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Dive into the research topics where Philip D. Taylor is active.

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Featured researches published by Philip D. Taylor.


Biological Conservation | 1995

EFFECT OF ROAD TRAFFIC ON AMPHIBIAN DENSITY

Lenore Fahrig; John H. Pedlar; Shealagh E. Pope; Philip D. Taylor; John Wegner

We studied the effect of traffic intensity on local abundance of anurans. We counted dead and live frogs and toads per km and estimated frog and toad local abundances using breeding chorus intensities on similar roads through similar habitats, but with different levels of traffic intensity. After correcting for effects of date, local habitat, time, and region, our analyses demonstrated that (1) the number of dead and live frogs and toads per km decreased with increasing traffic intensity; (2) the proportion of frogs and toads dead increased with increasing traffic intensity; and (3) the frog and toad density, as measured by the chorus intensity, decreased with increasing traffic intensity. Taken together, our results indicate that traffic mortality has a significant negative effect on the local density of anurans. Our results suggest that recent increases in traffic volumes worldwide are probably contributing to declines in amphibian populations, particularly in populated areas.


Oikos | 1998

An experimental assessment of landscape connectivity

Jason Pither; Philip D. Taylor

We experimentally assess the relative movement abilities of two sympatric, ecologically similar species of damselfly, Calopteryx maculata and Calopteryx aequabilis (Odonata: Calopterygidae), within two structurally dissimilar habitat types, forest and pasture. For both species, streams are required resources, forest is a potential resource, and pasture is neutral habitat. Experimental manipulations were conducted at a spatial scale approaching typical inter-stream distances within our study region. A portion of the individuals was displaced away from its required stream habitat within its native landscape, and the remaining individuals were transferred to another landscape of alternate habitat structure (either forest or pasture). Within each habitat type we equate relative movement ability, an essential component of landscape connectivity, with the proportion of displaced individuals observed to have reached the stream, as measured against reobservation rates of control individuals released at the stream. We found that C. maculata, the species more consistent in its use of forest as a resource, moved significantly more readily through 700 m of pasture habitat than through the same distance of forest, while C. aequabilis moved with equal abilities through both habitat types. Historical behavior - whether or not the individuals typically used forest as a resource before the manipulations did not have a statistically significant effect on the movement abilities of individuals of either species in either habitat type. There was, however, some evidence that C. maculata individuals native to non-forested landscapes moved more readily through forest than their forest-inhabiting counterparts. Both sexes moved with equal abilities irrespective of habitat type, but male C. aequabilis moved with greater ability through forest than females, while the reverse was true within pasture landscapes.


Ecological Applications | 2006

Independent Effects Of Fragmentation On Forest Songbirds: An Organism-Based Approach

Matthew G. Betts; Graham J. Forbes; Antony W. Diamond; Philip D. Taylor

The degree to which spatial patterns influence the dynamics and distribution of populations is a central question in ecology. This question is even more pressing in the context of rapid habitat loss and fragmentation, which threaten global biodiversity. However, the relative influence of habitat loss and landscape fragmentation, the spatial patterning of remaining habitat, remains unclear. If landscape pattern affects population size, managers may be able to design landscapes that mitigate habitat loss. We present the results of a mensurative experiment designed to test four habitat loss vs. fragmentation hypotheses. Unlike previous studies, we measured landscape structure using quantitative, spatially explicit habitat distribution models previously developed for two species: Blackburnian Warbler (Dendroica fusca) and Ovenbird (Seiurus aurocapilla). We used a stratified sampling design that reduced the confounding of habitat amount and fragmentation variables. Occurrence and reoccurrence of both species were strongly influenced by characteristics at scales greater than the individual territory, indicating little support for the random-sample hypothesis. However, the type and spatial extent of landscape influence differed. Both occurrence and reoccurrence of Blackburnian Warblers were influenced by the amount of poor-quality matrix at 300- and 2000-m spatial extents. The occurrence and reoccurrence of Ovenbirds depended on a landscape pattern variable, patch size, but only in cases when patches were isolated. These results support the hypothesis that landscape pattern is important for some species only when the amount of suitable habitat is low. Although theoretical models have predicted such an interaction between landscape fragmentation and composition, to our knowledge this is the first study to report empirical evidence of such nonlinear fragmentation effects. Defining landscapes quantitatively from an organism-based perspective may increase power to detect fragmentation effects, particularly in forest mosaics where boundaries between patches and matrix are ambiguous. Our results indicate that manipulating landscape pattern may reduce negative impacts of habitat loss for Ovenbird, but not Blackburnian Warbler. We emphasize that most variance in the occurrence of both species was explained by local scale or landscape composition variables rather than variables reflecting landscape pattern.


