In this study conducted in southeastern Ontario, Canada, we manipulated the length of outer tail feathers (streamers) of male barn swallows (Hirundo rustica) shortly after they returned to four small breeding colonies in the spring.
This study investigated the effect of exogenous 11-ketotestosterone (11KT) and testosterone (T), two important androgens involved in fish reproduction, as well as cyproterone acetate (CYA), an antiandrogen, on behaviors of male bluegill (Lepomis macrochirus) during prespawning and parental care periods.
Using field observations and laboratory experiments we examined the role of temperature in microhabitat selection by an eastern Ontario population of northern water snakes (Nerodia sipedon).
3-Chlorobenzoate (3Cba)-degrading bacteria were isolated from the waters and sediments of flowthrough mesocosms dosed with various concentrations of 3Cba and inoculated with a 3Cba-degrading Alcaligenes sp., strain BR60. Bacteria capable of 3Cba degradation which were distinct from BR60 were isolated...
Several studies concerned with mate choice, reproductive performance, and life history strategies have been conducted with secondary cavity nesting birds breeding in nest boxes. Although the need for comparative studies has been recognized, populations breeding in nest boxes often have...
Although bat detectors are used with increasing frequency for the identification of bats in the field (Aldridge and Rautenbach, 1987; Crome and Richards, 1988), only one study comparing performance of different models has been published (Downes, 1982). Some bat detectors...
We examined trap bias relative to body condition, age, and sex using data collected from Brown-headed Cowbirds (Molothrus ater) decoy trapped during the 1987 and 1988 breeding seasons. A condition bias was evident, as decoy-trapped birds were in poor condition...
Black-capped Chickadee (Parus atricapillus) song consists of two notes, termed fee and bee. Frequency measures at three key points (at the start and end of fee, and at the start of bee) were obtained from the...
The behavioural response of juvenile bluegill sunfish (Lepomis macrochirus ) to predation risk when selecting between patches of artificial vegetation differing in food and stem density was investigated. Bluegill foraging activity was significantly affected by all three factors. Regardless...
Parental care of nestling and fledgling American robins, Turdus migratorius, was studied in eastern Ontario. There was no evidence of brood division prior to fledging but brood division was the predominant pattern after fledging. Females initiating second nests reduced...
Nest cavities of Tree Swallows were examined at dawn during the period of territorial establishment to determine if Tree Swallows regularly roost in their cavity.
Field experiments were conducted over the summer of 1983 to determine food-evacuation rate and measure stomach fullness of bluegill sunfish (Lepomis macrochirus). A combination of these data gave estimates of daily food intake of fish. Fish were captured...
The population dynamics and feeding ecology of pumpkinseeds (Lepomis gibbosus) were examined inhabiting two isolated Ontario beaver ponds and adjacent Lake Opinicon to determine the persistence of and reasons for small body size in pond populations.
The fish community of a small (2.7 ha) Ontario beaver pond was analyzed relative to predictions based on its small size, shallow depth, brief existence and isolation from more permanent water bodies.
In situations where foraging sites vary both in food reward and predation risk, conventional optimal foraging models based on the criterion of maximizing net rate of energy intake commonly fail to predict patch choice by foragers. Recently, an alternative model...
The exoskeletal morphology, muscular organization, and innervation patterns of the tymbals of seven sound‐producing species of tiger moths (Arctiidae) were compared with the undifferentiated episterna of two silent species. At least three muscles are involved in sound production: the tymbal...
Displacement experiments can provide useful insights into the orientation and navigational abilities of animals (Gregory et al., 1987). Such experiments have shown that some individuals of some snake species are capable of returning to their home range after displacement (i.e...
One of the costs to female birds of mating polygynously is having to share the parental care provided by their mate. Nest defence, however, is one form of paternal care that females mated to the same male should be able...
A new method to mark sperm transfer events between birds, using microspheres inserted into males' cloacae, was employed to assess the frequency of extra-pair copulation in a population of tree swallows in Ontario, Canada.
Juvenile bluegill sunfish, Lepomis macrochira, are restricted to vegetated habitats by predators. Variation in plant stem density has a significant effect on bluegill foraging success. Given the mosaic nature of this habitat, plant stem density may provide a cue...
