequency and intensity of sexual investigation by males toward females, 2) an increase by 11% to 15% in aggression among males, and 3) a reduction (by one half) in copulation frequency for males that abandoned their territories to gain access to water for cooling.
Physiological and Biochemical Correlates of Individual Differences in Behavior of Wolf Cubs
Authors: Fox M.W. , Andrews R.V.
Published: April 2008

In two litters of wolf cubs, individual differences in exploratory behavior, prey killing ability and social dominance were demonstrated, test scores showing a high degree of correlation as shown in an earlier study (Fox, 1972). Subjects with high, intermediate and low scores were selected for heart rate determinations monitored biotelemetrically under a test sequence designed to evaluate emotional reactivity. After these temperament and emotional-autonomic reactions had been determined, cubs were subjected to confinement and handling stress, blood samples being taken serially for plasma cortisol estimations. This treatment was repeated after ACTH injection. These findings demonstrate a marked difference in sympathetic tone and adrenal responsiveness to stress between high and low ranking cubs. High ranking cubs showed a greater sympathetic tone (higher resting EKG) and the adrenal-pituitary response to stress and ACTH treatment was of greater magnitude than in subordinates. Subjects of middle rank and with intermediate behavioral scores had a higher sympathetic tone than subordinates and under stress had a shorter latency and greater magnitude of cortisol secretion than either their higher or lower ranking peers.
Triadic Differentiation: an Inhibitory Process Protecting Pair Bonds in Baboons
Authors: Kummer H. , Götz W. , Angst W.
Published: April 2008

Field observation and pilot field experiments suggested the hypothesis that a social inhibition prevents male hamadryas baboons from encroaching on each other's females. The hypothesis was tested in a set of enclosure experiments which led to the following results : 1. When two males were simultaneously confronted with an unfamiliar female, one would become her "owner", either by defeating his rival or by the latter's withdrawal. 2. No fights occurred, however, when one male was allowed to watch a troop mate interact with a new female before he was admitted to them. He then respected the pair bond even if he was dominant over the owner. This agreed with the inhibition hypothesis. The alternative dominance hypothesis was rejected at the 0.01 level. 3. When males from different troops were used, some rivals attacked the owners and took their females. Most attacks were directed by powerful rivals against the particularly inferior males of one troop, suggesting that dominance factors can, in extreme cases, override the rival's inhibition. 4. The inhibition appeared to be restricted to the context of owning females in that it did not significantly affect the male's performance in food dominance tests. 5. A few casual interactions between the pair sufficed to inhibit the rival. The owner's overt demonstrations of possession had no additional effect in these experiments. 6. The stabilizing functions of the inhibition in the hamadryas society are discussed. 7. The inhibited rivals performed a number of redirected and conflict activities. An analysis shows that the inhibition suppresses friendly as well as aggressive approaches in the rival, thus keeping him away from the pair. 8. The owner's interactions with the rival were also inhibited, but much less than the rival's interactions with the pair. In contrast, interactions between the pair were increased and intensified by the rival's presence. 9. In one exceptional test, the female appeared in the role of the excluded rival. The formation of triads thus seems to reduce two of the component dyadic relationships while furthering the third. The possible mechanisms of such "triadic differentiation" are mentioned and its probable function in the formation of groups and subgroups is outlined.
Aspects of Necrophoric Behavior in the Red Imported Fire Ant, Solenopsis Invicta
Authors: Howard Dennis F. , Tschinkel Walter R.
Published: April 2008