Oikos | 1995

Wing Morphology of a Forest Damselfly Is Related to Landscape Structure

Philip D. Taylor; Gray Merriam

We demonstrate that, after correcting for the effects of size, the wing lengths, wing widths and thoracic weights of the forest damselfly Calopteryx maculata differ between populations along forested streams, and those along streams through pasture. Pasture landscapes can be considered as fragmented forest landscapes; forest landscapes are continuous. In the fragmented landscapes some C. maculata fly across intervening pasture to reach foraging sites in forest. We propose that there is morphological plasticity within the species that is revealed through the landscape process of habitat fragmentation and that there is micro-scale selection within the fragmented landscapes for individuals that are better suited to make these flights


Avian Conservation and Ecology | 2010

Declines of Aerial Insectivores in North America Follow a Geographic Gradient

Silke Nebel; Alex Mills; Jon D. McCracken; Philip D. Taylor

North American birds that feed on aerial insects are experiencing widespread population declines. An analysis of the North American Breeding Bird Survey trend estimates for 1966 to 2006 suggests that declines in this guild are significantly stronger than in passerines in general. The pattern of decline also shows a striking geographical gradient, with aerial insectivore declines becoming more prevalent towards the northeast of North America. Declines are also more acute in species that migrate long distances compared to those that migrate short distances. The declines become manifest, almost without exception, in the mid 1980s. The taxonomic breadth of these downward trends suggests that declines in aerial insectivore populations are linked to changes in populations of flying insects, and these changes might be indicative of underlying ecosystem changes. RESUME. Les populations d’oiseaux nord-americains qui se nourrissent d’insectes aeriens montrent un declin a grande echelle. Une analyse des donnees de tendance du Releve des oiseux nicheurs (BBS) en Amerique du Nord de 1966 a 2006 indique que les declins dans cette guilde sont plus importants que ceux qui sont observes chez les passereaux en general, et ce, de facon significative. Le profil des declins montre egalement un gradient geographique frappant, la diminution des insectivores aeriens devenant plus frequente vers le nord-est de l’Amerique du Nord. La baisse est aussi plus marquee chez les especes qui migrent sur de longues distances, comparativement a celle observee chez les especes qui migrent sur de courtes distances. Ces declins sont devenus evidents, presque sans exceptions, dans le milieu des annees 1980. L’ampleur taxinomique de ces tendances a la baisse donne a penser que le declin des populations d’insectivores aeriens est lie aux changements dans les populations d’insectes volants, ces derniers etant possiblement le reflet de modifications au plan de l’ecosysteme.


PLOS ONE | 2011

Landscape Movements of Migratory Birds and Bats Reveal an Expanded Scale of Stopover

Philip D. Taylor; Stuart A. Mackenzie; Bethany G. Thurber; Anna M. Calvert; Alex Mills; Liam P. McGuire; Christopher G. Guglielmo

Many species of birds and bats undertake seasonal migrations between breeding and over-wintering sites. En-route, migrants alternate periods of flight with time spent at stopover – the time and space where individuals rest and refuel for subsequent flights. We assessed the spatial scale of movements made by migrants during stopover by using an array of automated telemetry receivers with multiple antennae to track the daily location of individuals over a geographic area ∼20×40 km. We tracked the movements of 322 individuals of seven migratory vertebrate species (5 passerines, 1 owl and 1 bat) during spring and fall migratory stopover on and adjacent to a large lake peninsula. Our results show that many individuals leaving their capture site relocate within the same landscape at some point during stopover, moving as much as 30 km distant from their site of initial capture. We show that many apparent nocturnal departures from stopover sites are not a resumption of migration in the strictest sense, but are instead relocations that represent continued stopover at a broader spatial scale.


Conservation Ecology | 1998

In Situ Behavioral Response of Common Loons Associated with Elevated Mercury (Hg) Exposure

Joseph J. Nocera; Philip D. Taylor

Common Loons (Gavia immer) in Nova Scotia, Canada have the highest blood mercury (Hg) concentrations of any loon population in North America. Previous studies have shown that exposure to varying levels of Hg in prey is associated with changes in pre-nesting adult behavior. We report here the first association of sublethal blood Hg contamination with changes in behavior of Common Loon young. As Hg levels in their blood rise, the amount of time that chicks spend brooding (by back-riding) decreases (P = 0.004) and time spent preening increases (P = 0.003). The sum increase in energy expenditure is not being compensated for with expected increases in feeding http://www.ecologyandsociety.org/vol2/iss2/art10/ (1 of 12) [1/27/2009 11:15:57 AM] Conservation Ecology: In situ behavioral response of common loons associated with elevated mercury (Hg) exposure rates or begging. We suggest that such altered time-activity budgets may disrupt the energetic balance of young. Our results show that variation in time spent back-riding is associated with changes in fledging rates. Adult behavior did not significantly vary with Hg, but results are suggestive that an association may exist. We also show that monitoring the time-activity budgets of very young chicks can serve to indicate the effects Hg concentrations in their blood. We confirm the hypothesis that loons and other upper trophic level predators could be at risk from elevated levels of bioavailable Hg. This may help to explain the chronically low productivity of such contaminated sites as Kejimkujik and allow for more focused management initiatives.


