Nest Environment Research Articles

Repeatability of microenvironment-specific nesting behaviour in a turtle with environmental sex determination

Evolutionary thermal adaptation is increasingly being elucidated in a variety of systems. However, one of the most striking examples, temperature-dependent sex determination (TSD) in reptiles, has proven stubbornly difficult to decipher. Theoretical models suggest that selection on and heritable variation in thermal sensitivity of embryonic sex determination and maternal behavioural choice of thermal qualities of nest sites control the microevolutionary potential of TSD. To begin addressing this important issue, we conducted a multiyear field study of nesting behaviour in painted turtles (Chrysemys picta), which display TSD. We detected a significant field repeatability for overstory vegetation cover around nests at oviposition, a trait that is correlated inversely with nest temperature during embryonic sex determination and positively with offspring sex ratio (percentage of male). Neither clustered nesting nor individual spatial repeatability in nest site choice caused this striking pattern. Instead, females consistently preferred nest environments with particular quantities of overstory vegetation cover. These findings confirm a crucial assumption of models concerning the microevolution and adaptive significance of TSD in reptiles. The results also indicate that this system may be able to evolve via long-term maternal nesting behaviour in response to skewed sex ratios caused by environmental perturbations, such as gradual long-term climate change.

Egg-Laying Activities and Reproductive Traits in Females of Oplurus cuvieri cuvieri

Egg-Laying Activities and Reproductive Traits in Females of Oplurus cuvieri cuvieri

Pollen Collection and Foraging Force by European and European × Africanized Hybrid Honey Bees (Hymenoptera: Apidae) in Mixed Genotype Colonies are Similar

The foraging force and pollen collection of European and European × Africanized hybrid worker honey bees, Apis mellifera L., housed in a common nest environment were compared. Significant heterogeneity was found within both genotype populations for the proportion of the bees that foraged, as well as for the proportion of foragers that collected pollen. However, there was not a consistent bias for either genotype to collect pollen or to field a greater proportion of the total foraging population. These results suggest that when sharing a common environment, European × Africanized hybrids and European honey bees do not differ with respect to individual foraging decisions. Results also suggest that the pollinating efficiency of commercial colonies maintained in Africanized areas will probably not diminish as a consequence of introgression of African honey bee genes, if problems associated with their management can be controlled.

Environmentally induced variation in body size and condition in hatchling snapping turtles (Chelydra serpentina)

We performed an experiment at a field site in north-central Nebraska, U.S.A., to assess the importance of the nest environment as a determinant of body size and condition in hatchling snapping turtles (Chelydra serpentina). The contents of newly constructed nests were manipulated by reciprocal transplant so that each of several nests received a complement of eggs from each of several females. The eggs were recovered from nests after 8 weeks and allowed to complete incubation under standard conditions in the laboratory. Live mass, dry mass and water content of carcasses, and dry mass of unused yolk varied significantly among hatchlings that incubated in different nests. This variation apparently resulted from variation in water exchange by eggs, because embryos in eggs that absorbed water during 8 weeks in the field consumed more of their yolk, grew to a larger size, and were better hydrated at hatching than embryos in eggs that lost water to the nest environment. Phenotypic variation of the magnitude observed in this investigation may affect survival of hatchlings, and therefore needs to be considered explicitly in theories for the evolution of life histories in these long-lived animals.

Nestling Feeding-Space Strategy in Arabian Babblers

Maintaining individual space is a foraging tactic widely used by many adult animals. However, this behavior has not been described for altricial nestling birds. In this study, nestling Arabian Babblers (Turdoides squamiceps) defended individual spaces around themselves and obtained food in relation to the size of these spaces. Each nestling created two circular feeding zones around itself: (1) an internal one (termed exclusive space), within which it usually succeeded in preventing nest mates from obtaining food; and (2) an external one (shared space), within which the nestling competed for food with siblings according to its relative strength. The first indication of the imminent death of a nestling was when sib- lings began receiving food inside its exclusive feeding space. Stability of feeding spaces was tested by adding a fifth nestling to the nest. None of the exclusive feeding spaces decreased, and feeding rates within them remained constant. In contrast, feeding rates in the shared feeding spaces diminished as a consequence of their reduction in size. It seems that a nes- tling's survival depends on its ability to defend its exclusive feeding space. This tactic may enable Arabian Babbler nestlings to obtain food and survive in their cooperative as well as competitive nest environment in a relatively nonaggressive manner. Received 22 December ject of much empirical and theoretical research since the appearance of O'Connor's (1978) sem- inal paper. So-called altruistic behaviors, as well as selfish ones, were explained through brood reduction using a wide range of theories such as inclusive fitness, the handicap princi- ple, parent-offspring conflict, and honest sig- naling.

