Do cavity‐nesting primates reduce scent marking before retirement to avoid attracting predators to sleeping sites?

The largest population of endangered golden lion tamarins (Leontopithecus rosalia, GLTs) decreased from approximately 330 to 220 individuals between 1995 and 2000 due to a dramatic increase in predation at sleeping sites. We used behavioral data from eight social groups in this population to test two hypotheses: First, if GLTs attempt to mitigate the risk of predation at sleeping sites, they should reduce their rates of scent marking just prior to retirement. Second, if the benefits of scent marking prior to entering the sleeping site merit an increase in the rate of marking, then tamarins should increase their rate of pre-retirement scent marking during the breeding season, when such behavior would have its greatest impact on reproductive fitness. We used a generalized linear model (GLM) repeated-measures analysis to compare rates of daytime scent marking with rates of marking just prior to retirement for males and females. In addition, we compared scent marking prior to retiring in the nonbreeding season to marking rates before retirement in the breeding season for males and both sexes considered concurrently. Contrary to our expectations, GLTs significantly increased their rates of scent marking during the 30 min prior to entering their sleeping site-an observation driven by an increase in male (but not female) rates of marking. Rates of marking before entering the sleeping site were greater in the nonbreeding season compared to the breeding season, when both sexes were considered concomitantly and when males were evaluated alone. We conclude that GLTs do not attempt to minimize predation risk by decreasing scent marking in the period before they enter their sleeping site, and that tamarins do not scent mark at this time of day in order to transmit information about reproductive status or to control reproduction of subordinates. We speculate that scent marking in the 30 min prior to entering sleeping sites may serve to reduce predation risk by enabling tamarin groups to return quickly to favored sleeping sites in the evening when crepuscular predators are active.     

Host selection in parasitic birds: are open‐cup nesting insectivorous passerines always suitable cuckoo hosts?

How do potential hosts escape detrimental interactions with brood parasites? Current consensus is that hole‐nesting and granivorous birds avoid brood parasites, like common cuckoos Cuculus canorus, by their inaccessible nest‐sites and food unsuitable for parasites, respectively. Any open‐nesting insectivorous hosts are believed to remain open to brood parasite exploitation which leads to the evolution of costly host defences like egg or chick discrimination. In contrast to this coevolutionary scenario, we show for the first time that a previously not studied but seemingly suitable host species escapes brood parasites. The Asian verditer flycatcher Eumyias thalassinus, feed newly hatched chicks entirely with beetles and grasshoppers. These are poor quality and hard to digest diet items that are rarely fed to own or cuckoo chicks by regular hosts. Indeed, chick cross‐fostering experiments showed that these food items remained undigested by either cuckoos or other sympatric passerines causing them to die quickly. Egg discrimination experiments showed that the flycatcher accepts any foreign eggs. Although most but not all other potential explanations can be safely excluded at present, the most parsimonious historical explanation for these patterns is that the flycatcher exploits a trophic niche that no other sympatric bird can exploit, and that any cuckoo lineages that switch from their original hosts to the flycatcher have no possibilities for establishing viable populations. Thus, the current classification of host suitability based on diet composition may need revision, raising an important cautionary tale for comparative studies and the interpretation of apparent host rejection of parasitic chicks.     

Are thyroid hormones mediators of incubation temperature-induced phenotypes in birds?

Incubation temperature influences a suite of traits in avian offspring. However, the mechanisms underlying expression of these phenotypes are unknown. Given the importance of thyroid hormones in orchestrating developmental processes, we hypothesized that they may act as an upstream mechanism mediating the effects of temperature on hatchling phenotypic traits such as growth and thermoregulation. We found that plasma T₃, but not T₄ concentrations, differed among newly hatched wood ducks (Aix sponsa) from different embryonic incubation temperatures. T₄ at hatching correlated with time spent hatching, and T₃ correlated with hatchling body condition, tarsus length, time spent hatching and incubation period. In addition, the T₃ : T₄ ratio differed among incubation temperatures at hatch. Our findings are consistent with the hypothesis that incubation temperature modulates plasma thyroid hormones which in turn influences multiple aspects of duckling phenotype.     

