ecology paper 1

Authors: Andrea Soriano-Redondo (Orcid ID: 0000-0003-0728-730X), Marta Acácio (Orcid ID: 0000-0002-9947-1181), Francisco Moreira (Orcid ID: 0000-0003-4393-8018)
Journal Name: Ecology
Manuscript Type: Article
Handling Editor: John P. Y. Arnould

Tracking data available from Movebank at: https://doi.org/10.5441/001/1.283
This article has undergone full peer review and is protected by copyright. All rights reserved.

Alternative migratory strategies co-exist within animal populations and species.
Impact of Anthropogenic Influences: Can shift the fitness balance among migratory strategies, altering behaviors.
Study Subject: White storks (Ciconia ciconia) that shifted migratory behavior towards year-round residency.
Sample Size: 75 adult storks tracked using GPS/GSM loggers over five years.
Findings:
- Long-distance migrants traveled more, spent more energy, and rested less.
- Increased energy expenditure while foraging for long-distance migrants.
- Late nest occupation correlates with lower reproductive output.
- Smaller-sized individuals likely migrate, incurring higher costs than larger ones.
Conclusion: Insights into migratory strategies emphasize the impact of anthropogenic changes on fitness and evolution dynamics.

Movement, survival, breeding success, overall dynamic body acceleration (ODBA), GPS tracking.

Rationale: Changes in migratory strategies due to anthropogenic influences (land transformation, climate change).
- Effects include altered migration timing and routes and disrupted migration resulting in transition towards residency (Pulido & Berthold, 2010; Plummer et al., 2015).
- Ecological and evolutionary implications from individual to ecosystem levels (Nathan et al., 2008; Dingle, 2014).
Within-population variability: Some individuals resident while others migrate (Sanz-Aguilar et al., 2012; Lok et al., 2017; Chambon et al., 2018).
Energetic costs associated with migration; longer distances generally waste more energy (Somveille et al., 2018; Sillett & Holmes, 2002).
Hypotheses: Migration strategies may fluctuate depending on breeding performance, phenotype, and environmental adaptations (Newton, 2008).

Data Collection: 75 breeding adult white storks captured in Southern Portugal (2016-2020).
- Capture Techniques: Remote clap nets at nests, nylon leg nooses at landfills.
- GPS/GSM loggers: Weight 60-90 g (1.5–3.7% of body mass).
Morphometrics: wing, tarsus, bill length, and weight measured at capture. Blood collected for molecular sexing.

Nests monitored weekly during breeding season for laying dates and fledgling counts.
Approximately 420 nests followed from 2016-2020 during breeding seasons.

ODBA Calculation: From GPS acceleration data to measure energy expenditure.
Behavioral Analysis: Machine-learning algorithms used for behavior classification (foraging, resting, soaring, flapping).
Migratory Strategy Classification: Based on GPS data cross-referencing movement between Southwest Europe and Africa.

Linear Mixed Models (LMM): Analyzed annual displacement and ODBA relative to migratory strategies.
General Linear Models (GLM): Analyzed relationships between wing length, sex, and migration probability.
Structural Equation Models: Evaluated causal relationships affecting reproductive success and survival.

Sample Tracking: 212 annual cycles tracked, demonstrating four strategies - local residency, regional residency, migration to Northwest Africa, and migration to Sub-Saharan Africa.
Findings on Energy Expenditure:
- Migrating storks to Sub-Saharan Africa had significantly higher ODBA than local residents (over 20% more) during migration.
- Migratory strategies influenced behavioral budgets; Sub-Saharan migrants exhibited less resting and more soaring behaviors.
Reproductive Outcomes:
- Indirect relationship noted between migratory strategies, nest occupation date, and number of fledglings.
Survival Probability:
- No significant differences found between resident and migratory populations.
Phenotypic Analysis: Smaller wing lengths correlated with higher migratory probabilities.

Comparison of Migratory Strategies:
- Long-distance migration incurs higher costs but may also correlate with lower reproductive success due to late nest occupation.
- Observations suggest smaller storks likely migrate while larger storks remain resident, possibly due to food competition.
Predictive Implications: Expect changes in migratory strategies based on environmental alterations in food resources, likely affecting future population dynamics.

Authors express gratitude for the assistance from multiple contributors and funding sources including FCT and NERC.

Comprehensive list of studies addressing migration, energetic costs, and survival along with ecological impacts on birds detailing specific findings relevant to white stork populations.