Biology subjects

Pierce, A. K.

Publications and source records attributed to Pierce, A. K..

3 recordsLinked to original sources

bioRxiv2026

Stage-specific habitat use of the Mountain Plover in Colorado

Habitat structure, food availability, and predation risk have spatiotemporal variation on the landscape that creates tradeoffs between risk and rewards for animals as they use habitat. These tradeoffs are associated with survival consequences and can vary by life or breeding stage, but stage-specific shifts in these relationships are often not considered in studies of habitat use and survival. We investigated habitat use for nests and broods in the Mountain plover as an example of a ground-nesting species with precocial, mobile young to explore breeding stage-specific responses to vegetation structure, food availability, and predation risk. We located and monitored nests and broods at two study sites in Colorado occupied by geographically separated breeding populations of plovers. We quantified the three covariate categories across standardized site-wide grids in 2021 and 2022. We employed a resource selection analysis to evaluate 10 a priori working hypotheses for how environmental covariates may influence the habitat used by plovers for nesting and brood-rearing. Model comparison results suggest that habitat use relative to availability is best explained by a linear relationship with vegetation structure while conditioning on breeding stage and site, with no effect of food availability or predation risk detected in our dataset. Specifically, probability of use for both nest and brood sites was highest in areas with taller vegetation, contrary to previous research about nest site selection. These unexpected results may be due to the unbalanced sample sizes of the two sites, as previous separate studies have shown opposing habitat use strategies, or due to the coarseness of our covariate data. Regardless of limitations, these results emphasize the importance of investigating stage-specific and potentially site-specific shifts in habitat use patterns for species with precocial young.

ecology↗

bioRxiv2023

Seasonal migration alters energetic trade-off optimization and shapes life history.

Trade-offs between current and future reproduction manifest as a set of co-varying life history and metabolic traits, collectively referred to as "pace of life" (POL). Seasonal migration modulates realized environmental dynamics and putatively affects realized POL, however, the mechanisms by which migratory behavior shapes POL remain unclear. We explored how migratory behavior interacts with environmental and metabolic dynamics to shape POL. Using an individual based model of movement and metabolism we compared fitness-optimized trade-offs among migration strategies. We found annual experienced seasonality and migration distance primarily drove POL differentiation through developmental and migration phenology trade-offs. Similarly, our analysis of empirically-estimated metabolic data from 265 bird species suggested seasonal niche conservatism and migration distance interact to drive POL. We show multiple viable life history strategies are conducive to a migratory lifestyle. Overall, our findings suggest metabolism mediates complex interactions between behavior, environment, and life history. Authorship statementAKP and SWY contributed equally to this work. AKP and SWY conceived the project, designed the model, performed analyses, and drafted the manuscript with support from MBW. Simulation and optimization model code written by AKP with input from SWY and MBW. Empirical data analysis and code lead by SWY with input from AKP and MBW. All authors contributed critical input to the manuscript. Data accessibility statementAll R code for models and analyses are available at https://doi.org/10.5281/zenodo.10145976 and https://github.com/allipierce/Pierce_et_al_2023_MigrationPOL. The empirically derived data used in this work are all publicly available. DEB data are available from the Add-My-Pet portal at https://www.bio.vu.nl/thb/deb/deblab/add_my_pet/. Geographic range data are available from BirdLife International at http://datazone.birdlife.org/species/requestdis. Niche dissimilarity data came from https://doi.org/10.1111/geb.13722 and phylogeny data are available from VertLife at http://vertlife.org/data/.

evolutionary biology↗

bioRxiv2021

A multiple hypotheses framework to study movement ecology and diet in a migratory songbird

Whether and how migratory organisms exhibit inter-individual behavioral and/or physiological variation across movement strategies remains an open question. The Dark-eyed Junco (Junco hyemalis) is a migratory songbird known for its intra-species variation displayed in relation to morphology, song repertoires, and migration. Thus, studies focusing on juncos can reveal how migratory strategy may covary with other individual-scale factors and, therefore, identify the selective forces driving intra-species variations throughout its distribution. We used Dark-eyed Junco hydrogen stable isotope feather values (delta2H) and implemented a Bayesian framework to infer the breeding and molting origin of migratory juncos captured on their winter grounds in Oklahoma, United States (U.S.). We modeled the distribution of feather hydrogen stable isotope values as a function of five morphological variables including body mass and fat deposition measured in Oklahoma during the winter. We then investigated the trade-off between longer and more energetically costly migration strategies in relation to diet preferences through carbon (delta13C) and nitrogen (delta15N) stable isotope analysis from feather values. Dark-eyed Juncos wintering in south central U.S. likely originate from multiple breeding populations in northern U.S. and Canada. Body condition at the wintering ground (e.g., mass) had no effect on feather hydrogen stable isotope abundance. However, we found a positive correlation between nitrogen and hydrogen stable isotopes, suggesting that a trophic level shift towards insect consumption might occur in individuals migrating from southern latitudes. Increased insect-derived protein consumption might be explained by reduced fatty-acid reserves necessary to complete a shorter migratory journey.

ecology↗