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

Abstract

ABSTRACT. The North American Breeding Bird Survey (BBS) is the principal source of data to inform researchers about the status of and trend for boreal forest birds. Unfortunately, little BBS coverage is available in the boreal forest, where increasing concern over the status of species breeding there has increased interest in northward expansion of the BBS. However, high disturbance rates in the boreal forest may complicate roadside monitoring. If the roadside sampling frame does not capture variation in disturbance rates because of either road placement or the use of roads for resource extraction, biased trend estimates might result. In this study, we examined roadside bias in the proportional representation of habitat disturbance via spatial data on forest "loss," forest fires, and anthropogenic disturbance. In each of 455 BBS routes, the area disturbed within multiple buffers away from the road was calculated and compared against the area disturbed in degree blocks and BBS strata. We found a nonlinear relationship between bias and distance from the road, suggesting forest loss and forest fires were underrepresented below 75 and 100 m, respectively. In contrast, anthropogenic disturbance was overrepresented at distances below 500 m and underrepresented thereafter. After accounting for distance from road, BBS routes were reasonably representative of the degree blocks they were within, with only a few strata showing biased representation. In general, anthropogenic disturbance is overrepresented in southern strata, and forest fires are underrepresented in almost all strata. Similar biases exist when comparing the entire road network and the subset sampled by BBS routes against the amount of disturbance within BBS strata; however, the magnitude of biases differed. Based on our results, we recommend that spatial stratification and rotating panel designs be used to spread limited BBS and off-road sampling effort in an unbiased fashion and that new BBS routes be established where sufficient road coverage exists.Représentativité biaisée des taux de perturbation dans le plan d'échantillonnage en bord de routes en forêt boréale : répercussions dans l'élaboration de suivis RÉSUMÉ. Le Relevé des oiseaux nicheurs (BBS) nord-américain est la principale source de données sur le statut et la tendance des oiseaux de la forêt boréale pour les chercheurs. Malheureusement, la couverture du BBS en forêt boréale est faible et les préoccupations grandissantes sur le statut des espèces nichant dans ce milieu ont amené les chercheurs à considérer étendre la couverture du BBS vers le nord. Toutefois, les taux élevés de perturbation en forêt boréale pourraient compliquer les suivis effectués le long des routes. Si l'échantillonnage réalisé en bord de routes ne tient pas compte des taux de perturbation variables tant dans l'emplacement des routes que dans l'utilisation des routes pour l'extraction des ressources, les estimations de la tendance qui en résultent pourraient être faussées. Nous avons examiné si les suivis en bord de routes p...

Potential benefits of augmenting road-based breeding bird surveys with autonomous recordings

“…The BBS is one of the most important tools to inform conservation and management of North American bird species, but it currently suffers from a lack of geographic coverage (Machtans et al 2014, Handel andSauer 2017), and potential biases (e.g., Matsuoka et al 2011, Van Wilgenburg et al 2015 may limit inferences about population trajectories (see also O'Connor et al 2000). We believe that ARU technology can address some of these limitations and enhance the quality of the BBS and other bird monitoring programs.…”

“…However, there are concerns when BBS data are used to (1) generate population size estimates (e.g., Partners in Flight; Blancher et al 2013), because roads influence bird behavior (Matsuoka et al 2011) and sound transmission relative to forest interiors (Haché et al 2014, and (2) assess trends for species that are systematically arriving earlier than the June survey period creating declines in population size owing to a change in phenology, but not abundance (Inouye et al 2000, Parmesan 2007). The BBS in boreal Canada also suffers from a nonrandom distribution of routes, poor habitat representation (Matsuoka et al 2011), and biased representation of disturbance rates (Betts et al 2007, Machtans et al 2014, Van Wilgenburg et al 2015, Handel and Sauer 2017. The degree to which these add variance to the data and reduce power and precision is a concern.…”

The role of the North American Breeding Bird Survey in conservation

“…Uneven geographic coverage may result in biased estimates of trends at regional or national scales if rates of population change vary between the areas covered by the BBS and the rest of the species' range. For example, recent work suggests that trends of species in the southern fringe of the Canadian boreal forest, which is covered by the BBS, differ from trends of the same species in the more northerly portions of the boreal forest where BBS coverage is lacking (Machtans et al 2014, Van Wilgenburg et al 2015.…”

A cost efficient spatially balanced hierarchical sampling design for monitoring boreal birds incorporating access costs and habitat stratification

“…networks [22] with few human settlements, there is little potential for volunteer surveys [23]. Similarly, a simple, design-based sampling strategy (e.g., a randomized design in which sample units are selected with the same probabilities) is logistically and financially impractical [9,24].…”