Intersexual spatial relationships in a lekking species: blue-crowned manakins and female hot spots

Leks offer an intriguing evolutionary problem: why do malesaggregate when this apparently leads to fitness costs? Aggregationcosts can be balanced if males settle on patches where theyare more likely to encounter females (hot-spot hypothesis).We evaluated whether female hot spots can account for patternsof lek structure in the blue-crowned manakin (Lepidothrix coronata)by modeling female distribution patterns relative to lek locationsin two 100-ha plots. Individual females were mapped based onnest locations and capture points and had their home ranges(HRs) modeled based on radiotelemetry data. The number of femalesthat lekking males can be expected to encounter was estimatedas the number of individual female HRs overlapping each maleterritory; hot spots were defined as patches where more femalesare found than average. We investigated how changes in femaleHR size and devaluation effects (decrease in female availabilitydue to the presence of neighboring males) influence male accessto females. Both factors strongly influenced the expected ratesof female encounter, but the hot-spot hypothesis was not supported:most male territories consistently overlapped fewer or justas many female HRs as expected by chance. Leks were not closerto hot spots than similar-sized nonlek sites. A proportion ofmales were, indeed, settled at hot spots, but, contrary to predictionsof the hot-spot hypothesis, they belonged to smaller leks thanmales located outside hot spots. Our results indicate that thislack of spatial correlation between males and females resultspartly from differences in sex-specific habitat preferences.     

Escape behaviour in blue‐winged grasshoppers,Oedipoda caerulescens

Blue‐winged grasshoppers Oedipoda caerulescens (Linnaeus, 1758) are commonly found in flat, open, unprotected areas. In the event of immediate danger, they leave their camouflaged position and jump away at the last moment. The present study conducted in a flight arena shows that, despite jumping at short notice from a crouching position, the grasshoppers achieve the correct timing for an optimal leap. If both compound eyes are blinded and the animals are stimulated by touch to execute an unprepared jump, the take‐off of the flightless nymphs is delayed, and adults are delayed in raising their wings; the animals tumble backward during the leap (in the case of adults, if they do not open their wings). This is a result of the unprepared take‐off position; because the entire length of the hind legs cannot be used for acceleration, the body is rotated backward. However, the escape path is not ultimately affected because, in the air, physical processes compensate for the unfavourable starting conditions. In addition, no disadvantage is evident upon landing. In each case, a hook landing was completed safely (i.e. the grasshopper landed and swung round to face the direction it had come from). The impact force is reduced and the grasshopper stabilizes itself by rotating from a forward to a backward position, immediately after the first contact with the ground. The hook landing also serves to confuse the potential attacker, and the disappearance of the bright blue hind wings of the adult makes it difficult for predators to shift quickly enough to a different kind of search to relocate their prey. In conclusion, the present study shows that the escape behaviour of blue‐winged grasshoppers is adapted to extremely short escape distances.     

Ranging behaviour of male capercaillie Tetrao urogallus outside the lekking ground in spring

During the breeding season, adult male capercaillies Tetrao urogallus display on leks in the early morning. During the day, they occupy more or less exclusive home ranges within 1 km of the lekking ground, but little is known about their movements and range use patterns during this period. In three spring seasons we monitored the daily movement of 15 radio-tagged adult males, associated with six different leks, in a coniferous forest of southeast Norway. The objective was to relate dynamics of male movement and spatial distribution to changes in food resource availability and mating-related activities. In late winter, males exhibited a pattern of short daily relocations (distance between bird locations in successive days) within small ranges. Relocation distances and home ranges then increased markedly during two weeks preceeding the main mating period. During the mating and post-mating periods, movements again decreased, followed by another short peak at the time when females with depredated nests return to the lek for remating. These temporal changes in range use were not related to changes in food resources and probably not to shifts in anti-predator behaviour, and they differed between age groups: The increase in relocation distance during the pre-mating period was most pronounced among young resident males (3 and 4 year-olds), and range area of older males were smaller and did not increase as much during this period. The observed age-related changes in space use may reflect an alternative mating strategy by young and subdominant males; they seek out females outside the lekking ground where competition from more dominant males is less intense.     