The control of optic flow during learning flights

Hymenopteran insects perform systematic learning flights on departure from their nest, during which they acquire a visual representation of the nest environment. They back away from and pivot around the nest in a series of arcs while turning to view it in their fronto-lateral visual field. During the initial stages of the flights, turning rate and arc velocity relative to the nest are roughly constant at 100–200° s−1 and are independent of distance, since the insects increase their flight speed as they back away from the pivoting centre. In this paper I analyse how solitary wasps control their flight by having them perform learning flights inside a rotating striped drum.

Patterns of Wood Duck Nest Temperatures during Egg-Laying and Incubation

We studied the thermal environment of Wood Duck (Aix sponsa) nests in southeastern British Columbia. Mean daily nest temperatures (T N ) were correlated with maximum daily air temperatures. T N increased as the egg-laying period advanced among both successful and unsuccessful nests, although T N was lower among unsuccessful nests. Hens began spending nights on nests when there were as few as four eggs in clutches. T N and the precision of nest thermoregulation increased among successful nests as the incubation period advanced, although there was a great deal of variation between days and nests. Length of the incubation period was not correlated with clutch size, nor with mean overall nest temperature during incubation, but was correlated with the variance of T N 's during incubation.

Questioning paradigms: caste-specific ventilation in harvester ants, Messor pergandei and M. julianus (Hymenoptera: Formicidae)

Do developmental constraints in ant colonies limit gas exchange strategies to those displayed by female alates (presumptive queens)? In the xeric harvester ant genus Messor, we found that M. pergandei and M. julianus female alates ventilated highly discontinuously, as predicted, but M. julianus workers ventilated less discontinuously and M. pergandei workers (which occur in more xeric habitats) ventilated continuously. We present the salient characteristics of the discontinuous ventilation cycles of the species and the manner in which they are modulated by CO2 emission rates at a single temperature (24 °C). We demonstrate that, in M. julianus workers, open-spiracle phase CO2 emission rate only slightly exceeds overall CO2 emission rate, making discontinuous ventilation marginal, a state extrapolated in M. pergandei to continuous ventilation. However, workers are plainly capable of far greater rates of CO2 emission than when inactive at 24 °C, so the lack of discontinuous ventilation in M. pergandei under normoxic conditions is not likely to be imposed by physiological constraints and may, in fact, be a response to its xeric environment. We hypothesize ­ aside from phylogenetic effects ­ that discontinuous ventilation occurs primarily in insects that may experience hypoxic and hypercapnic conditions, such as ant queens during claustral colony foundation and perhaps workers within the nest environment; that discontinuous ventilation is not necessarily essential to reduce respiratory water loss; and that it will not necessarily occur in castes or species routinely exposed to xeric but normoxic conditions.

Ground-nesting bees determine the location of their nest relative to a landmark by other than angular size cues

Bees and wasps acquire a visual representation of their nest's environment and use it to locate their nest when they return from foraging trips. This representation contains among other features cues to the distance of near-by landmarks. We worked with two species of ground-nesting bees, Lasioglossum malachurum (Hymenoptera: Halictidae), Dasypoda hirtipes (Hymenoptera: Melittidae) and asked which cues to landmark distance they use during homing. Bees learned to associate a single cylindrical landmark with their nest's location. We subsequently tested returning bees with landmarks of different sizes and thus introduced large discrepancies between the angular size of the landmark as seen from the nest during training and its distance from the nest. The bees' search behaviour and their choice of dummy nest entrances show that both species of ground-nesting bees consistently search for their nest at the learned distance from landmarks. The influence of the apparent size of landmarks on the bees' search and choice behaviour is comparatively weak. We suggest that the bees exploit cues derived from the apparent speed of the landmark's image at their retina for distance evaluation.

