DOI: 10.5061/dryad.hmgqnk9f3
title: Phenological synchronization of seasonal bird migration with vegetation greenness across dietary guilds

description: 1. The seasonal movement of animals has been linked to seasonal variation
 in ecological productivity, and it has been hypothesized that primary
 consumers synchronize migration with vegetation phenology. Within
 temperate regions of the Northern Hemisphere, herbivorous bird species
 often track the phenology of vegetation greenness during spring migration.
 Phenological synchronization with vegetation greenness by migratory birds
 in other dietary guilds, across the full extent of their annual
 distributions during both spring and autumn migration, has not been
 explored. 2. Here, we document population-level associations with a
 remotely sensed measure of vegetation greenness for 230 North American
 migratory bird species in seven dietary guilds across the full annual
 cycle using eBird occurrence information for the combined period
 2006-2018. 3. Evidence of phenological synchronization was strongest for
 omnivores, herbivores, herbivore-granivores, and granivores during spring
 and autumn migration, except for omnivores in the west during spring
 migration. Strong evidence of synchronization was also observed for
 insectivores during spring migration and carnivores during spring and
 autumn migration that migrated across the entire breadth of the continent.
 The level of evidence declined for insectivores in the west and east
 during spring migration, and for nectarivores in the west during spring
 and autumn migration. Limited evidence was also found for insectivores in
 the east during autumn migration, insectivores in the west and the center
 of the continent during spring and autumn migration, and carnivores in the
 west during spring migration. Carnivores in the west during autumn
 migration showed the weakest evidence of synchronization. 4. We found
 broad support across an array of dietary guilds for phenological coupling
 between vegetation greenness and seasonal bird migration within North
 America. Our results highlight the potential for many migratory bird
 species to encounter phenological mismatches as vegetation phenology
 responds to climate change. Our findings emphasize the need to better
 understand the environmental cues that regulate migratory behavior across
 dietary guilds, consumer levels, and migration tactics.
description: We compiled bird occurrence information from the eBird database
 from 1 January 2006 to 31 December 2018 within the Western Hemisphere. We
 querried the database on 1 February 2019. eBird contains bird obervations
 in checklist format where species detected by sight or sound are recorded
 during a sampling event. eBird represents a semi-structured database where
 each observer selects a predefined sampling protocol and survey effort is
 determined by the observer. We used occurrence information from single
 observer checklists and combined occurrence information across checklists
 that were identified as group sampling events into single checklists. A
 total of 28,520,138 checklists were available for analysis within our
 study area containing a total of 4,577 unique species.
description: A zip file containing 152 RData files organized by month (1-12)
 and year (2006-2018). Each RData files contains one R data frame (ebrd)
 containing all the eBird checkists submitted within the Western Hemisphere
 (170W-30W Longitude, 60S-90N Latitude) during that month and year. The
 fields in the data frame include the YEAR and DAY the checklists were
 compiled, the LATITUDE and LONGITUDE where the checklists were compiled,
 the common name of the bird species in each checklist (PRIMARY_COM_NAME),
 and the unique identifying number assigned to each checklist
 (SUB_ID).