Aim. Biotic interactions form a pillar of most niche concepts but are frequently overlooked as range-limiting factors. At local scales, bird species that nest in tree cavities but cannot create cavities themselves—“non-excavator” species—experience competition with other non-excavators but facilitation by excavator species such as woodpeckers. Our objective was to evaluate whether nest-site competition and facilitation mediate the range limits of non-excavator cavity-nesting birds.
Location. United States and Canada.
Time Period. Contemporary.
Group. Cavity-nesting birds (58 non-excavator species).
Methods. Using eBird relative abundance maps, we modeled abundance of non-excavator species within their non-coastal range limits as a function of either (1) summed abundances of all other non-excavators, (2) summed abundances of non-excavators within 50% body mass of the focal species, (3) summed abundances of all excavators, (4) summed abundances of excavators within 50% body mass of the focal species, or (5) abundances of either House Sparrows (Passer domesticus) or European Starlings (Sturnus vulgaris), two invasive ‘supercompetitors’.
Results. At a cross-species level, the effects of heterospecific non-excavator and excavator abundance were not significant. At a species level, only 3 species (5% of the total) showed strong (≥95% confidence) competitive effects of non-excavators and strong facilitative effects of excavators. However, non-invasive ‘supercompetitors’ were associated with low range-limit abundance of non-excavators; for example, House Sparrows showed negative effects on range-limit abundance for nine out of the seventeen (53%) non-excavators of similar size.
Main Conclusions. Our results are consistent with the ‘Eltonian Noise Hypothesis’, which suggests that biotic interactions get ‘washed out’ at broadening spatial scales such that only abiotic variables correlate with species distributions at broad scales. Among-species variation in habitat selection (e.g., preferences for cavities at different heights) and nesting phenology may contribute to the limited evidence we found of range limits being formed by nest-site competition or facilitation.
- 1.1_download_cavity_nester_range_maps.R. This script downloads eBird range maps for cavity-nesting species.
- 1.2_identify_north_american_cavity_nesters.R. This script identifies which cavity-nesters occur within North America
- 1.3_make_list_of_cavity_nesters_to_review.R. Script to make a table of species of manually review; there were some species that did not readily join to taxonomy shenanigans
- 1.4_create_list_of_species_to_download_abundance_maps.R. Quick script to assemblage the final species list to download abundance maps for
- 1.5_download_ebird_abundance_maps.R. Download eBird relative abundance maps for the focal species
- 1.6_create_focal_area_shapefile. Creates and saves a shapefile for the US and Canada joined.
- 1.7_join_van_der_hoek_dataset.R. Script to join with van der Hoek (2017) database.
- 2.1_calculate_coast_distance.R. Calculate distance between each grid cell and the nearest coastline
- 2.2_calculate_range_edge_distance.R. Calculate distance between each grid cell and nearest range edge for each species
- 2.3_calculate_diversity_per_cell.R. Calculate summed abundance of cavity-nesting heterospecifics within range-edge grid cells for every species
- 3.1_fit_cross_species_models.R. Fit brms models relating range-edge abundance to abundance of heterospecifics of different categories
- 3.2_supercompetitor_analysis_figure_06.R. Do "supercompetitor" analysis and create Figure 6
- 4.1_create_figure_01b.R. Create conceptual graph for Fig. 1b
- 4.2_create_maps_figure_02.R. Create species maps for Fig. 2
- 4.3_create_figures_03_04_05.R. Create the other figures
** NOTE ** eBird range maps and abundance maps are not included in this repository due to file size limitations. Upon running 1.1_download_cavity_nester_range_maps.R and 1.5_download_ebird_abundance_maps.R, you will have subfolders named abundance and ranges within the data folder.
- chia. Folder with tables from Chia et al. 2023. See that publication for further details
- avonet.csv. AvoNET database; see Tobias et al. 2022 for detail
- cavity_nesters_abundance_dists.csv. Table with cavity-nester abundance and columns for distance to coast and range edge.
