Incorporating breeding abundance into spatial assignments on continuous surfaces.

Area of Science:

• Ecology and conservation biology
• Stable isotope ecology
• Population dynamics

Background:

• Understanding migratory connectivity is vital for species conservation.
• Stable isotopes are a key tool for studying migratory connectivity in birds.
• Integrating abundance data with isotopes can improve assignment model resolution.

Purpose of the Study:

• To develop and assess statistical methods for combining stable isotopes and abundance data in migratory connectivity models.
• To optimize the weighting of isotope and abundance data for accurate geographic assignments.
• To provide guidelines for future studies on migratory connectivity.

Main Methods:

• Used known-origin stable-hydrogen isotope samples from six Neotropical migratory bird species.
• Assessed assignment models with varying contributions of isotope and abundance data.
• Applied Pareto optimality to identify optimal models minimizing error and assignment area for two species.
• Evaluated model performance on four additional species.

Main Results:

• Models integrating abundance data can increase precision but may also increase assignment error.
• Optimally weighted models can achieve higher precision and lower error than isotope-only models.
• The effectiveness of abundance data weighting depends on breeding abundance distribution.
• Patchier abundance distributions necessitate stronger downweighting of abundance data.

Conclusions:

• Breeding abundance is a valuable data source for inferring broad-scale movements of migratory birds.
• Optimized integration of abundance data enhances migratory connectivity inference.
• Developed guidelines for weighting abundance data in future connectivity studies.