DOI: 10.5061/dryad.9s4mw6mx2
title: Data from: Songbird population trajectories diverge under simulations of conifer encroachment vs removal in a sagebrush ecosystem

description: Woody plant encroachment into grasslands and shrublands is a global
 phenomenon, negatively impacting ecosystem services and wildlife
 populations. North American sagebrush ecosystems have experienced
 widespread degradation from encroaching conifers, leading to losses of
 sagebrush-obligate wildlife. Removal of encroaching trees is a primary
 restoration method, but whether management actions can influence wildlife
 populations at management-relevant scales is rarely investigated. We
 studied a local Brewer’s Sparrow in the Medicine Lodge Valley of southwest
 Montana to understand how their territory occupancy and nest success were
 impacted by tree and shrub cover. From 2019-2022, our data collection
 resulted in 1,161 mapped territories and 449 nests, which we used to build
 models of territory occupancy and reproductive productivity relative to
 tree and shrub cover. We then used tree and shrub cover extracted from
 historical imagery to estimate population size and productivity 70 years
 in the past. Finally, using models of tree growth and expansion, we
 estimated population size and reproductive productivity under two
 simulated scenarios 30 years in the future: with and without restoration
 through conifer removal. We observed that tree cover has more than tripled
 at the study site since 1954, which our models predicted have caused an
 almost 25 % decrease in the local population size and a 35 % decline in
 offspring production. In a future scenario where tree removal is conducted
 in areas with &lt; 20 % tree canopy cover after 30 years, we predict
 population size and offspring production will likely remain stable.
 Alternatively, if tree cover is allowed to increase unabated, our
 simulations predict a potential population decline of 60 %, with similar
 losses to offspring production. We saw a stark divergence in the potential
 futures of the local Brewer’s Sparrow population and implications for the
 species at large. Continuing tree encroachment drastically decreases the
 available habitat and causes a steep decline in population size. However,
 proactive and continuing management of encroaching trees can alleviate
 further losses in a species that has already experienced significant
 range-wide declines. We also highlight the importance of encroaching trees
 as a previously underappreciated conservation risk for sagebrush avifauna.
description: # Data from: Songbird population trajectories diverge under simulations of
 conifer encroachment vs removal in a sagebrush ecosystem Dataset DOI:
 [10.5061/dryad.9s4mw6mx2](https://doi.org/10.5061/dryad.9s4mw6mx2) ##
 Description of the data and file structure We conducted this study at the
 sagebrush-forest ecotone in the Medicine Lodge Valley of southwest
 Montana, USA, during the breeding seasons of May-August of 2019–2022. We
 placed a 70 m square grid over the study site to quantify Brewer's
 Sparrow occupancy and predict population size under alternate scenarios.
 We collected vegetation data for each grid cell using remote sensing and
 estimated vegetation data under historic and two future scenarios.
 Vegetation data were used to model Brewer's Sparrow territory
 occupancy, nest success, and fledglings produced in each scenario
 (historic, current, future restoration, and future with no action). ###
 Files and variables #### File: GriddedVegData.csv
 **Description:** Relevant vegetation data from each cell of the 70 m grid
 placed across the field site, including historic and simulated future
 data. ##### Variables * gridID: Unique number identifying the grid cell *
 period: Time period/scenario * elevation: Mean elevation of the grid cell
 * slope: Mean slope of the grid cell * heat: calculated heat load index of
 the grid cell * TRE: % tree cover within the grid cell * SHR: % shrub
 cover within the grid cell * TRE_300r: % tree cover in a 300 m round
 buffer around the grid cell centroid * SHR_300r: % shrub cover in a 300 m
 round buffer around the grid cell centroid * Year: Year * TRE_70s: % tree
 cover in a 70 m square buffer around the grid cell * TRE_30r: % tree cover
 in a 30 m round buffer around the grid cell centroid (NA indicates data is
 unavailable) #### File: BrewersSparrowNestData.csv
 **Description:** Detailed information about each Brewer's Sparrow
 nest included in the analysis ##### Variables * gridID: Unique number
 identifying the grid cell where the nest is located * Year: Year *
 Nest_ID: Unique identifier for each nest * SHR_30r: % shrub cover in a 30
 m round buffer around the nest * SHR_40r: % shrub cover in a 40 m round
 buffer around the nest * SHR_50r: % shrub cover in a 50 m round buffer
 around the nest * SHR_60r: % shrub cover in a 60 m round buffer around the
 nest * SHR_70r: % shrub cover in a 70 m round buffer around the nest *
 SHR_100r: % shrub cover in a 100 m round buffer around the nest *
 SHR_1000r: % shrub cover in a 1000 m round buffer around the nest *
 SHR_200r: % shrub cover in a 200 m round buffer around the nest *
 SHR_300r: % shrub cover in a 300 m round buffer around the nest *
 SHR_400r: % shrub cover in a 400 m round buffer around the nest *
 SHR_500r: % shrub cover in a 500 m round buffer around the nest *
