Pairs Of Birds Research Articles

Safety and efficacy of an aroA-deleted live vaccine against avian colibacillosis in a multicentre field trial in broilers in Morocco

The safety and efficacy of an aroA-deleted live vaccine against avian colibacillosis (Poulvac® E. coli) was evaluated in broilers in a multicentre field trial. The trial sites consisted of 18 paired bird houses (randomly assigned to either the vaccination or the control treatment groups) located in 15 farms in three different regions of Morocco. A field dose of vaccine was administered on day of hatch by the spray route. Both clinical and performance parameters were compared between vaccinated and control groups, in which the experimental unit was defined as the individual bird house. No adverse reactions attributable to the vaccine were observed throughout the study. Non-inferiority of the vaccinated bird houses versus the control houses during a 2-week period post vaccination was statistically demonstrated for mortality and average daily weight gain. Vaccine efficacy was confirmed based on significant differences between vaccinated and unvaccinated groups measured for the full duration of the trial, including colibacillosis-like lesions observed at slaughter (1.7 versus 3.5%; P = 0.0054), total mortality (9.3 versus 10.3%; P = 0.0203), average daily weight gain (47.8 versus 46.2 g/day; P = 0.0006), average number of antibiotic treatment days (0.5 versus 2.0; P = 0.0008) and percentage of the birds that was marketed (90.0 versus 89.0%; P = 0.0309). In conclusion, the vaccine was demonstrated to be both safe and efficacious under field conditions.

Aggressiveness in the domestic fowl: Distance versus ‘attitude’

It has been suggested that invasion of the personal space by flock members is the main trigger of aggressive interactions in the domestic fowl (Gallus gallus domesticus). In large and dense groups of birds high frequency of attacks should be expected as the chances of invading the personal space of others is likely to occur. However, other studies suggest that after surpassing a certain group size the frequency of aggressive interactions decline. It is possible that the behaviour of the individuals themselves may be more relevant in this context. To test this hypothesis we analysed the onset of aggressive interactions in a laying strain of domestic fowl from videotaped behavioural sequences. A total of 60 interactions were analysed, for which we recorded the location (XY coordinates) of the giver (G) and receiver (R) of an aggression, the position of the two closest individuals to G (G1, G2) and to R (R1, R2), in addition to the behaviour and head orientation of all these birds with the software Chickitizer®. Distances between pairs of birds were calculated as Euclidean distances and analysed by mixed model ANOVA. Behaviours were ordered by ranges of activity and differences analysed by Kruskal–Wallis. Our results indicate that inter-individual distances at the onset of an aggressive interaction varied according to the specific pair of individuals, but contrary to the expected, distances between the G-R remained similar to the distance among the G-G1 and G-G2. R birds however, were consistently involved in more energetic demanding behaviours and with their head oriented towards G. These results suggest that aggression in the domestic fowl does not depend on the invasion of the critical distance per se, but would greatly depend on the activity level and directionality of the individuals which would be perceived as a threat by the aggressor.

Gender identification in EMU (Dromaius novaehollandiae)-A review

Distinct phenotypic sexual dimorphism servers as one of the key factors that can enable one to categorize the individual to a particular sex. However in case of ratite bird emu (Dromaius novaehollandiae) this phenotypic distinctness between males and females is less evident and careful observation of adult birds would help to identify the sexes. Other methods of sex identification such as the sexing by feather pattern observation, vent sexing, surgical sexing and karyotyping do not appear to yield confirmatory results. The identification of a sequence of DNA on sex chromosomes and then its use as a marker for sex diagnosis in such species where sexing of the birds is difficult can solve the problem, as the pairing of the birds could be done at the chick stage. Such confirmatory methods of sexing would be highly beneficial for the emu farmers and breeders.

Robust estimates of divergence times and selection with a poisson random field model: a case study of comparative phylogeographic data.

