Solitary Pairs Research Articles

Coherent structures of elastoinertial instabilities in Taylor–Couette flows

We combine flow visualisation techniques and particle image velocimetry to experimentally investigate the higher-order transition to elastoinertial turbulence of Boger fluids ( $El = 0.11\unicode{x2013}0.34$ ) in Taylor–Couette flows. The observed route to turbulence is associated with the appearance of chaotic inflow jets, termed flame patterns, for increasing inertia, and stable structures of solitons, known as diwhirls, for decreasing inertia. We also report for the first time spatially and temporally resolved flow fields in the meridional plane for the three characteristic viscoelastic flow regimes (diwhirls, flame patterns and elastoinertial turbulence). We observe in all cases coherent structures of dynamically independent solitary vortex pairs. The stability of these coherent structures is jet-dominated and can be mainly ascribed to the high extension of the polymer chains in the inflow boundaries in the $r$ – $z$ plane. Solitary pairs are self-sustained when created through random events and do not split; instead, they merge when moving sufficiently close and annihilate when hoop stresses are not sufficient to sustain them. The highly localised and random events result in highly fluctuating, chaotic flow states. We estimate the decay exponent of spatial power spectral density, illustrating a universal scaling of $-2.5$ for elastoinertial turbulence. Based on our observations and in an effort to unify and combine precedent theories with our results, we suggest a mechanism for the origins of elastoinertial instabilities, accounting for both the effect of elasticity on the vortex formation and the effect of increasing/decreasing inertia on the flow dynamics.

Colonial breeding impacts potentially fitness-relevant cognitive processes in barn swallows

Many animals breed colonially, often in dense clusters, representing a complex social environment with cognitive demands that could ultimately impact individual fitness. However, the effects of social breeding on the evolution of cognitive processes remain largely unknown. We tested the hypothesis that facultative colonial breeding influences attention and decision-making. Barn swallows (Hirundo rustica) breed in solitary pairs or in a range of colony sizes, up to dozens of pairs. We tested for selective attention to social information with playbacks of conspecific alarm calls and for decision-making with simulated predator intrusions, across a range of colony sizes from 1 to 33 pairs. We also evaluated the adaptive value of both processes by measuring seasonal reproductive success. Swallows breeding in larger colonies were more selective in their attention to social information. Birds breeding in larger colonies were also less risk averse, deciding to return more quickly to their nests after a predator approach paradigm. Finally, birds that showed higher selective attention hatched more eggs and birds that returned to their nests more quickly after a predator intrusion had more nestlings. Although we cannot fully attribute these fitness outcomes to the cognitive measures considered in this study, our results suggest that social breeding plays a role in adaptively shaping both the acquisition of social information and decision-making.

Solitary breeding barn swallows pay a higher nest defense cost

Successful reproduction depends on the ability of parents to defend from nest predators. Breeding birds often put their life at risk to defend their offspring from predators. Communal nest defense has been proposed as an individual benefit of group living. We tested this by experimentally exposing a short-lived avian species to a potential risk of predation. We presented decoys of both a diurnal and a nocturnal predator to barn swallows Hirundo rustica breeding solitarily and in large colonies in South-western Spain. We found clear benefits of group living compared to solitary pairs in relation to investment in individual nest defense and the capacity to deter a challenging predator. Although we did not find differences in the time needed to detect the predator, we found that the number of individuals recruited to participate in nest defense was greater for colonial breeding pairs, leading to fewer attacks per individual in comparison to solitary breeding pairs. We also found that barn swallows defended their nests more vigorously against a nocturnal predator than against a diurnal predator. Therefore, barn swallows living in groups obtained clear benefits in communal nest defense by reducing the risk, energy and time dedicated to nest defense. Colonial breeding is thus a more effective strategy for decreasing nest predation rates.