Removal of dead ants from the nest (necrophoric behavior) is released solely by contact chemical cues in the fire ant, Solenopsis invicta Buren. Exhaustively extracted corpses do not release necrophoric behavior, but the extracts do when applied to filter paper bits. The necrophoric releaser is absent at death but appears rapidly and reaches a plateau within about an hour. The rate of signal appearance is identical in heat and freeze killed workers, implying a non-enzymatic origin. There is no specialized caste or size of worker which carries out necrophoric labor. In the field, in the absence of slope, corpse-bearing workers head outward from the nest on random radii and drop their corpses at unpredictable distances, making refuse piles rare. There is a positive relationship between slope and the presence of refuse piles, and these are located downhill from the mound. When the headings of necrophoric workers were measured in circular arenas in the lab, the only potential orientational cue (tested : landmarks, light, 5°, 10°, 15° slope) which resulted in non-random distribution of headings was slope. The concentration of the headings was a direct function of the slope and seemed to plateau at about 15°. Corpse-bearing ants show stereotyped behavior upon encountering refuse piles and adding their burden to it. Chemical stimuli probably issuing from the feces in the refuse pile bring about the end of necrophoric behavior and maintain the refuse pile. These chemical cues, as also those initiating necrophoric behavior, must be contacted to be effective.
Sexual Selection in the Three-Spined Stickleback: Ii. Nest Raiding During the Courtship Phase
Authors: Li Stacy K. , Owings Donald H.
Published: April 2008

The purpose of this experiment was to test the hypothesis that the disruptive acts (nest raiding), directed by male three-spined sticklebacks, Gasterosteus aculeatus L., toward the eggs and nests of conspecific males evolved as a result of intrasexual selection. We compared the frequency with which a resident male was raided by neighbors when a transparent cylinder containing a male was introduced into his territory, with the frequency of raiding during the presence of a similarly introduced female. On the basis of the intrasexual selection hypothesis, we predicted that raiding should occur more often when the female was present. We also studied the relationship between raiding and the relative dominance status of raided and raiding males. If raiding and dominance conflict are alternative strategies in intrasexual competition, then raiding should have been most intense when raided and raiding males were least discrepant in dominance status. Resident males responded appropriately to introduced fish, i.e., with more courtship and nesting behavior toward females and more aggression toward males. Introduced females were much more effective in eliciting raiding by neighbors than introduced males. The highest status neighbors tended to raid the most. There was some evidence that raiding reduced the raided male's courtship motivation. The outcome of the study is compatible with the hypothesis that nest raiding is adaptive because it increases the relative attractiveness of the raider to females.
The Influence of Size Differential On Agonistic Encounters in the Mantis Shrimp, Gonodactylus Viridis
Authors: Caldwell Roy L. , Dingle Jeri
Published: April 2008

The influence of size on the aggressive behavior of Gonodactylus viridis was examined by matching large animals against others 50, 60, 70, 80, 90, and 100% their size. With size discrepancies of 10% or greater, the larger animals won significantly more of their fights. The smaller participants of a contest avoided more, attacked less, and threatened more than did their larger opponents. When the contestants were evenly matched, attack and avoid values were intermediate, but the animals threatened as often as did the smaller animals. These results are reviewed in light of recent game theory analyses which suggest that threat should be used by the smaller contestant or when the risk of escalation is great compared to the expected pay-off.
The Temporal Pattern of Mosquito Flight Activity
Authors: Peterson Eric L.
Published: April 2008

48 Mosquitoes (Culex pipiens fatigans) were isolated in constant darkness and their flight activity monitored with an automatic acoustical recording system. Three basic features were recognized: (I) there was a strong endogenous circadian rhythm with activity in the subjective evening and morning (Fig. 9) ; (2) flights came in bouts with the bouts more closely spaced in the evening activity period (Fig. 10) ; (3) the distributions of flight and interval lengths suggested that the onset and cessation of flight were relatively simple stochastic processes (Figs. 5, 6, 7). A stochastic model, requiring a few simple assumptions, was proposed to accommodate these features. Computer simulation of mosquito activity, based upon the model, generated patterns which looked like the real thing (Fig. 15).
The Functions of Antlers
Authors: Clutton-Brock T.H.
Published: April 2008