Vegetational Cover Predicts the Sex Ratio of Hatchling Turtles in Natural Nests

I monitored natural nests of an Illinois population of the western painted turtle (Chrysemys picta bellii), a species with temperature—dependent sex determination, for 4 yr to investigate the relationships between vegetational cover at the nest site and hatchling sex ratio. Most nests produced hatchlings all of one sex (66% of 116 nests). Hatchling sex ratio within nests was predictably related to the nesting beach and to the quantity of solar exposure at the nest mainly from the south. The North beach tended to produce more all—male nests and an overall male—biased sex ratio than did the South beach. Within each beach, nests with more vegetational cover on the southern and perhaps western aspects produced more males than did more exposed nests. However, the relationship between solar exposure and nest sex ratio was absent during two atypically cool summers. This study suggests a possible mechanism by which female turtles choose the thermal environment of nests and, hence, the sex ratio of their offspring: they may assess vegetational cover on the nest site at oviposition.

Genetic and Posthatch Parental Influences on Growth in Pigeon Squabs

Four hundred fifty-six squabs from 72 pairs of Silver King × White King crosses were reared by either their genotypic parents or foster parents to study the effects of posthatch nest environment on squab growth. Posthatch parental performance interms of feeding and caring for the young accounted for 6.28%, 10.27%, 5.72%, and 0.00% of the total variance in 7-day, 14-day, 21-day, and 28-day weight, respectively. Parental performance accounted for 8.41%, 0.00%, 10.81%, and 8.39% of the total variance in 0–7-day, 8–14-day, 15–21-day, and 22–28-day gain periods, respectively. The combined weight of the two nest mates at 14 days maximizes the percentage of the posthatch component included in the total variance and thus can be taken as a measure of parental performance. Selection for increased egg pro-duction in one line and parental performance in another line so that squabs from the egg line can be fostered by the parental performance line is suggested as a breeding strategy to increase the annual rate of squab production.

Inheritance of size and shape in a natural population of collared flycatchers, Ficedula albicollis

AbstractFour external skeletal and three feather dimensions were measured on adult collared flycatchers (Ficedula albicollis) and their adult offspring. By using mid‐offspring‐midparent regressions, all traits were found to be heritable with an arithmetic mean heritability of 0.46. Heritability estimates from full‐sib analyses were about 1.5 times higher (mean 0.67), indicating that variation in traits was affected by shared nest environment among full‐sibs. The overall body size as measured by principal component one (PC1) was found to be heritable (h2 = 0.40). However, this multivariate measure of heritability was not significant in offspring‐father comparison, while highly so in offspring‐mother comparison (h2 = 0.60). Low offspring‐father resemblance was evident also in univariate estimates of heritability. Possible causes of this (extra‐pair copulations, maternal effects, sex‐linked variance) are discussed.Genetic correlations among seven traits were estimated to be low (mean 0.22), and of similar magnitude or higher than phenotypic correlations (mean 0.18). All genetic correlations were positive. Genetic and phenotypic correlations as well as covariances were fairly similar to each other (r = 0.85 and r = 0.87, respectively). Environmental correlations did not follow the pattern of genetic correlations (r = 0.11), but were more similar to phenotypic correlations (r = 0.60). Given the low genetic correlations and moderate heritabilities, the overall conclusion is that the external morphology of collared flycatchers is largely under additive genetic control and that there is a strong potential for evolutionary change in morphology even under complex multivariate selection.

Orientation flights of solitary wasps (Cerceris; Sphecidae; Hymenoptera)

Bees and wasps are known to use a visual representation of the nest environment to guide the final approach to their nest. It is also known that they acquire this representation during an orientation flight performed on departure. A detailed film analysis shows that orientation flights in solitary wasps of the genus Cerceris consist of a systematic behavioural sequence: after lift-off from the nest entrance, wasps fly in ever increasing arcs around the nest. They fly along these arcs obliquely to their long axis and turn so that the nest entrance is held in the left or right visual field at retinal positions between 30° and 70° from the midline. Horizontal distance from the nest and height above ground increase throughout an orientation flight so that the nest is kept at retinal elevations between 45° and 60° below the horizon. The wasps' rate of turning is constant at between 100°/s and 200°/s independent of their distance from the nest and their ground velocity increases with distance. The consequence of this is that throughout the flight wasps circle at a constant angular velocity around the nest. Orientation flights are strongly influenced by landmark lay-out. Wasps adjust their flight-path and their orientation in a way that allows them to fixate the nest entrance and to hold the closest landmark in their frontal visual field. The orientation flight generates a specific topography of motion parallax across the visual field. This could be used by wasps to acquire a series of snapshots that all contain the nest position, to acquire snapshots of close landmarks only (distance filtering), to exclude shadow contours from their visual representation (figure-ground discrimination) or to gain information on the distance of landmarks relative to the nest.

