This paper presents results from a series of studies investigating the causes underlying uneven style morph ratios in tristylous Decodon verticillatus, a clonal perennial that inhabits wetland habitats in eastern central North America.
Pairs of captive male brown-headed cowbirds (Molothrus ater) housed with a female formed clear dominance relationships, and when an older male was housed with a yearling male, the adult was usually dominant.
The purpose of the experiments presented here was to determine the location within the central nervous system (CNS) of the proposed tymbal central pattern generator (CPG) in Cycnia tenera. Motor neuron impulses that underlie tymbal activation were recorded extracellularly from...
We used a laboratory experiment to determine effects of a predator (other than straightforward prey consumption) and food availability, during the larval stage, on adult size, age at emergence and fecundity of Chironomus tentans.
Many fish species are protracted spawners, producing fry over a several-week breeding season. We demonstrate that this time dimension has important implications for recruitment by relating the body size and survival of yearlings to the day that they were born.
We report here an estimate of the time of day of egg laying in Eastern Bluebirds using the method developed by Scott (1993) to analyze data we collected during a study of mate guarding (Meek and Robertson 1994).
The winter dynamics of several chemical, physical, and biological variables of a shallow, polymictic lake (Opinicon) are compared to those of a deep, nearby dimictic lake (Upper Rock) during ice cover (January to early April) in 1990 and 1991. Both...
In this study, we used pumpkinseed populations in two east-central Ontario lakes to test for age and size-dependent effects on the probability and timing of reproduction of mature females.
These results support the hypothesis that sibling relatedness influences begging behaviour in birds, and suggests that increased intensity of begging can evolve whenever female promiscuity or brood parasitism lowers the coefficient of relatedness among nestmates.
If cavity-entrance orientation confers some benefit to secondary hole-nesting birds, individuals should use cavities with certain entrance orientations, and the orientation of a cavity's entrance should influence reproductive success.
We use data from field experiments and observations of Tree Swallows Tachycineta bicolor defending single and extra nest-sites at nest-box and cavity populations to determine the function of extra nest-site defense behaviour.
Mitochondrial DNA (mtDNA) variation was examined for two nominal subspecies of largemouth bass, Micropterus salmoides salmoides (northern largemouth bass) and M. s. floridanus (Florida largemouth bass).
Breeding density, synchrony, and experience are expected to influence the frequency of extrapair paternity in birds. Female tree swallows can influence the fertilization success of extrapair males by active selection and rejection of copulation partners. We suggest that this ability...
Removed male Eastern Bluebirs to examine the importance of male parental care and the behavioural responses of unaided females to loss of male assistance
Parental male burying beetles, Nicrophorus spp. (Coleoptera: Silphidae), are presented with a dilemma when conspecific females intrude on their nests. Although these females provide males with additional mating opportunities, they also pose a threat to the survival of the male's...
Studies of the mating strategies of birds are increasingly shifting their focus to the role that females take in controlling copulation (Hunter et al. 1993, Petrie 1992, Birkhead and Moller 1993). In some avian species, females appear able to control...
Therefore, we suggest that most extra-pair copulations occur at some unknown location, possibly at a feeding or roosting area where females may be able to choose from many more potential extra-pair fathers than at their nest-site.
We assessed the level of extrapair paternity in an Ontario population of Eastern Bluebirds. We examined the relationship between mate guarding and paternity by looking at the correlation between mate guarding and paternity for individual males, and by comparing paternity...
This study compares the compensatory response of female tree swallows without their mate's parental assistance (when females are widowed) and with reduced male parental care (when males are handi-capped by cutting some feathers).
In colonies of bluegill, some males provide parental care for broods in nests, whereas other males steal fertilizations and do not provide parental care. Using experimental pond populations of bluegill of known genotype (determined through protein electrophoresis), we demonstrate that...
I collected data on 27 pumpkinseed populations in eastern and central Ontario and conducted a transplant experiment with one of those populations to test growth competition-related predictions of several life history models.
This study examines the maintenance of inbreeding depression impartially self-fertilizing populations of the long-lived, herbaceous wetland plant, Decodon verticillatus.
To test this, we exposed dogbane tiger moths (Cycnia tenera) to a recording of the echolocation sequence emitted by a big brown bat (Eptesicus fuscus) as it attacked a stationary target. Our results demonstrate that, at normal echolocation intensities, C...
Black-capped chickadees (Parus atricapillus) have the ability to shift their songs up and down over a wide range of absolute frequencies. Males can shift their songs over 465 ± 52.9 (SE) Hz. During the dawn chorus, males shift...
Water mites of the genus Arrenurus vary in male sexual dimorphism and in sperm transfer behaviour. Possible adaptive functions of male courtship behaviour are discussed, including the hypothesis that male intromittant organs evolved in Arrenurus to circumvent female choice.
As a result of the viral identity of this parasite, we recommend that the etiologic agent of Toddia sp. Infections from this and other species of North American snakes be renamed Snake Erythrocytic Virus.
Movements of nonterritorial ("floater") male red-winged blackbirds (Agelaius phoeniceus) were monitored to test the hypothesis that floaters enhance their chances for territory acquisition by becoming familiar with a specific area, i.e., by restricting their geographical movements and monitoring only a...