1. This paper reviews evidence for five functional explanations of the evolution of antlers in male cervids: that they are used as weapons in fights; that they allow individuals to defend themselves against predators; that they act as heat radiators during their period of growth; that they advertise an individual's fighting ability and allow males to assess each other without fighting; and that they increase the chances that a male will be selected as a mate by females. 2. There is extensive evidence that antlers are used in fights between competing males. Contrary to some suggestions in the literature, fights are regular during the breeding season and can be damaging. In species where fighting behaviour has been studied in detail, antlers have proved to be effective weapons of defence and offense, and there is no systematic evidence to support the suggestion that antler-less males (hummels) are more successful in competition for females than antlered stags. 3. Though male deer sometimes use their antlers in defence against predators, the absence of antlers in females of most species suggests that this is not their principal function. Nor does it seem likely that antlers evolved as heat-regulating mechanisms - in some species, they are grown during the winter months and there is no tendency for them to be larger in tropical species than in temperate ones. 4. Despite many suggestions, there is no conclusive evidence that males assess each other by their relative antler size and most measures of antler size and shape are not closely correlated with dominance or fighting ability. Nor is there firm evidence that females selectively mate with large-antlered males. 5. The absence of unequivocal support for the importance of antlers in defence against predators, in heat regulation, in assessment between rivals and in attracting mates leaves open the possibility that, despite their bizarre appearance, antlers evolved as weapons and are retained by selection because of their function in intra-specific combat.
Semen Quality, Female Choice and Multiple Mating in Domestic Sheep: a Test of Trivers' Sexual Competence Hypothesis
Authors: Gibson R.M. , Jewell P.A.
Published: April 2008

TRIVERS (1972) proposed that females may choose to mate with males of high sexual competence (the ability to supply sufficient sperm for fertilisation). This hypothesis was tested by allowing ewes in oestrus to choose between four tethered adult rams, two of high and two of low semen quality. Contrary to the hypothesis, ewes did not prefer rams of higher semen quality and, even though frequent mating can depress the fertilising ability of ram semen, the attractiveness of each ram to oestrous ewes was not lowered by frequent ejaculation. Also, in contrast to TRIVERS' suggestion, semen quality and male courtship vigour were not consistently related either between or within individual rams. Ewes mated repeatedly during oestrus, receiving nearly six ejaculates each on average, and over two thirds of ewes mated with more than one ram. Repeated mating, rather than a preference for sexually competent males, might function to ensure fertilisation in female sheep and perhaps in other ruminants.
Time Budgets, Feeding Efficiency and Flock Dynamics in Mixed Species Flocks of Lapwings, Golden Plovers and Gulls
Authors: Barnard C.J. , Thompson D.B.A. , Stephens Hilary
Published: April 2008

1. In mixed species flocks of lapwings and golden plovers, lapwing net rate of energy intake was positively related to the number of conspecifics and the amount of time individuals spent crouching during feeding, but was unaffected by the presence of golden plovers. Plover net rate of energy intake, however, was positively related to crouching tendency, negatively related to the number of lapwings present but unaffected by the number of conspecifics. 2. Golden plovers appeared to join lapwing flocks because they could then crouch more and scan less. The independent negative effect of lapwing number may have been due to feeding interference when there were large numbers of lapwings relative to plovers. 3. When black-headed gulls joined a flock, both lapwings and plovers tended to crouch less and take smaller worms. However, in lapwings these changes appeared to reduce feeding efficiency but plover net rate of energy intake increased as a function of the gull: plover ratio. 4. When gulls were present, the effect of conspecifics on lapwing feeding efficiency disappeared and the presence of plovers had a negative effect. Conversely, in plovers the presence of conspecifics enhanced feeding efficiency and the negative effect of lapwing number disappeared. 5. The arrival of gulls resulted in a decrease in equilibrium lapwing number but no consistent, directional change in plover number. When gulls were present, lapwing number tended to decrease when large numbers of plovers arrived, but increase when small numbers arrived. Increased lapwing number had no significant directional effect on plover number. Changes in lapwing and plover energy intake and species numbers are interpreted in terms of feeding interference and 'dilution' of gull kleptoparasitism. 6. In the absence of gulls, there was no significant directional relationship between increased plover number and lapwing number, but the presence of plovers generally correlated with a reduction in lapwing number. Plover number, however, decreased when large numbers of additional lapwings arrived but increased with small numbers of arrivals. Changes in species energy intake and numbers here are interpreted in terms of feeding interference and time budget changes.
Ecological Constraints On the Social Development of Vervet Monkeys
Authors: Lee P.C.
Published: April 2008