Environmentally induced variation in body size of turtles hatching in natural nests.

Eggs from three snapping turtles (Chelydra serpentina) were divided between two natural nests in a factorial experiment assessing the role of the nest environment as a cause for variation in body size and energy reserves of hatchlings at our study site in northcentral Nebraska. Nest # 1 was located in an unshaded area on the south side of a high sandhill, whereas nest #2 was located in an unshaded area on level ground. Eggs in nest #1 increased in mass over the course of incubation, with eggs at the bottom of the nest gaining more mass than eggs nearer to the surface. In constrast, eggs in nest #2 lost mass during incubation, with eggs at the bottom declining less in mass than eggs at the top of the cavity. Hatchlings from nest #1 were much larger (but contained smaller masses of unused yolk) than hatchlings from nest #2. Additionally, eggs from the lower layers in both nests tended to produce larger hatchings (but with smaller masses of unused yolk) than eggs from the upper layers. Thus, ecologically important variation in body size and nutrient reserves of hatchling snapping turtles results from variation in the environment among and within nests.

Host, nest, and ecological relationships of species of Protocalliphora (Diptera: Calliphoridae)

A total of 4781 nests of 110 species of birds was examined for the presence of Protocalliphora in several localities in Ontario, Canada, and the intermountain region of northern Utah. Twenty species belonging to this genus were found in 1621 (33.8%) nests of 73 avian species. Some species, such as P. chrysorrhoea and P. halli, showed strong host preferences, whereas others, such as P. metallica and P. interrupta, preferred specific nest environments. The nests of birds that live in colonies and (or) return to the same site annually were more frequently and heavily infested than those of other birds. In Utah, where 17 species of Protocalliphora occurred, most species showed a degree of host preference, whereas in Ontario, where there were only 9 species, most species preferred specific nest sites. Of the 20 species of Protocalliphora collected during this study, 3 were found exclusively in Ontario and 11 in Utah, with 6 species common to both study areas.

Images of the environment in corporate America

Three nature images influence the environmental policies of major American corporations. Successively they are images of the (1) unfouled nest, (2) protected habitat, and (3) uncontaminated environment. Each contains unexpected surprises for its corporation, however. Polaroid, for example, does not foul its company precincts, but is now a Superfund “Potentially Responsible Party” for its deposited wastes in its home and neighboring states. This anomaly thus extends its unfouled-nest image to its dumpsites and beyond, but also implodes upon its workplace. Parallel extensions and inversions affect Martin Marietta's favored image of the protected habitat and Union Carbide's of the uncontaminated environment. These are shown with references to Kant and to Aristotle, but a concluding moral compares further neglect of the full consequences of such images to Dante's allegorical Circles 4 and 5 of Hell.

Environmental and genotype-by-environment influences on chick size in the Yellow-browed leaf warbler Phylloscopus inornatus.

I investigated genetic and environmental factors affecting fledgling chick size in the Yellow browed leaf warbler Phylloscopus inornatus. The proportion of variation among broods is >45% for both tarsus length and body weight; this can be attributed at least in part to effects of the shared nest environment. A high off-spring-parent regression for weight also appears to be partly due to an environmentally induced correlation and the regression is reduced when effects of laying date are controlled for. A cross-fostering experiment demonstrated a significant nest of origin x nest of rearing interaction. The presence of genotype-environment interaction affecting chick size may be quite general in birds. It is shown how this can account for observed patterns of the dependence of the magnitude of offspringparent regression on prevailing conditions, as has been found in other studies. In P. inornatus the failure to detect significant genetic variance in chick body weight and tarsus length may be due to high standard errors on the estimates, but it may also reflect true low levels of genetic variance in chick size if the genotype-interaction effect described occurs regularly in this species.

Wild mice in the cold: some findings on adaptation.

