DOI: 10.5061/dryad.gxd2547zv
title: Data from: River otter predation of nesting seabirds along the coasts of North America

description: River otter (Lontra canadensis) predation of seabirds has been
 periodically documented throughout North America, but most knowledge about
 this subject exists as anecdotal observations in the memories of
 experienced seabird biologists. Using surveys, interviews, white papers,
 and published literature, we collected detailed records of seabird
 predation by river otters at 73 islands on the coasts of North America.
 From this dataset, we were able to conclude the seabird species
 experiencing river otter predation, the geographic distribution of
 predation records, and factors associated with river otter occurrence at
 colony islands. River otters preferentially select for small-bodied
 burrow-nesting species, with predation of ground-nesting species occurring
 mostly opportunistically. Predation of nesting seabirds occurs across the
 entire Pacific range of the river otter and throughout the northern
 Atlantic, but we did not locate a single record of this behavior on the
 Atlantic coast south of Maine; we hypothesize that this is due to
 geographic differences in nesting seabird assemblages. The presence of
 burrow-nesting seabirds and proximity to the mainland are both strong
 predictors of river otter occurrence at colony islands. River otters will
 swim up to eight kilometers across open ocean to access seabird colonies,
 but predation is significantly more common at nearshore islands (median
 distance of 1.7km). Reports of seabird predation by river otters in
 published literature are rare, heavily biased towards an ornithological
 audience, and have decreased over time as “Field Notes” style publications
 have decreased in popularity. Despite being more widespread than
 previously reported, predation by river otters appears to be sustainable
 for most colony nesting seabird populations.
description: # Data from: River otter predation of nesting seabirds along the coasts of
 North America Dataset DOI:
 [10.5061/dryad.gxd2547zv](10.5061/dryad.gxd2547zv) ## Description of the
 data and file structure Anecdotal data on seabird predation by river
 otters at colony islands throughout the United States and Canada were
 collected through surveys of biologists, review of white papers, and
 scraping of published literature. These records are accompanied in this
 dataset by geographic information for seabird colony islands and
 biological information for nesting seabird species. ### Files and
 variables #### File: anecdotal_present_nopredation.csv
 **Description:** This tabular dataset indicates anecdotal records of
 seabird islands where river otters have been observed, but predation of
 nesting seabirds has not been observed. Records in this dataset come from
 direct communication/interview of seabird biologists and from white
 papers. ##### Variables * island_name: Common name of the island for the
 record. * State: State or province where the predation record occurred. *
 otter_presence: Binary indicating whether river otter activity was
 observed. Inherently, 1 for all records in this dataset. *
 Predation: Binary indicating whether river otter predation of seabirds was
 observed. Inherently 0 for all records in this dataset. *
 Notes: Additional notes about the anecdotal record. #### File:
 anecdotal_records.csv **Description:** This tabular dataset indicates
 anecdotal records of seabird predation by river otters that were supplied
 by seabird biologists via survey (Table S1) or direct
 communication/interview. ##### Variables * location_name: Common name of
 location for predation record. * Island: Binary indicating whether the
 location was a coastal seabird colony island. * State: State or province
 where the predation record occurred. * Species: IBP code for bird species
 experiencing predation. * Notes: Additional relevant notes about the
 anecdotal records. #### File: nonpredated_island_counts.csv
 **Description:** This tabular dataset indicates species occurrence and
 abundance records for seabird colony islands included in our final
 modelling dataset where river otter predation did not occur. Data were
 sourced from a variety of peer-reviewed papers, databases, white papers,
 and internal agency documents. ##### Variables * island_name: Common name
 of the island for the record. * State: State or province where the island
 is located. * Species: IBP code for bird species with nesting information.