Patterns of overwinter mortality in the sexually dimorphic red-winged blackbird (Agelaius phoeniceus)were examined to test the predictions of the sexual-selection hypothesis that male size is limited by directional selection favoring small males and that female size is maintained by stabilizing...
Age, height, number of shoot endings, neighbor density, and overhead cover from local neighbors were recorded for over 1,400 young sugar maple trees under 200cm tall and growing in open vs. closed (shaded) habitats from two sites.
This study on black-capped chickadees, Parus atricapillus, assesses whether social rank influences the behaviour of chickadees in predator situations. Chickadee flocks were restricted to an area of an outdoor aviary containing no vegetative cover to ensure that all flock...
It has recently become apparent that females of many species of birds often copulate with, and produce young sired by, males other than their social mates. Understanding the adaptive significance of this behaviour requires knowing whether extra-pair matings entail any...
The life cycle of Hepatozoon sipedon sp. nov. was studied in two snake species, the Northern water snake and the Eastern garter snake, in its mosquito hosts Culex pipiens and C. territans, and in the Northern leopard frog. Gametogenesis, fertilization...
Predation risk may have a profound impact upon foraging behaviour. I studied how potential exposure to predation affected the foraging behaviour of eastern chipmunks.
We studied the vocalizations of adult tree swallows in eastern Ontario during the prelaying period. We distinguished and named five call types and one song type using structural criteria, and quantified the percent occurrence of each vocalization type in various...
We re-examined tree swallows for the presence of the paternity protection tactic of mate guarding using less conservative criteria for its detection than did an earlier study.
Flowering occurrence and allozymic variation were studied in eight local populations of Lemna minor in eastern Ontario, Canada. After 2 years of survey, not a single flower was observed. This absence of flowering suggests the possibility of loss of sexual...
We investigated whether nestling American robins were capable of influencing food distribution in their nests by perceiving that certain sectors of the nest received a relatively high proportion of feedings and positioning themselves accordingly.
We performed an experiment to investigate effects of red leg bands on the behavior of male Red-winged Blackbirds (Agelaius phoeniceus). We presented models having either black, blue, or red leg bands to territorial male Red-winged Blackbirds to test the hypothesis...
We suggest that low-altitude erratic flight in moths is a protean insurance defence against bats, as it should reduce the chance of their being detected by these predators.
Previous studies provide evidence that cavity size influences clutch-size and reproductive success in some hole-nesting birds, because overcrowding in cavities may cause brood mortality due to trampling or hyperthermia. We tested this hypothesis with two experiments at nestbox populations of...
We removed the mates of ten male blackcapped chickadees (Parus atricapillus) during the nestbuilding period to determine the effect of female presence on dawn singing. During the first dawn chorus following mate removal, males sang significantly longer, increased movement within...
Surveys of style morph frequencies in 163 populations of the eastern North American, clonal, tritylous aquatic, Decodon verticillatus suggested a wide range of clonal diversity among populations.
Based on the model of Whittingham et al. (1992, Am. Nat., 139, 1115-1125), it is predicted that males in many monogamous species of birds will not decrease their level of parental care until their confidence of paternity is very low...
Black-capped Chickadees (Parus atricapillus) sing a two-note tonal song that has stereotyped frequency parameters (glissando and frequency interval). We hand-reared and tutored pairs of nestlings in acoustic isolation to determine the extent that learning is involved in the production of...
Canonical correspondence analysis (CCA) was used to explore the relationship between measured environmental variables and surficial diatom (Bacillariophyceae) assemblages in alkaline lakes from southeastern Ontario. Total nitrogen (TN), watershed area, alkalinity, and maximum depth each explain significant (P ≤ 0.05)...
Here we ask whether the population structure, reproductive systems, gene flow and patterns of genetic differentiation in aquatic plant populations is best attempted using demographic and genetic techniques for estimating effective population size.
Multilocus DNA fingerprinting of offspring of monogamous pairs of tree swallows revealed that 50% of broods contained young seed by extra-pair males, totalling 38% of all offspring analysed.
Females of the brood-parasitic brown-headed cowbird (Molothrus ater) search for host nests in which to lay their eggs. Females normally return to lay a single egg from one to several days after first locating a potential host nest and lay...
Fluctuating asymmetry of the first tarsal segment of the proleg of the forest tent caterpillar moth Malacosma disstria Hbn. (Lepidoptera: Lasiocampidae) was significantly inversely related to survival ability in the lab. The monitoring of population levels of fluctuating asymmetry could...
Foraging behaviour of pumpkinseed (Lepornis gribbosus) was investigated in feeding arenas containing different habitat structures and prey types in two sets of experiments, each of three successive 10-d blocks.
We examined associations among parasite infections, secondary sexual traits and testosterone in male red-winged blackbirds sampled at the start of the breeding season. Parasites quantified included ectoparasitic lice and mites and endoparasitic blood protozoans, nematodes, trematodes and cestodes. Secondary sexual...
During the final 10 d of a 22-d subchronic exposure of bluegills Lepomis macrochirus to a penta chlorophenol (PCP) concentration of 173 Mg/L, bluegill growth rate significantly decreased by 75% when compared with untreated controls, and food intake declined significantly...