Mutation frequencies can be modeled as a Poisson random field (PRF) to estimate speciation times and the degree of selection on newly arisen mutations. This approach provides a quantitative theory for comparing intraspecific polymorphism with interspecific divergence in the presence of selection and can be used to estimate population genetic parameters. Although the original PRF model has been extended to more general biological settings to make statistical inference about selection and divergence among model organisms, it has not been incorporated into phylogeographic studies that focus on estimating population genetic parameters for nonmodel organisms. Here, we modified a recently developed time-dependent PRF model to independently estimate genetic parameters from a nuclear and mitochondrial DNA data set of 22 sister pairs of birds that have diverged across a biogeographic barrier. We found that species that inhabit humid habitats had more recent divergence times and larger effective population sizes than those that inhabit drier habitats, and divergence time estimated from the PRF model were similar to estimates from a coalescent species-tree approach. Selection coefficients were higher in sister pairs that inhabited drier habitats than in those in humid habitats, but overall the mitochondrial DNA was under weak selection. Our study indicates that PRF models are useful for estimating various population genetic parameters and serve as a framework for incorporating estimates of selection into comparative phylogeographic studies.

Newly paired zebra finches have higher dopamine levels and immediate early gene Fos expression in dopaminergic neurons

Most birds are socially monogamous, yet little is known about the neural pathways underlying avian monogamy. Recent studies have implicated dopamine as playing a role in courtship and affiliation in a socially monogamous songbird, the zebra finch (Taeniopygia guttata). In the present study, we sought to understand the specific contribution to pair formation in zebra finches of the mesolimbic dopaminergic pathway that projects from the midbrain ventral tegmental area to the nucleus accumbens. We observed that paired birds had higher levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid in the ventral medial striatum, where the nucleus accumbens is situated, than unpaired birds. Additionally, we found that the percentage of dopaminergic neurons expressing immediate early gene Fos, a marker of neuronal activity, was higher in the ventral tegmental area of paired birds than in that of unpaired birds. These data are consistent with a role for the mesolimbic dopaminergic pathway in pair formation in zebra finches, suggesting the possibility of a conserved neural mechanism of monogamy in birds and mammals.

A test of multiple hypotheses for the function of call sharing in female budgerigars, Melopsittacus undulatus.

In many social species group, members share acoustically similar calls. Functional hypotheses have been proposed for call sharing, but previous studies have been limited by an inability to distinguish among these hypotheses. We examined the function of vocal sharing in female budgerigars with a two-part experimental design that allowed us to distinguish between two functional hypotheses. The social association hypothesis proposes that shared calls help animals mediate affiliative and aggressive interactions, while the password hypothesis proposes that shared calls allow animals to distinguish group identity and exclude nonmembers. We also tested the labeling hypothesis, a mechanistic explanation which proposes that shared calls are used to address specific individuals within the sender-receiver relationship. We tested the social association hypothesis by creating four-member flocks of unfamiliar female budgerigars (Melopsittacus undulatus) and then monitoring the birds' calls, social behaviors, and stress levels via fecal glucocorticoid metabolites. We tested the password hypothesis by moving immigrants into established social groups. To test the labeling hypothesis, we conducted additional recording sessions in which individuals were paired with different group members. The social association hypothesis was supported by the development of multiple shared call types in each cage and a correlation between the number of shared call types and the number of aggressive interactions between pairs of birds. We also found support for calls serving as a labeling mechanism using discriminant function analysis with a permutation procedure. Our results did not support the password hypothesis, as there was no difference in stress or directed behaviors between immigrant and control birds.

Dominance, pair bonds and boldness determine social-foraging tactics in rooks, Corvus frugilegus

Socially foraging animals can search for resources themselves (produce) or exploit the discoveries made by others (scrounge). The extensive literature on producerescrounger dynamics has mainly focused on scramble competition over readily accessible resources, thereby largely neglecting the variety of scrounging techniques individuals may use as well as the role of investment in food handling. Furthermore, although individual differences in boldness and social factors such as dominance have been described to influence foraging tactics, their potential interplay and effect in foraging contexts beyond the conventional producerescrounger game remains unclear. We investigated the relationship between social-foraging tactic use and dominance, pair bonds and boldness in a foraging experiment focused on food handling and alternative scrounging tactics. We conducted a producerescrounger experiment in a captive group of rooks in which individuals could produce by pulling up baited strings, or scrounge by retrieving fallen food items or joining a producer. There were three key findings: (1) dominant rooks adopted the producer tactic more often and more successfully than subordinates; (2) producing and scrounging by tolerance led to mixed benefits to paired birds; (3) bold birds scrounged by retrieving more often than shy birds. Importantly, individuals were highly consistent in their tactic use across conditions differing in food availability. Our study highlights the importance of taking both social factors and boldness (heterogeneity) into account when studying social-foraging dynamics and offers empirical data on food handling and alternative scrounging tactics that can be used to extend current models and experiments on social foraging.

