DOI: 10.5061/dryad.931zcrjg5
title: Reproductive success of the threatened San Clemente Bell's Sparrow in recovering habitats is similar to success in historical habitat

description: The San Clemente Bell’s Sparrow Artemisiospiza belli clementeae is a
 federally threatened subspecies endemic to San Clemente Island,
 California. Previous research suggested dependence on boxthorn (Lycium
 californicum) as breeding habitat and nesting substrate; however, this
 conclusion was based on data collected when introduced feral ungulates had
 severely degraded the soil and vegetation cover. Since removal of the
 ungulates, native vegetation has gradually increased and the San Clemente
 Bell’s Sparrows have expanded into areas where habitat had been
 unsuitable. To explore how Bell’s Sparrows use these areas, we examined
 reproductive metrics associated with habitat covariates gathered at 214
 nest sites used by Bell’s Sparrows from 2014 ̶ 2016. We found that nest
 success in boxthorn habitat, previously considered an essential habitat
 for Bell’s Sparrow nesting, was similar to success in alternative habitat
 types. Our findings contradict previous conclusions that Bell’s Sparrows
 were boxthorn-dependent. We believe this previously documented
 relationship was likely due to the lack of available alternative nesting
 habitat following years of feral ungulate degradation, and Bell’s Sparrows
 now reproduce in multiple habitat types and throughout most of San
 Clemente Island. Furthermore, our findings illustrate the importance of
 long-term monitoring and corresponding adaptive management when monitoring
 species in changing and recovering landscapes.The San Clemente Bell’s
 Sparrow Artemisiospiza belli clementeae is a federally threatened
 subspecies endemic to San Clemente Island, California. Previous research
 suggested dependence on boxthorn (Lycium californicum) as breeding habitat
 and nesting substrate; however, this conclusion was based on data
 collected when introduced feral ungulates had severely degraded the soil
 and vegetation cover. Since removal of the ungulates, native vegetation
 has gradually increased and the San Clemente Bell’s Sparrows have expanded
 into areas where habitat had been unsuitable. To explore how Bell’s
 Sparrows use these areas, we examined reproductive metrics associated with
 habitat covariates gathered at 214 nest sites used by Bell’s Sparrows from
 2014 ̶ 2016. We found that nest success in boxthorn habitat, previously
 considered an essential habitat for Bell’s Sparrow nesting, was similar to
 success in alternative habitat types. Our findings contradict previous
 conclusions that Bell’s Sparrows were boxthorn-dependent. We believe this
 previously documented relationship was likely due to the lack of available
 alternative nesting habitat following years of feral ungulate degradation,
 and Bell’s Sparrows now reproduce in multiple habitat types and throughout
 most of San Clemente Island. Furthermore, our findings illustrate the
 importance of long-term monitoring and corresponding adaptive management
 when monitoring species in changing and recovering landscapes.
description: Dataset: BESP_Nest_Fate-MARK.csv<br> This file contains
 data collected at each nest site for input into MARK program. Individual
 covariates: Year of nest and habitat characteristics of each nest at 4
 scales.<br> NestID = Unique ID for each nest in the sample<br>
 Day_of_Season_Start= Day of breeding season nest was first
 monitored<br> Day-of_Season_Last_Active= Day of breeding season when
 nest was still active<br> Day_of_Season_Nest_End_Monitoring= Day of
 breeding season nest successfully fledged OR day failure was
 documented<br> Nest Fate: 1=Failed, 0=Successfully fledged at least
 1 chick<br> Encounters = 1<br> Historic_Habitat= Covariate for
 historic habitat (1=historically delineated Bell's sparrow habitat,
 0=outside historic habitat)<br> Year_2014: 1=nest during year
 2014<br> Year_2015: 1=nest during year 2015<br>
 Plot_Category_Boxthorn: 1=Boxthorn plot-scale habitat category.<br>
 Plot_Category_Mixed Shrub: 1=Mixed-Shrub plot-scale habitat
 category.<br> Substrate_Boxthorn: 1=Boxthorn Substrate-scale habitat
 category.<br> Substrate_Non-boxthorn Shrub: 1=Non-boxthorn
 substrate-scale habitat category.<br> MeanVegHt-15mRadius: Mean of
 vegetation height measured in 15m radius around nest at 1m intervals in 4
 cardinal directions.<br> MeanShrubHt-15mRadius: Mean of shrub height
 measured in 15m radius around nest at 1m intervals in 4 cardinal
 direction.<br> ProportionBoxthorn-15m: Proportion of measurements
 around nest in 15m radius that are boxthorn.<br>
 ProportionShrub-15m: Proportion of measurements around nest in 15m radius
 that are shrub.    <br> ProportionNonboxthornShrub-15m: Proportion
 of measurements around nest in 15m radius that are shrub but not
 boxthorn.<br> Proportion Bare-15m: Proportion of measurements around
 nest in 15m radius that are bare ground.<br>
 Ratio_Bare_Ground_to_Shrub-15m: Ratio of proportions of bare ground/shrub
 cover.<br> 15m-Category_Boxthorn: 1=Boxthorn habitat category at
 15m.<br> 15m_Category_Nonboxthorn_Shrub: 1=Non-boxthorn shrub
 category. Dataset: BESP_Nests_Clutches.csv<br>
 This file contains data for clutch sizes of nests with eggs.<br>
 NestID = Unique ID for each nest in the sample<br> Historic_Habitat=
 Covariate for historic habitat (1=historically delineated Bell's
 sparrow habitat, 0=outside historic habitat)<br> Plot_Category:
 Habitat category assigned to plot in which nest was located (Boxthorn,
 Mixed Shrub, or Other).<br> Substrate_Category: Habitat category of
 nest substrate vegetation (Boxthorn, Non-boxthorn shrub, or
 Other).<br> 15m_Category: Habitat category of 15m radius around the
 nest (Boxthorn, Non-boxthorn Shrub, or Nonshrub)<br> Clutch_Size:
 Size of clutch. Dataset:
 BESP_Nests_Fledglings.csv<br> This file contains data for number of
 fledglings per successful nest.<br> NestID = Unique ID for each nest
 in the sample<br> Historic_Habitat= Covariate for historic habitat
 (1=historically delineated Bell's sparrow habitat, 0=outside historic
 habitat)<br> Plot_Category: Habitat category assigned to plot in
 which nest was located (Boxthorn, Mixed Shrub, or Other).<br>
 Substrate_Category: Habitat category of nest substrate vegetation
 (Boxthorn, Non-boxthorn shrub, or Other).<br> 15m_Category: Habitat
 category of 15m radius around the nest (Boxthorn, Non-boxthorn Shrub, or
 Nonshrub)<br> Fledglings: Number of fledglings.<br>