Identification of the Breeding Range of the Hooded Crane

Abstract The Hooded Crane Grus monacha remains the least known crane species in terms of its breeding range. Since 1985, typical wetlands meeting the characteristics of the typical Hooded Crane habitat have been surveyed between 56° and 66°N and between 108° and 136°E. Within the Lena River Basin, well-defined extensive breeding grounds of the Hooded Crane have been observed in the middle Aldan River Basin. Surveys of representative swampy headwaters, river reaches, and large watershed depressions, have revealed no other similar breeding grounds within the rest of the Lena River Basin, including areas attributed to the only known breeding grounds outside Manchuria. Within the extent of occurrence in the Lena River Basin and adjoining areas of the Olenyek, Khatanga and Yenisei river basins, breeding Hooded Cranes are presumably highly scattered. Solitary pairs are likely to breed hundreds of kilometers apart. Based on the distribution of wetlands, breeding grounds comparable to the middle Aldan River may occur in the basins of the upper Vilyui and the adjoining Moero and Kotui rivers. Evidence suggests that reports from local people are mostly plausible and consistent with maps and satellite images showing wetland habitat similar to that used by the Hooded Crane. Therefore, in the absence of direct data, the reports of the occurrence/nesting of Hooded Cranes beyond the Arctic Circle, particularly in the Olenyek River Basin quoted by Andreev ( 1974 ), should be given credence when delineating the breeding range. The region, including the Lena River Basin is too vast and difficult of access for aerial surveys to be practical. Tracking, based on navigation satellite systems, rather than stepwise ground surveys, is the only practical method for obtaining significant information over a short period of time.

Promoting Nanozyme Cascade Bioplatform by ZIF-Derived N-Doped Porous Carbon Nanosheet-based Protein/Bimetallic Nanoparticles for Tandem Catalysis

Nanozymes are a class of nanomaterials with enzyme-like activities that have been extensively studied for their possibilities and superiorities over natural enzymes. Intelligent design and fabrication of a nanozyme platform with highly efficient and stable tandem enzyme characteristics is necessary. Herein, a nanozyme cascade promoting bioplatform based on protein/bimetallic nanoparticles attached to ZIF-derived multilayer N-doped carbon nanosheets is proposed. Due to the carbon-based large surface area and solitary pairs of nitrogen electrons, the metal could be riveted to the carbon-based surface and reduced in situ to nanoparticles. Simultaneously, the addition of BSA has made it possible to establish a biological platform. The obtained BSA-PtAu@CNS has a linear range of 2 × 10-6 to 2 × 10-3 M for H2O2 and apparent dynamic Km of 0.005 × 10-3 M, which shows stronger affinity with H2O2 than HRP. The nanohybrid could adapt to severe reaction environment and enable prominent tandem dual-enzyme activity for glucose sensing. As a result, the cascade nanozyme bioplatform based on BSA-PtAu@CNS is accomplished and provides insights for subsequent biocompatible nanomaterials for use in medical and diagnostic applications.

The influence of sociality, caste, and size on behavior in a facultatively eusocial bee

Social cooperation requires increased tolerance of other individuals. We used social and solitary individuals of the facultatively eusocial bee Megalopta genalis to compare interactions with non-nestmate individuals in a standardized behavioral assay, a circle tube. We set up interactions between bees from different nests matched for caste (solitary, social: queen or worker). We found more tolerance in social than solitary pairs, but found no difference in aggression. We also found that workers continued expressing caste-typical behavior even when matched against other workers from different nests. However, there was no difference in expression of queen-typical behaviors between the three groups. Our data on social caste show that outside of the queen–worker social context, both queens and workers express similar levels of queen-like behavior. However, workers still express higher levels of worker-like behavior than do queens. We found no effect of variation in ovary size on behavior. We found that body size correlated positively with queen-like behaviors, and negatively with worker-like behaviors. Our body size data suggest that the worker phenotype may result from naturally occurring size-correlated variation in behavior, combined with maternal manipulation of both body size through nutrition and behavior and ovary development through social aggression.

