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Increasing abundance of Snow and Ross’s Geese ( Anser caerulescens and Anser rossii ; kangut and qaaraarjuk in Inuktut, respectively), referred to collectively as light geese, has caused alterations in various Canadian Arctic ecosystems. Inuit have harvested light geese for generations and hold knowledge that offers unique insights into the ecology and population dynamics of these species. By combining interviews with 40 light goose harvesters and Elders with results from aerial surveys in the Kivalliq region of Nunavut, we (1) describe changes in light goose distribution and abundance between the 1940s and the 2010s, (2) explore the effects of light geese on local ecosystems, and (3) identify factors driving these changes. Inuit observations gathered through lifetimes of land-based observations and results from aerial surveys concurred that (1) light goose numbers have increased regionally since the 1940s, and (2) light goose numbers decreased in several colonies within the Kivalliq region between the 1960s–1990s and the 2010s, including in two Migratory Bird Sanctuaries. Inuit have noted that habitat loss due to overgrazing and grubbing has pushed light geese to abandon altered habitats in favor of new breeding and foraging sites. Inuit observations also indicated that light geese have altered their migration behavior (how, when, and where they migrate and nest) in response to earlier spring snowmelt, the drying of ponds and lakes, and an increased number of predators. These conclusions add substantially to overall understanding about light geese in regions where aerial surveys are expensive and infrequent, and scientific studies are limited in geographic coverage.

For many taxa, ranges are shifting toward the poles and the timing of seasonal reproduction is advancing in response to climate change. For migratory birds, changes such as these could produce particularly strong impacts because of their potential to affect migratory timing and distance. Due to the relatively complex life histories of migratory species, however, it is difficult to intuit exactly what these impacts will be. Here, we develop a general population model for a long-distance migrant, introducing a framework for understanding the potential implications of changes in both phenology and migratory distance for bird abundances. We find that population sizes may increase with either shorter or longer migratory distances, depending on the nature of any concurrent phenological changes. This interaction between timing and distance suggests a need to consider multiple potential responses to climate change simultaneously in order to understand the overall impact of climate change on migratory populations. Our results reveal a degree of variability in the qualitative nature of this phenology-distance interaction, suggesting a possible explanation for observed variation in how migratory birds have already responded to climate change.

This first zooarchaeological analysis for the Islands of Four Mountains (IFM), Aleutian Islands, Alaska, provides data about local hunter-gatherer resource exploitation over three thousand yr. The majority of zooarchaeological material represents faunal resources that were harvested within several kilometers of villages. Our analysis shows that IFM subsistence system was shaped by the small size of these islands, which is mostly true for all of the Aleutian Islands. The archaeological middens indicate that Aleuts readily exploited new resources when they became available, expanding their dietary niche. Despite human harvesting, most faunal populations remained stable; however, Aleuts overexploited the storm-petrel colony on Carlisle Island.

Bird population dynamics are expected to change in response to increased weather variability, an expression of climate change. The extent to which species are sensitive to effects of weather on survival and reproduction depends on their life-history traits. We investigated how breeding bird species can be grouped, based on their life-history traits and according to weather-correlated population dynamics. We developed and applied the linear trait–environment method (LTE), which is a modified version of the fourth-corner method. Despite our focus on single traits, 2 strategies—combinations of several traits—stand out. As expected, breeding populations of waterfowl species are negatively impacted by severe winters directly preceding territory monitoring, probably because of increased adult mortality. Waterfowl species combine several traits: they often breed at ground or water level, feed on plant material, are precocial and are generally short-distance or partial migrants. Furthermore, we found a decline in population growth rates of insectivorous long-distance migrants due to mild winters and warm springs in the year before territory monitoring, which may be caused by reduced reproduction due to trophic mismatches. We identify species that are expected to show the most significant responses to changing weather variability, assuming that our conclusions are based on causal relationships and that the way species, weather variables and habitat interact will not alter. Species expected to respond positively can again be roughly categorized as waterfowl species, while insectivorous long-distance migrants are mostly expected to respond negatively. As species traits play an important role in constructing functional groups that are relevant to the provisioning of ecosystem services, our study enables the incorporation of ecosystem vulnerability to climate change into such functional approaches.

Conspecific brood parasitism (CBP), defined as parasitic laying of eggs in a conspecific nest without providing parental care, occurs in insects, fishes, amphibians, and many birds. Numerous factors have been proposed to influence the evolution of CBP, including nest site limitation; effects of brood size, laying order, or parasitic status on offspring survival; randomness of parasitic egg distribution; adult life‐history trade‐offs; and variation in parental female quality or risk of nest predation. However, few theoretical studies consider multiple possible types of parasitism or the interplay between evolution of parasitism and population dynamics. We review existing theory of CBP and develop a synthetic modeling approach to ask how best‐of‐a‐bad job parasitism, separate‐strategies parasitism (in which females either nest or parasitize), and joint‐strategies parasitism (in which females can both nest and parasitize) differ in their evolutionary conditions and impacts on population dynamics using an adaptive dynamics framework including multivariate traits. CBP can either stabilize or destabilize population dynamics in different scenarios, and the role of comparable parameters on evolutionarily stable strategy parasitism rate, equilibrium population size, and population stability can differ for the different modes of parasitism.