Pairs of pigeons act as behavioural units during route learning and co-navigational leadership conflicts

In many species, group members obtain benefits from moving collectively, such as enhanced foraging efficiency or increased predator detection. In situations where the group's decision involves integrating individual preferences, group cohesion can lead to more accurate outcomes than solitary decisions. In homing pigeons, a classic model in avian orientation studies, individuals learn habitual routes home, but whether and how co-navigating birds acquire and share route-based information is unknown. Using miniature GPS loggers, we examined these questions by first training pairs (the smallest possible flocks) of pigeons together, and then releasing them with other pairs that had received separate pair-training. Our results show that, much like solitary individuals, pairs of birds are able to establish idiosyncratic routes that they recapitulate together faithfully. Also, when homing with other pairs they exhibit a transition from a compromise- to a leadership-like mechanism of conflict resolution as a function of the degree of disagreement (distance separating the two preferred routes) between the two pairs, although pairs tolerate a greater range of disagreements prior to the transition than do single birds. We conclude that through shared experiences during past decision-making, pairs of individuals can become units so closely coordinated that their behaviour resembles that of single birds. This has implications for the behaviour of larger groups, within which certain individuals have closer social affiliations or share a history of previous associations.

The breeding biology of the Forest Red-tailed Black Cockatoo Calyptorhynchus banksii naso Gould in south-western Australia. II. Breeding behaviour and diet

Little is known of the breeding behaviour of the Forest Red-tailed Black Cockatoo Calyptorhynchus banksii naso (FRTBC), a large, iconic forest cockatoo, endemic to the south-west corner of Western Australia, currently listed as Vulnerable under the State Western Australian Wildlife Conservation Act and under the Commonwealth Environment Protection and Biodiversity Conservation Act. In this paper, we provide details of breeding behaviour of FRTBC based on observations throughout the year over 17 years, together with observations of diet and feeding behaviour over the same period. FRTBC are monogamous hollow-nesters. Breeding was recorded in all months, with peaks in autumn-winter (April– June) and spring (August–October), with few records in January and February. Breeding also varied between years, with little breeding in 1999, 2001 and 2008, but many observations in 2006 and 2009. Breeding occurred at times of fruiting of either of the principal feed trees, Jarrah Eucalyptus marginata or Marri Corymbia calophylla, so it does not depend solely on one or the other of these species. Courtship displays were noted at all times of the day, from before dawn at roost sites to dusk. In total, 205 breeding events were recorded, of which 69 (93%) of 72 nests had breeding confirmed on a second visit. Use of particular nest hollows varied considerably, with some used only once and some up to seven times. Only one egg is laid, which the female incubates for 29 to 31 days, before a nestling hatches weighing between 27 and 32 g. The female remains in the hollow during incubation and only leaves for a short period in the evening to be fed by the male, usually at dusk. The chicks are brooded for up to 10 days, after which the female leaves the nest between dawn and dusk. Pairs of birds appear to recognise each other by calls, not responding to calls by others in the area. Chicks only respond when the parent is heard. Chicks are fully feathered at 48 days. Fledgling success was estimated at 60%. Juveniles remain dependent on the adults 18 months to 2 years. Thirty-seven chicks were banded between 1997 and 2011. Juvenile-immature birds moved on average less than 3 km from their natal tree and older birds were observed moving up to 19 km. This suggests that FRTBC are generally sedentary. Immature birds took up to three times as long as their parents to open Jarrah or Marri nuts and eat the seeds. In recent years there has been an interesting change in foraging behaviour of birds in the northern Darling Range (adjacent to the Perth metropolitan area) with the FRTBC discovering and using a new food source, the introduced Cape Lilac Melia azedarach, and this species is of growing importance as food in the Perth region. In combination, the data on breeding biology and diet highlight the importance of identifying recruitment rates and food availability in managing populations of FRTBC.