Torque in Taylor–Couette flow of viscoelastic polymer solutions

When a polymer solution is sheared between concentric cylinders, with the inner rotating and the outer fixed, the torque on the inner cylinder is modified compared to a Newtonian fluid of the same viscosity revealing the different flow patterns that emerge above the linear stability threshold for circular Couette flow. Here, mixtures of relatively short and long linear polymers in dilute and semi-dilute concentrations were considered. Their shear viscosity and extensional relaxation time are quantified. The stability of the flow is monitored through torque measurements and flow visualisations for a constant rate of acceleration and deceleration of the inner cylinder in a wide range of polymer concentrations. The torque exhibits an hysteretic behaviour, typical of subcritical transition. For large concentrations, six different numbers of steady solitary pairs of vortices, called diwhirls, were observed depending on the deceleration rate and their torque contribution is reported.

Does the breeding performance differ between solitary and colonial breeding Red-throated Loons Gavia stellata in the core area of the Swedish population?

Most Red-throated Loons Gavia stellata are solitary breeders in small pools and provide fish prey to the chicks from larger waters at a distance seldom exceeding 10 km. More rarely, several pairs nest together in colonies. We compared the breeding performance of solitary and colonial breeders in South-central Sweden during 2000–2016 (except for 2007). Annual productivity was 0.63 and 0.52 chicks per pair and year for solitary and colonial breeding pairs respectively, and mean percentage per year of broods with two chicks did not differ, 24% and 18% (no significant differences). Average hatching probability was the same, 0.576 and 0.581 over years. The average probability however, that at least one chick would be fledged was significantly higher among solitary pairs, 0.915 and 0.731 respectively, although the overall probability of successful breeding did not differ, 0.530 and 0.443. Thus, any benefit with reference to coloniality can be questioned. More likely, colonial breeding was a result of habitat selection, with a concentration of several nesting pairs within a relatively small area with a profitable foraging lake nearby.

Effects of nest positioning on fledging success in a breeding colony of Passer montanus (Passeridae): a case study in Central Anatolia, Turkey

Tree sparrows exhibit a range of breeding tactics from nesting in solitary pairs to forming breeding aggregations. We present a case study on the reproductive consequences of nest positioning in a loose breeding colony of Eurasian tree sparrow (Passer montanus) in central Turkey. We tested whether height and centrality of nests, together with their interaction, influenced fledging success in a single breeding season by running a generalized linear mixed-effects model. Nest height did not influence fledging success in a significant way. Also, productivity did not differ relative to the distance from the colony edge. This study provides the first detailed information about the effects of nest location on productivity for tree sparrows outside Continental Europe, and emphasizes the need for further studies on this model species.

Living with strangers: direct benefits favour non-kin cooperation in a communally nesting bird

The greater ani (Crotophaga major), a Neotropical cuckoo, exhibits an unusual breeding system in which several socially monogamous pairs lay eggs in a single nest and contribute care to the communal clutch. Cooperative nesting is costly-females compete for reproduction by ejecting each other's eggs-but the potential direct or indirect fitness benefits that might accrue to group members have not been identified. In this study, I used molecular genotyping to quantify patterns of genetic relatedness and individual reproductive success within social groups in a single colour-banded population. Microsatellite analysis of 122 individuals in 49 groups revealed that group members are not genetic relatives. Group size was strongly correlated with individual reproductive success: solitary pairs were extremely rare and never successful, and nests attended by two pairs were significantly more likely to be depredated than were nests attended by three pairs. Egg loss, a consequence of reproductive competition, was greater in large groups and disproportionately affected females that initiated laying. However, early-laying females compensated for egg losses by laying larger clutches, and female group members switched positions in the laying order across nesting attempts. The greater ani, therefore, appears to be one of the few species in which cooperative breeding among unrelated individuals is favoured by direct, shared benefits that outweigh the substantial costs of reproductive competition.