Hypervariable genetic markers, including a novel locus-specific marker detected by a mouse major histocompatibility complex probe, reveal that multiple paternity is common in families of polygynous red-winged blackbirds (Agelaius phoeniceus). Almost half of all nests contained at least...
Data from a 3-year study of red-winged blackbirds (Agelaius phoeniceus) were used to test the hypothesis that parasites (in this case, haematozoa) reduce male fitness and cause diminished expression of secondary sexual traits, which, in turn, are used by females...
In this study, potential cues for detachment of parasitic larval Arrenurus danbyensis Mullen mites from Coquillettidia perturbans (Walker) mosquitoes were investigated. Contact with water did not induce a dramatic rate of dissociation. Crushing the host's abdomen was not as effective...
We found that larval damselflies actively defended against colonization by larval water mites (Arrenurus spp.) and that developmental stage of damselflies was related to their likelihood of being colonized. Because larval mites have a phoretic stage on damselflies, it...
We investigated habituation in killifish (Fundulus diaphanus) to repeated exposure of predator models of varying shades in two positions (above and below) against backgrounds of varying shades. Killifish that had habituated to a model of a given shade...
We examined the effects of variation in prey abundance on foraging site selection by juvenile bluegill sunfish, in the absence and presence of a predator. Groups of bluegills chose between two plots of artificial vegetation differing in plant stem density...
Food webs for 15 freshwater ecosystems in North America are reconstructed, based upon fish feeding habits in these ecosystems and established trophic categorizations for aquatic invertebrates. My own research in Goose Creek, Virginia, as well as literature data, provided the...
1. Most studies examining interactions between insectivorous bats and tympanate prey use the echolocation calls of aerially-feeding bats in their analyses. We examined the auditory responses of noctuid (Eurois astricta) and notodontid (Pheosia rimosa) moth to...
Empirically derived estimates of prey resources using conventional sampling methods are generally poor indices of actual food available to visually feeding benthivorous fish. We preferentially sampled the most active fraction of the benthos (presumably that most detectable by fish) utilizing...
Juvenile bluegill sunfish, Lepomis macrochirus, are known to use beds of aquatic vegetation as a refuge from predators. This study examines the effects of increasing plant stem density on juvenile bluegill foraging. Three stem densities (100, 250 and 500...
Twenty-seven species of water mites of the genus Arrenurus were compared with respect to allocation of reproductive effort. Clutch volume was positively correlated to female volume, female volume was positively correlated with clutch size and with larval volume, while clutch...
Laboratory-reared first-instar juvenile Gerris comatus Drake & Hottes, Gerris alacris Hussey, and Gerris buenoi Kirkaldy were exposed to larval Limnochares aquatica (L.). Development and mortality of parasitized juvenile water striders were monitored and compared with those of unparasitized insects. Duration...
Colored epaulets in female red-winged blackbirds (Agelaius phoeniceus) could be due either to direct sexual selection favoring the maintenance of this trait in females due to intrasexual competition for breeding opportunities, or to sexual selection favoring bright epaulets...
The size and age distributions of Acer saccharum Marsh. seedlings were studied in a mature hardwood forest in southeastern Ontario between 26 June and 26 September 1986. Ninety‐one percent of the seedlings surveyed were produced in 1984 which was a mast...
Several aspects of nest defence behavior were investigated in song sparrows (Melospiza melodia) in eastern Ontario. Two independent tests were made of the hypothesis that the increase in nest defence observed through a nesting attempt is due to...
We examined 10 characteristics of natural cavities and their influence on reproductive success of Tree Swallows (Tachycineta bicolor) nesting in dead trees in beaver ponds. Large ranges were found for entrance height and area, cavity volume, and nearness...
(1) The sensitivity of replacement-series experiments to variations in density was investigated in Agropyron repens, Phleum pratense and Poa pratensis collected from a hayfield in south-eastern Ontario, Canada. All pairwise combinations of species were grown in a replacement-series design...
In tristylous Pontederia cordata (Pontederiaceae), conspicuous differences in the size of pollen grains and discrete variation in the length of reproductive organs provide a suitable experimental system for the study of fine-scale pollination events. At a population of P. cordata...
Flocks of female Red-winged Blackbirds (Agelaius phoeniceus) were maintained in aviaries to determine whether variation in brightness of epaulette or chin plumage correlated with dominance status in nonbreeding situations. No correlation was found between natural plumage variation and...
