Abstract Forest ecosystems are threatened by a suite of factors including altered disturbance regimes, historic and modern harvest, invasive species, and climate change. In the face of these threats, seed dispersal is a crucial ecosystem service for maintaining forest integrity and resilience. Further, understanding the ecology and habitat needs of keystone seed dispersers at landscape scales is important for conservation planning. We used passive acoustic monitoring to investigate the ecology of a nomadic keystone seed disperser, Nucifraga columbiana (Clark’s nutcracker), at low- and mid-elevation conifer forests May 20 to July 12 of 2021, 2022, and 2023 across 25,000 km2 of the Sierra Nevada in California, United States. In particular, we aimed to understand how nutcracker occupancy dynamics were associated with coverage of conifers with different seed size classes—small: Douglas-fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta); medium: Jeffrey and ponderosa pines (P. jeffreyi and P. ponderosa); large: sugar pine (P. lambertiana)—fire age and severity, and topography (elevation and local slope). We also assessed evidence for changes in occupancy rates across the three years of the study. Occupancy in the beginning of each annual sampling period was negatively associated with coverage of sugar pines, while site colonization was positively associated with elevation and negatively associated with recent high-severity fire, as well as local slope and coverage of medium and large-seeded pines. Additionally, occupancy increased in 2022, compared to 2021 and 2023, despite highly destructive fire seasons in the late summer/fall of 2021. The nutcracker’s nomadic behavior may buffer it from the effects of high-severity wildfire, at least in the short term. Nutcrackers are mostly studied in the context of their mutualism with the threatened whitebark pine (P. albicaulis), but our work provides much needed insights into their habitat use at low- and mid-elevation sites where they are important seed dispersers for other pines, and suggests a possible means of persistence despite fire-induced loss of habitat.
Erickson-Harris et al. (Fri,) studied this question.