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The objectives of this study were to describe and evaluate potential drivers of genetic structure in Canadian breeding populations of the Ovenbird, Seiurus aurocapilla. We performed genetic analyses on feather samples of individuals from six study sites using nuclear microsatellites. We also assessed species identity and population genetic structure of quill mites (Acariformes, Syringophilidae). For male Ovenbirds breeding in three study sites, we collected light-level geolocator data to document migratory paths and identify the wintering grounds. We also generated paleohindcast projections from bioclimatic models of Ovenbird distribution to identify potential refugia during the last glacial maximum ( LGM, 21,000 years before present) as a factor explaining population genetic structure. Birds breeding in the Cypress Hills (Alberta/Saskatchewan) may be considered a distinct genetic unit, but there was no evidence for genetic differentiation among any other populations. We found relatively strong migratory connectivity in both western and eastern populations, but some evidence of mixing among populations on the wintering grounds. There was also little genetic variation among syringophilid mites from the different Ovenbird populations. These results are consistent with paleohindcast distribution predictions derived from two different global climate models indicating a continuous single LGM refugium, with the possibility of two refugia. Our results suggest that Ovenbird populations breeding in boreal and hemiboreal regions are panmictic, whereas the population breeding in Cypress Hills should be considered a distinct management unit. [ABSTRACT FROM AUTHOR]

Several studies have emphasized the importance of postfledging survival when estimating avian population growth rates, yet high variation exists in reported estimates. Mechanisms influencing postfledging survival also remain poorly understood. The influences of local habitat quality and landscape context on postfledging movements also remain largely undocumented. We measured daily postfledging survival and movements in Ovenbirds (Seiurus aurocapilla) in selection cut plots (30-40% basal area removal) and controls. Specifically, we tested predictions from the "concealment" hypothesis (higher survival/shorter movements with increased fledgling concealment), "body condition" hypothesis (higher survival/longer movements with increased body mass), and "predator abundance" hypothesis (higher survival/shorter movements when predator abundance is low) by monitoring fledgling survival (n = 55) and movements (n = 41) during the first 2 weeks postfledging. Fledglings were monitored over 2 breeding seasons in S pairs of experimental plots, 25 ha each (1 control and 1 treated plot per pair), located in mature hardwood stands. We found support for an effect of predator abundance on survival (i.e. effects of plot-level abundance of red squirrels and year). Models including habitat variables or body mass received weak support. A positive trend for effect of body mass on movement between successive locations was found but no evidence for an effect of predator abundance or habitat variables. These findings indicate that spatiotemporal variation in predator abundance was a key factor determining daily postfledging survival rate in this Ovenbird population; however, predator abundance did not influence movement rate, suggesting that fledgling Ovenbirds were unable to respond to predation risk. [ABSTRACT FROM AUTHOR]

According to the ideal despotic distribution (IDD), dominant individuals gain a fitness advantage by acquiring territories that areof higher quality, thereby forcing other individuals into lower quality habitat. In contrast, the ideal free distribution (IFD) predicts that local density is a function of habitat quality, but that individuals achieve the same fitness in different habitat types as a result of density-dependent variation in territory size. Although the IFD represents an alternative, population dynamics of territorial species are generally expected to be driven by an IDD. We tested the predictions of IFD and IDD by monitoring the demographic response of the Ovenbird (Seiurus aurocapilla) to selection harvesting (30- 40% tree removal) during the first five years postharvest in five pairs of 25-ha study plots, each comprising a control (undisturbed) and a treatment (harvested plot). In the first year following harvesting, Ovenbird territory size increased in treatment plots relative to controls, whereas density, prbductivity per unit area, and the abundance of litter invertebrates decreased. Treatment effects declined consistently as stands regenerated, and most effects were no longer significant by the fifth year postharvest. However, there was no treatment effect on daily nest survival rate nor on per capita productivity. These results are consistent with the IFD, whereby similar per capita prpductivity is achieved across habitat types through density adjustments facilitated by changes in territory size. To our knowledge, this is the first study providing evidence for an IFD in a territorial bird species. [ABSTRACT FROM AUTHOR]

1. Anthropogenic noise is rapidly increasing in wilderness areas as a result of industrial expansion. While many road studies have attempted to assess the effects of industrial noise on birds, conflicting factors such as edge effects often inhibit the ability to draw strong conclusions. 2. We assessed pairing success and age distribution of male ovenbirds Seiurus aurocapilla in the boreal forest of Alberta, Canada, in areas around noise-generating compressor stations compared with areas around habitat-disturbed, but noiseless, wellpads. This allowed us to control for edge effects, human visitation and other factors that are not controlled for in studies of noise generated by roads. Generalized estimating equations (GEE) were used to assess the impacts of noise on ovenbird pairing success, age structure and body morphology. 3. We found a significant reduction in ovenbird pairing success at compressor sites (77%) compared with noiseless wellpads (92%). These differences were apparent regardless of territory quality or individual male quality. Significantly more inexperienced birds breeding for the first time were found near noise-generating compressor stations than noiseless wellpads (48% vs. 30%). 4. While there are multiple proximate explanations for these results, the ultimate cause of the changes seems to be noise pollution. We hypothesize that noise interferes with a male's song, such that females may not hear the male's song at greater distances and/or females may perceive males to be of lower quality because of distortion of song characteristics. 5. Synthesis and applications. This work demonstrates that chronic background noise could be an important factor affecting bird populations. It can impact upon pairing success and age structure of passerines; in boreal Alberta this could pose a problem for certain species as energy development expands rapidly. [ABSTRACT FROM AUTHOR]

Presents information on a study that compared the pairing success of territorial male Ovenbirds (Seiurus aurocapillus) in forest fragments created by forestry and agriculture to contiguous forest plots in Saskatchewan between 1996 and 1998. Methodology of the study; Results and discussion on the study.

In spite of recent developments in tracking technology, leg bands are still the main marking method in songbird population studies. Yet, band-related injury rates and the effects of such injuries on survival and reproductive success have rarely been documented in songbirds. Over a 9-year period, we banded 525 male Ovenbirds using a numbered aluminum band and three celluloid color bands. Of these, 322 individuals returned to our study area in at least one of the subsequent years, including four males (1.2%) missing a foot. In all cases, foot loss occurred 2-3 years after banding, suggesting indirect effects of bands rather than injuries sustained at the time of capture or banding. Among returning individuals, 91 were recaptured and only one had noticeable leg injuries that did not result in foot loss. Three of the four males missing a foot were able to fledge young, one of which produced young during two successive breeding seasons. The fact that injured males could hold territories overlapping their previous one and produce young suggests that they could forage efficiently. Although leg injuries may carry a cost over the longer term, two of the four injured males were re-sighted in our study area the year following the first observation of foot loss. Our results, along with those of other studies, suggest that the benefits of bird banding greatly outweigh the costs associated with potential injuries, at least in this ground-foraging forest songbird. [ABSTRACT FROM AUTHOR]