Do neophobia and dietary wariness explain ecological flexibility? An analysis with two seed‐eating birds of contrasting habits

The neophobia threshold hypothesis (NTH) suggests that the acquisition and maintenance of a high behavioral and ecological flexibility in the evolutionary and adaptive history of a species is the consequence of lower levels of neophobia towards new micro‐habitats and of dietary wariness of novel foods. To test this idea we assessed the degree of neophobia and dietary wariness in two seed‐eating bird species with contrasting degrees of ecological flexibility that inhabit the central Monte desert (Argentina): a grass‐seed specialist, the many‐colored chaco‐finch, and a generalist feeder, the rufous‐collared sparrow. We expected that both species would exhibit neophobia and wariness when faced with new foraging opportunities but that the rufous‐collared sparrow would be less neophobic and less wary than the specialized many‐colored chaco‐finch. Experimental indicators of neophobia and dietary wariness included willingness to eat near novel objects and willingness to eat novel seeds, respectively. Both species showed similar levels of reluctance to novelty, although the sparrow could be slightly more reluctant than the finch. Contrary to our predictions, the sparrow was neither less hesitant nor faster or greedier than the finch. This experimental evidence does not support a negative relationship between neophobia/wariness and ecological flexibility in these two seed‐eating birds and it coincides with the growing evidence that challenges the NTH. Some of our results provide support for the dangerous niche hypothesis, especially as the rufous‐collared sparrow, that feeds on more diverse and potentially dangerous food, showed higher levels of neophobia in some cases. Although the idea of neophobia and wariness being plausible causes of ecological specialization sounds attractive, the current situation calls for further research so that the causes of ecological flexibility in granivorous birds can be better understood.     

Do Salmonella carry spare tyres?

Salmonellae are enterobacteria that have the unique ability to change their flagellar composition by switching expression among two loci that encode the major flagellin protein. This property is not available to all Salmonella, but is species, subspecies and serotype specific. Curiously, the subsequent loss of the second locus in some lineages of Salmonella has apparently been tolerated and, indeed, has led to considerable success for some lineages. We discuss here an evolutionary model for maintenance of this unique function and the possible evolutionary advantages of loss or preservation of this mechanism. We hypothesize that the second flagellin locus is a genetic 'spare tyre' used in particular environmental circumstances.     

Why are birds' eggs colourful? Eggshell pigments co‐vary with life‐history and nesting ecology among British breeding non‐passerine birds

The colourful appearance of bird eggshells has long fascinated biologists and considerable research effort has focused on the structure and biochemistry of the avian eggshell matrix. The presence of tetrapyrrole pigments was identified nearly a century ago. Surprisingly, how the concentrations of avian eggshell pigments vary among related species, and whether this variability is associated with either eggshell appearance and/or species life‐history traits, remains poorly understood. We quantified the concentrations of the two key eggshell pigments, protoporphyrin IX and biliverdin, from a diverse sample of eggshells stored at the Natural History Museum, Tring, UK. We explicitly tested how these two pigments are associated with physical measures of eggshell coloration and whether the pigment concentrations and colour diversity co‐vary with phylogenetic affiliations among species. We also tested a series of comparative hypotheses regarding the association between the concentrations of the two pigments and specific life‐history and breeding ecology traits. Across species, the average concentrations of protoporphyrin and biliverdin were positively correlated, and both strongly co‐varied with phylogenetic relatedness. Controlling for phylogeny, protoporphyrin concentration was associated with a higher likelihood of cavity nesting and ground nesting, whereas biliverdin concentration was associated with a higher likelihood of non‐cavity nesting habit and bi‐parental provisioning. Although unlikely to be explained by a single function, the breeding ecology and life history‐dependence of eggshell pigment concentrations in these comparative analyses implies that related species share pigment strategies, and that those strategies relate to broad adaptive roles in the evolution of variation in avian eggshell coloration and its underlying mechanisms. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 657–672.     

