The abundance of red-cockaded woodpeckers (Leuconotopicus borealis, RCW), an endangered species endemic to fire-dependent pine forests of the Southeastern U.S., is limited by foraging habitat availability. Areas of foraging habitat are constructed and managed under recommendations provided in the federal RCW recovery plan. This plan describes high-quality foraging habitat as areas of open, mature pine containing an herbaceous understory and little to no midstory. Supporting evidence is currently lacking for the recommendation of an herbaceous understory, though some hypothesize that it may increase the abundance or diversity of arthropod prey consumed by RCWs. In this study, we estimated the biodiversity of arthropod prey on RCW foraging substrate and examined the following questions: 1) Are arthropod biodiversity indices correlated to vegetation structure within RCW foraging areas? 2) Is RCW fecundity linked to arthropod biodiversity indices? We modeled arthropod family abundance on pine tree boles (i.e., foraging substrate) as a function of covariates including vegetation metrics derived from LiDAR data and on-the-ground vegetation surveys. Concurrently, we collected data on RCW reproductive success metrics and estimated dietary composition via DNA metabarcoding of RCW fecal samples. These data populated a hierarchical model relating observed RCW reproductive success to prey availability at each nest site.
Results/Conclusions:
Our preliminary findings indicated that overall arthropod family diversity on foraging substrate was negatively correlated with the percent cover of lianas and positively correlated with the amount of hardwood basal area located within a 10 meter radius of the sampled substrate. For just families identified in RCW fecal samples (i.e., consumed arthropod families), percent cover of liana in the understory was negatively correlated with abundance on foraging substrate. Using stochastic search variable selection we determined that the abundances of both Blattodea and Lepidoptera and the abundance of Neuroptera on foraging substrate were moderately positively and negatively correlated to RCW clutch size, respectively. Similarly, both Blattodeans and Lepidopterans were observed in RCW fecal samples while Neuropterans were not observed. These findings suggest that RCWs may be selecting for certain prey taxa which are correlated to higher fecundity at our site. The magnitude of this effect, however, is not fully understood as this study did not account for RCW breeder age, another metric which influences fecundity. Our preliminary findings should promote future interest in elucidating links between foraging site structure, RCW diet, and RCW reproductive success, as well as provide insight into the efficacy of a novel approach for managing endangered species.