While an extensive literature exists on the negative effects of invasive species, little is known about their facilitative effects on native species, particularly the role of invasives as trophic subsidies to native predators. The invasive gypsy moth (Lymantria dispar) undergoes periodic outbreaks during which it represents a super-abundant food source for predators capable of consuming it, particularly native cuckoos (Coccyzus erythropthalmus and C. americanus). We examined how gypsy moth outbreaks affect the abundance and distribution of cuckoos using the North American Breeding Bird Survey and 29 years of U.S. Forest Service gypsy moth defoliation records. Abundances of both Black-billed and Yellow-billed Cuckoos were significantly above average during outbreaks, but populations were average or below average in preceding and subsequent years, suggesting that cuckoos are immigrating to defoliations during outbreak years. Spatial analyses showed that cuckoo abundances approximately 40-150 km outside of defoliation areas were significantly below average, and these under-occupied breeding areas extended in all four compass directions around outbreaks. This result supports the idea that cuckoos locate gypsy moth outbreaks during a post-migratory nomadic phase. By shifting the annual distribution of cuckoos, gypsy moths may be shifting the trophic impact of cuckoos across large distances, which could affect native insect herbivores and plants.

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Environmental correlates and geographic spacing of leks were compared for six species of manakins (Pipridae) on two 100-ha study plots in eastern Ecuador. The “hotspot” hypothesis of lek evolution suggests that males should aggregate where females are most likely to be encountered. For ecologically similar species that co-occur at a site, leks are predicted to be clustered in space and, thus, to overlap in macroscale environmental characteristics. The geographic spacing and environmental characteristics of lek sites we observed were inconsistent with the hotspot hypothesis for lek evolution. In general, little geographic overlap occurred among leks, and geographic spacing of leks among heterospecifics more closely fit a regular than a clumped pattern. Further, environmental conditions of leks varied among species with respect to elevation and topography. Leks of some species were more likely to occur on hilltops or ridge tops (e.g., Machaeropterus regulus, Pipra erythrocephala), whereas others appeared to prefer highly dissected drainages (e.g., P. pipra), relatively flat terrain near streams (e.g., Chiroxiphia pareola), or seasonally inundated forests (e.g., P. filicauda). Using randomly placed leks, we found evidence that certain lek environments may be limited, which is consistent with observed levels of population abundances on the two plots. Such environmental limits may constrain lek placement and size. Further study is needed to determine the reproductive implications of placing leks in apparently suboptimal environments, though such compromises may reflect males making the best of a bad situation.Segregación Ambiental y Espacial de las Asambleas de Cortejo Entre Seis Especies Simpátricas de Saltarines (Pipridae) en el Oriente de Ecuador

Estimates of reproductive success are essential to understand life-history strategies, yet tropical species remain understudied relative to their temperate counterparts. Here, we report nest survival probabilities for two manakin species (Pipridae). We monitored 61 wire-tailed manakin Pipra filicauda and 45 blue-crowned manakin Lepidothrix coronata nests during three breeding seasons. Both species suffered high nest failure (84%). We modeled the effects of year, nest height, nest age (for P. filicauda only), as well as nest manipulation on daily survival rates (DSR) using program MARK. DSR decreased with nest age in P. filicauda whereas a constant survival model was best fitted for L. coronata. Average DSR was 89% for P. filicauda and 85% for L. coronata. This study reports some of the lowest nest survival rates among tropical passerines and poses important questions about population maintenance.

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