Positive Reinforcement Training Facilitates the Voluntary Participation of Laboratory Macaws With Veterinary Procedures

Psittacine birds are challenging laboratory subjects, as they are typically long-lived, very social, highly intelligent, and easily stressed. The benefits of positive reinforcement techniques in animal management have been well documented for mammalian species; however, there are few publications on such programs for birds. To demonstrate the practicality of positive reinforcement training of laboratory birds to cooperate with research procedures involving direct manipulation of individuals, 9 adult macaws (Ara species; 5 individuals and 2 pairs) were trained in 10-minute sessions, twice a day for 8 weeks. The trained behaviors were: target, stay, accept liquids from a syringe, step onto a perch, step onto a scale, allow pressing a syringe to the pectoral area (surrogate for an intramuscular injection), and step onto a towel. All individually housed birds reliably targeted, stayed, and accepted a syringe, and 4 of the 5 stepped onto a perch. One bird performed all of the behaviors. Paired birds learned advanced techniques significantly faster when trained by 2 trainers versus 1 trainer. All behaviors that were mastered during the initial phase of training were successfully transferred so that the birds would reliably perform for the husbandry staff. We conclude that positive reinforcement techniques provide an effective, practical way to train laboratory macaws in behaviors useful for veterinary practice and research. Positive reinforcement used to evoke voluntary participation in procedures will help reduce stress associated with capture and restraint and improve welfare for laboratory parrots.

Determination of the minimum anesthetic concentration of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha)

To determine the minimum anesthetic concentration (MAC) of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha) and compare MAC obtained via mechanical and electrical stimulation. 15 healthy thick-billed parrots. Anesthesia was induced in each parrot by administration of sevoflurane in oxygen. An end-tidal sevoflurane concentration of 2.5% was established in the first bird. Fifteen minutes was allowed for equilibration. Then, 2 types of noxious stimulation (mechanical and electrical) were applied; stimuli were separated by 15 minutes. Responses to stimuli were graded as positive or negative. For a positive or negative response to a stimulus, the target end-tidal sevoflurane concentration of the subsequent bird was increased or decreased by 10%, respectively. The MAC was calculated as the mean end-tidal sevoflurane concentration during crossover events, defined as instances in which independent pairs of birds evaluated in succession had opposite responses. A quantal method was used to determine sevoflurane MAC. Physiologic variables and arterial blood gas values were also measured. Via quantal analysis, mean sevoflurane MAC in thick-billed parrots determined with mechanical stimulation was 2.35% (90% fiducial interval, 1.32% to 2.66%), which differed significantly from the mean sevoflurane MAC determined with electrical stimulation, which was 4.24% (90% fiducial interval, 3.61% to 8.71%). Sevoflurane MAC in thick-billed parrots determined by mechanical stimulation was similar to values determined in chickens and mammals. Sevoflurane MAC determined by electrical stimulation was significantly higher, which suggested that the 2 types of stimulation did not induce similar results in thick-billed parrots.

Family Planning and Economic Development in CHINA

This colorful poster of a mother holding up her baby daughter against the blue sky projects an ideal image of a strong mother freed from the exhaustion of caring for many children including the burden of housework for a large family. With one child she can concentrate her time and energy on raising the child and playing an active role in the economic development of the country as well. The power lines symbolize the changes in the rural mountainous region brought about by industrial development. The mother and her baby girl-a familiar image-are now as free as the pair of birds flying high in the sky signifying their limitless future in the transformation of Chinese society.