We investigated factors at multiple scales that might influence nest predation risk for Spotted Towhees (Pipilo maculatus) along the Sacramento River, California, within the context of large-scale riparian habitat restoration. We used the logistic-exposure method and Akaike's information criterion (AIC) for model selection to compare predator search, predator abundance, restoration, and temporal effects hypotheses. Our candidate models represented restoration, temporal, nest activity, nest concealment, agriculture, and flood effects. Restoration sites did function as breeding habitat, with nest survival comparable to mature forest sites and some young being produced. The best-supported models contained the covariates cowbird young in host nest and calendar date. All supported models contained the covariate cowbird young, the only variable with a strong effect. In contrast to our prediction, nest survival increased with cowbird young in the nest, implicating adult cowbirds in nest predation events. Nest survival declined throughout the breeding season and increased marginally with nest concealment. We calculated the finite rate of population increase (λ), using a model that incorporated nest success estimates for parasitized and unparasitized nests, double brooding, the locally observed cowbird parasitism rate for Spotted Towhees, number of young fledged from successful parasitized and unparasitized nests, adult survival and a range of juvenile survival values, estimated as percentages of adult survival. Values of λ did not approach the replacement level of one, indicating that this population is not self-sustaining. We recommend extensive habitat restoration in the floodplain landscape, ideally in conjunction with cowbird control, to reduce nest predation and parasitism pressures.

Global temperature increases of 0.6°C over the past century and predicted increases of 2° to 6°C over the next century have prompted many studies on effects of global warming on the population dynamics of plants and animals. Studies of landbirds in Europe and North America have shown effects of climatic variation on productivity and survival. However, such effects have been seen to translate to changes in population densities in only a few studies of European landbirds. Thus, the extent to which global warming has the potential to cause population declines in North American landbirds has remained unclear. In the research presented here, I model 39 years of climatic data, including indices of the North Atlantic Oscillation and El Niño Southern Oscillation, and distribution-wide Breeding Bird Survey data on 21 North American landbird species, to examine potential relationships between large-scale climate change and changes in avian population densities. Results of these analyses indicate geographic variation in strength of the effect of climate on population densities, with stronger effects in regions in which climate has stronger effects on local temperatures. Results also indicate that for species exhibiting long-term declines, there is a relationship between strength of the effect of local temperatures on population densities and magnitude of population decline. Additional analyses indicate that Neotropical-Nearctic migratory species are more negatively affected by warm winter temperatures than are closely-related North American residents. These results support the hypothesis that differences in climatic effects on migrants and residents may follow from greater trophic mismatch for species that are unable to time migration in response to earlier peaks in food availability. Finally, results of this work show that species are more highly affected by densities of sympatric congeners in areas in which they are also affected by climate, indicating that increased effects of climate on food resources may increase the effects of competition between congeners. Overall, results of this research indicate that North American landbird densities are affected by annual changes in large-scale climate, such that continued increases in global temperatures have the potential to affect long-term changes in landbird population densities across the continent.

Determining the form of key predator-prey relationships is critical for understanding marine ecosystem dynamics. Using a comprehensive global database, we quantified the effect of fluctuations in food abundance on seabird breeding success. We identified a threshold in prey (fish and rill, termed \"forage fish\") abundance below which seabirds experience consistently reduced and more variable productivity. This response was common to all seven ecosystems and 14 bird species examined within the Atlantic, Pacific, and Southern Oceans. The threshold approximated one-third of the maximum prey biomass observed in long-term studies. This provides an indicator of the minimal forage fish biomass needed to sustain seabird productivity over the long term.

Migratory species depend on a suite of interconnected sites. Threats to unprotected links in these chains of sites are driving rapid population declines of migrants around the world, yet the extent to which different parts of the annual cycle are protected remains unknown. We show that just 9% of 1451 migratory birds are adequately covered by protected areas across all stages of their annual cycle, in comparison with 45% of nonmigratory birds. This discrepancy is driven by protected area placement that does not cover the full annual cycle of migratory species, indicating that global efforts toward coordinated conservation planning for migrants are yet to bear fruit. Better-targeted investment and enhanced coordination among countries are needed to conserve migratory species throughout their migratory cycle.

Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences on fitness and the importance of habitat on the breeding grounds used after breeding. Although detailed investigations have shed light on the ecology and population dynamics of a few avian species, knowledge is sketchy for most species. Replication of comprehensive studies is needed for multiple species across a range of areas. Information deficiencies are even greater during the wintering season, when birds require sites that provide security and food resources needed for survival and developing nutrient reserves for spring migration and, possibly, reproduction. Research is needed on many species simply to identify geographic distributions, wintering sites, habitat use, and basic ecology. Studies are complicated, however, by the mobility of birds and by sexual segregation during winter. Stable-isotype methodology has offered an opportunity to identify linkages between breeding and wintering sites, which facilitates understanding the complete annual cycle of birds. The twice-annual migrations are the poorest-understood events in a bird's life. Migration has always been a risky undertaking, with such anthropogenic features as tall buildings, towers, and wind generators adding to the risk. Species such as woodland specialists migrating through eastern North America have numerous options for pausing during migration to replenish nutrients, but some species depend on limited stopover locations. Research needs for migration include identifying pathways and timetables of migration, quality and distribution of habitats, threats posed by towers and other tall structures, and any bottlenecks for migration. Issues such as human population growth, acid deposition, climate change, and exotic diseases are global concerns with uncertain consequences to migratory birds and even less-certain remedies. Despite enormous gaps in our understanding of these birds, research, much of it occurring in the past 30 years, has provided sufficient information to make intelligent conservation efforts but needs to expand to handle future challenges.