Pollen extracts from live locally‐common grassland species in eastern Ontario, Canada were tested for in vitro allelopathic effect on the pollen germination of 17 sympatric target species in 1987. The flowering phenologies of the test and target species were recorded...
Numerous studies have demonstrated a negative relationship between increasing habitat complexity and predator foraging success. Results from many of these studies suggest a non-linear relationship, and it has been hypothesised that some "threshold level" of complexity is required before foraging...
This study examined the relationship between vegetation patterns at three spatial scales and five plant-growth attributes that were suspected to affect competitive ability in 10 species collected from two hayfield plots of different ages (cultivated in 1974 and 1984). Relative...
Male bluegill (Lepomis macrochirus) display a complex reproductive behavior involving two alternative life history pathways: delay of sexual maturation to become “parentals” or precocious maturation as “cuckolders.” The purpose of our study was to investigate the association of...
A chlorobenzoate-degrading Alcaligenes strain, BR60, was introduced to flowthrough lake microcosms and exposed to 3-chlorobenzoate (3Cba) concentrations from 0 to 25 μM. A DNA probe specific for BR60 chlorobenzoate catabolic genes was used with the most probable number (MPN) technique...
Radio telemetry was used to determine the time of emergence from and entry into communal hibernacula by black rat snakes (Elaphe obsoleta obsoleta) and to gain insight into the proximate factors involved in these behaviours. Emergence in mid-April...
Male parental care generally is assumed to improve survival of nestlings and increase female reproductive success (fitness). Consequently, the need for male assistance is considered by some to be responsible for the evolution of monogamy when the investment of the...
Phenotypic plasticity and genotypic variation were studied in Agropyron repens L. (Beauv.) collected from populations in two grassland communities which differed in the length of time since the last major disturbance. Twenty genotypes were collected from each population. Each genotype...
The auditory characteristics of two populations (laboratory reared and wild) of North American gypsy moths (Lymantriidae: Lymantria dispar L.) were sampled and the neurally derived thresholds of wild males and females to frequencies from 5 to 150 kHz compared. The...
We tested the hypothesis that the basis of the variation in reproductive strategy among male yellow warblers (Dendroica petechia) is a tradeoff in the allocation of reproductive effort to intrasexual competition (territorial effort) and to parental care (parental...
Field observations were conducted on four species of nesting male centrarchids to determine if guarding males discriminate intruders with respect to their potential threat to the brood, their size or position in the water column, or by the stage of...
Reverse-phase thin layer chromatography was used to quantify algal carotenoid degradation resulting from grazing by Daphnia magna in suspensions of lyophilized Oscillatoria utermöhlii, O. limnetica, Anabaena flos-aquae and Synechococcus sp. Three samples were removed every 24 h...
Testing predictions of mate-choice models often requires knowing the time a female settles in a particular territory. Because the effort necessary to observe settlement usually precludes direct observation of a large sample of females, researchers often rely on indices of...
Sexually selected infanticide, the killing of young to secure a mating opportunity, appears to be rare in birds, although it is relatively common in mammals. To examine the frequency of occurrence and the conditions under which male tree swallows, Tachycineta...
Certain families of atympanate (deaf) moths are more abundant during the summer at times when bat activity is low. Atympanate moths were collected at ultraviolet lights throughout the summer at a site in southeastern Ontario. Seasonal frequency distributions for individual...
Temporal changes in the composition of the pollinator fauna of the tristylous aquatic plant Pontederia cordata were documented during the flowering seasons of 1982 and 1983. A total of 18 species of insects, mainly bumblebees, and a single species of...
This study examines the compromise between predator avoidance and foraging in bluntnose minnows, Pimephales notatus, in shoals of different sizes and at three levels of hunger: 5, 24 or 72 h of deprivation. Trials were carried out in the...
The hypothesis that naive shoal members begin to feed more quickly on a food, novel in type, location and required foraging technique, when informed group members are present was tested with bluntnose minnows (Pimephales notatus) foraging in shoals...
The simple ears of months have responded evolutionarily to the varied levels of selection pressure exerted upon them by insectivorous bats. While frequency-matched (syntonic) bats exert the primary pressure that determines where a sympatric moth's best frequency (BF) lies, there...