Double domain structure of the pair contact process with diffusion

We investigate the domain structure of the pair contact process with diffusion (PCPD). PCPD is a stochastic reaction-diffusion model which evolves by the competition of two binary reactions, 2A-->3A and 2A-->0 . In addition, each particle diffuses isotropically, which leads to the bidirectional coupling between solitary particles and pairs. The spreading domain formed from localized activities in vacuum consists of two regions: The coupled region of size R{p} where pairs and solitary particles coexist and the uncoupled region of size R{U} where only solitary particles exist, respectively. The size of the whole domain R is given as R=R{p}+R{U} . At criticality, R{p} and R{U} scale as R{p} approximately t(1/Z{p}) and R{U} approximately t(1/Z{U}) with Z{U}>Z{p}. We estimate Z{p}=1.61(1) and Z{U}=1.768(8) . Hence the correction to the scaling of R,Q=R{U}/R{p} slowly decays extremely, which makes it practically impossible to identify the asymptotic scaling behavior of R. The double domain structure is another reason for the extremely slow approach to the asymptotic scaling regime of PCPD.

Annual Building-up of Great Crested Grebe Colonies: An Example from the Dutch IJsselmeer

Some species in the family of grebes (Podicipedidae) are gregarious and nest in extensive colonies, others are solitary breeders aggressively defending their territories. Others, including the Great Crested Grebe (Podiceps cristatus), can breed in colonies or as solitary pairs, suggesting that individuals are able to change from a solitary strategy to a more social pattern. This paper concentrates on observations during colony establishment and nesting in a colony of Great Crested Grebes near Lake Ijssel in the Netherlands. The arrival of the grebes at the colony and their egg laying was spread over a long period. From the start, the breeding birds tended to use the entire area of the vegetation available for building nest platforms and this led to a progressive reduction in the distances between neighboring pairs. The final nesting density was extremely high, with 14.3 nest platforms per 100 m2. On average, each nest held 3.75 eggs. The crowded nesting of the Great Crested Grebe was imposed upon the birds because of the absence of sufficient suitable nesting habitat. It is suggested that the extent of aggregation is dictated by the quality of the site and the ability of the grebes to reduce their aggressiveness towards one another. Social behavior did not primarily contribute to the breeding aggregation.

Habitat Characteristics and Nest Predation do not Explain Clustered Breeding in Least Flycatchers (Empidonax Minimus)

Abstract Animals often exhibit territorial spatial structure in their breeding habitat. This clustering behavior is not well understood. We reviewed eight hypotheses for clustering and tested two ecological hypotheses for the formation of dense, territorial clusters in the Least Flycatcher (Empidonax minimus), a socially monogamous forest bird. The material resources hypothesis suggests that clustering is a response to habitat heterogeneity in vegetation, food, or both. The predation hypothesis proposes that clustering may reduce nest predation. Univariate and multivariate analyses of 170 vegetation plots from 1997 to 1998 indicated that forest-stand structure and tree species composition could not explain clustering in our population (predictions 1–3). Comparison of mean arthropod biomass inside with arthropod biomass outside two clusters sampled in 1999 using Malaise traps revealed that potential food resources were also unrelated to clustering (prediction 4). Nest predation rates were not correlated with territory position in clusters or with cluster size. In addition, predation rates were similar for clustered and solitary pairs (predictions 5–7). We conclude that habitat characteristics and nest predation do not explain clustered breeding in Least Flycatchers, though further tests of those hypotheses would be helpful. We develop the idea that the pursuit of extrapair copulations may promote clustered breeding. Future studies of territorial spatial structure in Least Flycatchers and other species should consider explanations based on mating behavior concomitant with ecological explanations for clustering.

