Shorebird and Passerine Abundance and Habitat Use at a High Arctic Breeding Site: Creswell Bay, Nunavut

Shorebirds and passerines were surveyed at Creswell Bay, Somerset Island, in the High Arctic Ecozone (Canadian Arctic Islands) during the breeding season (June and July, 1995–97) and in August 1995 (post-breeding). The study area, situated on the north and south sides of Creswell Bay, consisted of sedge marsh and sedge wetland in the lowest areas, with shrub tundra dominated by Dryas spp. or Cassiope spp. and sparse herbaceous tundra over more upland areas. Surveys were carried out on 400 x 400 m plots distributed among the vegetation types according to their relative amounts within the study areas (34 plots in 1995; 33 plus 56 new plots in 1997). Eleven shorebird and three passerine species were observed during the surveys. Densities of breeding shorebirds were similar in 1995 and 1997 (37.3 and 33.1 birds/km2), while in 1996 a late spring with heavy snow cover resulted in reduced numbers of birds and no breeding. Shorebirds and passerines were much more numerous in sedge marsh and sedge wetland. White-rumped sandpiper (Calidris fuscicollis) and red phalarope (Phalaropus fulicarius) were the most abundant shorebirds breeding at Creswell Bay, and Lapland longspur (Calcarius lapponicus) was the most abundant breeding passerine. White-rumped sandpiper and sanderling (Calidris alba) were the most numerous species present after the breeding period. American golden-plover (Pluvialis dominica), red phalarope, and white-rumped sandpiper showed significant habitat preferences. An estimated 10 341 (± 6596; 95% CI) shorebirds were on the north area in 1995 and 14 840 (± 10 744) on both areas in 1997. The estimated maximum numbers over both years of white-rumped sandpiper (6769 ± 3725) and buff-breasted sandpiper (Tryngites subruficollis) (908 ± 1169) at Creswell Bay were more than 1% of the species’ estimated national populations (1.5% and 5.1%, respectively). This abundance, along with the relatively high species diversity at this high-latitude site, warrants its continued status as a Canadian Wildlife Service “key habitat site,” and every possible effort should be made to ensure its long-term protection.Les oiseaux de rivage et les passereaux ont fait l’objet d’une étude menée à la baie Creswell, dans l’île Somerset située dans l’écozone de l’Extrême-Arctique (archipel Arctique canadien) durant la saison de nidification (juin et juillet, 1995–97) et en août 1995 (période post-reproductrice). La zone d’étude, située sur les rivages nord et sud de la baie Creswell, consistait en des cariçaies de terrains marécageux et humides dans les terres les plus basses, avec une toundra arbustive dominée par Dryas spp. ou Cassiope spp. et une toundra herbacée clairsemée dans les terres plus hautes. L’étude a été effectuée sur des parcelles carrées de 400 m de côté réparties dans les divers types de végétation selon l’importance relative de ces derniers dans les zones d’étude (34 parcelles en 1995; 33 parcelles plus 56 nouvelles en 1997). On a observé 11 espèces d’oiseaux de rivage et trois espèces de passereaux durant l’étude. Les densités des oiseaux de rivage qui nidifiaient étaient semblables en 1995 et en 1997 (37,3 et 33,1 oiseaux/km2), alors qu’en 1996, un printemps tardif accompagné d’un important couvert nival a fait que le nombre des oiseaux a diminué et qu’aucun nid n’a été construit. Les oiseaux de rivage et les passereaux étaient beaucoup plus nombreux dans les cariçaies de terrains marécageux et humides. Le bécasseau à croupion blanc (Calidris fuscicollis) et le phalarope à bec large (Phalaropus fulicarius) étaient les oiseaux les plus nombreux à nidifier à la baie Creswell, et le bruant lapon (Calcarius lapponicus) était le passereau nidificateur le plus abondant. Le bécasseau à croupion blanc et le bécasseau sanderling (Calidris alba) étaient les espèces les plus nombreuses présentes après la période de nidification. Le pluvier bronzé (Pluvialis dominica), le phalarope à bec large et le bécasseau à croupion blanc affichaient une nette préférence quant à leur habitat. On a estimé à 10 341 (± 6596; intervalle de confiance à 95 %) le nombre des oiseaux de rivage présents sur la côte septentrionale en 1995, et à 14 840 (± 10 744) celui des oiseaux de rivage présents sur les côtes nord et sud en 1997. Au cours des deux années, le nombre maximal estimé pour le bécasseau à croupion blanc (6769 ± 3725) et celui pour le bécasseau roussâtre (Tryngites subruficollis) (908 ± 1169) à la baie Creswell représentaient plus de 1 % des populations nationales estimées de ces espèces (1,5 % et 5,1 % respectivement). Cette abondance, jointe à une diversité relativement forte des espèces dans cette région de haute latitude, justifie le maintien de son statut de «site d’habitat clé» du Service canadien de la faune, et toutes les mesures devraient être prises pour en garantir la protection à long terme

