Dawn Burke - Academia.edu (original) (raw)

Papers by Dawn Burke

Canadian Journal of Forest Research, Apr 1, 2016

Forestry Chronicle, Feb 1, 2010

We evaluated the immediate effects of group selection harvesting on the establishment of yellow b... more We evaluated the immediate effects of group selection harvesting on the establishment of yellow birch (Betula alleghaniensis Britt.) and black cherry (Prunus serotina Ehrh.) seedlings in maple-dominated hardwood stands of Algonquin Provincial Park, Ontario. Group selection gaps were compared to single-tree selection cutting and uncut reference stands pre-harvest and one growing season post-harvest using a before-after-control-impact (BACI) design. The percent cover of yellow birch seedlings increased significantly more in gaps than in single-tree selection and reference plots. Black cherry seedling cover increased significantly more in gaps than in reference plots, but increased at a similar rate in gaps and single-tree selection plots. Increased soil exposure and closer seed trees resulted in increased yellow birch recruitment when harvesting occurred in the late-summer-fall. These factors had little influence on yellow birch recruitment when harvesting occurred in the winter. The proportion of black cherry in the stand overstory had the greatest influence on black cherry recruitment; however, the uneven distribution of black cherry between stands may have precluded our ability to reliably test the influence of other factors. Concomitant increases in potential competitors such as wild red raspberry (Rubus strigosus Michx.) and sedges (Carex spp.) and the continued dominance of sugar maple (Acer saccharum Marsh) in gap openings may limit yellow birch and black cherry regeneration in successive growing seasons. While continued monitoring is required, our short-term results demonstrate that fall harvesting with group selection is effective at stimulating natural regeneration of yellow birch and black cherry.

The Wilson bulletin, Mar 1, 2002

We assessed edge avoidance, area sensitivity, and the relationship between local and regional for... more We assessed edge avoidance, area sensitivity, and the relationship between local and regional forest cover for nesting Red-eyed Vireos (Vireo olivaceus) in 13 forest fragments (1-2,353 ha in size) in southcentral Ontario, Canada. Red-eyed Vireo territories and nests were not significantly farther from the edge than random points in any of the forest fragments, and there was no relationship between the probability of a male pairing and the distance of the territory from the edge of the forest fragment. The density of singing males and the probability of a male being paired increased significantly with increasing local forest cover within a 2km radius of a study site, but not with forest fragment area or regional forest cover within a 10-km radius. Nest success was low and the probability of a nest being parasitized by the Brown-headed Cowbird {Molothrus ater) or successfully fledging > 1 host young did not vary with distance of the nest from the forest edge or with any of our area or forest cover measures. Red-eyed Vireos did not display edge avoidance nor did they appear to be area sensitive within our study region, but there was a positive relationship with the amount of local (2-km radius) forest cover. Maintaining localized regions with high forest cover has been recommended on numerous occasions for the conservation of area sensitive species; our results suggest high forest cover also may benefit species that do not appear to be area sensitive.

Journal of Wildlife Management, Jan 30, 2012

We tested the equal preference ecological trap hypothesis for breeding yellow-bellied sapsuckers ... more We tested the equal preference ecological trap hypothesis for breeding yellow-bellied sapsuckers (Sphyrapicus varius) along a time-since-harvest gradient (1-5 yr, 16-20 yr, 21-25 yr, and >60 yr) in selection system-logged hardwood forests in Algonquin Provincial Park, Ontario. Yellow-bellied sapsuckers preferred 1-5 year and >60-year-old cuts equally and more than 16-20 year and 21-25-year-old cuts. Moreabundant arthropod food and/or higher-quality sap resources may have attracted yellow-bellied sapsuckers to 1-5 year and >60-year-old cuts. Only 52% of pairs raised fledglings in 1-to 5-year-old cuts during years when nest predation by American black bears (Ursus americanus) was common, the incidence of which was negatively related to increased availability of American beech (Fagus grandifolia) nuts from the previous autumn. By contrast, 88% of pairs raised fledglings in all years in >60-year-old cuts. One-to 5-year-old cuts were demographic sinks that represent equal-preference ecological traps in years when nest predation by bears was common, whereas >60-year-old cuts were always demographic sources. High-quality habitat cues for nesting yellow-bellied sapsuckers appear to be retained for 1-5 years after selection system logging but fail to deliver safe nest sites. Cavities excavated in heart-rot-infected nest trees are least likely to be depredated because cavity walls are typically harder and deter entry by depredating bears. Retaining more potential nest trees per ha at harvest (especially American beech with heart-rot) may increase the proportion of sapsucker nests that are excavated in bear-resistant trees, thereby reducing nest predation and increasing fecundity. ß 2012 The Wildlife Society.

