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Cross‐ecosystem subsidies move substantial amounts of nutrients between ecosystems. Emergent aquatic insects are a particularly important prey source for riparian songbirds but may also move aquatic contaminants, such as mercury (Hg), to riparian food webs. While many studies focus on species that eat primarily emergent aquatic insects, we instead study riparian songbirds with flexible foraging strategies, exploiting both aquatic and terrestrial prey sources. The goal in this study is to trace reliance on aquatic prey sources and correlate it to Hg concentrations in common riparian arachnids (Families Tetragnathidae, Opiliones, and Salticidae) and songbirds (Common Yellowthroat Geothlypis trichas, Spotted Towhee Pipilo maculatus, Swainson's Thrush Catharus ustulatus, Song Sparrow Melospiza melodia, and Yellow Warbler Setophaga petechia). We used stable isotopes of δ13C and δ15N and Bayesian mixing models in MixSIAR to determine the reliance of riparian predators on aquatic prey sources. Using mixed effects models, we found that arachnid families varied in their reliance on aquatic prey sources. While songbird species varied in their reliance on aquatic prey sources, songbirds sampled earlier in the season consistently relied more on aquatic prey sources than those sampled later in the season. For both arachnids and songbirds, we found a positive correlation between the amount of the aquatic prey source in their diet and their Hg concentrations. While the seasonal pulse of aquatic prey to terrestrial ecosystems is an important source of nutrients to riparian species, our results show that aquatic prey sources are linked with higher Hg exposure. For songbirds, reliance on aquatic prey sources early in the breeding season (and subsequent higher Hg exposure) coincides with timing of egg laying and development, both of which may be impacted by Hg exposure., To understand how exploiting emergent aquatic prey sources could also expose the riparian community to aquatic‐based contaminants, we used stable isotopes of δ13C and δ15N in a MixSIAR Bayesian mixing model to trace emergent aquatic prey in riparian predators (songbirds and arachnids). We determined that individual reliance on aquatic prey was positively correlated with mercury exposure, with songbirds relying more in aquatic prey early in the season. Our results show the seasonal pulse of aquatic prey to terrestrial ecosystems is likely an important source of nutrients to riparian species but may also drive season‐dependent exposure to aquatic contaminants.

Parental care in birds varies among species and geographic regions. Incubation behavior influences embryonic development rate and varies substantially among species.We studied attendance at the nest by videoing nests or collecting data from the literature for 112 species in north temperate and lowland tropical sites, then associated patterns of incubation on‐ and off‐bouts with species and environmental traits.Songbirds nesting at low elevations incubate their eggs for an average of 74.1% (±12.9 SD, n = 60 species) of the time in temperate regions and 71.0% (±12.2 SD, n = 52 species) in tropical regions during daylight hours, and 84.3% (±8.2 SD) and 85.3% (±6.2 SD), respectively, of each 24‐hr cycle.While these attendance percentages do not differ significantly between latitudes, our data also show that lowland tropical songbirds make fewer visits to the nest and, consequently, have longer on‐bouts and off‐bouts during incubation. This pattern in attendance reflects a latitudinal contrast in parental care strategy, where lowland tropical birds reduce visits to the nest by increasing on‐ and off‐bout lengths while maintaining the same proportion of time spent incubating their eggs (constancy).Similar constancy across latitude suggests that tropical and temperate birds may be similarly constrained to maintain elevated egg temperatures for normal embryo growth.The different attendance strategies adopted in each region may reflect differences in ambient temperature, adult foraging time, and nest predation rate. Consistently warm ambient temperatures likely allow tropical birds to take longer off‐bouts, and thereby to reduce activity around the nest, compared to temperate birds., We compared avian attendance data during incubation of 112 New World temperate and tropical passerine species. The amount of time that parents incubated their eggs did not differ between regions, but tropical birds employed a different attendance strategy. Tropical parents spent longer periods of time on and off of the eggs, made fewer trips to the nest, but incubated for the same percentage of time.