21 research outputs found
Point Counts Underestimate the Importance of Arctic Foxes as Avian Nest Predators: Evidence from Remote Video Cameras in Arctic Alaskan Oil Fields
We used video cameras to identify nest predators at active shorebird and passerine nests and conducted point count surveys separately to determine species richness and detection frequency of potential nest predators in the Prudhoe Bay region of Alaska. From the surveys, we identified 16 potential nest predators, with glaucous gulls (Larus hyperboreus) and parasitic jaegers (Stercorarius parasiticus) making up more than 80% of the observations. From the video evidence, however, we identified arctic foxes (Alopex lagopus) as the predators in five of six predation events recorded with the cameras. These results indicate that estimated abundances of predators alone may not accurately reflect their true or proportional importance as nest predators. We also found that the identified predators removed all eggs and left the nests intact. Thus, attempts to identify predators solely on the basis of nest remains are not reliable for smaller bird species in this region. We found no evidence that camera-monitored nests were at greater risk of predation or desertion than camera-free nests. Overall, our ability to film predation events was hampered by the brief, highly synchronized breeding season, the harsh climate, and the higher nest survivorship for shorebirds in this region relative to temperate-breeding passerines, which have been the focus of most studies that use camera systems in attempts to identify nest predators at active nests.Nous avons recouru Ă des cameras vidĂ©o pour repĂ©rer les prĂ©dateurs de nids actifs dâoiseaux de rivage et de passĂ©riformes, puis nous avons effectuĂ© des calculs sĂ©parĂ©ment afin de dĂ©terminer la richesse des espĂšces et la frĂ©quence de dĂ©tection de prĂ©dateurs de nids potentiels dans la rĂ©gion de la baie de Prudhoe, en Alaska. Ă partir des calculs, nous avons dĂ©nombrĂ© 16 prĂ©dateurs de nids potentiels, les goĂ©lands bourgmestres (Larus hyperboreus) et les labbes parasites (Stercorarius parasiticus) reprĂ©sentant plus de 80 % des observations. Cependant, Ă partir des vidĂ©os, nous avons pu constater que les renards arctiques (Alopex lagopus) Ă©taient les prĂ©dateurs dans cinq des six cas de prĂ©dation enregistrĂ©s au moyen des camĂ©ras. Ces rĂ©sultats laissent croire que seules, les abondances estimĂ©es de prĂ©dateurs ne reflĂštent pas nĂ©cessairement leur importance vĂ©ritable ou proportionnelle Ă titre de prĂ©dateurs de nids. Nous avons Ă©galement constatĂ© que les prĂ©dateurs en question prenaient tous les oeufs, sans toutefois toucher aux nids. Par consĂ©quent, la possibilitĂ© dâidentifier les prĂ©dateurs seulement en fonction des restes de nids nâest pas fiable dans le cas des plus petites espĂšces dâoiseaux de cette rĂ©gion. Rien ne nous a laissĂ© croire que les nids surveillĂ©s Ă lâaide dâune camĂ©ra Ă©taient plus vulnĂ©rables Ă la prĂ©dation ou Ă lâabandon que les nids nâĂ©tant pas dotĂ©s de camĂ©ras. Dans lâensemble, la saison de reproduction hautement synchronisĂ©e â bien que brĂšve â le climat difficile et le taux de survie en nid plus Ă©levĂ© chez les oiseaux de rivage dans cette rĂ©gion comparativement aux passĂ©riformes se reproduisant dans les rĂ©gions tempĂ©rĂ©es sur lesquels la plupart des Ă©tudes faisant appel Ă des camĂ©ras se sont concentrĂ©es pour repĂ©rer les prĂ©dateurs de nids actifs ont nuit Ă notre aptitude Ă capter les cas de prĂ©dation sur vidĂ©o
Predictors of invertebrate biomass and rate of advancement of invertebrate phenology across eight sites in the North American Arctic
Average annual temperatures in the Arctic increased by 2â3 °C during the second half of the twentieth century. Because
shorebirds initiate northward migration to Arctic nesting sites based on cues at distant wintering grounds, climate-driven
changes in the phenology of Arctic invertebrates may lead to a mismatch between the nutritional demands of shorebirds
and the invertebrate prey essential for egg formation and subsequent chick survival. To explore the environmental drivers
afecting invertebrate availability, we modeled the biomass of invertebrates captured in modifed Malaise-pitfall traps over
three summers at eight Arctic Shorebird Demographics Network sites as a function of accumulated degree-days and other
weather variables. To assess climate-driven changes in invertebrate phenology, we used data from the nearest long-term
weather stations to hindcast invertebrate availability over 63 summers, 1950â2012. Our results confrmed the importance
of both accumulated and daily temperatures as predictors of invertebrate availability while also showing that wind speed
negatively afected invertebrate availability at the majority of sites. Additionally, our results suggest that seasonal prey avail ability for Arctic shorebirds is occurring earlier and that the potential for trophic mismatch is greatest at the northernmost
sites, where hindcast invertebrate phenology advanced by approximately 1â2.5 days per decade. Phenological mismatch
could have long-term population-level efects on shorebird species that are unable to adjust their breeding schedules to the
