Data and codes from: Causes of interspecific variation in avian migration distance
Data files
Jun 23, 2026 version files 1.28 MB
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AllBirdsHackett_50-random.tre
992.44 KB
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Distance_Comparative_brms.R
66.64 KB
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final_1-record_distance_dataset_map.csv
63.05 KB
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final_1-record_distance_dataset.csv
137.15 KB
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Publication_Figures.R
16.75 KB
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README.md
5.98 KB
Abstract
Migration is an awe-inspiring behavior employed by a diverse suite of taxa throughout the animal kingdom. Avian migration is arguably the most well-known animal behavior and birds vary widely in how far they migrate, but the ecological mechanisms underlying interspecific variation in migration distance remain unclear. We developed a novel set of predictions deduced from seven mechanistic hypotheses proposed to explain interspecific variation in avian migration distance. We then used a Bayesian phylogenetic comparative analysis to test predictions from these seven hypotheses based on migration data and species traits from 446 species of migratory birds throughout the world based on data from animal-borne tracking technology. Body mass, seasonal food availability, and morphological/behavioral traits that improve flight efficiency explained significant interspecific variation in migration distance after controlling for absolute breeding latitude (which was positively correlated with migration distance). Specifically, we found migration distance was negatively correlated with body mass and seasonal food availability but positively correlated with hand-wing index (a measure of wing elongation and pointedness) and soaring flight. Moreover, the negative relationship between body mass and migration distance was not ubiquitous but rather depended on flight mode and intraspecific nonbreeding group size such that species employing flapping flight during migration and those overwintering in smaller intraspecific groups had the strongest negative relationships between body mass and migration distance. Within group-living birds, smaller bodied species may gain a foraging or thermoregulatory advantage that shortens migration distances while larger bodied species may gain an energetic advantage by using flock formations during migration that facilitate longer migrations to more suitable nonbreeding areas. From a life history perspective, maximum annual reproductive investment was negatively correlated with migration distance while minimum annual reproductive investment and adult annual survival were not correlated with migration distance. Overall, our results support flight efficiency, food limitation, and thermoregulatory-based hypotheses as causes of interspecific variation in migration distances in birds. Our results also help to refine the numerous and often ambiguous mechanisms underlying the negative relationship between body size and migration distance, and refute several hypotheses previously proposed to explain interspecific variation in avian migration distance.
Dataset DOI: 10.5061/dryad.zw3r228hp
Description of the data and file structure
Migration distances were collected via literature review of publications tracking avian migration using animal-borne tracking technology. Species traits used as explanatory variables were gathered and calculated from a variety of published sources and species experts (see manuscript/supplemental methods). We included R scripts for all brms model outputs, raw data, and scripts used to produce publication figures.
Files and variables
File: final_1-record_distance_dataset.csv
Description: Primary comparative migration distance dataset. NA values represent data that were not available for a particular species or trait.
Variables
- ID: unique identified
- sp_common: species common name in English
- sp_latin: species Latin name using eBird/Clements taxonomy
- hackett_sp: species Latin name used in comparative analyses (from Hackett backbone)
- citation_short: short hand citation from which migration distance data was collected
- tracking_method: type of tracking technology used. When multiple used, separated by commas
- pub_year: publication year
- Family: taxonomic family
- Order: taxonomic order
- tag_season: season during which birds were captured. s_migration=spring migration; f_migration = fall migration. When multiple, separated by commas
- breed_lat: breeding latitude for population of interest. In decimal degrees
- breed_long: breeding longitude for population of interest. In decimal degrees
- nonbreed_lat: nonbreeding latitude for population of interest. In decimal degrees
- nonbreed_long: nonbreeding longitude for population of interest. In decimal degrees
- age_class: age class of birds sampled in row. juvenile = first year; immature = sub-adult. When multiple, separated by commas
- lit_mass: body mass (g)
- bill_length: culmen length (mm)
- hwi: hand-wing index (unitless)
- nest_sub_coarse: nest substrate limitation metric. 1 = nesting substrate very limited; 5 = nesting substrate not limited
- per_2cav: percent of nests that are secondary cavities.
- group_binary: binary intraspecific nonbreeding group size: S = solitary; F = flocking.
- group_mean: mean intraspecific nonbreeding group size
- group_filtered: was filtered eBird data used to calculate group_mean? If N, then all nonbreeding eBird checklists were used.
- diet_var: the availability of food on the breeding grounds during the nonbreeding period based on diet type on a scale of 1 (low availability) to 5 (high availability)
- diet_breadth: diet breadth on a possible scale of 1 (highly specialized diet) to 10 (highly diversified diet).
- ad_an_survival: adult annual survival on a scale of 0 (0% survival) to 1 (100% survival).
- survive_modeled: is "ad_an_survival" derived from modeling? If N, then adult annual survival was derived from estimates based on empirical data. If Y, then empirical adult annual survival was not available and estimates were based on comparative modeling used in Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S.T. et al. (2020) Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology, 34, 1252–1261.
- territorial: 1-3 metric of territoriality. 1 = non-territorial; 2 = weak/seasonally territorial; 3 = year-round territorial
- flight_3: flight mode. 1 = obligate flapping; 2 = flap/soar mix; 3 = obligate soaring
- egg_mass: single egg mass (g)
- egg_mass_mod: was egg mass modeled? Y = Yes or N = No
- egg_length: egg length (mm)
- egg_width: egg width (mm)
- clutch: mean clutch size (number of eggs)
- num_breed_att: maximum number of successful broods per breeding season.
- repr_percent1: minimum reproductive investment variable. Calculated as: (egg mass ÷ body mass) x clutch size
- repr_percent2: maximum reproductive investment variable. Calculated as: repr_percent1 x num_breed_att
- hackett_sp2: species Latin name from Hackett backbone with underscore inserted
- max_dir_dist: migration distance (km) reported from citation
- blat_abs: absolute breeding latitude
- tar_f_cont: metric of tarsus feathering. Tarsus feathering was scored as a continuous 0–10 metric as follows: 0 = no feathering on tarsus or ankle joint and 10 = tarsus and digits completely feathered.
- noct_cont: metric of nocturnality. 0–10 metric to estimate the daily temporal foraging activity patterns (i.e., degree of nocturnality) for species during the stationary nonbreeding period, where 0 = strictly diurnal and 10 = strictly nocturnal.
- polygamous2: polygamy. 0 = mostly monogamous (polygamy rate < 5%) or 1 = polygamous (polygamy rate ≥ 5%)
- zSurvival: residual survival corrected for body mass and standardized.
- zRepr_percent1: residual minimum reproductive investment corrected for body mass and standardized.
- zRepr_percent2: residual maximum reproductive investment corrected for body mass and standardized.
File: final_1-record_distance_dataset_map.csv
Description: comparative migration distance dataset used to plot map: Figure 2. NA values represent data that were not available for a particular species or trait.
Variables. Same as "final_1-record_distance_dataset.csv" except for:
- switch_hem: did species switch east-west hemispheres between breeding and nonbreeding? Y/N
File: Distance_Comparative_brms.R
Description: R script used to generate primary migration distance results.
File: Publication_Figures.R
Description: R script used to generate all publication figures.
File: AllBirdsHackett_50-random.tre
Description: 50 random phylogenetic trees from the Hackett backbone via birdtree.org (Jetz, W., Thomas, G.H., Joy, J.B., Hartmann, K., and Mooers, A.O. (2012) The global diversity of birds in space and time. Nature, 491, 444--448).