DOI: 10.5061/dryad.ss3r7
title: Data from: Low migratory connectivity is common in long-distance migrant birds

description: 1. Estimating how much long-distance migrant populations spread out and
 mix during the non-breeding season (migratory connectivity) is essential
 for understanding and predicting population dynamics in the face of global
 change. 2. We quantify variation in population spread and inter-population
 mixing in long-distance, terrestrial migrant land-bird populations (712
 individuals from 98 populations of 45 species, from tagging studies in the
 Neotropic and Afro-Palearctic flyways). We evaluate the Mantel test as a
 metric of migratory connectivity, and explore the extent to which variance
 in population spread can be explained simply by geography. 3. The mean
 distance between two individuals from the same population during the
 non-breeding season was 743 km, covering 10–20% of the maximum width of
 Africa / South America. Individuals from different breeding populations
 tended to mix during the non-breeding season, though spatial segregation
 was maintained in species with relatively large non-breeding ranges (and,
 to a lesser extent, those with low population-level spread). A substantial
 amount of between-population variation in population spread was predicted
 simply by geography, with populations using non-breeding zones with
 limited land availability (e.g. Central America compared to South America)
 showing lower population spread. 4. The high levels of population spread
 suggest that deterministic migration strategies are not generally
 adaptive; this makes sense in the context of the recent evolution of the
 systems, and the spatial and temporal unpredictability of non-breeding
 habitat. 5. The conservation implications of generally low connectivity
 are that the loss (or protection) of any non-breeding site will have a
 diffuse but widespread effect on many breeding populations. Although low
 connectivity should engender population resilience to shifts in habitat
 (e.g. due to climate change), we suggest it may increase susceptibility to
 habitat loss. We hypothesise that because a migrant species cannot adapt
 to both simultaneously, migrants generally may be more susceptible to
 population declines in the face of concurrent anthropogenic habitat and
 climate change.
description: Raw migratory
 connectivity dataData were extracted from
 the literature (see Materials & Methods), and essentially represent
 start and end points (i.e. breeding and non-breeding locations) of the
 migration routes of individual tracked migrants land-birds. Named
 variables are defined as follows: "system" (TEXT) - migration
 system; "afro" = Afro-Palearctice, "neo" = Neotropical
 "study" (TEXT) - data source; see Supplementary Materials for
 full citations "species" (TEXT) - species common name
 "family" (TEXT) - taxonomic family "order" (TEXT) -
 taxonomic order "popunique" (NUMERIC) - arbitrary code grouping
 individuals from the same species into unique populations separated by
 &lt; 100km. Typically, this means grouping individuals from the same study
 site into populations. "method" (NUMERIC) - tagging method; 1 =
 solar geolocator, 2 = GPS, 3 = satellite tag "sampledat"
 (NUMERIC) - sampling site; 1 = breeding site, 2 = non-breeding site
 "age" (NUMERIC) - age of bird; 0 = juvenile (first migration), 1
 = adult, blank = unknown "country" (TEXT) - tagging country
 "state" (TEXT) - tagging state / province (for USA and Canada)
 "year" (NUMERIC) - year of tagging (2014 = 2014/15 migration
 period); blank if unknown "blat" (NUMERIC) - latitude of tagging
 site in decimal degrees "blon" (NUMERIC) - longitude of tagging
 site in decimal degrees "wlat1" (NUMERIC) - latitude of first
 winter site in decimal degrees "wlon1" (NUMERIC) - longitude of
 first winter site in decimal degrees "wlat2" (NUMERIC) - (if
 applicable) latitude of second winter site in decimal degrees
 "wlon2" (NUMERIC) - (if applicable) longitude of second winter
 site in decimal degrees "wlat3" (NUMERIC) - (if applicable)
 latitude of third winter site in decimal degrees "wlon3"
 (NUMERIC) - (if applicable) longitude of third winter site in decimal
 degrees "notes" (TEXT) - additional notesdata.csvFull data packageIncludes raw migratory connectivity data & annotated, reproducible R scripts. See README.txt for more details.data_package.zip