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Joe Liebezeit

Publications and source records attributed to Joe Liebezeit.

5 recordsLinked to original sources
USGS2024

A circumpolar study unveils a positive non-linear effect of temperature on arctic arthropod availability that may reduce the risk of warming-induced trophic mismatch for breeding shorebirds

Seasonally abundant arthropods are a crucial food source for many migratory birds that breed in the Arctic. In cold environments, the growth and emergence of arthropods are particularly tied to temperature. Thus, the phenology of arthropods is anticipated to undergo a rapid change in response to a warming climate, potentially leading to a trophic mismatch between migratory insectivorous birds and their prey. Using data from 19 sites spanning a wide temperature gradient from the Subarctic to the High Arctic, we investigated the effects of temperature on the phenology and biomass of arthropods available to shorebirds during their short breeding season at high latitudes. We hypothesized that prolonged exposure to warmer summer temperatures would generate earlier peaks in arthropod biomass, as well as higher peak and seasonal biomass. Across the temperature gradient encompassed by our study sites (>10°C in average summer temperatures), we found a 3-day shift in average peak date for every increment of 80 cumulative thawing degree-days. Interestingly, we found a linear relationship between temperature and arthropod biomass only below temperature thresholds. Higher temperatures were associated with higher peak and seasonal biomass below 106 and 177 cumulative thawing degree-days, respectively, between June 5 and July 15. Beyond these thresholds, no relationship was observed between temperature and arthropod biomass. Our results suggest that prolonged exposure to elevated temperatures can positively influence prey availability for some arctic birds. This positive effect could, in part, stem from changes in arthropod assemblages and may reduce the risk of trophic mismatch.

Global Change Biology↗
USGS2020

Shorebird reproductive response to exceptionally early and late springs varies across sites in Arctic Alaska

While increases in overall temperatures are widely reported in the Arctic, large inter-annual variation in spring weather, with extreme early and late conditions, is also occurring. Using data collected from three sites in Arctic Alaska, we explored how shorebird breeding density, nest initiation, nest synchrony, nest survival, and phenological mismatch varied between two exceptionally early (2015 and 2016) and late (2017 and 2018) springs. We assessed these differences in the context of long-term data from each site and whether species exhibited conservative or opportunistic reproductive strategies. Conservative shorebirds typically display nest-site fidelity and territoriality, consistent population densities, relatively even individual spacing, and monogamous mating systems with bi-parental incubation. In contrast, opportunistic shorebirds display the opposite traits, and a polygamous mating system with uniparental incubation. In this study, we evaluated 2,239 nests from 13 shorebird species, 2015–2018, and found that shorebirds of both strategies bred earlier and in higher numbers in early, warm springs relative to historic levels (based on 3,789 nests, 2005–2014); opposite trends were observed in late springs. In early springs, nests were initiated less synchronously than in late springs. Nest survival was unrelated to spring type, but was greater in earlier laid nests overall. Invertebrate food resources emerged earlier in early springs, resulting in a greater temporal asynchrony between invertebrate emergence and chick hatching in early than late springs. However, invertebrate abundance was quite variable among sites and years regardless of spring type. Overall, our results were generally consistent with predicted relationships between spring conditions and reproductive parameters. However, we detected differences among sites that could not be explained by other ecological factors (e.g., predators or alternative prey). Differences in shorebird community composition and other subtler methodological/ecological differences among sites highlight the difficulty of understanding the complex nature of these ecological systems and the importance of evaluating questions at multiple sites across multiple years. Our study demonstrates that shorebirds exhibit a high degree of behavioral flexibility in response to variable Arctic conditions, but whether this flexibility is enough to allow them to optimally track changing environmental conditions or if evolutionary adjustments will be necessary is unknown.

Alaska↗
USGS2020

Black oystercatcher (Haematopus bachmani) population size, use of marine reserve complexes, and spatial distribution in Oregon

The Black Oystercatcher is a large shorebird found along the west coast of North America. Because of their small global population size, low reproductive rate, and dependence on rocky intertidal habitats, they are considered a “species of high conservation concern” and may act as an indicator of intertidal ecosystem health. In 2015, the Audubon Society of Portland initiated a 3-year shore-based population survey in Oregon building upon long-term monitoring previously conducted by the U.S. Geological Survey (USGS) and others. The objectives were to 1) Estimate the current minimum population of breeding Black Oystercatchers in Oregon and to compare that to previous estimates to better understand the population trend; 2) Document oystercatcher abundance adjacent to the Oregon’s system of Marine Reserves and Marine Protected Areas; and 3) Describe spatial distribution of breeding oystercatchers along the coast. We targeted all rocky shoreline habitats along Oregon’s coastline to perform abundance surveys each spring. A total of 75 survey routes were sampled using a standardized protocol. Trained volunteer community scientists conducted the majority of the surveys. We used N-mixture statistical models to estimate oystercatcher population size and probability of detection. Population estimates from the best fitting models were consistent, with estimates ranging from 506 oystercatchers in 2016 (95% credible interval, 463-560) to 629 (548-743) in 2015. These estimates indicated a small but stable population. Probability of detection remained consistent across years (ranging from 0.51 to 0.53). The effect of geographic region corresponded with greater bird density in the southern region of Oregon. Oystercatcher abundance adjacent to MR/MPAs accounted for between 12.4-18.3% of the total population estimate which was lower than expected (~25%). We recommend that subsequent conservation efforts directed on Black Oystercatchers in Oregon balance limiting human disturbance, particularly on the north and central coasts, with ensuring protection of core habitats on the south coast where much of the population resides.

Oregon↗