Effects of forest regeneration on songbird movements in a managed forest landscape of Alberta

Abstract Recent studies have shown that barrier effects exist even in relatively vagile species such as forest songbirds. The objectives of this study were to determine whether a 560 × 100 m riparian buffer strip of mature forest was used as a movement corridor by forest songbirds and, if so, to what extent corridor effects persisted as woody vegetation regenerated in the adjacent clearcut. Over a 4-yr period, juvenile movement rates decreased in the riparian buffer strip and increased in the regenerating clearcut. Adult movement rates increased in the riparian buffer strip in the first year after logging, then gradually decreased, while still increasing in the regenerating clearcut. However, both juvenile and adult movement rates were higher in the buffer strip than in an undisturbed control site. Results suggest that most adults we captured held territories in the vicinity of the net lanes, and that most of the juveniles captured were dispersing away from their natal territory. Four years after harvest, juvenile movement rates were higher in the regenerating clearcut than in the riparian buffer strip, but several species had not yet been captured or detected in the regeneration. Our results suggest that the use of the riparian buffer strip as a movement corridor decreased with forest regeneration for both adults and juveniles. However, the buffer strip still acted as a movement corridor for the following species: Philadelphia and Red-eyed Vireos, Red-breasted Nuthatch, and Ovenbird

Ovenbird (Seiurus aurocapilla) territory placement near seismic lines is influenced by forest regeneration and conspecific density

. 2013. Ovenbird (Seiurus aurocapilla) territory placement near seismic lines is influenced by forest regeneration and conspecific density. Avian Conservation and Ecology 8(1):5. http://dx.doi.org/10.5751/ACE-00596-080105 Research Paper Ovenbird (Seiurus aurocapilla) Territory Placement Near Seismic Lines is Influenced by Forest Regeneration and Conspecific Density Le positionnement des territoires de la Paruline couronnée (Seiurus aurocapilla) près des lignes sismiques est influencé par la régénération forestière et la densité des conspécifiques ABSTRACT. The boreal forest of western Canada is being dissected by seismic lines used for oil and gas exploration. The vast amount of edge being created is leading to concerns that core habitat will be reduced for forest interior species for extended periods of time. The Ovenbird (Seiurus aurocapilla) is a boreal songbird known to be sensitive to newly created seismic lines because it does not include newly cut lines within its territory. We examined multiple hypotheses to explain potential mechanisms causing this behavior by mapping Ovenbird territories near lines with varying states of vegetation regeneration. The best model to explain line exclusion behavior included the number of neighboring conspecifics, the amount of bare ground, leaf-litter depth, and canopy closure. Ovenbirds exclude recently cut seismic lines from their territories because of lack of protective cover (lower tree and shrub cover) and because of reduced food resources due to large areas of bare ground. Food reduction and perceived predation risk effects seem to be mitigated once leaf litter (depth and extent of cover) and woody vegetation cover are restored to forest interior levels. However, as conspecific density increases, lines are more likely to be used as landmarks to demarcate territorial boundaries, even when woody vegetation cover and leaf litter are restored. This behavior can reduce territory density near seismic lines by changing the spatial distribution of territories. Landmark effects are longer lasting than the effects from reduced food or perceived predation risk because canopy height and tree density take >40 years to recover to forest interior levels. Mitigation of seismic line impacts on Ovenbirds should focus on restoring forest cover as quickly as possible after line cutting. RÉSUMÉ. La forêt boréale de l'ouest du Canada subit un découpage par les lignes sismiques effectuées dans le cadre de l'exploration pétrolière et gazière. La grande quantité de bordures ainsi créées soulève des préoccupations quant à l'intégrité des milieux pour les espèces forestières de massifs continus, et ce, pour de longues périodes. La Paruline couronnée (Seiurus aurocapilla) est un passereau boréal reconnu pour sa sensibilité aux lignes sismiques récemment créées parce qu'elle exclut les bandes nouvellement coupées de son territoire. Afin d'examiner les nombreuses hypothèses pouvant expliquer les mécanismes possibles derrière ce comportement, nous avons cartographié les territoires de parulines situés près de lignes, selon différents stades de régénération de la végétation. Le modèle qui explique le mieux le comportement d'exclusion des lignes inclut le nombre de conspécifiques voisins, la superficie de sol nu, la profondeur de la litière forestière et la superficie du couvert forestier. Les parulines excluent les lignes sismiques récemment coupées de leur territoire en raison du manque de couvert de protection (couvert arbustif et en petits arbres) et des ressources alimentaires réduites attribuables aux grandes superficies de sol nu. La faible quantité de ressources alimentaires et les risques perçus de prédation semblent être compensés une fois que la litière forestière (profondeur et étendue) et le couvert forestier ont ratteint les niveaux des massifs continus de forêts. Toutefois, à mesure que la densité de conspécifiques augmente, les lignes sismiques servent vraisemblablement de repères pour démarquer les limites des territoires, même lorsque le couvert forestier et la litière ont été restaurés. En modifiant la répartition spatiale des territoires, ce comportement peut amener une réduction de la densité de territoires près des lignes sismiques. L'effet de repère dure plus longtemps que les effets imputables aux ressources alimentaires réduites et au risque perçu de prédation étant donné que la hauteur et la densité des arbres prennent plus de 40 ans à ratteindre les niveaux des massifs continus de forêts. Les mesures destinées à atténuer l'impact des lignes sismiques devraient viser à restaurer le couvert forestier dès que possible