 * Pairs: Reported number of nesting pairs present on the island. * Year:
 Year when the abundance survey occurred. * Source: Lead author or agency
 for data source. * Notes: Additional relevant notes about the abundance
 estimate. #### File: species_info.csv **Description:** This tabular
 dataset includes biological covariate data for all seabird species
 included in our model datasets. All information presented here was sourced
 from *Birds of the World*. ##### Variables * ibp: IBP code for bird
 species. * common_name: Full common name for bird species. * sci_name:
 Latin binomial name for bird species. * Genus: Genus of bird species. *
 Subfamily: Subfamily of bird species (if relevant). * taxagroup: Commonly
 used taxonomic group name, based on phylogenetic classification. * Family:
 Family of bird species. * Order: Order of bird species. * Burrowing:
 Binary indicating whether the species is a burrow-nester. * Nest:
 Categorical variable indicating whether the species is a surface-nester,
 burrow-nester, or crevice-nester. * Mass: Mean mass(g) of adult birds,
 averaged across sex (if applicable). * nocturnal_visits: Binary indicating
 whether the species primarily completes provisioning visits during the
 night. #### File: targeted_islands.csv **Description:** This tabular
 dataset includes data collected from targeted surveys (Table S2) of
 seabird biologists with experience working on identified islands with
 long-term monitoring programs. Data have been aggregated across multiple
 survey respondents (where applicable). ##### Variables * island_name:
 Common name of the island for the record. - Years: Number of cumulative
 years of monitoring activity reported by survey respondents. *
 total_weeks: Number of cumulative weeks of monitoring activity reported by
 survey respondents. Often cumulative/extrapolated/estimated. -
 nest_species: IBP codes of seabird species known to be nested on the
 island. * otter_presence: Binary indicating whether river otters have ever
 been observed on the island. - otter_residence: Categorical description of
 residence patterns for river otters occurring on the island. * Predation:
 Binary indicating whether river otter predation of nesting seabirds has
 ever been observed. - depredated_species: IBP codes of seabird species
 known to have been depredated by river otters on the island. * Notes:
 Additional notes from biologist survey responses. #### File:
 paper_scoring.csv **Description:** This tabular dataset includes results
 from the systematic review of references from peer-reviewed journals on
 seabird predation by river otters. ##### Variables * article: Full title
 of the published article. * Authors: Full author list for the published
 article. * Journal: The full title of the journal where the article was
 published. * Year: The year of publication. * journal_bg: Categorical
 classification of the journal focus. * journal_bg2: Categorical
 classification of the journal focus, with all naturalist journals grouped
 into one category. * author_institution: The affiliated institution for
 the lead author at the time of publication. * author_bg: Categorical
 classification of the professional/academic background/expertise of the
 lead author. * Mammalogist: Binary indicating whether a mammalogist was
 included in the author list. * ref_type: Categorical classification of the
 type of reference made to seabird predation by river otters; e.g., primary
 focus of a targeted study, anecdotal mention in a river otter diet study,
 anecdotal mention in a seabird predation study. * ref_type2: Coarse
 categorical classification of the type of reference made to seabird
 predation by river otters: anecdotal mention, natural history note, or
 primary study. * words_otter: Total number of words in the article
 discussing river otter predation of seabirds. If river otters or their
 impacts were mentioned or alluded to in any degree in a sentence, the
 entirety of words in that sentence were included in this count. *
 words_total: Total number of words in the published manuscript. *
 location_name: Common name of location for predation record. * Island:
 Binary indicating whether the location was a coastal seabird colony
 island. * State: State or province where predation record occurred. *
 Coordinates: Geographic coordinates for the location where predation
 occurred. * Family: Family name of the seabird species experiencing
 predation. * Species: IBP code for bird species experiencing predation. *
 resident_transient: Categorical class describing whether the river otters
 engaging in predation were transient visitors to the location or permanent
 residents. * Excavation: Binary indicating whether river otters were
 described as excavating the burrows of burrow-nesting seabirds in the
 article. * Notes: Additional notes about the described predation record.
 #### File: updated_geography.csv **Description:** This tabular dataset
 provides geographic data for all seabird colony islands included in our
 modeling datasets. All island sizes and shore distances were measured from
 aerial imagery using Google Earth Pro. ##### Variables * island_name:
 Common name of the island. * State: State or province where the island is
 located. * size_ha: Area of island in hectares, rounded to two significant
 digits. * Lat: Latitude of island location, rounded to a hundredth of a
 degree north. * Long: Longitude of island location, rounded to a hundredth
 of a degree west. * dist_e**X**ha: Minimum distance from the island to
 another landmass greater than 10**X** hectares in size. Measured in
 kilometers, rounded to two significant digits. * Freshwater: Categorical
 variable describing the presence of standing freshwater on the island (no
 freshwater, rainfed pools, temporary seasonal pools, persistent
 freshwater). * freshwater_notes: Notes about the information source for
 freshwater presence. If nothing is included in this column, information
 came from biologist survey respondents. #### File: white_papers.csv
 **Description:** This tabular dataset indicates anecdotal records of
 seabird predation by river otters that were sourced from white papers and
 internal agency documents. ##### Variables * location_name: Common name of
 location for predation record. * Island: Binary indicating whether the
 location was a coastal seabird colony island. * State: State or province
 where the predation record occurred. * Species: IBP code for bird species
 experiencing predation. * Source: Author and year of publication. * Notes:
 Additional relevant notes about the anecdotal records. #### File:
 RIOTRange.zip **Description:** This compressed shapefile indicates the
 approximated species range of the northern river otter, *Lontra
 canadensis*. This file was solely used for mapping purposes (Figure 1).
 The range map shown here was based on observation data from iNaturalist.
 ## Code/software All analysis was performed in R version 4.2.3. All
 packages required are listed at the top of each script. #### File:
 predation_mapping.R **Description:** This script generates maps of seabird
 predation records throughout North America. #### File:
 predation_record_linking.R **Description:** This script takes our many
 disparate sources of anecdotal data (anecdotal biologist surveys, targeted
 surveys, white papers, published literature) and combines them into
 unified datasets for further analysis. It must be run before the other
 scripts in this project. #### File: taxa_selection.R **Description:** This
 script uses anecdotal predation records and seabird assemblage data to
 evaluate prey selection by river otters via logistic modeling. #### File:
 island_risk_.R **Description:** This script uses both the targeted island
 survey and anecdotal records to perform logistic regression on island risk
 factors. #### File: paper_review.R **Description:** This script analyzes
 the results of the systematic literature review and paper scoring to
 analyze trends in publications about river otter seabird predation.