COOPERATIVE BREEDING OF THE YELLOW-RUMPED MARSHBIRD (ICTERIDAE) IN ARGENTINA AND PARAGUAY

Abstract We found helpers at eight of nine nests of Yellow-rumped Marshbirds (Pseudoleistes guirahuro) from northeastern Argentina and Paraguay. From one to four helpers were observed during the incubation and nestling periods, but during nest building we saw solitary pairs. The helpers, of unknown sex and age, provisioned food to the chicks and defended the nest against several raptors. The Yellow-rumped Marshbird had a similar breeding system to its congener the Brown-and-yellow Marshbird (P. virescens) except that the former did not nest in colonies. According to a recent molecular phylogeny both Pseudoleistes marshbirds plus the Saffron-cowled Blackbird (Xanthopsar flavus) form a well-defined clade. All three of these species have helpers. This result suggests that cooperative breeding in the Icteridae has a phylogenetic component. Cria Cooperativa de Pseudoleistes guirahuro en Argentina y Paraguay Resumen. Encontramos ayudantes en ocho de nueve nidos de Pseudoleistes guirahuro presentes encontrados e...

Frequency and distribution of behaviour of red-necked grebes breeding colonially and in classic territories

AbstractOver the two-year period, 1997 to 1998, nearly half of a population of over 200 red-necked grebes (Podiceps grisegena) breeding within a large lake (2,537 ha) in central Minnesota, chose to opportunistically nest in concentrated groups on large floating mats of cattail (Typha spp.). In this study, we examined how members of this typically territorial grebe species coped with living in a more social environment. The behaviour of pairs that nested close to conspecifics differed from that of solitary pairs throughout the nesting season. Colonial pairs tended to be less likely than solitary birds to leave their nest vacant and unguarded from competitors or predators. During the pre-nesting stage, colonial females and males spent more of their time in aggression than did solitary-nesting birds. However, after a pair established their nest and egg-laying began, female aggression declined dramatically in both colonial and solitary pairs. During the egg-laying period, females spent significantly more time on the nest than did males, while males were more active than females in nest defense. Throughout the incubation period, colonial males remained closer to the nest and their females than did solitary males. In general, birds nesting in close proximity exhibited a compressed use of the space surrounding their investments in the platform, mate, eggs, and even young, all of which may have become more vulnerable to competitors and predators in areas of higher aggregation. Examining how opportunistically colonial species adapt to breeding in close aggregations may provide insight into the early evolution of colonial nesting birds.

Bifurcation of gap solitons through catastrophe theory.

In the theory of optical gap solitons, slowly-moving finite-amplitude Lorentzian solutions are found to mediate the transition from bright to coexistent dark-antidark solitary wave pairs when the laser frequency is detuned out of the proper edge of a dynamical photonic band gap. Catastrophe theory is applied to give a geometrical description of this strongly asymmetrical "morphing" process.

Magnetic anisotropy of antiferromagnet (CH3)4NMnCl3

The parameters of the electron paramagnetic resonance (EPR) spectra of S ion pairs in diamagnetic crystals are analyzed. A relation between the spin Hamiltonian constants is established for solitary ions and pairs for (CH3)4NCdCl3: Mn2+ crystals. In contrast to solitary ions, an additional contribution (which is a linear function of the exchange field) to the “single-ion” spin Hamiltonian constants appears in the case of pairs. It is shown that anisotropic exchange mechanisms do not play a significant part in the formation of the axial constant of the spin Hamiltonian for this crystal. Some aspects of the method of studying “single-ion” anisotropy predicted by the two-ion model are developed with the help of an isostructural diamagnetic analog with impurity concentration of the paramagnetic ions of a magnetically concentrated substance sufficiently high for observing the EPR spectrum of the pairs. It is found that the microscopic quantities determined partially from the EPR spectra for pairs and solitary Mn2+ ions in (CH3)4NCdCl3 are in accord with the experimental value of the effective field for the (CH3)4NMnCl3 crystal anisotropy which can be described primarily by the dipole and “single-ion” mechanisms of the exchange origin.

