DOI: 10.5061/dryad.5dv41nscw
title: Data from: Abundance models of endemic birds of the Sierra Nevada de Santa Marta, northern South America, suggest small population sizes and dependence on montane elevations

description: Abundance measures are almost non-existent for several bird species
 threatened with extinction, particularly range-restricted Neotropical
 taxa, for which estimating population sizes can be challenging. Here we
 use data collected over nine years to explore the abundance of 11 endemic
 birds from the Sierra Nevada de Santa Marta (SNSM), one of Earth’s most
 irreplaceable ecosystems. We established 99 transects in the “Cuchilla de
 San Lorenzo” Important Bird Area within native forest, early successional
 vegetation, and areas of transformed vegetation by human activities. A
 total of 763 bird counts were carried out covering the entire elevation
 range in the study area (~175–2650 m). We applied hierarchical
 distance-sampling models to assess elevation- and habitat-related
 variation in local abundance and obtain values of population density and
 total and effective population size. Most species were more abundant in
 the montane elevational range (1800–2650 m). Habitat-related differences
 in abundance were only detected for five species, which were more numerous
 in either early succession, secondary forest, or transformed areas.
 Inferences of effective population size indicated that at least four
 endemics likely maintain populations no larger than 15,000–20,000 mature
 individuals. Estimates of species’ area of occupancy and effective
 population size were lower than most values previously described, a
 possible consequence of increasing anthropogenic threats. At least four of
 the endemics exceeded criteria for threatened species listing and a
 thorough evaluation of their extinction risk should be conducted.
 Population strongholds for most of the study species were located on the
 northern and western slopes of the SNSM between 1500–2700 m. We highlight
 the urgent need for facilitating effective protection of native vegetation
 in premontane and montane ecosystems to safeguard critical habitats for
 the SNSM’s endemic avifauna. Follow-up studies collecting abundance data
 across the SNSM are needed to obtain precise range-wide density
 estimations for all species.
description: # Data from: Abundance models of endemic birds of the Sierra Nevada de
 Santa Marta, northern South America, suggest small population sizes and
 dependence on montane elevations
 MS Reference Number:
 ORNITH-APP-23-061R2 Dataset name:
 Abundance_models_priority_endemics_SNSM.xlsx The whole dataset contains
 data for fitting hierarchical distance-sampling models for priority,
 endemic bird species from the Sierra Nevada de Santa Marta, northern
 Colombia. Models were used to assess elevation- and habitat-related
 variation in local abundance and obtain values of population density and
 total and effective population size for the study species. Details on
 other methods used for estimating extent of presence (EOP) and area of
 occupancy (AOO), and for generating abundance maps are provided in the
 manuscript and the supplementary material file that accompanies it.
 Abundance maps will be uploaded as distribution hypothesis for each
 species to the BioModelos online platform (Velásquez-Tibatá et al. 2019),
 available at . BioModelos is an
 initiative of the Instituto de Investigación de Recursos Biológicos
 Alexander von Humboldt (IAvH; ). The
 data set is divided into twelve spreadsheets, which are explained below.
 ## 1. Transect\_Info: This spreadsheet contains all information regarding
 location and habitat covariates at each of the 99 transects installed
 throughout the study area in the "Cuchilla de San Lorenzo" IBA,
 Sierra Nevada de Santa Marta (Colombia). These data matrices contain the
 following variables: VARIABLE DESCRIPTION * Location: Name of the locality
 where each transect is located. * TransectID: Name of each transect. *
 TLength: Length of each transect in m. * TReps: Total number of replicated
 surveys in each transect. * TDistance: Total distance surveyed for each
 transect during the study in m. * TBirdRecs: Total number of records of
 the study species in each transect. * Latitude: Coordinates in decimal
 degrees. * Longitude: Coordinates in decimal degrees. * Elevation:
 Elevation in m. * ElevCat: Elevation category as described in the main
 text (Low: lowland, 171–1200 m; Pre: premontane, 1200–1800 m; Monta:
 montane, 1800–2650 m). * LandCover: Land cover units considered as
 potential habitat for the study species. ## 2. Dryhel, 3. Graban, 4.
 Scylat, 5. Scysan, 6. Synfus, 7. Atlmel, 8. Arrbas, 9. Myicon, 10. Myifla,
 11. Animel: These spreadsheets contain ready-to-use datasets for fitting
 distance-sampling models in the R package unmarked (Fiske & Chandler
 2011). Each spreadsheet contains data collected during bird counts for all
 the 11 study species. * Dryhel: Drymophila hellmayri * Graban: Grallaria
 bangsi * Scylat: Scytalopus latebricola * Scysan: Scytalopus sanctaemartae
 * Synfus: Synallaxis fuscorufa * Atlmel: Atlapetes melanocephalus *
 Arrbas: Arremon basilicus * Myicon: Myiothlypis conspicillata * Myifla:
 Myioborus flavivertex * Animel: Anisognathus melanogenys These data
 matrices contain the following variables: VARIABLE DESCRIPTION * Location:
 Name of the locality where each transect is located. * TransectID: Name of
 each transect. * TransectID2: Unique name given to each transect for
 modeling purposes. * TransectRep: Code to identify each repetition for
 each transect. * Species: Species scientific name. * CodSpecies: Short
 name for each species. * NoInd: Number of individuals for every record. *
 Distance: Estimated distance to each individual recorded in m. * Record:
 Type of record (acoustic and/or visual). * Date: Date of survey (d/m/y). *
 Day: Day when the record was made. * Month: Month when the record was
 made. * Year: Year when the record was made. * StartTime: Survey starting
 hour in min. * Duration: Survey duration in min. * Observer: Nick Bayly
 (NB) or Enrick Meza (EM). * TDistance: Total distance surveyed for each
 transect during the study in m. * Elevation: Elevation in m. * LandCover:
 Land cover type where survey took place. *NA: not available. ##
 References: Fiske, I., and R. Chandler (2011). “unmarked”: an R package
 for Fitting Hierarchical Models of Wildlife Occurrence and Abundance.
 Journal of Statistical Software 43:1–23. Velásquez-Tibatá, J. I.,
 Olaya-Rodríguez, M. H., López-Lozano, D., Gutiérrez, C., González, I., and
 M. C. Londoño-Murcia (2019). BioModelos: A collaborative online system to
 map species distributions. PLoS ONE 14:e0214522. ## Contact information:
 Esteban Botero-Delgadillo, Dr.Sc. Director of Conservation Science SELVA:
 Research for Conservation in the Neotropics Diagonal 42A No 20 - 37 Barrio
 La Soledad, Bogotá, 111311, Colombia 
 e-mail: ;