increasingly earlier invertebrate phenologies.publishedVersio
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
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
Patterns in avian reproduction in the Prudhoe Bay Oilfield, Alaska, 2003â2019
The Arctic Coastal Plain is one of the most important avian breeding grounds in the world; however, many species are in decline. Arcticâbreeding birds contend with short breeding seasons, harsh climatic conditions, and now, rapidly changing, variable, and unpredictable environmental conditions caused by climate change. Additionally, those breeding in industrial areas may be impacted by human activities. It is difficult to separate the impacts of industrial development and climate change; however, longâterm datasets can help show patterns over time. We evaluated factors influencing reproductive parameters of breeding birds at Prudhoe Bay, Alaska, 2003â2019, by monitoring 1265 shorebird nests, 378 passerine nests, and 231 waterfowl nests. We found that nest survival decreased significantly nearer highâuse infrastructure for all guilds. Temporally, passerine nest survival declined across the 17 years of the study, while there was no significant evidence of change in their nest density. Shorebird nest survival did not vary significantly across years, nor did nest density. Waterfowl nest density increased over the course of the study, but we could not estimate nest survival in all years. Egg predator populations varied across time; numbers of gulls and ravens increased in the oilfields 2003â2019, while Arctic fox decreased, and jaeger numbers did not vary significantly. Longâterm datasets are rare in the Arctic, but they are crucial for understanding impacts to breeding birds from both climate change and increasing anthropogenic activities. We show that nest survival was lower for birds nesting closer to highâuse infrastructure in Arctic Alaska, which was not detected in earlier, shorterâterm studies. Additionally, we show that Lapland longspur nest survival decreased across time, in concert with continentâwide declines in many passerine species. The urgency to understand these relationships cannot be expressed strongly enough, given change is continuing to happen and the potential impacts are large
Geographic variation in the intensity of warming and phenological mismatch between Arctic shorebirds and invertebrates
Responses to climate change can vary across functional groups and trophic levels, leading to a temporal decoupling of trophic interactions or âphenological mismatches.â Despite a growing number of single-species studies that identified phenological mismatches as a nearly universal consequence of climate change, we have a limited understanding of the spatial variation in the intensity of this phenomenon and what influences this variation. In this study, we tested for geographic patterns in phenological mismatches between six species of shorebirds and their invertebrate prey at 10 sites spread across ~13° latitude and ~84° longitude in the Arctic over three years. At each site, we quantified the phenological mismatch between shorebirds and their invertebrate prey at (1) an individual-nest level, as the difference in days between the seasonal peak in food and the peak demand by chicks, and (2) a population level, as the overlapped area under fitted curves for total daily biomass of invertebrates and dates of the peak demand by chicks. We tested whether the intensity of past climatic change observed at each site corresponded with the extent of phenological mismatch and used structural equation modeling to test for causal relationships among (1) environmental factors, including geographic location and current climatic conditions, (2) the timing of invertebrate emergence and the breeding phenology of shorebirds, and (3) the phenological mismatch between the two trophic levels. The extent of phenological mismatch varied more among different sites than among different species within each site. A greater extent of phenological mismatch at both the individual-nest and population levels coincided with changes in the timing of snowmelt as well as the potential dissociation of longterm snow phenology from changes in temperature. The timing of snowmelt also affected the shape of the food and demand curves, which determined the extent of phenological mismatch at the population level. Finally, we found larger mismatches at more easterly longitudes, which may be affecting the population dynamics of shorebirds, as two of our study species show regional population declines in only the eastern part of their range. This suggests that phenological mismatches may be resulting in demographic consequences for Arctic-nesting birds. Arctic invertebrates; phenology; spatial gradient; structural equation modeling; timing of breeding; trophic interactions.acceptedVersio
Composition and Drivers of Gut Microbial Communities in Arctic-Breeding Shorebirds
Gut microbiota can have important effects on host health, but explanatory factors and
pathways that determine gut microbial composition can differ among host lineages.
