Variations in ambient light conditions across different microhabitats can modify the detectability of predators and prey. Prey have been shown to be more visible in sunlit than in shaded patches, leading to higher predation risk and more investment in vigilance (predation risk hypothesis). Additionally, prey have been hypothesized to take longer to detect predators in sunlit compared to shaded patches because of the excess of sunlight causing glare effects (disability glare hypothesis). We tested the predictions of these two non‐mutually exclusive hypotheses in a seminatural experiment with brown‐headed cowbirds by measuring vigilance behavior and detection of a ground predator in patches under the shade of vegetation and in the open. Light intensity and achromatic contrast were higher in the sunlit patches, which could enhance glare effects, but chromatic contrast was higher in the shaded patches. Brown‐headed cowbirds took longer to show alert reactions to and flee from a ground predator in sunlit compared to shaded patches. However, the two parameters associated with perceived predation risk (vigilance prior to the predator exposure and time to resume foraging after the attack) did not differ between sunlit and shaded patches. Our findings support to a greater extent the disability glare hypothesis than the predation risk hypothesis. Overall, ambient light conditions can affect two critical components of behavioral predator–prey interactions in terrestrial habitats: detection of and escape from predators. The effects of disability glare are expected to be more pronounced in bird species with wider visual fields or without sun‐shading structures; however, species may compensate through various behaviors (e.g. avoidance of sunlit patches and changes in head orientation).

BackgroundMale and female avian brood parasites are subject to different selection pressures: males compete for mates but do not provide parental care or territories and only females locate hosts to lay eggs. This sex difference may affect brain architecture in some avian brood parasites, but relatively little is known about their sensory systems and behaviors used to obtain sensory information. Our goal was to study the visual resolution and visual information gathering behavior (i.e., scanning) of brown-headed cowbirds.Methodology/Principal FindingsWe measured the density of single cone photoreceptors, associated with chromatic vision, and double cone photoreceptors, associated with motion detection and achromatic vision. We also measured head movement rates, as indicators of visual information gathering behavior, when exposed to an object. We found that females had significantly lower density of single and double cones than males around the fovea and in the periphery of the retina. Additionally, females had significantly higher head-movement rates than males.ConclusionsOverall, we suggest that female cowbirds have lower chromatic and achromatic visual resolution than males (without sex differences in visual contrast perception). Females might compensate for the lower visual resolution by gazing alternatively with both foveae in quicker succession than males, increasing their head movement rates. However, other physiological factors may have influenced the behavioral differences observed. Our results bring up relevant questions about the sensory basis of sex differences in behavior. One possibility is that female and male cowbirds differentially allocate costly sensory resources, as a recent study found that females actually have greater auditory resolution than males.

When Ms. was first introduced as an alternative to Miss or Mrs. it was perceived as a radical feminist innovation. Today, its use is unremarkable, even normative. This study examines two aspects of the meaning of Ms.: changes in its connotative meaning over time, and its current comparability to other titles. Female (n = 83) and male (n = 54) college students rated courtesy titles (Ms., Miss, Mrs., Mr.) on a set of bipolar adjective pairs composing a semantic differential scale in an exact replication of a 1978 study. Of the four titles, the largest change in meaning over time was for Ms., and the direction of the change was positive. These results document the social assimilation of a new gender‐related concept.