Copulatory Behavior of Semi-Colonial Montagu's Harriers

The copulatory behavior of the monogamous Montagu's Harrier (Circus pygargus) was studied between 1992 and 1995 near Madrid, Spain. Copulations started around 20 days before laying, and typically stopped at the end of the laying period. Copulation frequency peaked just before the start of the laying period, averaging 2.2 copulations day -1 . Females copulated on average 39 times per brood. Copulation rates apparently were not related to food provisioning by males except in the early pre-laying period. At least 5 and up to 11 (4-8%) of the copulations observed were extra-pair copulations (EPCs), and all occurred within the fertile period. Montagu's Harriers increased their copulation rate in situations of increased EPC risk: solitary pairs copulated for a shorter period of time and at an overall lower frequency, whereas pairs nesting in clumps showed higher copulation rates with increasing number of neighboring pairs. This increase was most marked during the laving period, when there is a higher risk of EPCs producing extra-pair fertilizations.

The annual cycle and breeding behaviour of the Mauritius Fody Foudia rubra

Safford, R.J. 1997. The annual cycle and breeding behaviour of the Mauritius Fody Foudia rubra. Ostrich 68 (24): 58–67. The Mauritius Fody Foudia rubra, a highly endangered species of weaver (Ploceidae) endemic to Mauritius, was studied from 1989–1993. The plumage, various display postures (typical of the family), and seven adult and two juvenile vocalisations are described. The diet consisted of insects, nectar and fruit. Males were in breeding plumage, and breeding took place, between late August and early April, although severe weather in February 1992 terminated breeding activity early. The species appeared to be monogamous and was suspected to maintain a long-term pair bond. Pairs occupied exclusive territories of not less than 0.9 ha. Both sexes built the nest from the outset, but only the female lined it. Between breeding attempts, some pairs habitually started but then abandoned one or more nests. Clutch sizes of two to four were recorded, three being the norm. Incubation and brooding were carried out by the female; the male joined in feeding the young after daytime brooding ceased. Juvenile dependency appeared to last around two weeks after which the young were ousted from the territory. The potential productivity of up to three broods per pair per year was not achieved by any pair studied because of poor nesting success. A complete moult followed breeding. Territorial defence continued throughout the year, and no evidence for seasonal movements was seen. Two behavioural features seem unexpected: 1) male nest invitation and nest advertisement behaviour appeared to be absent; 2) females participated from the outset of nest-building (including prospecting). These could be explained by the existence of a long-term pair bond, which needs to be confirmed but would not be surprising in a species that remains on territory all year. Hypotheses that could be tested to find a mechanism responsible for the unusual features of the fody are suggested. In comparison with other fodies studied, the breeding behaviour most resembled that of the Seychelles Fody F. sechellarum (also a monogamous, non-graminivorous omnivore that breeds in solitary pairs in evergreen forest). The annual cycle was similar to that of other native passerines and most other fody taxa.

Release control of albumin from polylactic acid microspheres

This paper reports how poly(DL-lactide) microspheres of different molecular weight and BSA content were manufactured in order to evaluate the influence of these two variables on the protein release profile, using a composite central rotational design. The microspheres were prepared by a double emulsion method using different w/o phase ratios. The BSA encapsulated was about 80% of the theoretical amount incorporated. The resulting microspheres proved porous except for three batches. The release of BSA from microspheres presented two phases, first a high burst effect ranging from 37.3 to 75% of the protein incorporated, and a second slower one. Analysis of the release results clearly shows a positive linear dependence of the slope of the slow release phase on the molecular weight of polymer, due most likely to the formation of hydrogen bridges between the terminal -OH groups of the polymer chains and the solitary pairs of donor atoms of the protein. Non-porous microspheres with a lesser burst effect were obtained by decreasing the w/o ratio of the first emulsion during the preparation process.