Population trend status of Ontario’s forest birds

Abstract

Recent population trends of Ontario's forest birds were assessed by integrating results across 8 bird surveys to provide an estimate of trend status for all of Ontario, and for 2 forested regions of Ontario separately. Surveys with mid-and longterm trends were relied on most extensively in this assessment. Comparison of the first and second Breeding Bird Atlases was especially important for estimating trends in northern forests, but overall reliability of status assessments in the north was considered poor due to limited coverage and significant potential for bias. Trends of most forest birds were stable or positive at the Ontario-wide scale, with trends at least as positive as forest birds elsewhere in North America, and showing more positive trends overall than birds of agricultural landscapes. Nevertheless, individual species trends ranged from large declines to large increases, and several forest birds have been added to Species at Risk lists largely because of population declines. There were few differences in trend status among forest birds grouped by habitat association or migratory guild, although all 5 aerial insectivore species have declined. Better monitoring coverage of the boreal will be needed if improved reliability of trends is desired in the near future.Key words: Ontario, forest birds, boreal forest, population trend, bird surveys, monitoring reliability RÉSUMÉLes fluctuations récentes des populations d' oiseaux forestiers de l'Ontario ont été évaluées au moyen de l'intégration des résultats de 8 relevés d' oiseaux pour produire un estimé de la tendance actuelle pour tout l'Ontario ainsi que particulière-ment pour 2 régions forestières de la province. Les relevés indiquant les fluctuations à moyen et à long terme ont fait l' objet d'une utilisation plus poussée pour cette évaluation. La comparaison entre le premier et le second atlas des oiseaux nicheurs a été particulièrement importante pour pouvoir estimer les fluctuations dans les forêts boréales, mais la fiabilité générale des tendances actuelles dans le nord de la province a été jugée faible compte tenu de la couverture restreinte et du potentiel significatif de biais. Les fluctuations de la plupart des populations d' oiseaux forestiers se sont révélées être stables ou positives pour l' ensemble de la province, ces fluctuations étant au moins aussi positives par rapport aux oiseaux forestiers ailleurs en Amérique du Nord et elles étaient encore plus positives dans l' ensemble par rapport aux oiseaux des milieux agricoles. Néanmoins, les fluctuations des espèces individuelles variaient entre des déclins importants et des accroissements majeurs et quelques oiseaux forestiers ont été ajoutés à la liste des espèces en péril principalement suite à un déclin des populations. Peu de différence a été relevée pour ce qui est des tendances chez les oiseaux forestiers regroupés en fonction de leur habitat ou de leur regroupement migratoire, même si 5 espèces insectivores se nourrissant en vol sont en déclin. Une meilleure étude des territoire...

Biased representation of disturbance rates in the roadside sampling frame in boreal forests: implications for monitoring design

“…In addition, roads in several regions may be too dangerous to sample via roadside sampling. Thus, it is apparent that trends for these strata will require reliance either on off-road point counts or BBS style surveys (e.g., via all-terrain vehicle) such as those conducted for bird atlases (Blancher et al 2009), dedicated regional monitoring programs (e.g., Machtans et al 2014), or reliance on trends from the Christmas Bird Count (Niven et al 2004) or migration monitoring in combination with methods to infer catchment areas (Hobson et al 2015). As such, it would be beneficial to build on other work (e.g., Sólymos et al 2013, Amundson et al 2014 to develop and validate a framework for trend estimation from combining on-road and off-road point counts.…”

How well do regional or national Breeding Bird Survey data predict songbird population trends at an intact boreal site?

“…Carlson and Schmiegelow (2002). Given pragmatic considerations the program would also have to integrate results from disparate methods such as point counts, migration monitoring, and other relevant studies such as was done qualitatively by Blancher et al (2009). Only then will we be able to make sense of the contrasting sources of information that often raise more questions than they answer.…”

“…Several regional studies have documented trends that differ from BBS results (e.g., Linder andBuehler 2005, Howe andRoberts 2005), and each other (Blancher et al 2009). Trend maps on the United States Geological Survey BBS website (http://www.mbr-pwrc.…”

“…Earlier studies (Bart et al 2004, Dunn et al 2005) defined a threshold of two-thirds of a species' range covered for BBS results to be considered reliable. More recently, Blancher et al (2009) advocated lower thresholds; ≥ 50% range covered for a "reliable" trend and ≥ 25% an "acceptable" trend.…”

Temporal changes in avian abundance in aspen-dominated boreal mixedwood forests of central Saskatchewan, Canada

“…Local surveys and revisits to historic study areas have previously been used to provide external validation of reported trends (Machtans et al 2014), test hypotheses for the causes of trends (Holmes and Sherry 2001), and examine whether continent-wide declines reported from Christmas Bird Count (Butcher et al 1990) data reflect broad-scale vs. local declines on the breeding grounds (Machtans et al 2007). More recently, results from multiple monitoring programs across Ontario were integrated to provide broader insight and certainty around changes in species status and thereby address limitations and biases associated with individual monitoring programs (Blancher et al 2009). Blancher et al (2009) included off-road point-count data from the Ontario Breeding Bird Atlas, which was the primary source of trend data for 90% of species in the boreal shield (Bird Conservation Region [BCR] 8), highlighting the potential utility of local studies employing repeat visits to historic survey locations.…”