Search

Sea-level rise (SLR) threatens the nesting success of salt marsh breeding birds, Including Seaside Sparrows (Ammodramus maritimus), by Increasing the magnitude and frequency of extreme high tides that flood nests. However, the threat to nesting success from tidal flooding Is Intertwined with that of predation because the threats are connected through a trade-off along a nest height gradient. Therefore, to understand the risk to nesting success from SLR, It Is necessary to consider predation threats simultaneously. I used an Individual-based model of Seaside Sparrow nesting behavior, calibrated using empirical data on nest success rates and nest-site selection behaviors, to project the effects of SLR conditions on the relative Importance of predation and flooding threats In affecting nesting success, and to Investigate whether nest-site selection along a gradient of nest height can modulate the risk of SLR. Outputs from the model revealed that present-day levels of predation risk pose as great a risk to nesting success as tidal flooding under simulated SLR conditions with extreme flooding risks. Nest success rates could become very low under extreme SLR scenarios, especially when predation risk Is very high. The risks of failure from either threat are linked through nest-slte selection behaviors; In hlgh-predatlon-rlsk seasons, failure probability from flooding Is greater than It would be under lower predation risk, due to the predation avoidance behavior of nesting closer to the ground. Therefore, management actions to reduce the risk of excessive failures from predation could reduce the risk of failures from both threats--a potentially useful management strategy, given that controlling predation Is more tractable than controlling Increased flooding from SLR at a local level. [ABSTRACT FROM AUTHOR]

Habitat selection trade-offs between avoiding predation and gaining energy are well studied, but similar trade-offs resulting from multiple threats to survival remain poorly understood. We studied how seaside sparrows, Ammodramus maritimus , approach nest site selection decisions to avoid threats to nesting success from predation and tidal flooding. Along a nest height gradient, nest site selection to avoid tidal flooding (i.e. placing nests higher) may make seaside sparrow nests more vulnerable to predation, and selection to avoid predation may make nests susceptible to flooding. We monitored nesting success rates and nest site selection decisions of breeding seaside sparrow pairs at five sites near Brunswick, Georgia in April–July of 2013–2015. We found that seaside sparrows encountered a nest site selection trade-off along a gradient of nest height. Nest height had an effect on survival probability during each of our study years, with positive effects of nest height on predation probability and negative effects of nest height on flooding probability observed in some years. Sparrows dealt with this trade-off by altering their nest site selection in relation to a threat's predictability; low within-season variability in predation risk and high information about predator presence in open marshes make predation risk more predictable than the magnitude of tidal flooding, which is governed by unpredictable and variable winds. Sparrows responded to predictable predation threats by nesting at lower nest heights in years with higher predation risk, but sparrows responded to unpredictable flooding threats by placing nests higher off the ground but only following nest failure from flooding. Understanding decision making through a lens of threat predictability could provide a useful approach for studies of other animals' habitat selection trade-offs. [ABSTRACT FROM AUTHOR]

We document the first recorded instance of a fish depredating a hatchling bird while in the nest. Some coastal marsh-nesting avian species, such as the Seaside Sparrow (Ammospiza maritima), experience tradeoffs between the threat of nest predation and nest flooding. Nesting too low may result in nest flooding during the twice-daily high tides and increasing nest height increases the risk of nest predation. However, not much is known about how nest height affects exposure to different predators. We observed a mummichog (Fundulus heteroclitus) enter a Seaside Sparrow nest during a nest flooding event and depredate a hatchling. This observation expands our understanding of the predator–prey relationships experienced by coastal marsh-nesting birds, and the potential detriments of intensifying sea level rise on their nesting success. [ABSTRACT FROM AUTHOR]

Both biotic and abiotic factors can affect whether seagrass meadows establish as large, continuous features or as a mosaic of smaller patches, and these processes act across multiple spatial scales. Of these processes, sexual recruitment is considered vital for the recovery and resilience of seagrass meadows. Because numerous estuarine fauna can impact sexual recruitment by consuming seeds, it is important to understand variation in seed consumption throughout the seascape.We sought to determine how cross‐scale processes affected seed consumption of Zosteramarina, a widely distributed seagrass species. We deployed seed predation units (SPU) within patches ranging in size from 0.28 to 28.48 m2, and on unvegetated, sandy bottom. Seed consumption was analysed across patch sizes, at patch centres and edges and within the context of total seagrass cover within buffer zones surrounding SPU locations.Using structural equation modelling, we found that measured seascape parameters explained 34% of the observed variation in seed consumption. Specifically, we found that seagrass presence had the strongest effect on seed predation followed by a negative effect of patch size on seed consumption. Although there was no direct effect of percent seagrass cover (within a 4‐m buffer of the SPU) on seed predation, percent seagrass cover had a negative indirect effect through its positive correlation with patch size. However, we found that once variation due to patch size and areal cover were accounted for, seeds placed at patch interiors actually experienced greater consumption rates. We did not find similar relationships with our potential seed consumers, although our snapshot sampling likely obscured transient effects.We argue that seagrass recruitment could be affected by seed predation, which is influenced by multiple processes, including predator dispersal, behaviour and aggregation. Since seed‐based restoration is becoming more common, and the role of sexual recruitment in meadow maintenance appears to be increasingly important for seagrass resilience, our results demonstrate that for current management strategies to be successful, there is a need to better understand seed predation in seagrass‐dominated seascapes.Synthesis. Factors that influence propagule supply and recruitment success of seagrass operate and interact across multiple spatial scales, which can have implications for management. [ABSTRACT FROM AUTHOR]