Do energetic demands constrain incubation scheduling in a biparental species?

The high energetic demands of incubation in birds may be animportant ecological factor limiting the evolution of life-historytraits, such as clutch size. In biparental species, however,the demands of incubation may not be a major constraint becausethere may always be sufficient feeding time available for theoff-duty bird to regain energy used during an incubation bout.We investigated whether the energetic demands of incubationconstrain optimum incubation bout length in a biparental incubatorby decreasing the energetic demands of incubation. We put aninsulated cup around the lining of semipalmated sandpiper nestsso that the rate of cooling of eggs was reduced by 21%. Semipalmatedsandpipers responded by increasing their mean incubation boutlength of around 11.1 h by about 10%. Bout lengths in unmanipulatednatural nests became longer as hatch approached (incubationstage), and this was independent of weather. Bout lengths mayhave decreased with increasing rainfall and were independentof time of day. The results suggest that bout length in semipalmatedsandpipers is constrained by their cumulative energetic expenditureduring an incubation bout, and this is determined partly bythe high costs of steady-state incubation. The results alsosuggest that the incubating bird determines the bout lengthrather than the returning bird. Semipalmated sandpipersmay havemaximized incubation bout length to minimize changeovers duringincubation because these probably increasepredation risk. Selectionto minimize the frequency of changeover may then be a factorcontributing to the evolution ofbiparental care and life-historytraits in semipalmated sandpipers.     

Alarm in a wasp-wasp nesting association: Do members signal cross-specifically?

Summary We studied interspecific alarm communication between two species of social wasps in a nesting association in northwestern Costa Rica by testing the alarm responses ofPolybia occidentalis andMischocyttarus immarginatus to venom of both species. This is the first investigation of alarm pheromone in the genusMischocyttarus. M. immarginatus did not respond with alarm behavior to the venom of either species.P. occidentalis, which responds to its own venom with alarm behavior (Jeanne, 1981), also responded with alarm behavior to the venom ofM. immarginatus, but with much less intensity. Since heterospecific venoms did not release species-typical levels of alarm behavior, we conclude that interspecific alarm signalling plays no role in the nesting association.     

Do changes in climate patterns in wintering areas affect the timing of the spring arrival of trans‐Saharan migrant birds?

The life cycles of plants and animals are changing around the world in line with the predictions originated from hypotheses concerning the impact of global warming and climate change on biological systems. Commonly, the search for ecological mechanisms behind the observed changes in bird phenology has focused on the analysis of climatic patterns from the species breeding grounds. However, the ecology of bird migration suggests that the spring arrival of long‐distance migrants (such as trans‐Saharan birds) is more likely to be influenced by climate conditions in wintering areas given their direct impact on the onset of migration and its progression. We tested this hypothesis by analysing the first arrival dates (FADs) of six trans‐Saharan migrants (cuckoo Cuculus canorus, swift Apus apus, hoopoe Upupa epops, swallow Hirundo rustica, house martin Delichon urbica and nightingale Luscinia megarhynchos), in a western Mediterranean area since from 1952 to 2003. By means of multiple regression analyses, FADs were analysed in relation to the monthly temperature and precipitation patterns of five African climatic regions south of the Sahara where species are thought to overwinter and from the European site from where FADs were collected. We obtained significant models for five species explaining 9–41% of the variation in FADs. The interpretation of the models suggests that: (1) The climate in wintering quarters, especially the precipitation, has a stronger influence on FADs than that in the species' potential European breeding grounds. (2) The accumulative effects of climate patterns prior to migration onset may be of considerable importance since those climate variables that served to summarize climate patterns 12 months prior to the onset of migration were selected by final models. (3) Temperature and precipitation in African regions are likely to affect departure decision in the species studied through their indirect effects on food availability and the build‐up of reserves for migration. Our results concerning the factors that affect the arrival times of trans‐Saharan migrants indicate that the effects of climate change are more complex than previously suggested, and that these effects might have an interacting impact on species ecology, for example by reversing ecological pressures during species' life cycles.     