Seasonal variation in lek attendance and lekking behaviour by male Black Grouse Tetrao tetrix

Eleven Black Grouse Tetrao tetrix leks in the Scottish Highlands were visited at dawn once every week for a year. Apart from July and three leks which were unoccupied in winter, males visited leks throughout the year. Total numbers of males attending leks peaked in March in one study area (six leks) and in April in the second (five leks). The number of males present and the proportion of leks occupied varied seasonally. The proportion of males at leks was at a maximum in April (80% of males) when all leks were attended, with a secondary peak in September when 60% of leks had males present. Males spent the most time displaying in April. The optimal conditions for attendance were calm, dry mornings just after dawn. Most reliable counts of numbers of males were those made between the last week of March and the end of the first week of May.     

Effects of male call pitch on female behaviour and mate fidelity in little penguins

Playback experiments with two loudspeakers were conducted to examine how female little penguins (Eudyptula minor) respond to bray calls of males that varied in (1) dominant frequency (low vs high) and (2) familiarity (current partner vs stranger). In the first experiment, there was no statistically significant difference in the number of approaching females between low- and high-pitch calls. In the second experiment, using calls from the current partner and a stranger, females were more likely to approach closer to their own partners calls, regardless of the pitch of the strangers call. We conclude that female little penguins may recognize their partners calls (or at least familiar male calls) and appear to maintain mate fidelity even when larger, potentially more successful, strangers are on offer.     

No evidence that genetic compatibility drives extra‐pair behavior in female blue‐footed boobies

The function of female birds' extra‐pair (EP) behavior has remained an unresolved question in ornithology and behavioral ecology for > 30 yr. The genetic compatibility hypothesis (GCH) proposes that females benefit by acquiring biological sires that yield more heterozygous, and therefore fitter, offspring than their social mates. We used ten polymorphic microsatellite loci to test GCH predictions and its assumption that fitness increases with heterozygosity in blue‐footed boobies Sula nebouxii, a long‐lived tropical seabird. Our predictions were not supported. Heterozygosity was uncorrelated with quality indicators (fledging probability, fledgling or adult body size or mass, adult ornamentation, mean breeding success). Females were no more likely to have EP behavior or chicks when their social mates were less heterozygous or compatible, nor were EP males more heterozygous or compatible than the males they cuckolded. Finally, EP chicks were no more heterozygous than within‐pair chicks overall or in half‐sib comparisons, nor were within‐pair chicks from all‐within‐pair nests more heterozygous that those with EP nest‐mates. There are both methodological and biological explanations for these consistently negative results. Inadequate sample size is possible but unlikely, since our samples were comparable or larger than those of similar studies with significant findings. Lack of identity disequilibrium (within‐individual heterozygosity correlation) among our marker loci could be responsible, and suggests either insufficient marker coverage or lack of inbreeding, bottleneck, and/or admixture. An independent social pedigree revealed infrequent inbreeding, suggesting that pressure on females to select sires that maximize offspring heterozygosity may be genuinely lax. Alternatively, it is possible that the GCH is only upheld when selection on young is strongest; this would not be detected in our sample, which was taken during an extremely productive year. Whatever their cause, our results expand the taxonomic breadth of avian EP behavior analyses and should be considered in future evaluations of the GCH.     

Courtship behaviour in a lekking species: individual variations and settlement tactics in male little bustard

We analysed the display behaviour of male little bustard Tetrax tetrax to identify displays that are used in the context of male-male competition and those that are used for attracting females. Courtship was the main activity of males during the breeding season. Calling activity occurred throughout the day, and leks were attended for more than 4 months. Male sexual displays included snort call, wing-flash, and jump display. Snort call was performed throughout the day and mainly involved male-male interactions. In contrast, the wing-flash display was given only at twilight, and was performed most commonly when a female was present, supporting an inter-sexual function for this display. The jump display was performed only in the presence of female at anytime of the day. Analysis of individual variations in display behaviour revealed that intra-individual variation was low compared to inter-individual variation, especially for the jump display. It is, therefore, possible that display rates provide information on male quality. Four male settlement patterns could be defined, singles, paired, lekking and satellite lekking, but only wing-flash display and stamped snort call differed among those categories. We suggest that satellite males are attempting to benefit from proximity to higher status males, in accordance with the hotshot hypothesis of lek evolution.     

