67 research outputs found
Pond Characteristics and Occupancy by Red-Necked Phalaropes in the Mackenzie Delta, Northwest Territories, Canada
Red-necked phalaropes (Phalaropus lobatus) breed in Arctic and Subarctic lowlands throughout the circumpolar region. They are highly reliant on shallow freshwater ponds for social interaction, copulation, and foraging for small aquatic invertebrates. Threats related to warmer continental temperatures could lead to encroachment of shrub vegetation and premature drying of wetlands that serve as breeding habitat. We documented patterns of pond use over the breeding season and investigated pond characteristics associated with high occupancy by red-necked phalaropes. Research was conducted during two breeding seasons in a large wetland on Niglintgak Island, located in the mouth of the Mackenzie Delta, Northwest Territories. The frequency of pond occupancy declined between the onset of incubation and average hatch dates. Neither invertebrate assemblages (potential prey) nor physical characteristics (water chemistry and vegetation characteristics) varied significantly between ponds categorized as high-use, low-use, and no-use, in either year. Dry weight of potential prey (g/m3) was higher during the incubation period than during the nest initiation period. Pond occupancy both prior to and during incubation showed a clumped distribution, suggesting that choice of ponds was related in part to social stimulation. Future studies should examine the proximity of ponds to nest sites, the effects of premature drying of ponds on food availability, the distribution of resources surrounding ponds, and the occupancy of ponds by broods during the period preceding fall migration.Les phalaropes Ă bec Ă©troit (Phalaropus lobatus) se reproduisent dans les basses terres arctiques et subarctiques Ă lâĂ©chelle de la rĂ©gion circumpolaire. Ils dĂ©pendent beaucoup des Ă©tangs dâeau douce peu profonds car câest lĂ que se passent leur interaction sociale, la copulation et la consommation de petits invertĂ©brĂ©s aquatiques. Les menaces liĂ©es au rĂ©chauffement des tempĂ©ratures continentales pourraient se traduire par un empiĂštement sur la vĂ©gĂ©tation dâarbrisseaux et lâassĂšchement prĂ©maturĂ© des terrains marĂ©cageux qui servent dâhabitat de reproduction. Nous avons documentĂ© les tendances dâutilisation des Ă©tangs pendant la saison de reproduction et avons analysĂ© les caractĂ©ristiques des Ă©tangs frĂ©quentĂ©s par de grands nombres de phalaropes Ă bec Ă©troit. Notre recherche a Ă©tĂ© effectuĂ©e pendant deux saisons de reproduction sur une vaste zone marĂ©cageuse de lâĂźle Niglintgak, situĂ©e Ă lâembouchure du delta du Mackenzie, dans les Territoires du Nord-Ouest. La frĂ©quence de lâachalandage aux Ă©tangs chutait entre le dĂ©but de lâincubation et les dates dâĂ©closion moyennes. Ni les assemblages dâinvertĂ©brĂ©s (proies potentielles) ni les caractĂ©ristiques physiques (chimie de lâeau et caractĂ©ristiques de la vĂ©gĂ©tation) variaient considĂ©rablement entre les Ă©tangs classĂ©s comme Ă©tangs achalandĂ©s, Ă©tangs moins achalandĂ©s ou Ă©tangs pas achalandĂ©s du tout, pendant lâune ou lâautre des annĂ©es. Le poids sec des proies potentielles (g/m3) Ă©tait plus Ă©levĂ© pendant la pĂ©riode dâincubation que pendant la pĂ©riode dâinitiation du nid. La rĂ©partition de lâachalandage des Ă©tangs avant et pendant lâincubation Ă©tait contagieuse, ce qui laisse croire que le choix dâĂ©tang se faisait, en partie, en fonction de la stimulation sociale. Les Ă©tudes effectuĂ©es Ă lâavenir devraient examiner la proximitĂ© des Ă©tangs aux nids, les effets de lâassĂšchement prĂ©maturĂ© des Ă©tangs sur la disponibilitĂ© de nourriture, la rĂ©partition des ressources entourant les Ă©tangs et lâachalandage des Ă©tangs par les couvĂ©es pendant la pĂ©riode prĂ©cĂ©dant la migration automnale
Responses of Syrphids, Elaterids and Bees to Single-tree Selection Harvesting in Algonquin Provincial Park, Ontario
The species composition of hoverflies (Syrphidae), click beetles (Elateridae), and bees (Apoidea) was studied to determine whether there was a positive response in these flower-seeking insect groups to gaps in the canopy created through single-tree selection harvesting of Sugar Maple (Acer saccharum) and Yellow Birch (Betula alleghaniensis) in hardwood forests of the Great Lakes-St. Lawrence forest region of Algonquin Provincial Park, Ontario. There were significantly more hoverflies and bees collected in forest stands harvested within the previous five years than in wilderness zone (unharvested at least for 40 years) stands or stands harvested 15-20 years previously (old logged stands). Click beetles, especially Selatosomus pulcher (LeConte), were collected most often in old logged stands. Bees and click beetles were collected significantly later in the season in logged than in wilderness zone stands. Malaise traps resulted in higher capture rates for syrphids than pan traps, and only with these higher capture rates did we detect a significant increase in species richness in recently logged stands over that in wilderness stands. Changes in the numbers and phenology of flower-visiting insects may impact on reproductive success of flowering plants of the forest understory and deserves further study
Testing Whether Camera Presence Influences Habitat Specific Predation Pressure on Artificial Shorebird Nests in the Arctic
