Data and code from: Migration speed, timing, and long-term shifts in age structure in North American passerines during fall migration
Data files
Mar 18, 2026 version files 636.65 MB
-
Other_Data.zip
48.43 MB
-
Processed_BBL_Data.zip
55.31 MB
-
Raw_BBL_Data.zip
532.61 MB
-
README.md
12.33 KB
-
Speed__Timing_and_Migrant_Community_Age.Rmd
280.91 KB
Abstract
Migration is challenging for birds, particularly juveniles, who experience increased mortality. Conservation efforts that increase juvenile survival could support the recovery of depleted populations. Understanding where and when juvenile abundances peak during migration would help identify priority conservation locations. However, it is unknown whether the age structure of migrant communities shifts spatiotemporally during migration. To investigate, we analyzed age-related differences in migration speed and timing using 6,567,747 bird banding encounters, as variability in these traits could drive demographic shifts. We found adults generally migrate faster than juveniles, with timing differences tied to adult molt strategy. Our analyses reveal previously undocumented shifts in community demographics: the proportion of juveniles decreases at northerly latitudes and increases at southerly latitudes throughout migration. Over the past 53 years, the juvenile proportions have increased in the north and decreased in the south. Integrating these findings with stopover abundance data can inform targeted conservation efforts.
Dataset DOI: 10.5061/dryad.xd2547dvt
Description of the data and file structure
Data and code included herein can be used to recreate the analyses and figures included in the manuscript- Migration speed, timing, and long-term shifts in age structure in North American passerines during fall migration, by Osterhaus, Desmond, and Wright.
Files and variables
File: Speed__Timing_and_Migrant_Community_Age.Rmd
Description: This file is the code file written in R Markdown that is used to process the raw bird banding lab data, run the analyses included in the manuscript, and produce all figures and tables associated with the manuscript. The code file is annotated within to guide readers through all steps of the analyses.
File: Other_Data.zip
Description: This folder includes three data files, Cleaned_BBL_Data.csv, ebirdspecies.csv, and Species_Counts_Strategies.csv. The "Cleaned_BBL_Data.csv" is generated by processing raw BBL data using the code file provided. Each row of data in included in this table corresponds to a single bird capture event and includes species, age, date, and location information. The "ebirdspecies.csv" data file is pulled from eBird and is used to associate the most up-to-date names with each species included in the BBL dataset. The "Species_Counts_Strategies.csv" file includes information for each species considered for analyses, the total number of banding encounters for that species, migrant type, adult molt strategy, level of overlap between breeding and non-breeding ranges, whether the species is to be retained for analyses, and the family associated with each species.
SubFile: Cleaned_BBL_Data.csv
Variables:
- LatBand - Latitude band from which the data originates.
- LonBand - Longitude band from which the data originates.
- species_code - 6-letter species code
- SPECIES_NAME - species common name
- BAND - band number associated with the individual
- EVENT_DATE - date on which the individual was encountered
- LAT_DD - latitude in decimal degrees associated with the banding encounter
- LON_DD - longitude in decimal degrees associated with the banding encounter
- AGE_CODE_HY_AHY - age code for the individual, either hatch year (HY) or after hatch year (AHY)
- EVENT_YEAR - year in which the individual was encountered
- OrdinalDate - ordinal date on the day the individual was encountered
SubFile: ebirdspecies.csv
This file is a dataset listing the species included in the eBird status and trends data products and additional information as to which status and trends products are available for each species. Descriptions for each of the variables included in this dataset can be found at: https://www.rdocumentation.org/packages/ebirdst/versions/3.2023.1/topics/ebirdst_runs. The final two columns have been added and are described below in addition to the original columns.
Variables:
- species_code – alphanumeric eBird species code uniquely identifying the species
- scientific_name – scientific name
- common_name – English common name
- is_resident – classifies the species as resident or migrant
- breeding_quality – breeding season quality
- breeding_start – breeding season start date
- breeding_end – breeding season end date
- nonbreeding_quality – non-breeding season quality
- nonbreeding_start – non-breeding season start date
- nonbreeding_end – non-breeding season end date
- postbreeding_migration_quality – post-breeding migration season quality
- postbreeding_migration_start – post-breeding migration start date
- postbreeding_migration_end – post-breeding migration end date
- prebreeding_migration_quality – pre-breeding migration season quality
- prebreeding_migration_start – pre-breeding migration start date
- prebreeding_migration_end – pre-breeding migration end date
- resident_quality – resident season quality
- resident_start – year-round start date for resident species
- resident_end – year-round end date for resident species
- has_trends – whether the species has trend estimates
- trends_season – season for which the trend was estimated (breeding, nonbreeding, or resident)
- trends_region – geographic region used for the trend model (may be a subset of the full range)
- trends_start_year – start year of the trend period
- trends_end_year – end year of the trend period
- trends_start_date – start date (MM-DD) of the trend season
- trends_end_date – end date (MM-DD) of the trend season
- rsquared – R² value comparing actual vs. estimated trends from simulations
- beta0 – intercept from linear model (actual ~ estimated); positive values indicate underestimation of simulated trends
- order - taxonomic order of the species
- family - taxonomic family of the species
SubFile: Species_Counts_Strategies.csv
Variables:
- Common.Name - common name of the species
- total_count_BBL - total number of encounters of the species included in the dataset
- Migrant.Type - type of migrant, either neotropical or temperate
- Adult.Molt.Strategy - timing of when adult birds molt their flight feathers, either fall, winter, breeding, or unknown
- Breeding.and.Wintering.Overlap - a qualitative assessment of the level of overlap between wintering and breeding ranges for the species, either none, low, moderate, or high
- Retain. - whether or not the species should be retained for analyses, either Yes or No
- Reason.for.Not.Including - reasoning for not retaining the species for analysis
- family - taxonomic family of the species
File: Processed_BBL_Data.zip
Description: The files included within this folder are all generated through processing the raw BBL data as specified in the manuscript. Each row corresponds to the banding/encounter event for a particular bird and includes information for species, age, date, and location.