Landscape Ecology, Oct 19, 2010

We studied the effects of anthropogenic edges on predation and parasitism of forest bird nests in... more We studied the effects of anthropogenic edges on predation and parasitism of forest bird nests in an agriculturally fragmented landscape and a continuously forested landscape in Ontario, Canada. Nesting data were collected at 1937 nests across 10 species in the fragmented landscape from 2002–2008, and 464 nests across 4 species in the continuously forested landscape from 2006–2008. Brood parasitism only

The Auk, Apr 1, 2009

Nous avons évalué des hypothèses expliquant les risques de prédation par Ursus americanus à  n... more Nous avons évalué des hypothèses expliquant les risques de prédation par Ursus americanus à  nids de Sphyrapicus varius et de Picoides villosus en fonction des cris des oisillons et des caractéristiques de l'habitat aux sites de nidification au parc provincial Algonquin, en Ontario. Des S. varius habitant des érablières, % ont creusé des cavités dans des Acer saccharum ou des Fagus grandifolia morts ou défaillants tandis que % de ceux habitant des peupleraies (Populus spp.) ont niché dans des P. tremuloides défaillants. Des ours noirs ont détruit % des  nids de S. varius dans des érablières, ce qui explique % de tous leurs échecs. Seulement  sur  nids (%) de P. villosus dans les mêmes érablières a été détruit par U. americanus. De  nids de S. varius dans des peupleraies, aucun n'a échoué à cause d'un prédateur. Dans les érablières, le taux de survie quotidien des nids de S. varius était le plus bas lorsque les cris des oisillons étaient plus forts et portaient plus loin, dans les peuplements récemment exploités, et dans les essences (principalement A. saccharum) autres que F. grandifolia. Les parois des cavités de nidification étaient les plus dures aux nids de P. villosus, suivi par celles des nids réussis de S. varius dans les F. grandifolia et les P. tremuloides. Les nids de S. varius étaient les moins résistants dans les peuplements exploités pendant les  dernières années. Notre étude suggère que le risque de prédation par U. americanus aux nids de pics est fonction des cris des oisillons (qui attirent des ours) et des caractéristiques de l'habitat (qui influent sur la possibilité d'accéder à l'intérieur du nid).

Forest Ecology and Management, Mar 1, 2010

The Condor, 2005

We studied the impacts of low density, exurban housing developments on Wood Thrushes (Hylocichla ... more We studied the impacts of low density, exurban housing developments on Wood Thrushes (Hylocichla mustelina) breeding in small forest fragments in two regions of rural southern Ontario. In both regions, Wood Thrushes breeding in woodlots with embedded houses (housing penetrating the forest border) experienced significantly higher rates of parasitism by Brown-headed Cowbirds (Molothrus ater) than Wood Thrushes breeding in woodlots with adjacent houses (houses within 100 m of the forest edge), or undeveloped woodlots (no houses within 100 m of the forest edge). Wood Thrushes breeding in Peterborough area woodlots with embedded or adjacent houses experienced significantly increased rates of nest predation compared to Wood Thrushes breeding in undeveloped woodlots. This increased nest predation resulted in significant reductions in seasonal productivity in developed woodlots. No increase in nest predation was experienced by Wood Thrushes nesting in developed woodlots in the Ottawa region. The effects of housing developments appear to be region-specific and may depend on other factors influencing the overall abundance of cowbirds.