When monitoring the breeding ecology of birds, the causes and times of nest failure can be difficult to determine. Cameras placed near nests allow for accurate monitoring of nest fate, but their presence may increase the risk of predation by attracting predators, leading to biased results. The relative influence of cameras on nest predation risk may also depend on habitat because predator numbers or behaviour can change in response to the availability or accessibility of nests. We evaluated the impact of camera presence on the predation rate of artificial nests placed within mesic tundra habitats used by Arctic-breeding shorebirds. We deployed 94 artificial nests, half with cameras and half without, during the shorebird-nesting season of 2015 in the East Bay Migratory Bird Sanctuary, Nunavut. Artificial nests were distributed evenly across sedge meadow and supratidal habitats typically used by nesting shorebirds. We used the Cox proportional hazards model to assess differential nest survival in relation to camera presence, habitat type, placement date, and all potential interactions. Artificial nests with cameras did not experience higher predation risk than those without cameras. Predation risk of artificial nests was related to an interaction between habitat type and placement date. Nests deployed in sedge meadows and in supratidal habitats later in the season were subject to a higher risk of predation than those deployed in supratidal habitats early in the season. These differences in predation risk are likely driven by the foraging behaviour of Arctic fox (Vulpes lagopus), a species that accounted for 81% of observed predation events in this study. Arctic fox prey primarily on Arvicoline prey and goose eggs at this site and take shorebird nests opportunistically, perhaps more often later in the season when their preferred prey becomes scarcer. This study demonstrates that, at this site, cameras used for nest monitoring do not influence predation risk. Evaluating the impact of cameras on predation risk is critical prior to their use, as individual study areas may differ in terms of predator species and behaviour.Lors de la surveillance de lâĂ©cologie de reproduction des oiseaux, les causes et les pĂ©riodes de dĂ©faillance des nids peuvent ĂȘtre difficiles Ă dĂ©terminer. Des camĂ©ras placĂ©es prĂšs des nids permettent une surveillance prĂ©cise du sort des nids, mais leur prĂ©sence peut augmenter le risque de prĂ©dation en attirant les prĂ©dateurs, ce qui entraĂźne des rĂ©sultats biaisĂ©s. Lâinfluence relative des camĂ©ras sur le risque de prĂ©dation des nids peut Ă©galement dĂ©pendre de lâhabitat, car le nombre ou le comportement des prĂ©dateurs peut changer en fonction de la disponibilitĂ© ou de lâaccessibilitĂ© des nids. Nous avons Ă©valuĂ© lâimpact de la prĂ©sence de camĂ©ras sur le taux de prĂ©dation des nids artificiels placĂ©s dans les habitats de la toundra mĂ©sique utilisĂ©s par les limicoles se reproduisant dans lâArctique. Nous avons installĂ© 94 nids artificiels, la moitiĂ© avec des camĂ©ras et lâautre moitiĂ© sans camĂ©ras, pendant la saison de nidification des limicoles de 2015 dans le Refuge dâoiseaux migrateurs de la baie Est, au Nunavut. Les nids artificiels Ă©taient rĂ©partis uniformĂ©ment dans les cariçaies et les habitats supratidaux gĂ©nĂ©ralement utilisĂ©s par les limicoles nicheurs. Nous avons utilisĂ© le modĂšle Ă risques proportionnels de Cox pour Ă©valuer la survie diffĂ©rentielle des nids en fonction de la prĂ©sence de camĂ©ras, du type dâhabitat, de la date dâinstallation des camĂ©ras et de toutes les interactions potentielles. Les nids artificiels Ă©quipĂ©s de camĂ©ras ne prĂ©sentaient pas de risque de prĂ©dation plus Ă©levĂ© que ceux sans camĂ©ras. Le risque de prĂ©dation des nids artificiels Ă©tait liĂ© Ă une interaction entre le type dâhabitat et la date dâinstallation des camĂ©ras. Plus tard dans la saison, les nids placĂ©s dans les cariçaies et dans les habitats supratidaux ont fait lâobjet dâun risque de prĂ©dation plus Ă©levĂ© que ceux des habitats supratidaux en dĂ©but de saison. Ces diffĂ©rences de risque de prĂ©dation sont probablement attribuables au comportement dâalimentation du renard arctique (Vulpes lagopus), une espĂšce qui reprĂ©sentait 81 % des Ă©vĂ©nements de prĂ©dation observĂ©s dans cette Ă©tude. Le renard arctique se nourrit principalement dâarvicolinĂ©s et dâoeufs dâoie sur ce site, et sâempare des nids de limicoles de maniĂšre opportuniste, peut-ĂȘtre plus souvent plus tard dans la saison, lorsque ses proies prĂ©fĂ©rĂ©es se font plus rares. Cette Ă©tude dĂ©montre que, sur ce site, les camĂ©ras servant Ă la surveillance des nids nâinfluencent pas le risque de prĂ©dation. Il est essentiel dâĂ©valuer lâimpact des camĂ©ras sur le risque de prĂ©dation avant leur utilisation, car chacune des zones Ă©tudiĂ©es peut diffĂ©rer sur le plan des espĂšces de prĂ©dateurs et des comportements
Drought at a coastal wetland affects refuelling and migration strategies of shorebirds
