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Young animals often solicit care from their parents using behaviors and morphologies collectively termed begging. Many nestling altricial birds add to their familiar postures and vocalizations by displaying colorful mouthparts, hypothesized to enhance their visual conspicuousness and/or be favored by choosy parents. We evaluated these two hypotheses with experimental manipulations of the flange tissue of house sparrow (Passer domesticus) nestlings. We allowed parents to interact with nestlings that appeared to have either carotenoid-rich or carotenoid-poor flanges, and then with nestlings that appeared similar in carotenoid-richness but differed in either brightness (total light reflected) or ultraviolet (UV) richness. These three features of flange color comprise much of the variation observed both within and among species. None of our three manipulations shaped parents' ability to transfer prey efficiently to nestlings, a proxy for how visually detectable nestlings were. Parents preferentially allocated prey to nestlings that appeared carotenoid-rich, but did not bias allocation when we manipulated brightness or UV reflectance. These patterns suggest that nestlings displaying carotenoid-rich flanges benefit from parental favoritism, but that variation in brightness and UV reflectance do not independently shape parental care, at least within the range a house sparrow parent might encounter in nature. Efforts to understand mouth color in the context of offspring-parent communication and visual signal evolution may benefit from considering the component parts of color, as they may function, be constrained, and evolve independently. [ABSTRACT FROM AUTHOR]

Global urbanization processes have highlighted the importance of understanding the effects of urban habitats on animal behavior. Behavioral changes are usually evaluated along an urbanization gradient, comparing urban and rural populations. However, this metric fails to consider heterogeneity between urban habitats that can differ significantly in their characteristics, such as their level of environmental variability. We suggest incorporating dimensions of environmental variability into the urbanization metric when evaluating behavioral changes. We tested the importance of both level of urbanization and level of urban change (i.e. the rate of anthropogenic changes measured as the change in the level of urbanization over time) on animals' behavioral flexibility by comparing reversal learning abilities in house sparrows from sites differing in the rate of urbanization and urban change levels. We show that at least for males, urban change better explains levels of behavioral flexibility than urbanization level. We further show that urban change corresponds to other behavioral traits such as scrounging behavior and foraging activity. Thus, considering environmental stability and predictability in the form of urban changes can help better understand the mechanisms allowing behavioral changes and adaptations to urban environments. Evaluating the dynamics of the urban built environment could provide a better metric with which to understand urbanization effects on wildlife behavior and an important next step in urban ecology. [ABSTRACT FROM AUTHOR]