In mammals, host phylogeny is one of the main drivers of gut microbiota, a result of
vertical transfer of microbiota during birth. In birds, it is less clear what the drivers might
be, but both phylogeny and environmental factors may play a role. We investigated
host and environmental factors that underlie variation in gut microbiota composition in
eight species of migratory shorebirds. We characterized bacterial communities from 375
fecal samples collected from adults of eight shorebird species captured at a network
of nine breeding sites in the Arctic and sub-Arctic ecoregions of North America, by
sequencing the V4 region of the bacterial 16S ribosomal RNA gene. Firmicutes (55.4%),
Proteobacteria (13.8%), Fusobacteria (10.2%), and Bacteroidetes (8.1%) dominated the
gut microbiota of adult shorebirds. Breeding location was the main driver of variation in
gut microbiota of breeding shorebirds (R2 = 11.6%), followed by shorebird host species
(R2 = 1.8%), and sampling year (R2 = 0.9%), but most variation remained unexplained.
Site variation resulted from differences in the core bacterial taxa, whereas rare, lowabundance
bacteria drove host species variation. Our study is the first to highlight a
greater importance of local environment than phylogeny as a driver of gut microbiota
composition in wild, migratory birds under natural conditions.publishedVersio
Composition and Drivers of Gut Microbial Communities in Arctic-Breeding Shorebirds
Gut microbiota can have important effects on host health, but explanatory factors and
pathways that determine gut microbial composition can differ among host lineages.
In mammals, host phylogeny is one of the main drivers of gut microbiota, a result of
vertical transfer of microbiota during birth. In birds, it is less clear what the drivers might
be, but both phylogeny and environmental factors may play a role. We investigated
host and environmental factors that underlie variation in gut microbiota composition in
eight species of migratory shorebirds. We characterized bacterial communities from 375
fecal samples collected from adults of eight shorebird species captured at a network
of nine breeding sites in the Arctic and sub-Arctic ecoregions of North America, by
sequencing the V4 region of the bacterial 16S ribosomal RNA gene. Firmicutes (55.4%),
Proteobacteria (13.8%), Fusobacteria (10.2%), and Bacteroidetes (8.1%) dominated the
gut microbiota of adult shorebirds. Breeding location was the main driver of variation in
gut microbiota of breeding shorebirds (R2 = 11.6%), followed by shorebird host species
(R2 = 1.8%), and sampling year (R2 = 0.9%), but most variation remained unexplained.
Site variation resulted from differences in the core bacterial taxa, whereas rare, lowabundance
bacteria drove host species variation. Our study is the first to highlight a
greater importance of local environment than phylogeny as a driver of gut microbiota
composition in wild, migratory birds under natural conditions.publishedVersio
Effects of leg flags on nest survival of four species of Arctic-breeding shorebirds
Marking wild birds is an integral part of many field studies. However, if marks affect the vital rates or behavior of marked individuals, any conclusions reached by a study might be biased relative to the general population. Leg bands have rarely been found to have negative effects on birds and are frequently used to mark individuals. Leg flags, which are larger, heavier, and might produce more drag than bands, are commonly used on shorebirds and can help improve resighting rates. However, no one to date has assessed the possible effects of leg flags on the demographic performance of shorebirds. At seven sites in Arctic Alaska and western Canada, we marked individuals and monitored nest survival of four species of Arctic-breeding shorebirds, including Semipalmated Sandpipers (Calidris pusilla), Western Sandpipers (C. mauri), Red-necked Phalaropes (Phalaropus lobatus), and Red Phalaropes (P. fulicarius). We used a daily nest survival model in a Bayesian framework to test for effects of leg flags, relative to birds with only bands, on daily survival rates of 1952 nests. We found no evidence of a difference in nest survival between birds with flags and those with only bands. Our results suggest, therefore, that leg flags have little effect on the nest success of Arctic-breeding sandpipers and phalaropes. Additional studies are needed, however, to evaluate the possible effects of flags on shorebirds that use other habitats and on survival rates of adults and chicks.acceptedVersio