Potential evidence of parasite avoidance in an avian malarial vector

Epidemiological studies of malaria or other vector-transmitted diseases often consider vectors as passive actors in the complex life cycle of the parasites, assuming that vector populations are homogeneous and vertebrate hosts are equally susceptible to being infected during their lifetime. However, some studies based on both human and rodent malaria systems found that mosquito vectors preferentially selected infected vertebrate hosts. This subject has been scarcely investigated in avian malaria models and even less in wild animals using natural host–parasite associations. We investigated whether the malaria infection status of wild great tits, Parus major , played a role in host selection by the mosquito vector Culex pipiens . Pairs of infected and uninfected birds were tested in a dual-choice olfactometer to assess their attractiveness to the mosquitoes. Plasmodium -infected birds attracted significantly fewer mosquitoes than the uninfected ones, which suggest that avian malaria parasites alter hosts' odours involved in vector orientation. Reaction time of the mosquitoes, that is, the time taken to select a host, and activation of mosquitoes, defined as the proportion of individuals flying towards one of the hosts, were not affected by the bird's infection status. The importance of these behavioural responses for the vector is discussed in light of recent advances in related or similar model systems.

Individual identity, song repertoire and duet function in the Crimson-breasted Shrike (Laniarius atrococcineus)

Avian vocal duets are joint displays where paired birds produce temporally and structurally coordinated vocalisations. Duets show great variety in form that can reflect different functions, such as mate guarding, mutual recognition, pair bond maintenance or territory defence. By describing the structure of duets and singing behaviour, we can investigate whether these signals are based on cooperation or conflict and which functions they might have. Here we describe the singing behaviour and song repertoire of the Crimson-breasted Shrike in the Kalahari Desert, and assess four main hypotheses proposed for the function of duets. We found that Crimson-breasted Shrikes have a sex-specific repertoire, and the individuality of males, females and pairs is expressed acoustically. Differences in vocal strategies between the sexes indicate male mate guarding as one possible function. Temporal coordination is high and duetters follow strict codes, suggesting that duetting could be a cooperative endeavour in this species. The observed duetting behaviour is also consistent with the predictions for mutual recognition because each bird has its individual vocal characteristics that are consistent over time. Our results provide no support for the hypothesis that duets serve pair bond maintenance in this species as no partner-directed adjustment of temporal coordination took place.

Colourful characters: head colour reflects personality in a social bird, the Gouldian finch, Erythrura gouldiae

Remarkable diversity in behaviour and morphology (phenotypes) are often observed within a species; this diversity can be understood in terms of individuals maximizing their fitness. Based on evidence from studies linking different phenotypes to individual behaviours we hypothesize that discrete colour polymorphism can reflect personality. We tested for such a relationship in a social bird, the Gouldian finch, which shows two major head-colour morphs: red and black. Forty birds of differing head colours were used in five controlled laboratory tests. We found that three of the five tests were repeatable over time, and that bird performance in these tests differed with respect to head colour. Specifically: (1) pairs of red-headed birds were more aggressive than pairs of black-headed birds; (2) black-headed birds approached and touched a novel object quicker than red-headed birds (they were bolder); (3) black-headed birds returned to feed faster following the presentation of a false predator (they were less risk-averse); (4) boldness was positively correlated with risk taking (within the whole sample, within the red-headed birds and trending in the black-headed birds). Together, our results are consistent with our hypothesis that colour polymorphism could be indicative of consistent behavioural differences, and we make a number of predictions about how we expect this to function as a signal in competitive and cooperative (social) contexts.

Quantitative trait loci underlying hatching weight and growth traits in an F2 intercross between two strains of Japanese quail

A three-generation resource population was developed using two distinct Japanese quail strains, wild and white, to map quantitative trait loci underlying hatching weight and growth traits. Eight pairs of white and wild birds were crossed reciprocally and 34 F1 birds were produced. The F1 birds were intercrossed to generate 422 F2 offspring. All of the animals from three generations (472 birds) were genotyped for eight microsatellite markers on chromosome 1. Liveweight data from hatch to 5 weeks of age were collected on the F2 birds. Quantitative trait loci (QTL) analysis was conducted applying the line-cross model and the least-squares interval mapping approach. The results indicated QTL affecting hatching weight and several growth related traits on chromosome 1. The F2 phenotypic variance explained by the detected additive QTL effects ranged from 1.0 to 3.7 for different traits. Modelling both additive and dominance QTL effects revealed additional QTL with significant dominance mode of action affecting pre-slaughter weight. However, there was no evidence for imprinting (parent-of-origin) effects. The variance due to the reciprocal cross effect ranged between 3.0 and 19.1% for weight at 1 week of age and hatching weight, respectively.