A Synthesis of Human-related Avian Mortality in Canada

Many human activities in Canada kill wild birds, yet the relative magnitude of mortality from different sources and the consequent effects on bird populations have not been systematically evaluated. We synthesize recent estimates of avian mortality in Canada from a range of industrial and other human activities, to provide context for the estimates from individual sources presented in this special feature. We assessed the geographic, seasonal, and taxonomic variation in the magnitude of national-scale mortality and in population-level effects on species or groups across Canada, by combining these estimates into a stochastic model of stage-specific mortality. The range of estimates of avian mortality from each source covers several orders of magnitude, and, numerically, landbirds were the most affected group. In total, we estimate that approximately 269 million birds and 2 million nests are destroyed annually in Canada, the equivalent of over 186 million breeding individuals. Combined, cat predation and collisions with windows, vehicles, and transmission lines caused > 95% of all mortality; the highest industrial causes of mortality were the electrical power and agriculture sectors. Other mortality sources such as fisheries bycatch can have important local or species-specific impacts, but are relatively small at a national scale. Mortality rates differed across species and families within major bird groups, highlighting that mortality is not simply proportional to abundance. We also found that mortality is not evenly spread across the country; the largest mortality sources are coincident with human population distribution, while industrial sources are concentrated in southern Ontario, Alberta, and southwestern British Columbia. Many species are therefore likely to be vulnerable to cumulative effects of multiple human-related impacts. This assessment also confirms the high uncertainty in estimating human-related avian mortality in terms of species involved, potential for population-level effects, and the cumulative effects of mortality across the landscape. Effort is still required to improve these estimates, and to guide conservation efforts to minimize direct mortality caused by human activities on Canada's wild bird populations. As avian mortality represents only a portion of the overall impact to avifauna, indirect effects such as habitat fragmentation and alteration, site avoidance, disturbance, and related issues must also be carefully considered

Ovenbird (Seiurus aurocapilla) Territory Placement Near Seismic Lines is Influenced by Forest Regeneration and Conspecific Density

The boreal forest of western Canada is being dissected by seismic lines used for oil and gas exploration. The vast amount of edge being created is leading to concerns that core habitat will be reduced for forest interior species for extended periods of time. The Ovenbird (Seiurus aurocapilla) is a boreal songbird known to be sensitive to newly created seismic lines because it does not include newly cut lines within its territory. We examined multiple hypotheses to explain potential mechanisms causing this behavior by mapping Ovenbird territories near lines with varying states of vegetation regeneration. The best model to explain line exclusion behavior included the number of neighboring conspecifics, the amount of bare ground, leaf-litter depth, and canopy closure. Ovenbirds exclude recently cut seismic lines from their territories because of lack of protective cover (lower tree and shrub cover) and because of reduced food resources due to large areas of bare ground. Food reduction and perceived predation risk effects seem to be mitigated once leaf litter (depth and extent of cover) and woody vegetation cover are restored to forest interior levels. However, as conspecific density increases, lines are more likely to be used as landmarks to demarcate territorial boundaries, even when woody vegetation cover and leaf litter are restored. This behavior can reduce territory density near seismic lines by changing the spatial distribution of territories. Landmark effects are longer lasting than the effects from reduced food or perceived predation risk because canopy height and tree density take >40 years to recover to forest interior levels. Mitigation of seismic line impacts on Ovenbirds should focus on restoring forest cover as quickly as possible after line cutting