Droughts can affect invertebrate communities in wetlands, which can have bottom-up effects on the condition and survival of top predators. Shorebirds, key predators at coastal wetlands, have experienced widespread population declines and could be negatively affected by droughts. We explored, in detail, the effects of drought on multiple aspects of shorebird stopover and migration ecology by contrasting a year with average wet/dry conditions (2016) with a year with moderate drought (2017) at a major subarctic stopover site on southbound migration. We also examined the effects of drought on shorebird body mass during stopover across 14 years (historical: 1974â1982 and present-day: 2014â2018). For the detailed comparison of two years, in the year with moderate drought we documented lower invertebrate abundance at some sites, higher prey family richness in shorebird faecal samples, lower shorebird refuelling rates, shorter stopover durations for juveniles, and, for most species, a higher probability of making a subsequent stopover in North America after departing the subarctic, compared to the year with average wet/dry conditions. In the 14-year dataset, shorebird body mass tended to be lower in drier years. We show that even short-term, moderate drought conditions can negatively affect shorebird refuelling performance at coastal wetlands, which may carry-over to affect subsequent stopover decisions. Given shorebird population declines and predicted changes in the severity and duration of droughts with climate change, researchers should prioritize a better understanding of how droughts affect shorebird refuelling performance and survival
A global threats overview for Numeniini populations: synthesising expert knowledge for a group of declining migratory birds
The Numeniini is a tribe of thirteen wader species (Scolopacidae, Charadriiformes) of which seven are near-threatened or globally threatened, including two critically endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian - Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for speciesâ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species
Logging Affects Fledgling Sex Ratios and Baseline Corticosterone in a Forest Songbird
Silviculture (logging) creates a disturbance to forested environments. The degree to which forests are modified depends on the logging prescription and forest stand characteristics. In this study we compared the effects of two methods of group-selection (âmoderateâ and âheavyâ) silviculture (GSS) and undisturbed reference stands on stress and offspring sex ratios of a forest interior species, the Ovenbird (Seiurus aurocapilla), in Algonquin Provincial Park, Canada. Blood samples were taken from nestlings for corticosterone and molecular sexing. We found that logging creates a disturbance that is stressful for nestling Ovenbirds, as illustrated by elevated baseline corticosterone in cut sites. Ovenbirds nesting in undisturbed reference forest produce fewer male offspring per brood (proportion maleâ=â30%) while logging with progressively greater forest disturbance, shifted the offspring sex ratio towards males (proportion male: moderateâ=â50%, heavyâ=â70%). If Ovenbirds in undisturbed forests usually produce female-biased broods, then the production of males as a result of logging may disrupt population viability. We recommend a broad examination of nestling sex ratios in response to anthropogenic disturbance to determine the generality of our findings
Unexpected diversity in socially synchronized rhythms of shorebirds
The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within-and between-species diversity in incubation rhythms. Between species, the median length of one parent's incubation bout varied from 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.</p
Long-distance migratory shorebirds travel faster towards their breeding grounds, but fly faster post-breeding
Long-distance migrants are assumed to be more time-limited during the pre-breeding season compared to the post-breeding season. Although breeding-related time constraints may be absent post-breeding, additional factors such as predation risk could lead to time constraints that were previously underestimated. By using an automated radio telemetry system, we compared pre- and post-breeding movements of long-distance migrant shorebirds on a continent-wide scale. From 2014 to 2016, we deployed radio transmitters on 1,937 individuals of 4 shorebird species at 13 sites distributed across North America. Following theoretical predictions, all species migrated faster during the pre-breeding season, compared to the post-breeding season. These differences in migration speed between seasons were attributable primarily to longer stopover durations in the post-breeding season. In contrast, and counter to our expectations, all species had higher airspeeds during the post-breeding season, even after accounting for seasonal differences in wind. Arriving at the breeding grounds in good body condition is beneficial for survival and reproductive success and this energetic constraint might explain why airspeeds are not maximised in the pre-breeding season. We show that the higher airspeeds in the post-breeding season precede a wave of avian predators, which could suggest that migrant shorebirds show predation-minimizing behaviour during the post-breeding season. Our results reaffirm the important role of time constraints during northward migration and suggest that both energy and predation-risk constrain migratory behaviour during the post-breeding season
Unexpected diversity in socially synchronized rhythms of shorebirds
The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1, 5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parentâs incubation bout varied from 1â19âh, whereas period lengthâthe time in which a parentâs probability to incubate cycles once between its highest and lowest valueâvaried from 6â43âh. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h lightâdark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms
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