Coming soon to a rooftop near you…

“Conceived was I by sea and sky/Their elements are fused in me/Of brigand birds that float and fly/I am the freest of the free” (Robert Service, Grey Gull) With these lines, poet Robert Service (1874–1958) appears to describe the gull as freedom personified. And it's all too easy to agree. In our mind's eye, his words conjure up images of a soaring, confident spirit with the gift of being able to take from life whatever it pleases without consequence or cost. But beware: despite the poem concluding with the author's declaration that he might happily choose the life of his subject, the bird in his poem is actually making a rather self-important after-dinner speech to some chickens who, having seen him by hunger goaded and by cold, allow him to share their feed. For all his apparent liberty, Service's gull is free to go only where his needs demand. This understanding that freedom is in some way always fettered might help explain a phenomenon that has been gathering pace over recent years: the nesting of gulls in cities. Most of us probably think of gulls as seabirds, wheeling around cliffs, raucously gallawking in harbors, or racing along the seafronts of vacation towns. However, in many coastal cities you are just as likely to see a gull swoop between buildings to snatch an abandoned sandwich as to see one pick over seaweed for crabs. And for decades now, gulls of different species have forayed miles inland to feast at our landfills, while blackheaded gulls (Larus ridibundus), like those that roost on the King Charles Bridge in Prague, have long been doing their best to shrug off the name “sea” gull by living and even nesting hundreds of miles from the ocean. But, by breeding on city rooftops, some gulls are taking a giant leap toward abandoning the life marine. Meet the new neighbor. For some 60 years, this phenomenon has been reported from Canada, the US, Australia, and Europe. At first, instances were no more than anecdotal, with just a few pairs of birds taking up rooftop residences. But these pioneer populations grew, and nowhere more dramatically than in the UK. Some experts now number the country's roof-nesting gulls at over 100 000 pairs – a figure currently growing at an annual rate of 13%. Herring gulls (Larus argentatus), which prefer to nest on houses, and lesser black-backed gulls (Larus fuscus), which find industrial roofing more to their taste, are by far the most common, but great black-backed gulls (Larus marinus), common gulls (Larus canus), black-legged kittiwakes (Rissa tridactyla), and black-headed gulls are all in on the action. Even towns like Hereford, miles from the sea, have large nesting populations. Unfortunately, nesting gulls cause serious damage to roofing materials, their excrement corrodes and dirties buildings, some birds can be aggressive toward people, and lots of them are loud! In fact, they are such bad neighbors that many UK cities have begun gull control programs. Certainly, the great adaptability of gulls made this invasion possible. Able to feed on scraps thrown from fishing boats, to follow plowing tractors for worms, and to gobble up garbage from trash cans, they have proven themselves well able to make use of human-provided opportunities. So perhaps it was only a matter of time before they figured out that well-lit cities could provide them with 24/7 scavenging, and that rooftops are rather like cliffs, but unoccupied and without the spray. However, the fact that they could colonize our towns may not be the reason they did, for while British urban gull numbers are rapidly growing, their overall numbers are falling fast. According to the Royal Society for the Protection of Birds, all the UK's gull species have been designated of conservation concern. Indeed, the herring gull's decline is so serious (over 50% in the 30 years prior to the year 2000) that it has been placed on the IUCN Red List. As John Calladine, Senior Research Ecologist with the British Trust for Ornithology, points out, this might reflect a return to the situation before fishing discards (now rarer because of downsized fishing fleets) and other anthropogenic wastes (perhaps now better managed) led to inflated gull numbers. But it could mean that marine pollution and falling fish stocks have so altered coastal ecology that large, sea-going gull colonies can no longer be supported. Birds raising chicks in towns may be doing very well, but they may be pursuing this option because the sea no longer offers them what they need. Thus, rather than exercising any boundless freedom, the gulls taking over British rooftops may be doing so for the same reason that Service's bird fed with the chickens: to survive. Soaring brigands they may be, but tied to rooftops to be free?

