Citizen‐science data provides new insight into annual and seasonal variation in migration patterns

S R Supp,Susan M Wethington,Scott Goetz,Donald R Powers,Tina A Cormier,Catherine H Graham,Frank A La Sorte,Marisa C.W Lim

doi:10.1890/es14-00290.1

Abstract

Current rates of global environmental and climate change pose potential challenges for migratory species that must cope with or adapt to new conditions and different rates of change across broad spatial scales throughout their annual life cycle. North American migratory hummingbirds may be especially sensitive to changes in environment and climate due to their extremely small body size, high metabolic rates, and dependence on nectar as a main resource. We used occurrence information from the eBird citizen‐science database to track migratory movements of five North American hummingbird species (Archilochus alexandri, A. colubris, Selasphorus calliope, S. platycercus, and S. rufus) across 6 years (2008–2013) at a daily temporal resolution to describe annual and seasonal variation in migration patterns. Our findings suggest that the timing of the onset of spring migration generally varies less than the arrival on the wintering grounds. Species follow similar routes across years, but exhibit more variation in daily longitude than latitude. Long distance migrants generally had less annual variation in geographic location and timing than shorter distance migrants. Our study is among the first to examine variation in migration routes and timing for hummingbirds, but more work is needed to understand the capacity of these species to respond to different rates of environmental change along their migratory routes.

Highlights

Global environmental changes are impacting species’ populations and movement behavior (e.g., La Sorte and Thompson 2007, Wilcove and Wikelski 2008)
Population-level migration routes and timing were substantially impacted by the effect of vagrant individuals and by the high density of year-round eBird observers in the southeastern USA (Appendix B: Fig. B5)
Bird Banding Lab (BBL) data support our decision to confine our observations of western species to the western flyway, as western birds were banded and recaptured in the east mainly during the winter season, and

Summary

Introduction

Global environmental changes are impacting species’ populations and movement behavior (e.g., La Sorte and Thompson 2007, Wilcove and Wikelski 2008). Because migratory species carry out parts of their annual life cycle in different locations, they must cope with shifting conditions across regional to continental scales (Møller et al 2008, Both et al 2010, Klaassen et al 2012). Across these scales, environmental change will vary in rate and magnitude (e.g., drought, extreme temperature) requiring different biological responses throughout the migratory route. Fewer studies have attempted to evaluate the form and magnitude of annual variation in populationlevel migration patterns across broad scales as opposed to evaluating migration for a subset of marked individuals or at a single site (but see Marra et al 2005, Gordo and Sanz 2006, Van Buskirk et al 2009, Vardanis et al 2011)

Methods

Results

Conclusion