Fine‐scale distribution modeling of avian malaria vectors in north‐central Kansas

Infectious diseases increasingly play a role in the decline of wildlife populations. Vector‐borne diseases, in particular, have been implicated in mass mortality events and localized population declines are threatening some species with extinction. Transmission patterns for vector‐borne diseases are influenced by the spatial distribution of vectors and are therefore not uniform across the landscape. Avian malaria is a globally distributed vector‐borne disease that has been shown to affect endemic bird populations of North America. We evaluated shared habitat use between avian malaria vectors, mosquitoes in the genus Culex and a native grassland bird, the Greater Prairie‐Chicken (Tympanuchus cupido), by (1) modeling the distribution of Culex spp. occurrence across the Smoky Hills of north‐central Kansas using detection data and habitat variables, (2) assessing the occurrence of these vectors at nests of female Greater Prairie‐Chickens, and (3) evaluating if shared habitat use between vectors and hosts is correlated with malarial infection status of the Greater Prairie‐Chicken. Our results indicate that Culex occurrence increased at nest locations compared to other available but unoccupied grassland habitats; however the shared habitat use between vectors and hosts did not result in an increased prevalence of malarial parasites in Greater Prairie‐Chickens that occupied habitats with high vector occurrence. We developed a predictive map to illustrate the associations between Culex occurrence and infection status with malarial parasites in an obligate grassland bird that may be used to guide management decisions to limit the spread of vector‐borne diseases.     

Effects of male paragonial gland secretion on sexual receptivity and courtship behaviour of female Drosophila melanogaster

Female Drosophila melanogaster show a switch-off in sexual receptivity and an increase in oviposition rate following impregnation. These effects are also observed in unfertilized virgin females which receive transplants of intact male paragonia into the abdominal body cavity. Virgin Amherst wildtype females show a repertoire of responses to male courtship characterized by high rates of kicking and fending and a low rate of genital extrusion. Fertilized females show low rates of kicking and fending but a high rate of genital extrusion. Virgin female hosts receiving paragonial gland implants show an altered pattern of courtship rejection with low rates of kicking and fending. Studies on these host females, and on females homozygous for the mutant allele female-sterile, suggest that the expression of genital extrusion depends, in addition to the paragonial gland substance, upon additional information input from abdominal stretch receptors or from the ovary.     

Effects of male removal on the behaviour and reproductive success of female Eastern Bluebirds Sialia sialis

We removed male Eastern Bluebirds Sialia sialis to examine the importance of male parental care and the behavioural responses of unaided females to loss of male assistance. Unaided females fed young significantly more than control females (females with male assistance) fed young, but young in experimental nests were fed significantly less frequently in total than young in control nests. Unaided females had significantly lower nesting success (fledged at least one young) than control females. At control nests, males defended the young more strongly than did their mates. Unaided females defended their young as strongly as control females. Unaided and control females spent the same amount of time brooding young, and there was no tradeoff between feeding and brooding young. Most early season experimental nests failed, but late in the season many unaided females were as successful as pairs. Unaided females were able to match the feeding rat'e in control broods at late nests but not at early nests, where control nestlings were fed at a higher rate. In our population, male bluebirds played an important role in provisioning young, and early in the season unaided females were unable to provide sufficient bod to raise any young to fledging.     

Sexual selection in a lekking bird: the relative opportunity for selection by female choice and male competition