Sex-biased survival and philopatry in birds: Do they interact?

A review of studies of sex-biased dispersal and philopatry and sex-biased survival in birds is presented. The comparison between sex-related mortality and natal and breeding dispersal at the species-level shows that dispersing birds (mainly females) suffer higher mortality, while philopatric birds (mainly males) have higher survival. The interaction between sex-biased survival and spatial behavior is a crucial component of avian vital strategy, which determine population dynamics and genetic structure.     

Do Canada geese (Branta canadensis Linnaeus, 1758) carry infectious agents for birds and man?

Currently, large groups of Canada geese (Branta canadensis Linnaeus, 1758) aggregate in recreational areas of north-western Germany. Questions have arisen as to whether these birds represent a special risk factor as a source of zoonotic agents for humans and as a source of viruses, causing notifiable or reportable diseases, for domestic poultry and waterfowl. To answer these questions, a total of 289 eggs were collected in 2002 and 2003 on a recreation site and assayed. Chlamydia psittaci was not isolated and neither was chlamydial antigen detected by polymerase chain reaction. All virus-isolation attempts were unsuccessful. Neither Salmonella spp. nor Campylobacter spp. was isolated from embryonic tissues, chorioallantoic membranes or yolk-sac membranes. The presence of antibodies against Newcastle disease virus and influenza A virus (haemagglutinin subtypes H5 and H7) was demonstrated in egg yolk. Antibodies were also detected against the egg-drop syndrome 1976 and duck plague viruses. It is concluded that further surveillance studies are needed for a reliable risk assessment.     

Do Micrognathozoa have micro‐genomes?

Based on the extremely small sizes of their jaw components, I predict that members of the Micrognathozoa will have some of the smallest nuclear genomes of any metazoans or, possibly, even of any free‐living (non‐parasitic) eukaryotes. Micrognathozoan jaws may also be enervated by anucleate neurons. Consistent with the prediction of small genomes, micrognathozoan jaw parts have remarkably small cell nuclei. Identical arguments may apply to other members of the Gnathifera, namely Rotifera and Gnathostomulida. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 640–644.     

Physiological costs of growing fast: does accelerated growth reduce pay-off in adult fitness?

Accumulating evidence suggests that, in contrast to earlier assumptions, juvenile growth rates are optimised by means of natural and sexual selection rather than maximised to be as fast as possible. Owing to the generally accepted advantage of growing fast to adulthood, such adaptive variation strongly implies the existence of costs attached to rapid growth. By using four populations of protandrous copper butterflies with known differences in intrinsic growth rates within and across populations, we investigate a potential trade-off between rapid growth and the proportionate weight loss at metamorphosis. While controlling for effects of pupal time and mass, we demonstrate that (1) protandrous males, exhibiting higher growth rates, suffer a higher weight loss than females throughout, that (2) population differences in weight loss generally follow known differences in growth rates, and that (3) males have by 6 higher metabolic rates than females during pupal development. These results support the notion that a higher weight loss during the development to adulthood may comprise a physiological cost of rapid development, with the pay-off of accelerated growth being reduced by a disproportionally smaller adult sizeCo-ordinating editor: Leimer     

Plasticity in body composition in breeding birds: what drives the metabolic costs of egg production?

