BACKGROUND Territory owners usually defeat intruders. One explanation for this observation is the uncorrelated asymmetry hypothesis which argues that contests might be settled by an arbitrary convention such as "owners win." We studied the effect of territorial residency on contest asymmetries in the white-eared hummingbird (Hylocharis leucotis) in a fir forest from central Mexico. METHODS Tw...

For birds, plumage color perception is critical in social interactions such as courtship, in both monochromatic and dichromatic species. In the Eared Dove (Zenaida auriculata), perhaps the most abundant South American Columbiforme, the plumage of males and females looks alike and both sexes share the same melanistic coloration with gray and pink tones. The aim of this study was therefore to det...

AB=RA~T.-Rafinesque's bii-eared bats (Corynmhinus ra-t] use bridges as day roosts in parts of their range, but information on bridge use across their range is lacking. From May to Aug. 2002 we surveyed 1129 bridges (12.5%) within all 46 counties of South Carolina to determine use and selection of bridges as day roosts by big-eared bats and to document their distribution across the state. During...

Prior to this study the circumscription of the endangered black-eared miner (Manorina melanotis) and the common yellow-throated miner (Manorina ¯avigula) has been clouded by the existence of hybrid individuals. We examined the intra-and inter-speci®c phenotypic variation of the two taxa. All available museum specimens (n=138) and a sample of live individuals (n=83) were examined. Cluster analys...

Habitat degradation and species introductions are two of the leading causes of species declines on a global scale. Invasive species negatively impact native species through predation and competition for limited resources. The impacts of invasive species may be increased in habitats where habitat degradation is higher due to reductions of prey abundance and distribution. Using stable isotope ana...

Abstract Acetylcholinesterase (AChE) activity levels can be used as an indicator for AChE inhibition due to pesticide poisoning in bird species. We assessed the comparative brain cholinesterase level of five species inhabiting exposed croplands and Protected Area i.e. Deva Vatala National Park (DVNP), Bhimber by using a spectrophotometric method. ranged from 56.3 85.9 µmol/min/g tissue birds re...