Geology topics

Meghan P. Keating

Publications and source records attributed to Meghan P. Keating.

2 recordsLinked to original sources

USGS2026

Wetland characteristics influence dabbling duckling habitat use and movements

The availability of inundated wetlands, near upland nesting habitats, during the brood-rearing period is critical to dabbling duck brood survival and population recruitment. Yet, in some breeding areas, wetland habitats often are drained or dry out during the waterfowl breeding season, which can limit the habitat available for ducklings. In a brackish marsh (Suisun Marsh, California, USA), we evaluated the specific types of wetlands selected by ducklings and quantified the habitat variables that affected wetland selection by dabbling duck hens and their broods from 2016 to 2019. Anas platyrhynchos (Mallard) and Mareca strepera (Gadwall) broods selected semi-permanent wetlands (flooded in the fall and winter and remained inundated until at least August 1) and avoided permanent wetlands (inundated year-round). Mareca strepera broods also selected summer flooded seasonal wetlands (flooded in the spring and summer and remained inundated through August). Anas platyrhynchos and M. strepera broods demonstrated selection for intermediate to larger sized wetlands, wetlands with lower salinity concentrations, and wetlands with intermediate levels of vegetation cover. Ducklings of both species moved rapidly away from the nest during the first week after hatch (mean distance from the nest for 5-day old ducklings: 0.8–1.4 km for the 4 study years), after which ducklings exhibited limited additional movement away from the nest (14-day old ducklings: 1.0–1.6 km among the 4 study years). Increasing the availability of semi-permanent wetlands and summer-flooded seasonal wetlands within 1.4 km of upland nesting sites could decrease the distance ducklings would need to travel to reach preferred wetland types. Decreased travel distance may reduce risk of duckling depredation and improve both duckling survival rates and population recruitment.

California↗

USGS2025

The American black bear (Ursus americanus) as an apex predator: Investigating the ecological role of the world’s most abundant large carnivore

Introduction American black bears ( Ursus americanus ) have been documented to have top-down effects, both consumptive (through predation) and nonconsumptive (through fear effects). However, their behavioural and dietary adaptability has led to uncertainty about the conditions under which these may occur. Objectives We aimed to (1) investigate when, where, and how often black bears influence lower trophic levels, and (2) critically assess the experimental design of such studies to determine trends and biases. Methods We conducted a systematic literature search and used linear mixed-effects models to assess the relationships among prey age class, the presence of other large carnivores, and the percentage of ungulate mortality due to black bears. We also summarised the measured effects of black bears on other carnivores and the results of any experimental studies. Results We found a strong negative relationship between puma presence and the percentage of ungulate mortality due to black bears, but only in areas with at least one other large carnivore (e.g., wolves). Among 16 studies of black bears' impacts on other carnivores, most documented negative behavioural effects. While only 5% of studies had strong experimental design, bear removal consistently increased juvenile ungulate survival. Discussion and Synthesis Our findings highlight black bears' strong top-down effects, resembling or exceeding those of other large carnivores. These effects were greatest when no other large carnivores were present, but as highly effective kleptoparasites, black bears can alter the feeding habits of other large carnivores. Thus, we argue that ‘apex’ is a conditional state, not a species-wide status.

Mammal Review↗