The evolution of the avian bill as a thermoregulatory organ

The avian bill is a textbook example of how evolution shapes morphology in response to changing environments. Bills of seed‐specialist finches in particular have been the focus of intense study demonstrating how climatic fluctuations acting on food availability drive bill size and shape. The avian bill also plays an important but under‐appreciated role in body temperature regulation, and therefore in energetics. Birds are endothermic and rely on numerous mechanisms for balancing internal heat production with biophysical constraints of the environment. The bill is highly vascularised and heat exchange with the environment can vary substantially, ranging from around 2% to as high as 400% of basal heat production in certain species. This heat exchange may impact how birds respond to heat stress, substitute for evaporative water loss at elevated temperatures or environments of altered water availability, or be an energetic liability at low environmental temperatures. As a result, in numerous taxa, there is evidence for a positive association between bill size and environmental temperatures, both within and among species. Therefore, bill size is both developmentally flexible and evolutionarily adaptive in response to temperature. Understanding the evolution of variation in bill size however, requires explanations of all potential mechanisms. The purpose of this review, therefore, is to promote a greater understanding of the role of temperature on shaping bill size over spatial gradients as well as developmental, seasonal, and evolutionary timescales.     

The birth of a lowland gorilla in captivity

A 7 year-old captive-born mother-reared gorilla gave birth to a healthy infant after being in labor for 27 min. The young female was a wholly competent mother although she had never observed gorilla mothers or interacted with gorilla infants. This reinforces previous evidence, still often ignored by zoo officials, that gorillas do not have to learn maternal behavior.     

The anatomy of a shrike bite: bill shape and bite performance in Loggerhead Shrikes

There is evidence that fisheries are altering the phenotypic composition of fish populations, often in ways that may reduce the value of fish stocks for the exploiters. Despite the increasing number of theoretical and field studies, there is still debate as to whether these changes are genetic, can be reversed, and are occurring rapidly enough to be considered in fisheries management. We review the contribution that selection experiments have already provided with respect to the study of the evolutionary effect of fisheries, identify issues that still require more study, and outline future directions for doing so. Selection experiments have already been crucial in showing that harvesting can lead to phenotypic and genetic evolution over relatively short time frames. Furthermore, the experiments have shown the changes involve many other traits than those under direct selection, and that these changes tend to have population‐level consequences, including a decreasing fisheries yield. However, experiments focused on fisheries‐induced evolution that fulfil all our requirements are still lacking. Future studies should have more controlled and realistic set‐ups and assess genetic changes in maturation and growth (i.e. traits most often reported to change) to be more relevant to exploited populations in the wild. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 485–503.