DOI: 10.5061/dryad.1jwstqjxd
title: Seaside Sparrow nest location, fate, and nest predator distribution data

description: Nest failure for coastal marsh bird species is primarily caused by
 predation and nest flooding. As sea level rise makes nest flooding more
 likely, the threat of nest predation will constrain the potential adaptive
 responses of marsh nesting species. Thus, understanding the predictors of
 nest predation is important for the conservation of salt marsh-dwelling
 bird species, such as Seaside Sparrows (Ammospiza maritima; SESP).
 Predator activity may be influenced by landscape features (particularly
 habitat edges), potentially making nest predation predictable. We aimed to
 understand the predictability of SESP nest predation relative to two major
 landscape features: roads and tidal rivers, as both of these edges may be
 entryways or attractants for predators in  marshes. In coastal
 Georgia, USA, we assessed mammalian predator activity relative to the two
 features of interest, and hypothesized that mammalian predator activity
 would be greater close to roads and tidal rivers. We also recorded SESP
 nest locations and nest predation events and hypothesized that nest
 predation events would increase with increasing predator activity.
 Consistent with our first hypothesis, mammalian predator activity
 increased close to roads and tidal rivers, but mammalian predator
 distribution did not explain the spatial variation in SESP nest predation
 thus not supporting our second hypothesis. SESP also placed their nests in
 locations with high mammalian predator activity, indicating that the
 ability to avoid nesting in high-risk areas may be constrained by habitat
 or resource limitations. Additionally, mammals may not be the primary nest
 predators, as we found that one bird species (Marsh Wren, Cistothorus
 palustris) contributed substantially to nest predation rates.
 Understanding the predictability of mammalian predator distribution can
 allow for focused predator management efforts, such as exclusion, to
 habitat edges where we found the highest mammalian predator activity,
 which could relax the constraint of nest predation on SESP’s ability to
 respond to the intensifying threat of sea level rise.
description: Camera trapping for mammalian predators: Camera traps units were
 a modified version of the Hunt trap design outlined in a study by McCleery
 et al. (2014). We modified the Hunt trap design to be pointed toward the
 ground, but positioned higher above the ground to prevent damage from
 inundation during high tides and to avoid filling up camera trap memory
 cards with images of moving grass. We affixed the cameras to the inside of
 upside-down 26.5 L buckets, and each bucket was held above the ground by
 four 3 m PVC poles (Figure 2). Because of the small range of vision of
 each camera due to their orientation, we attached cotton balls soaked in
 sardine juice to each PVC pole to encourage any mammalian predators near
 the camera trap to walk under the bucket. The cotton balls were refreshed
 with sardine juice every two weeks.  When mammalian predators appeared on
 the camera trap, we recorded the species, time, and date. Two consecutive
 camera trap appearances by the same species were marked separately only
 when there were 2 or more minutes between camera triggers (only 4% of
 detections were &lt; 10 minutes apart, and only 11% were &lt; 30
 minutes apart). To account for differences in the number of days that each
 camera trap recorded data, we standardized counts by dividing the number
 of recorded predator occurrences on each camera trap by the number of days
 that the camera trap was active, and multiplied that value by the number
 of recording days for the longest-running camera trap: S = [X/D]* 92;
 where S is the standardized number of detections at a given camera, X is
 the number of predator detections at that camera, D is the number of days
 the camera trap was active, and 92 is the number of days the longest
 running camera was active.   Nest
 monitoring: We searched for nests every 4-5 days in May-July using the
 protocol outlined by Hunter et al. (2016). We placed iButtons (Thermochron
 iButton DS1921G, Maxim Integrated Products, San Diego, CA, U.S.A.)  inside
 the nests to record nest temperature every 20 minutes for as long as the
 nests were active, using the protocol from Hunter et al. (2016). This
 enabled us to determine nest fate and estimate the date and time of nest
 failure, because nest temperature destabilized upon nest failure due to
 the lack of incubation (Hunter et al. 2016). We visually checked active
 nests every 4-5 days for predation activity. In the absence of a nest
 video camera (see below), we determined the cause of nest failure by
 comparing the time of destabilized nest temperature (failure) with the
 timing of extremely high tides, such as spring tides that occur every 14
 days. We used tidal gauge data from the Fort Pulaski NOAA station
 (http://tidesandcurrents.noaa.gov/), approximately 100 km from our sites,
 to assign the maximum tidal height in meters above mean sea level to each
 nest during that nest's period of observation (from date found to
 date of fledging or failure). If there was no spring tide (or other
 extremely high tide due to a storm) within 1 hour of nest failure, we
 attributed the nest failure to predation. During April-July 2019 and 2020,
 we equipped a subset of nests with a video monitoring system (Hart et al.
 2021) to continuously record nest activity until the nest fledged or
 failed. Video recording enabled identification of nest predator species
 and validation of nest fate assignment using iButton data. For each video
 monitoring unit, we used a security camera connected to a digital video
 recorder (DVR), which was located inside of a waterproof case along with a
 25-volt battery to power both the camera and DVR. Each camera was affixed
 to a garden pole and placed directly above the nest. The wires connecting
 the camera to the DVR were waterproofed using electrical tape and marine
 epoxy and were approximately 6 m in length, allowing the DVR to be kept
 away from the nest. This recording system has also been used successfully
 for monitoring Seaside Sparrows in Gulf coast marshes, and did not
 increase the risk of nest predation for video-monitored nests (Hart et al.
 2021). 
description: .csv files can be opened with any text editor.