1. Immature animals from three social groups of vervet monkeys (Cercopithecus aethiops) living in adjacent territories were observed in Amboseli National Park, Kenya. Measures of diets and food densities suggested that food quality and distribution differed both between the groups and between the dry and wet seasons, such that the dry season was a period of low food quality, and Group A had the lowest food density. 2. Seasonal differences in dietary quality and the time spent feeding produced seasonal differences in the rates of high energy social interactions: play, aggression, and competition. 3. Differences between groups in food availability and quality affected rates of social interactions such that Group A generally had the lowest frequency of interactions. Both between groups and between seasons, low food quality reduced the frequency of interactions and increased the time spent feeding. 4. Play rates were shown to be highly responsive to the energy estimated to be available from the diet during the different seasons such that play was eliminated from the immature social repertoire during the stressful dry season. 5. The time course of weaning also appeared to be influenced by seasonal and inter-group differences in habitat. Few females gave birth in consecutive years, and many suckled their infants into the second year of life. Stressed females weaned infants earlier. It is suggested that prolonged investment is a response to environmental variation and plays an important role in female reproductive strategies. 6. It is suggested that the immatures in these groups maximised the time and energy available for different types of social interactions in a different way in each season and in the different groups. This social flexibility may be viewed as part of an adaptive complex of behaviour during the immature stage of a life history.
Vocal Communication in a Neotropical Treefrog, Hyla Ebraccata: Aggressive Calls
Authors: Wells Kentwood D. , Schwartz Joshua J.
Published: April 2008

We studied the aggressive calls of Hyla ebraccata in Panama by recording natural interactions in the field and by playing recordings of natural and synthetic calls to males. Aggressive calls of this species had higher pulse repetition rates than advertisement calls and often were much longer. Aggressive calls also were much more variable in introductory note duration, pulse rate, rise time, and the number and structure of click notes. Pulse repetition rate was negatively correlated with the duration of the introductory note, as were the number of click notes in the call and the number of pulses in each click. In natural encounters, the duration of introductory notes increased as the distance between interacting males decreased. Males gave aggressive calls in response to playbacks of both advertisement and aggressive calls, but aggressive calls were much more effective in eliciting such responses. The proportion of aggressive calls and the duration of introductory notes generally increased with increasing playback intensity. Playbacks of synthetic calls which varied in pulse repetition rate and rise time showed that a high pulse repetition rate was the most important feature in eliciting aggressive responses from males, but rise time also was important when calls had fast pulse rates. The aggressive calls of this species appear to be a graded signaling system, the first to be documented in amphibians.
Parent-Offspring Conflict in Budgerigars
Authors: Stamps Judy , Clark Anne , Arrowood Pat , Kus Barbara
Published: April 2008

Despite widespread theoretical interest in genetic conflict between parents and offspring, there is little empirical evidence that it exists in nature. Theoretical models suggest two outcomes of conflict not predicted by alternate theories: (1) offspring that control the allocation of parental investment might show escalated demand behaviours (e.g., begging) and demand more resources than they could efficiently use and (2) parents might evolve behavioural counterstrategies which prevented offspring from obtaining extra resources, but which were more costly than a "laissez-faire" parental strategy allowing offspring control. These predictions were tested in budgerigars, (Melopsittacus undulatus) in large flight cages at Davis, California. Budgerigar clutches hatch extremely asynchronously, yet all nestlings grew at similar rates and fledged at similar sizes and ages. This independence of hatch order and performance seemed due primarily to the mother budgerigar's allofeeding strategy: females allofed offspring mainly on the basis of size, and only secondarily attended to begging rate. Offspring of a given age and size were treated the same by their mothers regardless of hatch order, and offspring undersized for their age were fed as if they were younger. In contrast, male budgerigars attended to offspring begging rates. Males tended to initiate feeding bouts when offspring begged, and to allofeed vigorous beggers more often. Variance in male allofeeding behaviour allowed comparisons of size-matched families in which females performed nearly all of the allofeeds to nestlings (= female-fed families) with families in which males and females both allofed nestlings (= male-aided families). The parent controlled the allocation of food in female-fed families, while offspring had greater control over food allocation in male-fed families. As was predicted by conflict theory, the female counterstrategy was effective but potentially costly: the food delivery rate of females was only half as fast as males'. Conversely, offspring control resulted in an escalation of beg rate for the same degree of need (as measured by size and growth), and male-aided offspring obtained nearly three times more regurgitations than female-fed nestlings, yet grew at comparable rates and fledged at comparable sizes and ages. Hence, offspring demanded and obtained more food than they could effectively use. Other avian parents also seem to use effective but potentially costly counterstrategies, and other avian offspring may demand more food than they require. Even if initial hatch asynchronies functioned in brood reduction, the parental strategies described here would allow parents to retain control over the timing and conditions for offspring loss.
Splendid Wren Malurus Splendens Response To Cuckoos: an Experimental Test of Social Organization in a Communal Bird
Authors: Payne Robert B. , Payne Laura L. , Rowley Ian
Published: April 2008