Leks are classic models for studies of sexual selection due to extreme variance in male reproductive success, but the relative influence of intrasexual competition and female mate choice in creating this skew is debatable. In the lekking lance-tailed manakin (Chiroxiphia lanceolata), these selective episodes are temporally separated into intrasexual competition for alpha status and female mate choice among alpha males that rarely interact. Variance in reproductive success between status classes of adult males (alpha versus non-alpha) can therefore be attributed to male-male competition whereas that within status largely reflects female mate choice. This provides an excellent opportunity for quantifying the relative contribution of each of these mechanisms of sexual selection to the overall opportunity for sexual selection on males (I males). To calculate variance in actual reproductive success, we assigned genetic paternity to 92.3% of 447 chicks sampled in seven years. Reproduction by non-alphas was rare and apparently reflected status misclassifications or opportunistic copulations en route to attaining alpha status rather than alternative mating strategies. On average 31% (range 7-44%, n=6 years) of the total I males was due to variance in reproductive success between alphas and non-alphas. Similarly, in a cohort of same-aged males followed for six years, 44-58% of the total I males was attributed to variance between males of different status. Thus, both intrasexual competition for status and female mate choice among lekking alpha males contribute substantially to the potential for sexual selection in this species.     

Distinct properties of the egress‐related osmiophilic bodies in male and female gametocytes of the rodent malaria parasite Plasmodium berghei

Gametogenesis is the earliest event after uptake of malaria parasites by the mosquito vector, with a decisive impact on colonization of the mosquito midgut. This process is triggered by a drop in temperature and contact with mosquito molecules. In a few minutes, male and female gametocytes escape from the host erythrocyte by rupturing the parasitophorous vacuole and the erythrocyte membranes. Electron‐dense, oval‐shaped organelles, the osmiophilic bodies (OB), have been implicated in the egress of female gametocytes. By comparative electron microscopy and electron tomography analyses combined with immunolocalization experiments, we here define the morphological features distinctive of male secretory organelles, hereafter named MOB (male osmiophilic bodies). These organelles appear as club‐shaped, electron‐dense vesicles, smaller than female OB. We found that a drop in temperature triggers MOB clustering, independently of exposure to other stimuli. MDV1/PEG3, a protein associated with OB in Plasmodium berghei females, localizes to both non‐clustered and clustered MOB, suggesting that clustering precedes vesicle discharge. A P. berghei mutant lacking the OB‐resident female‐specific protein Pbg377 displays a dramatic reduction in size of the OB, accompanied by a delay in female gamete egress efficiency, while female gamete fertility is not affected. Immunolocalization experiments indicated that MDV1/PEG3 is still recruited to OB‐remnant structures.     

Spatial determinants of infection risk in a multi‐species avian malaria system

Spatially‐variable processes can be an important element of host–parasite interactions, but their longer term demographic and evolutionary effects depend on the magnitude of variation in space, the scale at which variation occurs and the degree to which such processes are temporally stable. Here, we use multiple years of data from a study of two closely related tit species (Paridae), infected with two congeneric species of avian malaria (Plasmodium), to evaluate the roles of extrinsic and intrinsic factors in driving spatial heterogeneity in infection risk, and to address questions of scale and temporal stability in these vector‐driven host–parasite interactions. We show that the two malaria parasite species exhibit markedly different spatial epidemiology: P. relictum infections are effectively randomly distributed in space, with no temporal consistency, whereas P. circumflexum infections exhibit pronounced spatial structuring that is stable over the six years of this study and similar in both host species. We show that both conspecific and heterospecific host density contribute to elevated infection risk, but that the main determinants of elevated risk of P. circumflexum infection risk are habitat features probably associated with vector distribution and abundance. We discuss the implications of these findings, both for our understanding of the epidemiology of malaria in the wild, but also in terms of the longer‐term evolutionary and demographic consequences that spatially variable parasite‐mediated selection may have on host populations.     

Influence of male aggregation size on female visitation in Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Abstract  The importance of male aggregation size for female visitation and initiation of male pheromone-calling was investigated in Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) using artificial male aggregations in large laboratory cages. Female B. tryoni visited the largest aggregation more frequently than single males in association with a higher proportion of calling males, but there was no correlation between aggregation size and female visitation. Female B. tryoni had a limited capacity to perceive a difference between the number of calling males. Calling propensity of male B. tryoni was increased by the presence of conspecific males. Increased calling propensity in larger groups of male B. tryoni may be due to social facilitation of male calling behaviour. Female visitation at aggregations was only weakly associated with male calling, suggesting that aggregation size and the number of pheromone-calling males are not the only factors important in locating mates in B. tryoni , and it is possible that low-density populations could persist so long as females can encounter single males.