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.
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...
A multiterminal neurone, recently identified at the wing-hinge of the atympanate moth Manduca sexta, is shown to respond as a proprioceptor monitoring elevatory movements of the hind wing.
Black-capped chickadee (Parus atricapillus) adults are aggressive toward their young after the young have fledged. We examine two hypotheses to explain the function of this aggression. Eight families were observed throughout the period after fledging to see if aggressionfunctions in...
Parent birds generally eat their nestlings' feces when the nestlings are young and carry the feces from the nest as the nestlings get older. This change in behavior may be due to the decline in energy content of the feces...
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...
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...
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...
The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences...
Observations of radio-tagged Brown-headed Cowbirds (Molothrus ater) indicated that individual males and females engage in extended associations through the breeding season. Persistent courtship by males directed at particular females and extended time spent together by certain males and...
We review parental investment decision theory and provide an experimental test of the decision rule used by male bluegill sunfish (Lepomis macrochirus) in allocating parental investment to their young. The alternative decision rules tested are: (1) invest according...
A littoral zone assemblage of six planktivorous fishes (Pimephales notatus, Notropis heterodon, Fundulus diaphanus, Lepomis macrochirus, Ambloplites rupestris, Perca flavescens), and five zooplankter species, was analysed relative to three hypotheses concerning prey consumption...
In order to determine the preferred dispersion of a population of breeding Tree Swallows (Tachycineta bicolor) in Ontario, we set up an abundant supply of nest boxes with a variety of distances between them. The 72 boxes were...
Stamps (1978) suggested that the type and extent of parental care can influence the behavioural ontogeny of the offspring. Largemouth bass (Micropterus salmoides) males guard the fry for up to a month after they leave the nest while...
Why is parental care performed by the female in some species and the male in others?Several answers have been proposed by theoretical studies (Trivers,1972;Williams,1975;Dawkins and Carlisle, 1976;Maynard Smith,1977, 1978;Perrone and Zaret,1979), but there have been few efforts to test alternative...
Male bluegill sunfish (Lepomis macrochirus) construct nests in densely packed colonies characterized by high breeding synchrony. Females deposit eggs in the nests and males alone provide parental care for eggs and larvae. During the 7-day care period, males...
The purpose of this study was to determine whether parental investment decisions are made on the basis of cumulative past investment or the prospects of expected benefits minus costs. Through clutch size manipulations at nests of Redwinged Blackbirds, Agelaius phaeniceus...
The lepidopteran family Arctiidae contains a number of species that emit high frequency sounds when tactually stimulated or exposed to the intense hunting cries of insectivorous bats. The sounds are produced as rapidly repeated clicks generated by the buckling action of...
