Joint evolution of the biogeography and phenology of seasonal migration

In migratory species, the temporal phases of the annual cycle are linked to seasonally shifting geographic ranges. Here, we investigate the spatiotemporal structure of the annual cycle in a phylogenetic comparative framework by developing a method to demarcate the pacing of annual cycle stages using eBird, a massive avian occurrence dataset, and applying it to migratory passerine birds breeding in North America. The analyses focus on 150 species of migratory passerine birds breeding in North America, filtered from a starting list of 206 species based on data quality. The analyses use eBird data averaged across the years 2002-2021 to calculate daily distributional centroids of the geographic range of each species. Next, the centroids are used to estimate demarcations of the annual cycle stages for downstream analyses. Our analyses reveal a striking negative correlation between the durations of the breeding versus nonbreeding stationary periods, indicating that a tradeoff between the leng..., , # Dryad dataset

Dataset DOI: [10.5061/dryad.18931zd8h](10.5061/dryad.18931zd8h)

## Description of the data and file structure

Species distributional data were downloaded from [www.ebird.org](http://www.ebird.org) for the period 1 January 2002 to 25 September 2021. The data could be expanded to additional, more recent years by the user through download from [www.ebird.org](http://www.ebird.org).

### Files and variables

#### File: calculate_migration_dates.R

**Description:** This script reads in daily centroids of the geographic distribution for each species, from the directory ./centroids. The script uses GAM functions and analysis of the inflection points of the GAMs to estimate dates demarcating the annual cycle for each species. The script also filters out species that did not pass the quality checks described in the paper and in the script. The script outputs a tabular data file of annual cycle date demarcations for use in the script statistical_analyses.R. Three versions of th...,