DOI: 10.5061/dryad.6q573n64f
title: Data from: Nonbreeding season survival of northern bobwhite in northeastern Colorado

description: Northern bobwhites have experienced population declines in Colorado and
 range-wide. Estimating vital rates can provide clues to factors limiting
 population growth rate. Although recent estimates of breeding season
 survival in the northwest corner of the northern bobwhite range are
 available, there have been no recent studies on nonbreeding season
 survival. We used radio-telemetry to estimate nonbreeding season (Oct–Mar)
 survival of northern bobwhites at two study sites in northeastern Colorado
 during winter 2019–2020 and 2020–2021. Based on our sample of 157
 bobwhites, we found that survival was highly variable between years and
 was negatively affected by colder daily minimum temperatures and deeper
 snow depths. Seasonal (6-month) survival during the first year was
 0.219 (SE = 0.040) and during the second year was 0.006 (SE =
 0.005). We found no evidence that sex, age, or study site influenced
 survival, and very weak support for an effect of body mass. During our
 study, there were two extreme winter weather events, during which we found
 unusually high numbers of non-predation mortality. Overall, northern
 bobwhite nonbreeding season survival in the northwest corner of their
 range appears to be generally similar to other regions, except during
 extreme winter weather events, which resulted in high mortality. We
 encourage managers to create or maintain vegetation characteristics that
 will provide shelter from winter weather while also providing abundant
 food in close proximity.
description: Capture and marking We trapped bobwhites
 using baited walk-in traps (Stoddard 1931, Smith et al. 1981, Behney et
 al. 2020) from 6 September until 17 October 2019 at 288 trap locations,
 and 1 September to 23 October 2020 at 493 trap locations on Tamarack SWA
 and Dune Ridge SWA. Trap locations were spread throughout each property to
 achieve representation of all areas of the properties. Traps were moved if
 areas became saturated with radio-marked bobwhites or if no bobwhites were
 being caught. During the second season, we also used targeted
 night-lighting, where we tracked previously radio-marked birds at night to
 locate coveys and used spotlights and a hoop net to capture untagged
 birds. Bobwhites were affixed with ≤ 6.5-g
 necklace-style VHF radio transmitters equipped with an 8-hour mortality
 sensor (American Wildlife Enterprises, Monticello, FL), which have been
 used frequently for bobwhites (Burger et al. 1995, DeMaso et al. 1997,
 Taylor et al. 1999). We did not deploy transmitters on quail weighing less
 than 130 g to keep the transmitter mass less than 5% of the bird’s body
 mass. These transmitters have been reported to not affect survival on
 bobwhites when making up &lt;5% of individuals’ mass (Palmer and
 Wellendorf 2007, Terhune et al. 2007, Wann et al. 2020). We captured 25
 birds in year one and three birds in year two that were deemed lighter
 than the allowable weight to be fitted with transmitters. All captured
 bobwhites received a numbered aluminum leg band (National Band &
 Tag Company, Newport, Kentucky, USA) and were weighed using a Pesola 300 g
 spring scale. Sex and age (subadult: hatched previous breeding season,
 adult: hatched prior to previous breeding season) were determined based on
 plumage. After processing, birds were released at the site of capture. All
 trapping, handling, and marking procedures were consistent with the
 guidelines of the University of Nebraska, Institutional Animal Care and
 Use Committee (Project ID #1844). Survival
 monitoring We attempted to assess status (live or
 dead) of all radio-marked bobwhites four or five times each week from
 October – March. When the transmitter’s mortality sensor indicated a dead
 bird, we retrieved the transmitter and assessed cause of mortality (i.e.,
 mammal, avian, hunter cripple, etc.). In the event a bird was no longer
 able to be detected, we extensively searched the site and continued to
 monitor for it until the end of the season.
 Statistical analysis Deaths determined to be
 caused by the radio-collar (n=1) were excluded from analysis. We defined
 the nonbreeding season as a 6-month period (26 weeks) from 1 October to 31
 March based on our observations during previous research of when nesting
 behaviors began and ended. We limited our analysis to birds alive at the
 start of the nonbreeding season (1 October) and censored birds after they
 went missing from the site or transmitters were believed to be no longer
 functional. We used the RMark package (Laake 2013) in R (R Core Team 2023)
 to construct known fate models for program MARK (White and Burnham 1999)
 to estimate and assess variation in weekly survival. We included year,
 study site, age, sex, body mass at capture, weekly mean of daily minimum
 temperatures, and weekly mean snow depth as predictor variables. We used
 Akaike’s Information Criterion corrected for sample size (AICc) to rank
 the models (Burnham and Anderson 2002). We began by comparing
 single-variable models including individual-specific predictors (age, sex,
 year, site, and mass). We then combined variables that appeared in a model
 that performed better than the null model (lower
 AIC<sub>c</sub>) with weather variables (minimum temperature
 and snow depth). Minimum temperature and snow depth were correlated
 (<em>r</em> = -0.6), so we did not include them in the same
 model. The two winters during our study had very different weather
 conditions, so we included year (1: 2019–2020 and 2: 2020–2021) in
 interactive relationships with the weather variables. We also included
 mass in interactions with weather variables because lighter individuals
 may be more sensitive to harsh weather than heavier individuals. Variables
 appearing in interactions were also included as main effects.
description: # Data from: Nonbreeding Season Survival of Northern Bobwhite in
 Northeastern Colorado
 [https://doi.org/10.5061/dryad.6q573n64f](https://doi.org/10.5061/dryad.6q573n64f) These data are encounter histories of radio-marked northern bobwhites. ## Description of the data and file structure "Quail Locations Winter 2019.inp" and "Quail 2020 Survival.inp" are the encounter history files for bobwhites during the winter of 2019-2020 and 2020-2021, respectively. Columns are bird id, encounter history, number of birds this row represents, sex, age, mass at capture (g), and study site.