 SHR_80r: % shrub cover in a 80 m round buffer around the nest * SHR_90r: %
 shrub cover in a 90 m round buffer around the nest * TRE_30r: % tree cover
 in a 30 m round buffer around the nest * TRE_40r: % tree cover in a 40 m
 round buffer around the nest * TRE_50r: % tree cover in a 50 m round
 buffer around the nest * TRE_60r: % tree cover in a 60 m round buffer
 around the nest * TRE_70r: % tree cover in a 70 m round buffer around the
 nest * TRE_100r: % tree cover in a 100 m round buffer around the nest *
 TRE_1000r: % tree cover in a 1000 m round buffer around the nest *
 TRE_200r: % tree cover in a 200 m round buffer around the nest *
 TRE_300r: % tree cover in a 300 m round buffer around the nest *
 TRE_400r: % tree cover in a 400 m round buffer around the nest *
 TRE_500r: % tree cover in a 500 m round buffer around the nest *
 TRE_80r: % tree cover in a 80 m round buffer around the nest * TRE_90r: %
 tree cover in a 90 m round buffer around the nest * heat: calculated heat
 load index of the grid cell where the nest is located * TRE: % tree cover
 in the grid cell where the nest is located * SHR: % shrub cover in the
 grid cell where the nest is located * Plot: plot the nest is located in *
 elevation: mean elevation of the grid cell where the nest is located (NA
 indicates data is unavailable) * aspect: mean aspect of the grid cell
 where the nest is located (NA indicates data is unavailable) * slope: mean
 slope of the grid cell where the nest is located (NA indicates data is
 unavailable) * Precision_Incubate: code indicating the precision with
 which the incubation period is known (1 is within 24 hr, 2 is within 48
 hr, and 3 or more is uncertain, NA indicates data is unavailable) *
 Nest_Fate: code indicating the final fate of the nest (1 is a successful
 nest where at least one nestling fledged, 2 is a failed nest where no
 nestlings fledged, and 4 is a nest whose final fate is unknown) *
 Clutch_Size: number of eggs laid if known for sure (if clutch size is
 uncertain cell contains NA and NFCS is filled out instead) * NFCS
 (Non-Final Clutch Size): likely number of eggs laid, but exact number is
 unknown (if clutch size is certain, then cell contains NA and Clutch_Size
 is filled out instead) * Hatched: number of eggs that hatched (NA
 indicates that the exact number hatched is unknown) * Unhatched: number of
 eggs that remained in the nest without hatching (NA indicates that the
 number unhatched is unknown) * Hatching_Lost: number of offspring lost
 around the time of hatching (NA indicates that the number lost is unknown)
 * Nestlings_Lost: number of nestlings lost (NA indicates that the number
 lost is unknown) * Researcher_Attrition: offspring lost due to researcher
 error (NA indicates that the number lost is unknown) * Brood_Size: number
 of nestlings (NA indicates that the exact brood size is unknown) *
 Fledged: number of offspring that left the nest (NA indicates that the
 number fledged is unknown) * Fledged_Exact: code indicating the precision
 with which the number of fledglings are known (1 means the number of
 offspring were observed 24 hr or less before fledging, NA indicates not
 applicable if no offspring fledged) * Comments: comments about the fate of
 the nest (NA indicates no comments were made) * fate: binomial nest fate
 code (1 is successful, 0 is failed) * Total_Days: number of days the nest
 was observed for #### File: GriddedSimulatedBirdData.csv
 **Description:** Simulated bird data for each grid cell in each time
 period ##### Variables * hist.num: number of pairs in the cell in the
 historic period * gridID: unique identifier for the grid cell *
 hist.num.suc: number of successful nests in the grid cell in the historic
 period (assumes each pair attempts a nest) * hist.num.fldg: number of
 fledglings produced in the grid cell in the historic period *
 curr.num: number of pairs in the cell in the current period *
 curr.num.suc: number of successful nests in the grid cell in the current
 period (assumes each pair attempts a nest) * curr.num.fldg: number of
 fledglings produced in the grid cell in the current period *
 fNR.num: number of pairs in the cell in the future period, no tree removal
 scenario * fNR.num.suc: number of successful nests in the grid cell in the
 future period, no tree removal scenario (assumes each pair attempts a
 nest) * fNR.num.fldg: number of fledglings produced in the grid cell in
 the future period, no tree removal scenario * fCR.num: number of pairs in
 the cell in the future period, conifer removal scenario *
 fCR.num.suc: number of successful nests in the grid cell in the future
 period, conifer removal scenario (assumes each pair attempts a nest) *
 fCR.num.fldg: number of fledglings produced in the grid cell in the future
 period, conifer removal scenario ## Code/software CSV files can be opened
 using Microsoft Excel or Google Sheets. All code was run on R Software
 using open-access packages cited in the text. ## Access information Data
 was derived from the following sources: *
 [https://rangelands.app/](https://rangelands.app/) *
 [https://www.landscapeexplorer.org/#ll=39.4652601427090417,-106.4514315190140508&b=hybrid&z=9&sl=-108.1982576908890508](https://www.landscapeexplorer.org/#ll=39.4652601427090417,-106.4514315190140508&b=hybrid&z=9&sl=-108.1982576908890508)