Search

Recent signaling resolution models of parent-offspring conflict have provided an important framework for theoretical and empirical studies of communication and parental care. According to these models, signaling of need is stabilized by its cost. However, our computer simulations of the evolutionary dynamics of chick begging and parental investment show that in Godfray's model the signaling equilibrium is evolutionarily unstable: populations that start at the signaling equilibrium quickly depart from it. Furthermore, the signaling and nonsignaling equilibria are linked by a continuum of equilibria where chicks above a certain condition do not signal and we show that, contrary to intuition, fitness increases monotonically as the proportion of young that signal decreases. This result forces us to reconsider much of the current literature on signaling of need and highlights the need to investigate the evolutionary stability of signaling equilibria based on the handicap principle.

American avocets appear to recognize their young, with chick recognition becoming more developed as chicks grow older. This was gleaned from the results of a chick-exchange experiment designed to determine whether chick recognition exists in the avocets and its timing during chick development. Results also showed that adults show no aggression toward their young and that some discrimination may exist in the first week of the chick's life, as evidenced by the greater frequency of acceptance behavior in control trials than in fostering trials.

The response of pen-raised, six-day old northern bobwhite to red imported fire ants was studied in an experiment in 1993. The animal's behavior in a 30 square meter area where fire ants had been removed and in a similarly- sized area where fire ants are abundant was observed. The activities of the animal were classified as response to fire ants, moving, inactivity, sleeping, and food-pecking. Time spent at responding directly to the ants affected time allotted for daily activities such as moving, sleeping, and food-pecking. Ant activity and chick age affect time alloted to activities.

The idea that sensitivity to self-produced motion could lie at the foundations of the clear-cut divide that the brain operates between the two basic domains of inanimate and animate objects dates back to Aristotle. Sensitivity to self-propelled objects is apparent in human infants from around the fifth month of age, which leaves undetermined whether it is acquired by experience with animate objects or whether it is innately predisposed in the brain. Here, we report that newly hatched, visually naive domestic chicks presented with objects exhibiting motion either self-produced or caused by physical contact prefer to associate with self-propelled objects. This finding supports the idea of an evolutionarily ancient, predisposed neural mechanism in the vertebrate brain for the detection of animacy. animated object | self-propelled motion | filial imprinting | predisposition doi/10.1073/pnas.0908792107

The warning signals of toxic insects often combine pyrazine odors with conspicuous colorations, such as red or yellow. An investigation of these warning signals in prey choice experiments with birds shows that pyrazine interacts with red and yellow to trigger strong aversions to these typical aposematic colors that are not shown in the absence of the odor. Pyrazine is not inherently aversive and does not produce aversion when combined with a less conspicuous color. These provide the first proof that the purpose of multicomponent signals lies in the psychological responses produced by the interaction of different sensory components.

Several field experiments are conducted to explain the impact of different levels of forb cover in brood habitat on the mass gain and feather growth of the human-imprinted sage-grouse chicks. An increase in the forb cover is shown to lead to an equivalent increase in the chick survival and productivity of the grouse.

The aggregated attacks of Protocalliphora within broods of nestling blue tits are examined. The tasty chick hypothesis of potential aggregation of ectoparasite attacks on the smallest chicks in a brood is discussed.