Integration of pecking, filter feeding and drinking mechanisms in waterfowl

Comparative Analysis of Morphometric, Densitometric, and Mechanical Properties of Skeletal Locomotor Elements in Three Duck Species (Anatidae: Anatinae)

Ducks (Anatinae) play a crucial role in wetland ecosystems, contributing to seed dispersal and nutrient cycling. This study investigates the skeletal adaptations of three duck species: the Mallard (Anas platyrhynchos), Tufted Duck (Aythya fuligula), and Green-Winged Teal (Anas crecca). The focus is on the tibiotarsus and humerus bones to understand how these adaptations support their different locomotion and habitat preferences. Bone samples n = 6 of deceased ducks (both male and female) from each species (for a total of 36 samples) were cleaned and measured for length, weight, and density. Dual-energy X-ray absorptiometry was used to determine bone mineral density (BMD) and bone mineral content (BMC), and mechanical properties like yield force and stiffness were tested using a 3-point bending test. The results show significant differences in body weight, bone weight, and bone length among the species, with Mallards being the largest and Teals the smallest. Male Teals displayed higher relative bone weight (RBW) in their tibia compared to male Mallards, and male Mallards had significantly lower RBW in the humerus compared to the other species. Female Teals had higher RBW than the other species. Teals also exhibited much lower BMD in the tibia, whereas female Mallards had lower BMD in the humerus. The Seedor index revealed that male Mallards had the highest values in the tibia, while female Teals had the lowest. Mechanical testing indicated that Teals had lower yield force and breaking force in the tibia, whereas Mallards showed the highest stiffness in both bones. Tufted Ducks had intermediate values, consistent with their diving behaviour. These findings suggest that the Mallard's robust bones support its adaptability to various environments and diverse locomotion and foraging strategies. The Teal's lighter and less dense bones facilitate rapid flight and agility in shallow wetlands. The Tufted Duck's intermediate bone characteristics reflect its specialization in diving, requiring a balance of strength and flexibility. Understanding these skeletal differences may provide valuable insights into the evolutionary biology and biomechanics of these species, aiding in their conservation and enhancing our knowledge of their roles in wetland ecosystems. By exploring the functional morphology of these ducks, this study aims to shed light on the biomechanical mechanisms that underpin their locomotion and foraging behaviours.

Food transport in Reptilia: a comparative viewpoint

Reptilia exploit a large diversity of food resources from plant materials to living mobile prey. They are among the first tetrapods that needed to drink to maintain their water homeostasis. Here were compare the feeding and drinking mechanisms in Reptilia through an empirical approach based on the available data to open perspectives in our understanding of the evolution of the various mechanisms determined in these Tetrapoda for exploiting solid and liquid food resources. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Experimental functional response and inter-individual variation in foraging rate of teal (Anas crecca)

The functional response, i.e. the change in per capita food intake rate per time unit with changed food availability, is a widely used tool for understanding the ecology and behaviour of animals. However, waterfowl remain poorly explored in this context. In an aviary experiment we derived a functional response curve for teal (Anas crecca) foraging on rice (Oryza sativa) seeds. We found a linear relationship between intake rate and seed density, as expected for a filter-feeder. At high seed densities we found a threshold, above which intake rate still increased linearly but with a lower slope, possibly reflecting a switch from filter-feeding to a scooping foraging mode. The present study shows that food intake rate in teal is linearly related to food availability within the range of naturally occurring seed densities, a finding with major implications for management and conservation of wetland habitats.

The spirit of D'arcy Thompson dwells in empirical morphospace

Applications of the concept of a morphological space to the study of biological form during the past three decades are reviewed. Common features of the various types of morphological spaces constructed by morphometricians during this period are identified and used to construct a space of morphological spaces. This semiquantitative analysis reveals that the use of empirical morphospace by contemporary researchers is similar to Thompson's classic method of coordinate grid transformations, in the description of biological form.