The house mouse, Mus domesticus, can thrive in natural environments much below its optimum temperature. Thermogenesis is then above that at more usual temperatures. In addition, body weight, and the weights of brown adipose tissue and the kidneys, may be higher than usual. In free populations of house mice cold lowers fertility and may prevent breeding. Other possible limiting factors on breeding are food supply, shelter for nesting and social interactions. In captivity, wild-type house mice exposed to severe cold (around 0 degrees C) at first adapt ontogenetically by shivering and reduced activity. But raised thermogenesis is soon achieved without shivering; nest-building improves; and readiness to explore may be enhanced. Endocrine changes probably include, at least initially, a rise in adrenal cortical activity and in catecholamine secretion. Some females become barren, but many remain fertile. The maturity of fertile females is, however, delayed and intervals between births are lengthened; nestling mortality rises. A limiting factor during lactation may be the capacity of the gut. Similar adaptive changes are observed during winter in some species of small mammals that do not hibernate. But neither the house mouse nor other species present a single, universal pattern of cold-adaptation. Wild-type mice bred for about 10 generations in a warm laboratory environment (20-23 degrees C) change little over generations. In cold they become progressively heavier and fatter at all ages; they mature earlier, and nestling mortality declines. The milk of such 'Eskimo' females is more concentrated than that of controls. If 'Eskimo' mice are returned to a warm environment, they are more fertile, and rear heavier young, than controls that remained in the warm. Despite the heavier young, litter size is not reduced: it may be increased, probably as a result of a higher ovulation rate. Parental effects have been analyzed by cross-fostering and hybridizing. Survival, growth and fertility are all favourably influenced by the intra-uterine and nest environments provided by 'Eskimo' females. 'Eskimo' males are also better fathers. Hence after ten generations the phenotype of cold-adapted house mice shows the combined effects of (a) an ontogenetic response to cold, (b) a superior parental environment and (c) a change genotype. The secular changes in the cold that lead to this phenotype give the appearance of evolution in miniature; but it is equally possible that they represent a genetical versatility that allows rapid, reversible shifts in response to environmental demands.(ABSTRACT TRUNCATED AT 400 WORDS)

Myrmecochory in Polygala vulgaris L., Luzula campestris (L.) DC. and Viola curtisii Forster in a Dutch dune area.

Seed dispersal by ants in Polygala vulgaris, Luzula campestris and Viola curtisii was studied in a primary dune valley on the island of Terschelling, The Netherlands. Normally developed seeds of all three species are taken by the ants into their nests. The ants show a distinct preference for the seeds of the specialized myrmecochore Polygala vulgaris, as compared with the two diplochorous species. It could be demonstrated that the elaiosome is the attractive part of the seed. Mapping studies demonstrate that the dispersal of the seeds by ants has a marked effect on the distribution pattern of the standing population of Polygala and Viola. Adult plants are often found on or close to the active nest mounds of all ant species present, while the growing sites of juvenile individuals and seedlings are practically restricted to the nest environment. The nests of two of the seed-dispersing ant species, viz., those of Lasius niger and Tetramorium caespitum, show differences in soil chemistry with the surroundings. The ant nests are significantly richer in some essential plant macronutrients, such as phosphate, potassium and nitrate. The advantage of myrmecochory in the dune area of Terschelling is discussed.

Effect of biologically active plants used as netst material and the derived benefit to starling nestlings.

The European starling Sturnus vulgaris preferentially incorporates fresh sprigs of particular plant species for use as nesting material. Chemicals found in these plants may act to reduce pathogen and ectoparasite populations normally found in nest environments. The present experiments were performed to test this Nest Protection Hypothesis. In the fild, we experimentally determined that wild carrot Daucus carota, a plant species preferred as nest material, effectively reduced the number of hematophagous mites found within nests relative to control nests without green vegetation. Chicks from nests containing wild carrot had higher levels of blood hemoglobin than chicks from control nests. However, there were no differences in weight or feather development. In the laboratory, we found that wild carrot and fleabane, Erigeron philadelphicus, (also preferred by starlings as nest material) substantially reduced the emergence of feeding instars of mites, while garlic mustard, Alliaria officinalis, (commonly available but not preferred) had little effect on the emergence of mites. We infer that preferred plant material may act to inhibit feeding or otherwise delay reproduction of mites, thereby reducing risk of anemia to developing nestlings.