Conservation Biology, Jun 1, 2005

For some species of forest-breeding birds, productivity is much higher in large forest fragments ... more For some species of forest-breeding birds, productivity is much higher in large forest fragments than in small forest fragments and is higher than the level needed to replace individuals within the fragment (sources). Thus large forest fragments potentially provide excess individuals to neighboring small fragments where productivity is much lower and not adequate for replacement (sinks). We used occurrence data and distances between putative sources and sinks for four species of forest birds with this pattern of demography in large and small forest fragments to predict occupancy in small fragments. For the Ovenbird (Seiurus aurocapilla), Wood Thrush (Hylocichla mustelina), Veery (Catharus fuscescens), and Rose-breasted Grosbeak (Pheucticus ludovicianus), distance from large woodlots was a significant predictor of occurrence in small woodlots. Distance from large woodlots did not predict occupancy of Red-eyed Vireos (Vireo olivaceus), a species with no apparent difference in productivity in relation to fragment size. Neither vegetation features nor area of the small woodlots adequately explained patterns of occupancy for any species. These results suggest that maintenance of large, productive forest fragments benefit regional occurrence of forest-breeding birds by providing individuals to neighboring small woodlots. Limited reproduction in these small woodlots means that they may act as a reservoir for excess individuals in the case of catastrophic events that result in vacancies in source woodlots. Conservation and sound forest management of small forests should be directed particularly toward those closer to large regional forests.

Conservation Biology, Apr 1, 2004

Artificial nest experiments have been used in an attempt to understand patterns of predation affe... more Artificial nest experiments have been used in an attempt to understand patterns of predation affecting natural nests. A growing body of literature suggests that neither relative rates nor patterns of predation are the same for artificial and natural nests. We studied nest predation and daily mortality rates and patterns at real and artificial ground and shrub nests to test the validity of artificial nest experiments. We monitored 1667 artificial and 344 natural nests, over seven trials, in three regions, across 58 sites in Ontario. We controlled for many of the factors thought to be responsible for previously reported differences between predation rates on natural and artificial nests. Although artificial nests in our study resembled natural nests, contained eggs of appropriate size, shape, and color of target bird species, and were placed in similar microhabitats as natural nests, the rates of predation on these nests did not parallel rates on natural nests for any region in terms of absolute rate or pattern. Predation rates on artificial nests did not vary between years, as they tended to for natural nests, and the magnitude of predation pressure on artificial ground nests compared with shrub nests did not show the same pattern as that on natural nests. In general, rates of predation on artificial nests were significantly higher than on natural nests. Our results suggest that conclusions derived from artificial nest studies may be unfounded. Given that many influential ideas in predation theory are based on results of artificial nest experiments, it may be time to redo these experiments with natural nests.

Se documentan las adiciones de la Bijirita de Canadá Wilsonia canadensis y la Bijirita de Nashvil... more Se documentan las adiciones de la Bijirita de Canadá Wilsonia canadensis y la Bijirita de Nashville Vermivora ruficapilla para las avifaunas del Archipiélago de Sabana-Camagüey y Cayo Coco, Cuba, respectivamente. También se comentan otras observaciones de otras especies de parúlidos realizadas durante los períodos de residencia invernal del 2005–06.

The Wilson Journal of Ornithology, 2007

Abstract Rose-breasted Grosbeaks (Pheucticus ludovicianus) commonly breed in the deciduous woodla... more Abstract Rose-breasted Grosbeaks (Pheucticus ludovicianus) commonly breed in the deciduous woodlands of southern Ontario, but have become a species of conservation concern due to recent population declines (2% per year in Ontario from 1966 to 2004). We investigated whether habitat alterations may be contributing to these declines through decreases in nest survival at nest and randomly selected sites in 23 woodlots varying in the intensity of partial harvest. Rose-breasted Grosbeaks consistently selected nest sites with more sapling cover, less canopy cover, and a lower surrounding basal area than available. The best supported model of daily nest survival included a measure of nest concealment, with the top 15 models containing nest concealment indicating higher nest survival rates at less concealed nests. Model-averaged estimates produced positive slopes for canopy cover, sapling cover, and nest height indicating higher survival at higher canopy cover, sapling cover, and nest height. Heavy-cutting practices appear to create woodlots that act as ecological traps. These woodlots provide “preferred” nest sites that result in low nest survival probabilities for the Rose-breasted Grosbeak.