A population of cooperatively breeding, group-living splendid wrens was tested with a mounted parasitic cuckoo. At all nests with incubated eggs or nestlings, wrens attacked the cuckoo. The timing and intensity of attacks was independent of the nest day and of the age and breeding experience of the wrens. The breeding female usually spotted and attacked the cuckoo first. Her mate and the nonbreeding helpers responded to her call and mobbed and attacked the cuckoo. Response was no quicker in groups with nonbreeding auxiliaries than in single pairs. Discovery time was independent of the number of birds in a group and depended on the movements of the breeding female. Most wrens fed the young and mobbed the cuckoo. When a wren did not attack, it usually was caring for the young of another breeding female or an earlier brood. Variance in helping behavior was not closely associated with variance in the genetic relationship between helper and the breeding female or the young beneficiaries of mobbing. Use of a common territory, attendance at a nest, feeding the young, and mobbing and hitting a cuckoo were all associated cooperative activities. The main limitation of cooperative behavior in defense against the cuckoo is the same as the observed constraint on care of the young during the prolonged period of parental feeding-a conflict of interest among breeding females for care of their own young.
Determinants of Social Rank in Goose Flocks: Acquisition of Social Rank in Young Geese
Authors: Black Jeffrey M. , Owen Myrfyn
Published: April 2008

The paper describes a study of social rank acquisition in goslings reared from eggs taken from a full-winged flock of barnacle geese (Branta leucopsis) at the Wildfowl Trust, Slimbridge. Eggs were taken from pairs of known history and the adult's aggressiveness was ranked according to their reaction to humans. This rank was shown to be meaningful intraspecifically both by the outcome of encounters between geese and by the fact that no pairs scored as non-aggressive were able to nest in the preferred colony. A group of goslings reared by their own parents and cross-fostered goslings were also examined. 1. Within a rearing group of goslings (sibling-reared broods), the oldest and heaviest birds ranked highest in the first month and males performed better in encounters than females of the same size in the second month. 2. In encounters between unfamiliar goslings from different sibling-broods in the third month of life, the most important determinants of the new rank were body size, weight and sex. Previous experience also influenced rank; previous success yielded continued success. Goslings lost weight during the test; loss was negatively correlated with rank. The performance of goslings reared without adults bore no relationship to their parent's aggressive score. 3. In the semi-captive flock, parents that scored as "aggressive" reared more and larger goslings than non-aggressive pairs. The rank of these in the third month correlated with their size and sex (independent of size). The cross-fostering experiment suggested that there was a genetic as well as an environmental influence on rank acquisition. 4. In encounters between goslings of similar rank from sibling-broods and parent-reared ones, the latter ranked significantly higher. Parent-reared goslings, though less familiar to the experimental regime, gained weight and goslings from sibling-broods lost weight. 5. Once established, rank order remained stable; the few reversals related either to changes in size or to cooperation between goslings in confrontations. 6. Parental quality clearly affects, through learning and heredity, the physical and social development of goslings, and consequently their chances of survival and reproduction. We suggest that these effects are reinforced by brood size; larger families gain better resources in competitive situations. In wild geese, competitive ability is crucial both to survival in winter and to the acquisition of nesting sites and rearing areas for the young.
Feeding-Vigilance Trade-Off in the Teal (Anas Crecca): Effects of Feeding Method and Predation Risk
Authors: Pöysä Hannu
Published: April 2008

