Population and Nesting Behaviour of Weaver Ants, Oecophylla smaragdina from Meghalaya, India

Weaver ants are known for their unique nest-building skills using leaves and larval-silk as a binding agent. The weaver ants, Oecophylla smaragdina are present in large numbers in the Ri-Bhoi district, Meghalaya. Ri-Bhoi district is a hot and humid place with 22 -30°C. This is the first study from this region to examine the nesting behavior along with the population of these ants from here. It was noted that they build nests in different types of trees but it is more abundant in needlewood trees (Schima wallichi) locally known as ‘diengngan.’ From the central trunk of the S. wallichi tree, the nearest distance of the nest is about 0.7 m and the farthest up to 3.4 m. The nests of O. smaragdina are somewhat round-oval and use leaves of different sizes ranging from 8-32 cm2. The nests are made at a height ranging from 4-25 m and their average nest size is about 9,483 cm3. They utilize about twenty leaves with a specific number of chambers to keep their broods, the queen, and food. The number of worker ants, pupae, and larvae are variable in different nests because of nest size, location/height of the nests, and the trees. When the nest population increases, they locate a new spot and build a satellite nest where they get the right amount of sunlight and shelter from predators and adverse environmental factors. These weaver ants are also used as medicine, food and fish bait by the indigenous people in Meghalaya.

Ant nest architecture is shaped by local adaptation and plastic response to temperature

Social insects are among the most abundant arthropods in terrestrial ecosystems, where they provide ecosystem services. The effect of subterranean activity of ants on soil is well-studied, yet little is known about nest architecture due to the difficulty of observing belowground patterns. Furthermore, many species’ ranges span environmental gradients, and their nest architecture is likely shaped by the climatic and landscape features of their specific habitats. We investigated the effects of two temperature treatments on the shape and size of nests built by Formica podzolica ants collected from high and low elevations in the Colorado Rocky Mountains in a full factorial experiment. Ants nested in experimental chambers with soil surface temperatures matching the local temperatures of sample sites. We observed a plastic response of nest architecture to conditions experienced during excavation; workers experiencing a high temperature excavated deeper nests than those experiencing a cooler temperature. Further, we found evidence of local adaptation to temperature, with a significant interaction effect of natal elevation and temperature treatment on nest size and complexity. Specifically, workers from high elevation sites built larger nests with more tunnels when placed in the cool surface temperature treatment, and workers from low elevation sites exhibited the opposite pattern. Our results suggest that subterranean ant nest architecture is shaped by a combination of plastic and locally adapted building behaviors; we suggest that the flexibility of this ‘extended phenotype’ likely contributes to the widespread success of ants.

Population density, habitat preference, and breeding biology of Chukar Partridge (Alectoris chukar) in Malakand division, Khyber Pakhtunkhwa, Pakistan

The field biology of Chukar Partridge (Alectoris chukar) was studied in Malakand division, which is an important range of its distribution in Pakistan. The abundance of the species at different altitudes was studied using both transect trails of various lengths and point counts at certain spots. The average monthly population density was estimated to be 1.448±0.466 birds/ha. The population density in August, September, and October 2020 was significantly (P<0.05) higher, as compared to the rest of the months. Chukar Partridge sightings were the lowest in December, with mean±SD = 0.996±0.147 birds/ha and the highest in October 2.333±0.202 birds/ hae in all the study sites. At each study site, maximum activity habitats were marked and selected for breeding ecology study. Data was collected on breeding time, nest site selection, nest size, incubation period, and hatching success. The breeding season in this species starts in February, with the peak months being March and April, when calls are frequently heard. The frequency of calls varied from 0.15 to 0.3 per minute. Throughout the breeding season, twelve nests were observed using binoculars and camera traps from a distance to avoid disturbance, wherever possible and without disrupting the species. Nesting sites were mostly on slopes under the eaves of Dodonea viscosa, Calotropis procera and Zizyphus oxyphylla. Dry leaves of Poa annua, Cynodon dactylon, Dichanthium annulatum, small twigs of bushes, and downy feathers were used as nesting materials. The average diameter of nest (n=12) was 25.43±3.4 (mean±SD) cm. Overall, the mean clutch size was 94.5±30.187 egg/nest with an incubation period of 22–24 days. The hatching success rate was 82% with 315 successfully hatched chicks, while the fledging rate was 83% (265 fledged out of 315 hatched in, n=42 nests).

Prey preference of a wasp determined by nest size supports the role of natural selection in body size evolution in Cassidinae leaf beetles

The prey preference of a predator can impose natural selection on prey phenotypes, including body size. Despite evidence that large body size protects against predation in insects, the determinants of body size variation in Cassidinae leaf beetles are not well understood. We examined the prey preference of the digger wasp Cerceris albofasciata, a specialist predator of adult Cassidinae leaf beetles, and found evidence for natural selection on prey body size. The wasp hunted prey smaller than the size of their nest entrance. However, the wasp preferred larger prey species among those that could be carried into their nest. Thus, the benefits of large prey and the cost associated with nest expansion might determine the prey size preference. As expected from the prey species preference, the wasp preferred small individuals of the largest prey species, Thlaspida biramosa, and large individuals of the smallest prey species, Cassida piperata, resulting in natural selection on body sizes. In intermediate-sized prey species, however, there was no evidence for selection on body size. Natural selection on body size might explain the variation of prey morphologies that increase body size, such as explanate margins, in this group.