SubFiles: set1.csv through set16.csv
All SubFiles in this folder have the same variables, which are described below-
Variables:
- SPECIES_NAME - common name of the species
- BAND - band number of the individual
- EVENT_DATE - date on which the individual was encountered
- LAT_DD - latitude in decimal degrees of the encounter
- LON_DD - longitude in decimal degrees of the encounter
- AGE_CODE_HY_AHY - age code of the individual, either hatch year (1) or after hatch year (2)
- species_code - 6-letter species code for the species
- EVENT_YEAR - year in which the encounter occurred
File: Raw_BBL_Data.zip
Description: The set of files included in this folder was downloaded directly from the United States Geological Survey Bird Banding dataset via the 2023 data release, which is shared with the CC0 1.0 Universal rights.
SubFiles: NABBP_2023_grp_24.csv through NABBP_2023_grp_57.csv
All SubFiles in this folder have the same variables, which are described below. Detailed lookup information for each categorical variable can be found at- https://www.sciencebase.gov/catalog/item/653fa806d34ee4b6e05bc57d within attached files in the NABBP_lookups_2023.zip folder. All locations for sensitive species and gamebirds are generalized to larger areas; 10-minute and 1-degree block coordinate precisions, respectively. Sensitive species include diurnal raptors, US Threatened, Endangered, and Canadian Species at Risk Act (SARA) species. Gamebirds include waterfowl, cranes, rails, woodcock, doves, crows, and ravens.
Variables:
- RECORD_ID - Integer representing a unique identifier for the record within the NABBP database.
- EVENT_TYPE - Two event types: B-Banding, E-Encounter. The definition of encounter here includes record sources for both encounters and recaptures.
- BAND- Twelve-digit alphanumeric identifier representing individual federal metal band on bird at time of data retrieval. Band number is obfuscated.
- ORIGINAL_BAND - Original band, usually (for original banding) is the same as band. Twelve-digit alphanumeric identifier for an individual federal metal band attached to a bird at the time of original banding. Band number is obfuscated.
- OTHER_BANDS - Twelve-digit alphanumeric identifiers for other federal metal bands on a bird at some point in its life. Bands may be replaced during the lifetime of a bird. All bands associated with this bird other than this band are included here. Band number is obfuscated.
- EVENT_DATE - Text in format mm/dd/yyyy. The event date for a banding record is the date of release. The event date for encounter and recapture records is the date of capture or observation.
- EVENT_DAY - Day of month bird was banded, recaptured, or encountered.
- EVENT_MONTH - Month a bird was banded, recaptured, or encountered. It may include inexact month values.
- EVENT_YEAR - Year bird was banded, recaptured, or encountered.
- SPECIES_ID - Four-digit BBL numeric code to identify species.
- SPECIES_NAME - Currently accepted common species names for birds in the NABBP dataset.
- ISO_COUNTRY - Two-letter abbreviation of country for bird banding release location, country of capture for encounters, and recapture location.
- ISO_SUBDIVISION - Five-character code for US and Canada, empty for others. For example, US-MD, CA-ON. For bandings, the country subdivision represents the location of bird release. For encounters and recaptures, subdivision represents the location of bird capture. The US and Canada only are subdivided to state and provinces.
- LAT_DD - Latitude, decimal degrees. Location of bird banding, recapture, or encounter.
- LON_DD - Longitude, decimal degrees. Location of bird banding, recapture, or encounter record.
- COORD_PREC - Includes numeric codes for 13 coordinate precision categories. All banding and encounter records for sensitive species are released at 10-minute block coordinate precision. Game birds include waterfowl, cranes, rails, woodcock, doves, crows, and ravens. All bandings are released at 1-degree block coordinate precision; encounters are released at coordinate precisions as originally provided.
- AGE_CODE - numeric codes and descriptions of 9 bird age categories.
- SEX_CODE - numeric codes and descriptions of 5 bird sex categories.
- BIRD_STATUS - Bird status is a single-digit numeric code describing aspects of the bird or circumstances at the time of banding.
- EXTRA_INFO - Two-digit numeric code used with bird status code to describe additional aspects of the bird or circumstances at time of banding.
- HOW_OBTAINED - 2-digit numeric codes and descriptions of 75 how the record was obtained categories. The how_obtained_code describes how a bird was obtained in encounter and recapture records.
- WHO_OBTAINED - 2-digit numeric codes and descriptions of 10 categories. The who_reported_code describes the finder of a bird obtained in encounter and recapture records.
- REPORTING_METHOD - 2-digit numeric codes and descriptions of 19 categories of reporting methods.
- PRESENT_CONDITION - present condition refers to the condition of the bird and the condition of the band at the time of encounter or recapture.
- MIN_AGE_AT_ENC - Minimum age of a bird at time of encounter or recapture is calculated using the difference of dates between banding and encounter records. Decimal value translates to years and months (e.g., 12.25 = 12 years 3 months).
- PERMIT - Eight-digit alphanumeric identifier representing a bird banding permit. Permit numbers are obfuscated.
- BAND_STATUS - alphanumeric codes and descriptions of 10 band status categories. The range of values is 0-8, F, X.
- BAND_TYPE - Two-digit alphanumeric codes and descriptions of band types and closures.
- RECORD_SOURCE - Indicates source of record in NABBP database.
Code/software
All code was written and run through R Markdown.
Access information
Other publicly accessible locations of the data:
- All bird banding data is publicly accessible through the United States Geological Survey Bird Banding dataset 2023 data release.