DOI: 10.5061/dryad.8kprr4z14
title: The positive influence of wetlands on reproductive success and body mass in an aerial insectivore is more pronounced in intensively cropped agroecosystems

description: Weather and land-use changes can act in complex ways to affect species’
 annual demographics and distributions. Biodiversity and agriculture are
 frequently intertwined, where climatic conditions, such as flooding and
 drought, may be exacerbated by intensive agricultural practices.
 Understanding how climate change and agricultural land use influence avian
 populations is key to retaining biodiversity in working landscapes. Here
 we examined a large dataset of breeding Tachycineta bicolor (Tree Swallow)
 in Canada’s Prairie Pothole Region (PPR) across eight years at eight sites
 representing a gradient in agricultural intensity and wetland
 availability, for a total of 42 site-years. We analyzed the influence of
 agricultural land use, wetland availability, and seasonal temperature on
 Tachycineta bicolor reproductive success and body mass, while testing for
 potential interactive and curvilinear effects. As predicted, fitness
 measures were negatively affected by agricultural intensity; specifically,
 clutch initiation date was later and nestling body mass was lower at
 cropped versus non-cropped sites. Also, as predicted, interactions
 revealed that the beneficial effects of wetland availability were more
 pronounced at cropped sites. Associations between temperature and fitness
 measures were less clear but suggested the potential for detrimental
 effects of temperature extremes that might also depend on agricultural
 intensity. Our results contribute to a growing body of literature
 demonstrating the negative impact of intensive cropping practices and the
 importance of retaining natural and semi-natural habitats, including
 wetlands, in working landscapes to conserve biodiversity and buffer
 against temperature extremes and future climate changes.
description: Data were collected on <em>Tachycineta
 bicolor</em> from 2012 to 2019 at eight sites (n = 42 site-years)
 east of Saskatoon, Saskatchewan, Canada (52.1579°N, 106.6702°W) to analyze
 the influence of agricultural land use, wetland availability, and
 temperature on reproductive success (clutch initiation date and fledging
 success) and adult and nestling body mass. Refer to the associated
 manuscript for specific details on the calculation of agricultural land
 use (crop category), wetland availability (pond area), and temperature
 (mean daily maximum temperatures) variables.
description: # The positive influence of wetlands on reproductive success and body mass
 in an aerial insectivore is more pronounced in intensively cropped
 agroecosystems Dataset DOI:
 [10.5061/dryad.8kprr4z14](10.5061/dryad.8kprr4z14) ## Description of the
 data and file structure This README was generated on 2025-08-28 by Lisha
 Berzins. Point of contact: Lisha Berzins
 ([lisha.berzins@gmail.com](mailto:lisha.berzins@gmail.com)) or Ann
 McKellar ([Ann.McKellar@ec.gc.ca](mailto:Ann.McKellar@ec.gc.ca)). Data
 were collected on *Tachycineta bicolor* (Tree Swallow; "TRES" in
 file names) breeding at eight sites (n = 42 site-years) east of Saskatoon,
 Saskatchewan, Canada (52.1579°N, 106.6702°W) from 2012 to 2019 to analyze
 the influence of agricultural land use (crop category), wetland
 availability (pond area), and temperature on *Tachycineta bicolor*
 reproductive success (clutch initiation date and fledging success) and
 adult and nestling body mass. ## Files and variables #### File:
 A_McKeller_et_al_TRES_clutch_initiation_code.R **Description:** Code for
 clutch initiation date analysis #### File:
 A2_McKeller_et_al_TRES_clutch_initiation_data_n941.csv
 **Description:** Data for clutch initiation date analysis ##### Variables
 * year: study year * site: study site * siteID: unique identification for
 each site * year_siteID: year and siteID combined as a variable *
 boxID: unique identification for each box * attempt: breeding attempt at
 the box * site_first_year: indicates if this is the year a site was
 established (levels: yes, no) * cid_julian: recorded clutch initiation
