Red‐winged Blackbirds (RWBL; Agelaius phoeniceus) have a polygynous mating system and, because territorial males commonly have harems of two to five females, some second‐year (SY) and after‐second‐year (ASY) males do not establish nesting territories, but become floaters. Previous studies have revealed high rates of extra‐pair copulations in this species and that sexually mature male floaters and territory owners do not differ in size, testosterone levels, or reproductive capability, suggesting that floaters may occasionally gain paternity. During May and June 2008, we observed the behavioral responses of floater males to taxidermic mounts (models) of female RWBL placed in a precopulatory position. Floaters intruded into territories during 46% of model presentations, with 20% of intrusions by ASY floaters and 80% by SY floaters. During intrusions, ASY floaters attempted to copulate with models 93% of the time compared to 80% for SY floaters. Copulations were successful during 30% of attempts by ASY males and 25% of attempts by SY floaters. The frequency of intrusions by ASY and SY floaters, attempted copulations by SY floaters, and successful copulations by ASY floaters increased as territorial males spent more time off their territories. Responses of floater males toward models in our study suggest that floater male RWBL attempt to exploit available breeding opportunities. The lack of evidence for extrapair young (EPY) fathered by floater male RWBL in previous studies, combined with our results indicating that the presence of territorial males limits floater intrusions, copulation attempts, and successful copulations, suggests that the reproductive success of floater males is limited in part by the aggressive behavior of territorial males.

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Oaks (Quercus spp.) are currently declining worldwide due to a multitude of threats. Woodland management is often heavily focused on thinning and burning nontarget species to reduce competition and promote oak dominance in the overstory. These techniques have typically been developed in temperate regions, such as eastern U.S. forests, but whether they are the most effective strategy for promoting oak regeneration in semiarid woodlands has not been sufficiently examined. We conducted our study on the eastern Edwards Plateau in central Texas, where several oak species are codominant with Ashe juniper (Juniperus ashei) over karst limestone terrane. These juniper‐oak woodlands provide habitat for many endemic species and play an essential role in the maintenance of key aquifers. A history of canopy clearing and a severe drought in 2011 generated patches of living and dead juniper‐oak canopy interspersed with canopy gaps in our study area. In November 2013, we planted 200 shin oak (Quercus sinuata var. breviloba) acorns in each of three habitat treatments, replicated six times: (1) live canopy, (2) dead canopy, and (3) open invasive grassland. We monitored emergence and survival each year, harvesting five seedlings from each replicate in October 2017 to assess shoot height, rooting depth, biomass, ectomycorrhizal colonization, and foliar nutrients. Canopy trees, living or dead, significantly enhanced seedling emergence and survival. Survival was positively associated with increasing Ashe juniper and oak basal area, shrub cover, and soil organic matter, and negatively associated with increasing canopy gap size (complete mortality in gaps >220 m2). Seedling biomass increased significantly in dead and open treatments along with foliar nutrients N, P, and S (dead treatments) or S and Fe (open treatments), whereas ectomycorrhizal colonization and foliar nutrients Ca, Mg, and Mn increased under living canopy. Our findings suggest that oak regeneration in these juniper‐oak woodlands closely resembles that of Mediterranean regions, where canopy facilitates seedling survival. Both living and dead trees and shrubs enhanced oak regeneration, with seedling survival depending on proximity to larger trees, living roots, shrubs, and juniper‐oak canopy. Planting acorns under canopy is an inexpensive, sustainable, and effective restoration practice in drought‐prone ecosystems.

We examined beterozygosity at bypervariable microsatellite loci and blood parasite presence-absence in five populations of Golden-winged Warblers {Vermivora chrysoptera) tbat span tbe species' Canadian range. All populations were predominantly composed of genetically pure individuals, witb small proportions of pbenotypic and genetic bybrids. By comparing beterozygosity and infection status in concert, we tested wbether more-heterozygous individuals bave lower parasite prevalence, perbaps because tbey possess a more robust immune system. By considering tbe genetic status (pure vs. bybrid) of individuals in relation to infection by parasites and beterozygosity, we build on existing researcb tbat examines tbe effect of Blue-winged Warbler {V. cyanoptera) hybridization on Golden-winged Warbler populations. Finally, by looking at populations across tbe east-west range of tbe species, we could bypotbesize what role geographic variation in vectors might play in population-level infection rates. We found no difference in infection probability between pure and bybrid individuals, but a greater frequency of infection in populations in the western portion of tbe range. Our results add to tbe growing evidence tbat bybrids in this system do not face postzygotic selection, and tbat Golden-winged Warblers breeding in the most northwestern extent of their range may face challenges that could impede their conservation. Ongoing work that compares reproductive success of Ontario and Manitoba populations is likely to add an important dimension to our findings and could furtber inform conservation efforts for tbe species. Infección por Parásitos Sanguineos y Heterocigosidad en Lineas Genéticamente Puras e Híbridas deVermivora chrysoptera en Canadá RESUMEN.-Examinamos la beterocigosidad en loci microsatelitales bipervariables y la presencia/ausencia de parásitos en la sangre de cinco poblaciones de Vermivora chrysoptera a lo largo del área de distribución de la especie en Canadá. Todas las poblaciones estuvieron compuestas predominantemente por individuos genéticamente puros, con pequeñas proporciones de bíbridos genotípicos y morfológicos. Mediante la comparación de la heterocigosidad con el estado de infección, evaluamos si los individuos más heterocigotos tienen menor prevalencia de parásitos, tal vez debido a que poseen un sistema inmune más robusto. Al considerar el estado genético (puro vs. bíbrido) de los individuos en relación con la infección parasitaria y la beterocigosidad, aprovecbamos las investigaciones ya existentes sobre el efecto de la bibridación con V. cyanoptera en las poblaciones de V. chrysoptera. Finalmente, mediante el análisis de poblaciones localizadas a lo largo del sector oriente-occidente de la distribución de esta especie, podemos proponer bipótesis sobre cuál es el efecto que puede tener la variación geográfica de los vectores sobre las tasas de infección especificas de cada población. No encontramos diferencias en la probabilidad de infección entre individuos puros e bibridos, pero si una mayor frecuenc...