Feeding and vigilance are conflicting demands in teals (Anas crecca) that use feeding methods where the eyes are beneath the water surface. This trade-off was compared across different beneath-surface feeding methods (head submerged, neck submerged, upending) and between the absence and presence of live predators, ospreys (Pandion haliaetus). A comparison across feeding methods indicated that the proportion of time spent scanning for predators and scanning rate decreased from head submerged to upending. Similarly, within a particular feeding method the level of vigilance decreased as average feeding bout length increased. Teals thus sacrificed vigilance as foraging demands increased. When a predator was present, however, teals increased the proportion of time spent scanning at the expense of feeding time in all feeding methods. This was achieved by lengthening scanning bouts, not by increasing scanning rate. As a consequence, feeding efficiency decreased. Feeding methods differed in terms of predator detection probability. An examination of the role of grouping in increasing predator detection probability indicated, however, that grouping would provide only a marginal benefit to foraging teals in this respect, whatever the feeding method.
Risk and Effectiveness in the Use of Agonistic Displays By American Goldfinches
Authors: Popp James W.
Published: April 2008

In aggressive contests over access to feeders, American goldfinches (Carduelis tristis) appeared to be using displays based on their risk and effectiveness. Display types varied in both their effectiveness and the risk of their use. The effectiveness of using a display was positively related to the risk of using that display. When the value of the resource under dispute was increased individuals used more of the riskier yet more effective displays. Associated with the increased use of the riskier displays was a greater number of encounters ending in fights. Individuals also used each display type with different frequency depending on the relative dominance status of their opponent. Bluffing may have been kept at low levels among the goldfinches by the ease of detecting bluffing, due to individual recognition, and by the costs of being detected.
Copulation Behaviour of Birds
Authors: Møller A.P. , Atkin L. , Birkhead T.R.
Published: April 2008

Inter-specific variation in copulation behaviour among birds is described. The following factors explaining variation in copulation rate are examined: (i) the number of eggs which have to be fertilized (the fertilization hypothesis), (ii) the importance of the pair-bond (the social bond hypothesis), (iii) predation risk during copulation (the predation hypothesis), and (iv) cuckoldry risk (the sperm competition hypothesis). These hypotheses were investigated in preliminary analyses at the generic level using data on copulation behaviour in 131 bird species. The sperm competition hypothesis was supported by several lines of evidence: (i) frequent copulations among genera where males are not able to guard their mates (colonial birds, diurnal birds of prey, and owls), (ii) frequent copulations in polyandrous genera, (iii) copulations inside hole-nests of colonial birds but outside the hole-nests of solitarily nesting genera, and (iv) by the occurrence of forced pair copulations following extra-pair copulation in some species. The predation and social bond hypotheses were not totally dismissed, but there was no evidence that fertilization ability was limited by copulation frequency (i.e. the fertilization hypothesis).
Scramble and Contest in Feeding Competition Among Female Long-Tailed Macaques (Macaca Fascicularis)
Authors: Van Noordwijk Maria A. , Van Schaik Carel P.
Published: April 2008

Most previous studies of feeding competition in gregarious primates compared some average or group-level characteristic over a range of group sizes. Here an attempt is made to separate the effects of within-group scramble (the "group size" effect) and of within-group contest (the "dominance" effect) on energy expenditure and food intake in female long-tailed macaques (Macaca fascicularis). Significant or consistent scramble and contest components were demonstrated for locomotion and energy expenditure, for the presence in the main party of the group, and for birth rate. The intake of fruit or animal matter was not increased in compensation, but the intake of dispersed vegetable matter probably was. It is concluded that both components of feeding competition exist in long-tailed macaques, but that contest for food is often transferred into contest for safety. A framework is proposed to relate interspecific variation in contest effects to food distribution and group cohesion.
A Phonological Analysis of Male Gibbon Singing Behavior
Authors: Mitani John C. , Marler Peter
Published: April 2008

