DOI: 10.5061/dryad.h70rxwdwn
title: From declines to recovery: 52 years of changes in autumn migratory songbird abundance at an island stopover site in southern New England

description: Migratory birds are declining across North America, and many studies have
 used long-term datasets to estimate trends in abundance for migratory
 birds. To most efficiently prioritize at-risk populations, it is critical
 to know the current trend status of migratory species, which involves
 accurately assessing the most appropriate timescale for monitoring changes
 in populations. In this study, we analyzed autumn hatch-year bird banding
 data from the Block Island Banding Station on Block Island, Rhode Island
 over a 52-year period (1970-2021) to examine long-term abundance trends
 for 22 species of migratory songbirds and compared our results to trends
 from Manomet Conservation Sciences and the USGS Breeding Bird Survey. We
 ran four models (no change, linear, quadratic, and breakpoint model) for
 each species and used model selection with AICc to determine the best
 model. Eighteen of the 22 species were best represented by breakpoint
 models, indicating that they experienced a sudden change in slope during
 the study period. For our 18 breakpoint species, all experienced the
 majority of their decline in the first two decades of the study (between
 1976 and 1986), and 17 of 18 species were stable or recovering after the
 breakpoint. Of the four species without a significant breakpoint, one
 species had no change over the study period, two were best represented by
 linear models, and one was best represented by a quadratic model. Trend
 classifications varied across time, space, methods, and the geographic
 regions of the sub-populations sampled. These results present evidence
 that many species are currently stable or in recovery, despite initial
 declines, and that modern conservation efforts need to account for abrupt
 changes in trend direction within long-term time series analyses to most
 accurately assess current abundance trends for the conservation of
 vulnerable species. 
description: # From declines to recovery: 52 years of changes in autumn migratory
 songbird abundance at an island stopover site in southern New England
 Dataset DOI: [10.5061/dryad.h70rxwdwn](10.5061/dryad.h70rxwdwn) ##
 Description of the data and file structure The provided R Scripts and data
 are used to analyze 52 years of autumn bird banding data (hatch-year birds
 only) from the Block Island Banding Station on Block Island, RI, USA.
 Specifically, this code runs four models (no change, linear, quadratic,
 and breakpoint) for 22 species of migratory songbirds, selects the best
 model, runs a leave-one-out analysis, and classifies each trend based on
 trend direction. ### Files and variables #### File:
 AOU\_species\_codes.csv **Description:** This file contains taxonomic
 classifications for each species, downloaded from the American
 Ornithological Society.  ##### Variables * SPECIES_ID: Taxonomic order *
 AOU: Assigned four-letter AOU code * SPECIES_NAME: Common name * spp:
 Scientific name * order: Order number #### File:
 Ornithological\_Applications\_Capture\_Rate\_Data\_1970\_2021.csv
 **Description:** This file contains the 98% migratory window and
 associated captures, net-hours, and capture rates for 22 species of
 migratory songbirds (1970-2021).  ##### Variables * BANDING_YEAR: The
 banding year for each entry * SPECIES_NAME: The common name for each
 species * AOU: The four-letter AOU code for each species *
 Start_Date: Start date of the 98% migratory window for a given species in
 a given year * End_Date: End date of the 98% migratory window for a given
 species in a given year * Start_Date_Julian: Start date of the 98%
 migratory window for a given species in a given year, expressed as the day
 of the year * End_Date_Julian: End date of the 98% migratory window for a
 given species in a given year, expressed as the day of the year *
 Length_Mig_Window: The total length of the 98% migratory window for a
 given species in a given year * Sum_Captures: The total number of captures
 for that species in that year, within the migratory window *
 Total_Net_Hours: The total number of net-hours accumulated during the
 migratory window (includes days where the station was open, even if a
 species was not captured that day) * Capture_Rate: Captures per unit
 effort. In this case, captures per 100 net-hours *
 Log_Capture_Rate: Log-transformed capture rate * Scale_Banding_Year: The
 scaled version of banding year (mean of 0, SD of 1) Note: 98% migratory
 window is defined as the period of time where 98% of a given species
 passed through Block Island in a given year, removing 1% of captures on
 either side. ## Code/software This script was run on R version 4.4.0. 
 This analysis uses the following packages: 1. Tidyverse: used for data
 manipulation 2. broom: used for storing/tidying model output 3. MuMIn:
 used for calculating AICc 4. segmented: used for running breakpoint models
 5. conflicted: used to deal with package conflicts (optional)