 date, where January 1 = 1 * cid_calender: clutch initiation date as the
 date on the calendar (e.g., 18-May) * cid_consecutive_number: clutch
 initiation date numbered consecutively across all years of study (e.g., 1,
 2, 3) * female_age_code: indicates whether females were second-year or
 after-second-year (levels: SY = second-year; ASY = after-second-year) *
 pond: percent pond area (%) for each site year * crop: crop category for
 each site year (levels: 1 = non-crop; 2 = cereal-pulse; 3 = oilseed) *
 temp: daily maximum temperature (°C) averaged for the month of May at each
 site each year #### File: B_McKeller_et_al_TRES_fledging_success_code.R
 **Description:** Code for the fledgling success analysis #### File:
 B2_McKeller_et_al_TRES_fledging_success_data_n741.csv
 **Description:** Data for the fledgling success analysis ##### Variables *
 year: study year * site: study site * siteID: unique identification for
 each site * year_siteID: year and siteID combined as a variable *
 boxID: unique identification for each box * attempt: breeding attempt at
 the box * hatch: Julian hatch date for each clutch, where January 1 = 1 *
 relHatch: hatch date standardized so it reflects a clutch's relative
 hatching date within a season (e.g., 1, 2, 3...) * hatched: number of eggs
 that hatched for each clutch * fledged: number of nestlings that fledged
 for each clutch * did_not_fledge:  the number of nestlings that did not
 fledge for each clutch (hatched - fledged = did not fledge) *
 pond: percent pond area (%) for each site year * crop: crop category for
 each site year (levels: 1 = non-crop; 2 = cereal-pulse; 3 = oilseed) *
 temp: daily maximum temperature (°C) averaged from days 2 to 12 post hatch
 #### File: C_McKeller_et_al_TRES_adult_body_mass_code.R
 **Description:** Code for adult body mass analysis #### File:
 C2_McKeller_et_al_TRES_adult_body_mass_data_n1523.csv
 **Description:** Data for adult body mass analysis ##### Variables *
 year: study year * site: study site * siteID: unique identification for
 each site * year_siteID: year and siteID combined as a variable *
 boxID: unique identification for each box * attempt: breeding attempt at
 the box * fws: band number of each nestling (if not banded, fws = NA or
 given a unique code) * individual_ID: unique identification for each adult
 * sex: sex of the adult (levels: F = female; M = male) * hatch: Julian
 hatch date for each clutch, where January 1 = 1 * relHatch: hatch date
 standardized so it reflects a clutch's relative hatching date within
 a season (e.g., 1, 2, 3...) * nestling_age: age of nestlings when adults
 measured, where hatch date = day 0 * mass: body mass (g) of each adult *
 pond: percent pond area (%) for each site year * crop: crop category for
 each site year (levels: 1 = non-crop; 2 = cereal-pulse; 3 = oilseed) *
 temp: daily maximum temperature (°C) averaged from the date adults were
 weighed plus 3 days before #### File:
 D_McKeller_et_al_TRES_nestling_body_mass_code.R **Description:** Code for
 nestling body mass analysis #### File:
 D2_McKellar_et_al_TRES_nestling_body_mass_data_n4220.csv
 **Description:** Code for nestling body mass analysis ##### Variables *
 year: study year * site: study site * siteID: unique identification for
 each site * year_siteID: year and siteID combined as a variable *
 boxID: unique identification for each box * attempt: breeding attempt at
 the box * fws: band number of each nestling (if not banded, fws = NA) *
 hatch: Julian hatch date for each clutch, where January 1 = 1 *
 relHatch: hatch date standardized so it reflects a clutch's relative
 hatching date within a season (e.g., 1, 2, 3...) * measure_age: age
 nestlings at which were measured, where hatch date = day 0 * mass: body
 mass (g) of each nestling * pond: percent pond area (%) for each site year
 * crop: crop category for each site year (levels: 1 = non-crop; 2 =
 cereal-pulse; 3 = oilseed) * temp: daily maximum temperature (°C) averaged
 from days 2 to 12 post hatch ## Code/software We used the program R
 version 4.5.0. (R Core Team 2025). Loaded packages used are listed in the
 R scripts, and package versions are provided in the text of the associated
 manuscript.