column meaning cell_id unique ID for grid cell (27 x 27 km ) com common name per eBird scientific_name scientific name per eBird species_code 6-letter ebird code n relative abundance coast_dist distance in meters from the grid cell's centroid to the nearest coastline range_dist distance in meters from the grid cell's centroid to the nearest range edge - cavity_nesters_review.csv. Table we generated to review the Chia et al classifications
column meaning order species order family species family sci scientific name com common name code 6-letter code primary binary indicator of whether or not species is a primary (excavator) cavity-nesting species secondary binary indicator of whether or not species is a secondary (non-excavator) cavity-nesting species tree binary indicator of whether or not species nests in trees - cavity_species_REVIEWED.csv. Final table (same as above, but with our annotations added)
column meaning order species order family species family sci scientific name com common name code 6-letter code primary binary indicator of whether or not species is a primary (excavator) cavity-nesting species secondary binary indicator of whether or not species is a secondary (non-excavator) cavity-nesting species tree binary indicator of whether or not species nests in trees feral binary indicator of whether species occurs only as small feral populations in North America; this was done for parrots only neil_classification First author (Neil) did a initial screening and classified species as "good", "omit" (not cavity nesters), or "idk" (species he was unsure of) hallie_classification Last author (Hallie) did a subsequent screening of species marked "idk" in the previous step and classified species as "good" (cavity nesters) or "omit" (not cavity nesters) notes Notes taken during manual review - cavity_species_with_other_species_abundance_v02.csv. Table with cavity-nester abundance and columns for distance to coast and range edge, and abundance of heterospecifics
column meaning cell_id unique ID for grid cell (27 x 27 km ) com common name per eBird scientific_name scientific name per eBird species_code 6-letter ebird code n relative abundance coast_dist distance in meters from the grid cell's centroid to the nearest coastline range_dist distance in meters from the grid cell's centroid to the nearest range edge position Position within range (edge or core) mass species' mass from avonet order species order family species family primary binary indicator of whether or not species is a primary (excavator) cavity-nesting species secondary binary indicator of whether or not species is a secondary (non-excavator) cavity-nesting species tree binary indicator of whether or not species nests in trees n_secondary summed abundance of other non-excavators within the grid cell sr_secondary species richness of other non-excavators within the grid cell n_secondary_0.5 summed abundance of other non-excavators - similar sized only - within the grid cell sr_secondary_0.5 species richness of other non-excavators - similar sized only - within the grid cell n_primary summed abundance of obligate excavators within the grid cell sr_primary species richness of obligate excavators within the grid cell n_primary_0.5 summed abundance of obligate excavators - similar size only - within the grid cell sr_primary_0.5 species richness of obligate excavators - similar size only - within the grid cell n_primary2 summed abundance of excavators (obligate and facultative) within the grid cell sr_primary2 species richness of excavators (obligate and facultative) within the grid cell n_primary2_0.5 summed abundance of excavators (obligate and facultative) - similar size within the grid cell sr_primary2_0.5 species richness of excavators (obligate and facultative) within the grid cell - cell_coast_dist.csv. Distance from each grid cell centroid to the nearest coastline
column meaning cell_id grid cell identifier coast_dist distance to nearest coastline (meters) - ddi12601-sup-0001-tables1.xlsx. Data from van der Hoek et al. 2017. See that paper for further details.
- download_range_maps_for_these_species.csv. Species to download range maps for
column meaning order species order family species family species_code 6-letter ebird code scientific_name scientific name per eBird common_name common name per eBird primary binary indicator of whether or not species is a primary (excavator) cavity-nesting species secondary binary indicator of whether or not species is a secondary (non-excavator) cavity-nesting species tree binary indicator of whether or not species nests in trees - final_species_list.csv. Species list after some filtering/review, etc.
column meaning order species order family species family sci scientific name per eBird com common name per eBird code 6-letter ebird code primary binary indicator of whether or not species is a primary (excavator) cavity-nesting species secondary binary indicator of whether or not species is a secondary (non-excavator) cavity-nesting species tree binary indicator of whether or not species nests in trees - focal_area2.shp. Focal area (mainland US and Canada); this polygon was created in 1.6_create_focal_area_shapefile. The other extensions (
.dbf, etc) are in this folder but not described here. - focal_species_van_der_hoek_classification.csv. Non-excavators from analysis with van der Hoek classifications.
column meaning com common name per eBird sci scientific name per eBird code 6-letter ebird code ob describes species as either an "obligate" or "facultative" cavity-nester type describes species as either "excavator" or "non-excavator" - north_america_cavity_nesters_to_review.csv. Cavity-nesting species occuring within North America to review manually for accuracy
column meaning species_code 6-letter ebird code within indicates whether species breeding range is entirely within USA, Canada, and Mexico inter indicates whether species breeding range intersects with USA, Canada, and Mexico com common name per eBird sci scientific name per eBird order species order family species family scientific_name scientific name per eBird common_name common name per eBird primary binary indicator of whether or not species is a primary (excavator) cavity-nesting species secondary binary indicator of whether or not species is a secondary (non-excavator) cavity-nesting species - review_species_van_der_hoek_join.csv. Small table of species to manually review due to taxonomy idiosyncracies
column meaning com common name per eBird scientific_name scientific name per eBird code 6-letter ebird code - review_species_van_der_hoek_join_v2.csv Same table as above, but post-review
column meaning com common name per eBird scientific_name scientific name per eBird code 6-letter ebird code Obligate or Facultative Indicates whether species is an obligate or facultative cavity nester type Non-excavator or excavator
- figure_01.png Figure 1
- figure_01.pptx Figure 1 (PowerPoint format for annotation)
- figure_01b.png Figure 1b
- figure_02.png Figure 2
- figure_02.pptx Figure 2 (PowerPoint format for collation/annotation)
- figure_03.png Figure 3
- figure_04.png Figure 4
- figure_04.pptx Figure 4 (PowerPoint format for annotation)
- figure_05.png Figure 5
- figure_06.png Figure 6
- figure_06.pptx Figure 6 (PowerPoint format for annotation)
- us_canada_edge_results2.RData. Model results generated from 3.1_fit_cross_species_models.R