Comparing the results of recall surveys and standardized searches in understanding bird-window collisions at houses

Every year a large number of birds die when they collide with windows. The actual number is difficult to ascertain. Previous attempts to estimate bird-window collision rates in Canada relied heavily on a prior citizen-science study that used memory-based surveys. Such an approach to data collection has many potential biases. We built upon this study and its recommendations for future research by creating a citizen-science program that actively searched for collision evidence at houses and apartments for an extended period with the objective to see how standardized approaches to data collection compared with memory recall. Absolute collision estimates as well as relative differences were compared between residence types in the two studies, and we found considerable differences in absolute values for collisions but similar rankings of collision rates between residence types. Collision recall rates in our study (56.5%) were very similar those in the prior 2012 study, where 50.5% of participants remembered a bird colliding with a window at some time in the past. Fatality estimates, however, were 1.4 times higher in the 2012 study than in our study based on standardized searches. Rural houses with a bird feeder consistently had the highest number of collisions. This suggests that memory recall surveys may be a useful tool for understanding the relative importance of different risk factors causing bird-window collisions

Retrospective Comparison of the Occurrence and Abundance of Rusty Blackbird in the Mackenzie Valley, Northwest Territories

Rusty Blackbird is listed as a species of "special concern" by the Committee On the Status of Endangered Wildlife In Canada, and has shown steep population declines in recent decades. Forty-five locations with historical survey data from the 1970s in the Mackenzie Valley, Northwest Territories, Canada were revisited in 2006 to check for changes in the occurrence or abundance of Rusty Blackbird. Our retrospective analysis revealed a number of analytical challenges for such comparisons that we describe. The number of lakes on which this species occurred does not appear to have declined significantly in the past three decades when a correction for survey duration was applied. The range-wide decline of 5.1%/yr based on Christmas Bird Count data would have resulted in 2006 occupancy at ≈5 lakes. We estimate that with correction this would have increased to ≈26. However, naive or unadjusted analyses with a Chi-squared test showed a significant decline. A simulated resampling of the historical data was performed using a repeatability factor of 62% that was derived from a subset of historical lakes that was visited twice in the 1970s. Only 8 of 13 lakes resurveyed had the same results on both historical visits. Our unadjusted 2006 results are a likely outcome, i.e., a 14.9% chance of finding this result, when this repeatability factor is considered, and the likelihood of no change is higher when our corrected data are considered. The possibility of double counting in the historical data further reduced the likelihood of a large decline in relative abundance. Therefore, Rusty Blackbird occurrence does not appear to have changed significantly in the past 33 yr in the Mackenzie Valley. We conclude with a qualitative discussion that supports the notion that declines in the southern parts of their range may be a large factor in the observed rates of population decline

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

Predicting and mitigating impacts of climate change and development within the boreal biome requires a sound understanding of factors influencing the abundance, distribution, and population dynamics of species inhabiting this vast biome. Unfortunately, the limited accessibility of the boreal biome has resulted in sparse and spatially biased sampling, and thus our understanding of boreal bird population dynamics is limited. To implement effective conservation of boreal birds, a cost-effective approach to sampling the boreal biome will be needed. Our objective was to devise a sampling scheme for monitoring boreal birds that would improve our ability to model species-habitat relationships and monitor changes in population size and distribution. A statistically rigorous design to achieve these objectives would have to be spatially balanced and hierarchically structured with respect to ecozones, ecoregions and political jurisdictions. Therefore, we developed a multi-stage hierarchically structured sampling design known as the Boreal Optimal Sampling Strategy (BOSS) that included cost constraints, habitat stratification, and optimization to provide a cost-effective alternative to other common monitoring designs. Our design provided similar habitat and spatial representation to habitat stratification and equal-probability spatially balanced designs, respectively. Not only was our design able to achieve the desired habitat representation and spatial balance necessary to meet our objectives, it was also significantly less expensive (1.3-2.6 times less) than the alternative designs we considered. To further balance trade-offs between cost and representativeness prior to field implementation, we ran multiple iterations of the BOSS design and selected the one which minimized predicted costs while maximizing a multi-criteria evaluation of representativeness. Field implementation of the design in three vastly different regions over three field seasons showed that the approach can be implemented in a wide variety of logistical scenarios and ecological conditions. We provide worked examples and scripts to allow our approach to be implemented or adapted elsewhere. We also provide recommendations for possible future refinements to our approach, but recommend that our design now be implemented to provide unbiased information to assess the status of boreal birds and inform conservation and management actions