The Wilson Bulletin, 2002

Northeastern Naturalist, 2007

We report one instance of conspecifi c nest reuse by Hylocichla mustelina (Wood Thrush) within th... more We report one instance of conspecifi c nest reuse by Hylocichla mustelina (Wood Thrush) within the same breeding season, two instances of conspecifi c nest reuse in subsequent breeding seasons, and two instances of Wood Thrushes reusing nests originally constructed by Pheucticus ludovicianus (Rose-breasted Grosbeaks) during a three-year study in Ontario. Rates of nest reuse were higher than previously reported for Wood Thrush, with conspecifi c nest reuse accounting for 8-12% of the observed nesting activity, and interspecifi c nest reuse accounting for 8-9%. Nest reuse occurred following periods of colder minimum temperatures or greater precipitation than in other years. We suggest that instances of nest reuse within and between breeding seasons may occur in response to time or energy constraints on females resulting from unusual weather conditions. Documenting instances of nest reuse behaviour contributes to our understanding of some of the constraints experienced during breeding and may shed light on factors affecting annual reproductive success.

Landscape Ecology, 2010

The Journal of Wildlife Management, 2012

We tested the equal preference ecological trap hypothesis for breeding yellow‐bellied sapsuckers ... more We tested the equal preference ecological trap hypothesis for breeding yellow‐bellied sapsuckers (Sphyrapicus varius) along a time‐since‐harvest gradient (1–5 yr, 16–20 yr, 21–25 yr, and >60 yr) in selection system‐logged hardwood forests in Algonquin Provincial Park, Ontario. Yellow‐bellied sapsuckers preferred 1–5 year and >60‐year‐old cuts equally and more than 16–20 year and 21–25‐year‐old cuts. More‐abundant arthropod food and/or higher‐quality sap resources may have attracted yellow‐bellied sapsuckers to 1–5 year and >60‐year‐old cuts. Only 52% of pairs raised fledglings in 1‐ to 5‐year‐old cuts during years when nest predation by American black bears (Ursus americanus) was common, the incidence of which was negatively related to increased availability of American beech (Fagus grandifolia) nuts from the previous autumn. By contrast, 88% of pairs raised fledglings in all years in >60‐year‐old cuts. One‐ to 5‐year‐old cuts were demographic sinks that represent equal‐...

The Forestry Chronicle, 2010

Forest Ecology and Management, 2012

Single-tree selection harvesting is frequently used in the tolerant hardwood forests of North Ame... more Single-tree selection harvesting is frequently used in the tolerant hardwood forests of North America, but little is known about how it affects the reproductive success of migratory songbirds. Many songbirds that breed in tolerant hardwoods, including the Rose-breasted Grosbeak (Pheucticus leudovicianus) are experiencing population declines across their breeding ranges. We studied habitat characteristics and reproductive success of Rose-breasted Grosbeaks in stands harvested 0-5, 16-20, and 21-25 years previously and in reference stands (un-harvested for >50 years) in Algonquin Provincial Park, Ontario, Canada (n = 3 per age class). Recently harvested stands had higher cover from regenerative growth and lower sapling, understory, and canopy cover than other treatments, whereas reference stands had higher basal area and sapling cover. Pairing success was significantly lower in the reference stands than in all other post-harvest treatments, and the number of fledglings per successful nest was significantly lower in the reference stands than in the 0-5 years post-harvest stands. Density and population growth rate were significantly positively correlated, suggesting that density may be an adequate indicator of habitat quality for Rosebreasted Grosbeaks in forested landscapes. Older males were present at higher densities, initiated their nests earlier, and produced significantly more fledglings per nest than younger males in all treatments. Habitat characteristics did not differ significantly between nests with second-year and after-second-year males, suggesting greater reproductive output of older males was likely due to experience rather than monopolization of better quality territories. We concluded that single-tree selection harvesting was beneficial to Rose-breasted Grosbeaks in our predominantly forested study area. Population growth rates were below replacement levels in the 21-25 years post-harvest and reference treatments, but populations were stable in the younger regenerating stands. Thus, in a continuously forested landscape this species' declines are probably not attributable to single-tree selection harvesting.

Forest Ecology and Management, 2010