Body composition in vertebrates is known to show phenotypic plasticity, and changes in organ masses are usually rapid and reversible. One of the most rapid and reversible changes is the transformation of the female avian reproductive organs before breeding. This provides an excellent system to investigate the effects of plasticity in organ size on basal metabolic rate (BMR) through relationships between organ masses and BMR. We compared body composition of female European starlings (Sturnus vulgaris) during various reproductive stages over 3 yr and investigated the pattern of changes in reproductive and nonreproductive organ mass during follicular development and ovulation. Furthermore, we analyzed the relationship between organ mass and resting metabolic rate (RMR) in nonbreeding, laying, and chick-rearing females. Our analysis revealed marked variation in organ masses between breeding stages but no consistent pattern among years except for kidney and pectoralis muscle. Furthermore, changes in nonreproductive organs did not parallel the cycle of growth and regression of the reproductive organs. The oviduct gained 62% of its 22-fold increase in mass in only 3 d, and oviduct regression was just as rapid and began even before the final egg of the clutch was laid, with 42% of the oviduct mass lost before laying of the final egg. In laying females, 18% of variation in mass-corrected RMR was explained by the mass of the oviduct (r2=0.18, n=80, P<0.0005), while pectoralis muscle mass in nonbreeding individuals and liver and gizzard mass in chick-rearing females were the only organs significantly related to RMR (r2=0.31-0.44). We suggest that the nonreproductive organs are affected more by changes in local ecological conditions than the reproductive state itself and that the activity and maintenance cost of the oviduct is high enough that selection has led to a very tight size-function relationship for this organ.     

Do monk seals exert top‐down pressure in subphotic ecosystems?

Patterns of subphotic fish assemblages on seamounts in the Northwestern Hawaiian Islands were identified and compared for potential structuring influences, including the bottom-up effects of regional oceanic productivity and top-down predation pressure exerted by visiting monk seals ( Monachus schauinslandi ). Patterns in fish size, density, and biomass were evaluated at the deep extreme (350–500 m) of the seals feeding range to avoid confounding effects of diverse shallow habitats ( e.g. , coral reefs). Fish number and size were used to calculate biomass density of the seamount fish assemblages that were then compared to the independent variables of summit depth, substrate type, relief, oceanic productivity, distance to seal colonies, and seal colony population. Only the variables of distance to seal colony and seal colony population were retained in a multiple regression model that explained 31% of the variance. Despite the presence of obvious regional differences in oceanic productivity, the overall patterns in the subphotic fish assemblages are better explained by the top-down hypothesis of predation pressure from monk seals.     

Why Do Dolphins Form Mixed‐Species Associations in the Azores?

Mixed‐species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed‐species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed‐species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed‐species groups were compared with those of single‐species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed‐species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed‐species groups depends on several environmental factors, and therefore may constitute an adaptive response.     

Do weaver ants affect arthropod diversity and the natural‐enemy‐to‐pest ratio in horticultural systems?

High biodiversity is an important component of sustainable agricultural systems, and previous studies have found that increases in the diversity of the natural enemies of pests are associated with decreases in pest populations. Weaver ants are well known for their highly territorial and aggressive behaviour and for their control efficiency of many insect pests in tropical crop trees. Because of this, the ants have been used as a key component in integrated pest management (IPM) programmes for tropical crop trees. In implementing the IPM programmes, we received a number of enquiries related to whether weaver ants have negative effects on arthropod diversity and other natural enemies in orchard systems due to their aggressive behaviour. To answer these questions, we regularly sampled canopy arthropods in cashew and mango orchards in the Northern Territory of Australia in 1996, 2002 and 2003. We sampled, using a vacuum sampler, orchards with and without weaver ants. Cashew and mango plots with abundant weaver ants had similar or higher canopy arthropod and natural enemy diversity and similar ratios of natural enemies to insect pests, compared with plot where the weaver ant was absent. The study also showed that the application of insecticides reduced arthropod diversity and the ratio of natural enemies to insect pests in a mango orchard. However, insecticide spray did not affect natural enemy diversity and abundance, which may be related to a high immigration rate of natural enemies in small plots surrounded by areas that were not sprayed.