We developed a demographic model to perform a population viability analysis (PVA) of the Blue-throated Macaw (Ara glaucogularis), a critically endangered species endemic to Bolivia. PVA simulations were run using individualbased (VORTEX 9.72) and cohort-based (RAMAS GIS 4.0) programs. A baseline simulation allowed for the assessment of the status of the species based on estimates of extinction ...

EFFECTIVE CONSERVATION AND MANAGEMENT of migratory bird species requires an understanding of when and how their populations are limited and regulated. From 1986 to 1999, we studied the processes that determine the abundance of a temperate-tropical migrant passerine, the Black-throated Blue Warbler (Dendroica caerulescens), during the breeding portion of its annual cycle. We found that young fle...

In the polymorphic white-throated sparrow (Zonotrichia albicollis), tan-striped males provision nestlings at higher rates than do white-striped males. In a previous study, we found that tan-striped males had lower baseline corticosterone levels than white-striped males during the nestling stage. To determine if this variation in corticosterone influences morph-specific differences in nestling p...

—Phenological patterns in birds appear to be temperature-dependent in part, and global temperatures are undergoing change. Many studies of bird phenology are conducted at broad temporal but local spatial scales, making it difficult to assess how temperature affects bird migration across landscapes. Recently, networks of “citizen science” volunteers have emerged whose collective efforts may impr...

Groups of the photosensitive female yellow-throated sparrow were placed under various light-dark cycles, in which a fixed ultrashort photophase of 3 h was combined with dark phases of varying duration, resulting in cycles of 18-30 h. Simultaneously, two groups of birds, one in short days (8L/16D) and the other in long days (15L/9D), were kept as controls. Significant ovarian growth, observed at...