Linking Male Reproductive Success to Effort Within and Among Nests in a Co-Breeding Stream Fish

Nest construction is an energetically costly behavior displayed by males in many taxa. In some species, males construct nests and co-breed with other males and they may construct multiple nests in a breeding season. However, little is understood about how allocation of effort within and among nests affects male reproductive success. We characterized reproductive effort of male bluehead chub (Nocomis leptocephalus) on nests in an entire breeding season using PIT antennas deployed around nests and linked effort within and among nests to reproductive success, measured by number of offspring assigned genetically to each male, in a small stream in South Carolina, USA. We monitored time spent by a total of 34 males on each of 18 nests during the spawning season in 2017. A Bayesian hierarchical analysis showed that larger males spent more time constructing and maintaining a given nest, and consequently were more reproductively successful than smaller males on the same nest. Combined with aggressive behavior displayed by larger males toward smaller males, this finding suggested that reproductive effort including agonistic interactions within nests was a determinant of reproductive success. In contrast, more males together constructed larger nests, which led to higher reproductive success of members that constructed those nests. Number of nests that male constructed, a measure of effort across nests, was not a predictor of reproductive success, indicating that reproductive success varied among nests due to nest size. Our study showed that male reproductive success was determined by both aggressive and cooperative behaviors in a co-breeding species.

Extrinsic stressors modulate resource evaluations: insights from territoriality under artificial noise

Background Competition is considered to rely on the value attributed to resources by animals, but the influence of extrinsic stressors on this value remains unexplored. Although natural or anthropogenic environmental stress often drives decreased competition, assumptions that this relies on resource devaluation are without formal evidence. According to theory, physiological or perceptual effects may influence contest behaviour directly, but motivational changes due to resource value are expected to manifest as behavioural adjustments only in interaction with attainment costs and resource benefits. Thus, we hypothesise that stressor-induced resource devaluations will impose greater effects when attainment costs are high, but not when resource benefits are higher. Noise may elicit such effects because it impacts the acoustic environment and imposes physiological and behavioural costs to animals. Therefore, we manipulated the acoustic environment using playbacks of artificial noise to test our hypotheses in the territorial male Siamese fighting fish, Betta splendens. Results Compared to a no-playback control, noise reduced defense motivation only when territory owners faced comparatively bigger opponents that impose greater injury costs, but not when territories also contained bubble nests that offer reproductive benefits. In turn, nest-size decreases were noted only after contests under noise treatment, but temporal nest-size changes relied on cross-contest variation in noise and comparative opponent size. Thus, the combined effects of noise are conditional on added attainment costs and offset by exceeding resource benefits. Conclusion Our findings provide support for the hypothesised modulation of resource value under extrinsic stress and suggest implications for competition under increasing anthropogenic activity.

Nest Size Matters: Common Cuckoos Prefer to Parasitize Larger Nests of Oriental Reed Warblers

BackgroundAvian brood parasites leave parental care of their offspring to foster parents. Theory predicts that parasites should select for large host nests when they have sufficient available host nests at a given time. We developed an empirical experimental design to address this hypothesis by studying nest choice of common cuckoos (Cuculus canorus) among nests of its Oriental reed warbler (Acrocephalus orientalis) hosts.ResultsWe presented two groups of experimental nests: 1) nest dyads comprise one large and one small artificial nest from reed leaves, and 2) nest triads tied together use the modified old own warbler nests including enlarged, reduced and medium sized nests to elicit parasitism by common cuckoos. We predicted that cuckoos prefer larger nests over medium sized ones, and over the smallest nest. Our experimental findings show that common cuckoo females generally prefer large nests over medium or small sized nests. Furthermore, experiments showed that cuckoo parasitism was significantly more common than in previous studies of the same warbler population.ConclusionsOur results implying that larger, taller and more exposed host nests effectively increased the probability of cuckoo parasitism.

Nesting habitat and density, nest characteristics, home ranges and group sizes of the Rufous-fronted Thornbird (Phacellodomus rufifrons) in Central Brazil

Rufous-fronted Thornbird (Phacellodomus rufifrons) reproduction has been studied under a few environmental conditions but might show some variations among regions throughout its wide geographic distribution. We describe here nesting habitat and density, nest characteristics, home ranges and group sizes of Rufous-fronted Thornbird in a Cerrado reserve in central Brazil. We found 131 nests in 2003, 2004, and 2011, and studied four groups inside a 100-ha grid. Nests were found only in cerrado típico and cerrado ralo but changed in abundance and density over the years, with a higher density in 2004 (0.37 nest/ha) than in 2011 (0.23 nest/ha). Nests were built 3.2 ± 1.0 m above the ground at 6.3 ± 0.2 m high trees of 31 species, but mostly of Qualea spp. Nests were 0.66 ± 0.27 m high and 0.44 ± 0.11 m wide. Home ranges had an average of 3.1 ± 0.3 ha, used by family groups of 4.6 ± 0.5 individuals. This study consolidates the findings of previous ones, but also highlights differences in habitat use, nest size, and nesting tree among regions or study sites, and changes in density among years, stressing the importance of studying the reproductive biology of the same bird species under different environmental conditions since different conditions might affect reproductive traits, such as reproductive investment and timing.