Acoustic analyses and experimental field playbacks were conducted to investigate the nature and communicative significance of the phonological structure and organization of male gibbon (Hylobates agilis) songs. Males use a limited number of spectrographically discrete elements or note types to construct songs. A classification of these note types was produced initially through a visual sorting process using gross spectral and temporal features. Measurement of single acoustic variables and a digital sound program, which compared the two-dimensional cross-correlation values of note spectrograms, were employed to check the results of the qualitative sorting procedure. The sequential organization of notes composing songs was examined by tabulating the frequencies of occurrence of each note type in different positions and the transition probabilities between note types. These analyses revealed that songs are formed within a framework of rules, which define regular patterns in the placement and order of note types. To investigate whether the gibbons employ these rules in a biologically meaningful fashion, a field playback experiment was conducted comparing the responses of animals to normal and phonologically rearranged songs. Although the gibbons identify rearranged songs as conspecific territorial signals, responses to playbacks suggested that the hypothesized rules generating songs are communicatively significant; male gibbons responded in a qualitatively different fashion to normal and phonologically rearranged songs. These results are evaluated in light of other studies of animal vocal communication.
Family Planning in the Great Tit (Parus Major): Optimal Clutch Size as Integration of Parent and Offspring Fitness
Authors: Tinbergen Joost M. , Daan Serge
Published: April 2008

Fitness variations due to natural variation in the size of the first clutch and its laying date were estimated using Fisher's reproductive value for both the clutch (Vc) and the parent (Vp) in a population of great tits. In order to test the hypothesis that individual birds maximize their reproductive value by the choice of clutch size, artificial variation in brood size was introduced and the consequences in terms of reproductive value estimated. Maximal Vc, computed on the basis of natural variation in clutch size, occurred at a clutch size of 15.2, and increased slightly with laying date (Fig. 1A) Vp increased with natural variation in clutch size and decreased with date (Fig. 1B). The total reproductive value V (= Vc+Vp) was maximal at a clutch size of 15.4 (Fig. 1C), substantially higher than the population mean clutch size (9.2). The components of the reproductive value of the clutch (Vc) that were negatively affected by manipulation were the survival of the nestlings and the recruitment rate. The reproductive value of the parent (Vp) was negatively affected only through the probability of having a second clutch. Maximal Vc computed on basis of artificial variation in clutch size, occurred at a clutch size of 10.0, and also increased with date (Fig. 1D). Vp decreased with artificial variation in clutch size (Fig. 1E causing the clutch size maximising reproductive value V to shift to a value of 9.4 (Figs 1F, 3), very close to the population mean clutch size (9.2). It is concluded that the majority of great tits produces the number of eggs (9-10) that maximizes their individual fitness, even though those individual birds laying 15 eggs have the highest reproductive value in the population. The fact that birds laying very large clutches have the highest reproductive value points in the direction of a selection pressure towards larger clutches. Yet, over the last 30 years clutch sizes have not increased in the study population. This apparent contradiction is discussed. Either no genetic variation in clutch size is involved, or a complex polymorphism exists.
Instability of Harems of Feral Horses in Relation To Season and Presence of Subordinate Stallions
Authors: Franke Stevens Elizabeth
Published: April 2008

Male horses (Equus caballus) defend harems of females (bands) year-round and throughout their lifetimes. A male's lifetime reproductive success depends upon the number of females in his harem. Although harems have previously been reported as remaining stable over many years, during the two years of this study 30 % of the adult females in an island population of feral horses changed harems during late winter. The seasonal differences in harem stability resulted from seasonal differences in the abundance and distribution of food. The spacing between band members was greater and the frequency of social interactions between them was lower in winter than in summer. In addition, the amount of time devoted to grazing increased in winter. These differences are attributed to the lower availability of suitable vegetation duirng winter. Harem stability did not depend on the age of females, the size of the harem, nor the age of the harem stallion, but did depend on the presence of subordinate stallions attached to the band. All of the females that changed bands left single-male bands; multi-male bands were stable throughout the study.