Aggressive responses to playback of solos and duets in a Neotropical antbird

Duetting behaviour is a unique form of animal communication that occurs in many diverse taxa in the animal kingdom. Hypotheses for the function of duets can be grouped into two broad categories to explain why individuals coordinate with their partner’s songs to create duets: (1) duets are cooperative displays where pair members have a shared goal, such as joint resource defence, and (2) duets are conflicting displays where pair members have different goals, such as guarding against divorce or extrapair copulations. To distinguish between cooperative versus conflicting functions of vocal duets, we conducted a playback experiment to 40 breeding pairs of barred antshrikes, Thamnophilus doliatus . We broadcast five playback treatments to territorial pairs of birds: solos of males and females, duets created by males responding to female songs and by females responding to male songs, and a heterospecific control. We categorized subjects’ behaviour in terms of vocal and physical responses. Male vocal and physical responses were significantly higher towards conspecific stimuli than towards heterospecific stimuli. Males tended to show more vocal responsiveness towards duet stimuli, although this tendency was not significant. We observed a similar pattern for female vocal responses. However, for physical responses, females showed significantly more intense responses towards female solo stimuli than towards any other conspecific treatment, suggesting that female antshrikes perceive rival females as an especially intense threat. Our results provide some support for a joint resource defence function for duetting in this species, while the high intrasexual aggression observed between females may indicate a form of mate guarding.

Effect of isolation and conspecific presence in a novel environment on corticosterone concentrations in a social avian species, the zebra finch (Taeniopygia guttata)

Zebra finches are a highly social and monogamous avian species. In the present study, we sought to determine the effect of social isolation (separation from the flock) in a novel environment with and without a conspecific present on the adrenocortical activity of paired and unpaired individuals of this species. With regard to paired birds, we hypothesized that the presence of the mate during isolation from the group would act as a social buffer against the stressful effects of isolation. We observed that 10 but not 30minutes of social isolation resulted in elevated concentrations of corticosterone in unpaired and paired male zebra finches in comparison to baseline concentrations of corticosterone. Furthermore, the presence of a mate during isolation in a novel environment did not have a buffering effect against increases in corticosterone concentrations. Additionally, to compare concentrations of corticosterone in response to isolation (in a novel environment) to a previously well-established stressor, we subjected groups of birds to restraint. We observed that 10 or 30minutes of restraint led to significantly higher concentrations of corticosterone as compared to baseline. Finally, to rule out the possibility that merely handling a bird would result in significantly elevated concentrations of corticosterone as compared to baseline samples, we measured corticosterone concentrations 10 or 30minutes after handling involving capture and release only. Our results suggest that handling alone might have contributed to the elevation of corticosterone in birds exposed to 10minutes but not 30minutes of restraint. Handling by itself did not account, however, for the elevated corticosterone in birds socially isolated for 10minutes.

A single vaccination of commercial broilers does not reduce transmission of H5N1 highly pathogenic avian influenza

Vaccination of chickens has become routine practice in Asian countries in which H5N1 highly pathogenic avian influenza (HPAI) is endemically present. This mainly applies to layer and breeder flocks, but broilers are usually left unvaccinated. Here we investigate whether vaccination is able to reduce HPAI H5N1 virus transmission among broiler chickens. Four sets of experiments were carried out, each consisting of 22 replicate trials containing a pair of birds. Experiments 1-3 were carried out with four-week-old birds that were unvaccinated, and vaccinated at day 1 or at day 10 of age. Experiment 4 was carried out with unvaccinated day-old broiler chicks. One chicken in each trial was inoculated with H5N1 HPAI virus. One chicken in each trial was inoculated with virus. The course of the infection chain was monitored by serological analysis, and by virus isolation performed on tracheal and cloacal swabs. The analyses were based on a stochastic SEIR model using a Bayesian inferential framework. When inoculation was carried out at the 28th day of life, transmission was efficient in unvaccinated birds, and in birds vaccinated at first or tenth day of life. In these experiments estimates of the latent period (~1.0 day), infectious period (~3.3 days), and transmission rate parameter (~1.4 per day) were similar, as were estimates of the reproduction number (~4) and generation interval (~1.4 day). Transmission was significantly less efficient in unvaccinated chickens when inoculation was carried out on the first day of life. These results show that vaccination of broiler chickens does not reduce transmission, and suggest that this may be due to the interference of maternal immunity.