Journal of Animal Ecology | 2012

Migratory stopover in the long‐distance migrant silver‐haired bat, Lasionycteris noctivagans

Liam P. McGuire; Christopher G. Guglielmo; Stuart A. Mackenzie; Philip D. Taylor

1. Some bat species make long-distance latitudinal migrations between summer and winter grounds, but because of their elusive nature, few aspects of their biology are well understood. The need for migratory stopover sites to rest and refuel, such as used by birds, has been repeatedly suggested, but not previously tested empirically in bats. 2. We studied migrating silver-haired bats (Lasionycteris noctivagans) at Long Point, ON, Canada. We used digital radio-transmitters to track 30 bats using an array of five towers that effectively covered the entire region (c. 20 × 40 km). We measured stopover duration and departure direction, and documented movement patterns, foraging activity and roost sites. We measured body composition on arrival using quantitative magnetic resonance and simulated long-distance migration using observed body composition to predict migration range and rate. 3. Migration occurred in two waves (late August and mid-September). Most bats stayed 1-2 days, although two remained >2 weeks. One third of the bats foraged while at the site, many foraging opportunistically on nights when rain precluded continued migration. Bats roosted in a variety of tree species and manmade structures in natural and developed areas. Half of the bats departed across Lake Erie (minimum crossing distance c. 38 km) while half departed along the shoreline. 4. Simulations predicted a migration rate of c. 250-275 km per day and suggest that all but one of the bats in our study carried sufficient fuel stores to reach the putative wintering area (estimated distance 1500 km) without further refuelling. 5. Our results suggest that migrating bats stopover for sanctuary or short-term rest as opposed to extended rest and refuelling as in many songbirds. Daily torpor could reduce energy costs when not in flight, minimizing the need for extended stopovers and allowing bats to potentially complete their migration at a fraction of the time and energy cost of similar sized birds.


Biology Letters | 2015

Transoceanic migration by a 12 g songbird.

William V. DeLuca; Bradley K. Woodworth; Christopher C. Rimmer; Peter P. Marra; Philip D. Taylor; Kent P. McFarland; Stuart A. Mackenzie; D. R. Norris

Many fundamental aspects of migration remain a mystery, largely due to our inability to follow small animals over vast spatial areas. For more than 50 years, it has been hypothesized that, during autumn migration, blackpoll warblers (Setophaga striata) depart northeastern North America and undertake a non-stop flight over the Atlantic Ocean to either the Greater Antilles or the northeastern coast of South America. Using miniaturized light-level geolocators, we provide the first irrefutable evidence that the blackpoll warbler, a 12 g boreal forest songbird, completes an autumn transoceanic migration ranging from 2270 to 2770 km (mean ± s.d.: 2540 ± 257) and requiring up to 3 days (62 h ± 10) of non-stop flight. This is one of the longest non-stop overwater flights recorded for a songbird and confirms what has long been believed to be one of the most extraordinary migratory feats on the planet.


Landscape Ecology | 1996

Habitat fragmentation and parasitism of a forest damselfly

Philip D. Taylor; Gray Merriam

We compared populations of a forest damselfly —Calopteryx maculata — in two kinds of landscapes. In fragmented landscapes, forested foraging patches were separated from streams (where oviposition and mating occur) by up to 500 m of pasture. In non-fragmented landscapes, there was continuous forest cover adjacent to streams. The prevalence and intensity of midgut infections of a gregarine parasite were significantly lower in the fragmented landscapes than in the non-fragmented landscapes. We have shown elsewhere that in the fragmented landscapes, damselflies move over greater areas to forage than in the non-fragmented landscapes. We postulate that these movements lower the rate of encounter between damselflies and oocysts, thus lowering the prevalence and intensity of infection. The differences suggest that actual habitat fragmentation events would alter the relationship between host and parasite, but that populations of both species would persist after fragmentation. Prevalence of parasitism is related to age but we found no residual effects of size on parasitism.

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Tara L. Crewe

University of New Brunswick

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