Table 1 Intrinsic advantages and drawbacks of the four main approaches to study migratory connectivity
From: A synthesis of recent tools and perspectives in migratory connectivity studies
Approach/data | Main advantages | Main drawbacks | Developmentsa | References |
|---|---|---|---|---|
A. Bird banding | • Huge datasets • Inexpensive • Explicit information of marking origin • Quantification of links between populations | • Sometimes unknown number of banded birds (MS) • Survival bias (MS) • Recapture and recovery spatial and temporal heterogeneity (MS) • Low probability of recovery • Advanced models to become quantitative (DC) | MS: Multi-state models DC: Division coefficient | |
B. Tracking technologies | • Explicit data on the whole migratory route | • Cost (limited number of tagged individuals) • Weight (constraints on equippable species, effects on behaviour/survival) |  |  |
> Radio telemetry | • Cheap • Light (< 1 g) | • Proximity of receiver station needed (RN) | RN: Receiver networks (Motus Wildlife Tracking System) | [24] |
> Archival geolocators | • Cheap • Light (< 2 g) | • Low spatial resolution (TA, SM) • Recovery needed (survival and recapture bias) (RM) | TA: Technical advances (e.g. light stalks, archival GPS tags) SM: Spatial models RM: Recovery models | |
> Satellite transmitters | • High spatial resolution • No recovery needed | • Most expensive (TA) • Heaviest (2–100 g) (TA) | TA: Technical advances (e.g. miniaturisation) | |
C. Genetics | • Intrinsic marker: allows information on many birds | • Detectable genetic structure needed (dependent on recent evolutionary history) (G) • Species-specific markers needed (G) • Low spatial resolution (G) • Only natal origin • Cost of genome-wide analyses • Transit of biological samples for analysis | G: Genomic analysis | |
D. Stable isotopes | • Intrinsic marker: allows information on many birds • Inexpensive • Universal | • Extensive mapping needed • Low spatial resolution (MI, PIA, SSM) • Local variation sometimes higher than regional variation (e.g. elevation effect on precipitation) (SSM) • Inter-individual variation in discrimination (SSM) • Transit of biological samples for analysis | MI: Multi-isotope PIA: Probabilistic isoscape-based assignments SSM: Site-specific models |