Liberal Arts

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The hummingbird beak, specialized for feeding on floral nectars, is also uniquely adapted to eating flying insects. During insect capture the beak often appears to close at a rate that cannot be explained by direct muscular action alone. Here we show that the lower jaw of hummingbirds has a shape and compliance that allows for a controlled elastic snap. Furthermore, hummingbirds have the musculature needed to independently bend and twist the sides of the lower jaw. According to both our simple physical model and our elastic instability calculation, the jaw can be smoothly opened and then snapped closed through an appropriate sequence of bending and twisting actions by the muscles of the lower jaw.► During insect capture hummingbirds flex their mandibles dorsoventrally. ► They appear to close their jaws at a rate that cannot be explained by direct muscular action alone. ► Closure was investigated using a paper model and mathematical calculations. ► We show how hummingbirds might smoothly flex and elastically snap their jaws closed. ► We discuss mandible shape and compliance and propose a driving sequence of muscular actions.

Our analysis is based on 496 Anna's Hummingbirds (146 museum specimens, 350 banding records) and 218 Rufous Hummingbirds (131 museum specimens, 87 banding records). Specimens of all Anna's and most Rufous Hummingbirds were from the collections at the California Academy of Sciences (CAS), Moore Laboratory of Zoology (MLZ), Museum of Vertebrate Zoology (MVZ), and PRBO. To augment our sample of fall and winter Rufous Hummingbirds (collected in Mexico), we also examined specimens at the Natural History Museum of Los Angeles County (LACM), San Diego Natural History Museum (SDNHM), and Western Foundation of Vertebrate Zoology (WFVZ). Specimens of Anna's Hummingbirds were taken from throughout the species' breeding range, although a majority __

Migratory birds have been declining, in some cases rapidly, for the past 30 years due in part to loss of habitat and habitat fragmentation. Forestry for the Birds provides information connecting sustainable forestry management practices to the habitat needs and natural history of birds, creating an accessible way for private forest owners to “let forest forests function as forests and keep common birds common”. The program brings together foresters, landowners, academics, non-profits, and state and federal agencies to find management solutions that support bird populations and promote sustainable forestry on working lands. This program has been funded in Washington County by the Tualatin Soil and Watershed Council from 2019-2022. Here we outline the goals of the program, its methods, and how to get involved

Feeding is an aspect of animal performance that has clear consequences for individual fitness and morphological evolution. Hummingbirds (Family Trochilidae) are an excellent group for the study of feeding performance because they are a speciose family of small, hovering, nectar specialists evolved from insectivorous ancestors. My dissertation research explored the role of insectivory in the evolution and ecology of hummingbirds. Here I begin with a review of the interaction of diet, morphology, physiology, and ecology to illustrate the importance of insectivory to all aspects of hummingbird biology. ^ In the second chapter, I characterize variation in hummingbird beak morphology based on museum specimens and examine this variation with respect to diet and ecology in a phylogenetic context. I find that hummingbird beak length is variable but that the distal dimensions of hummingbird beaks do not vary with respect to beak width and depth. This narrowness in beak dimension is presumably driven by the physical demands of nectar transport, but may hinder effective arthropod capture and transport, representing a potential tradeoff in beak function. ^ In chapters three and four, I investigate how hummingbirds catch and consume arthropod prey. I use high speed videography to document the feeding behaviors, performance, and kinematics of six hummingbird species. I discover that hummingbirds use a novel form of dorsoventral mandibular flexion during aerial arthropod capture. I examine the mechanics of dorsoventral mandibular flexion and discuss the consequences of kinesis for arthropod capture and transport. This study of feeding mechanics and kinematics looks at variation in feeding performance at the individual and species level in a group of birds with two distinct modes of feeding to provide insight into how morphology, behavior, and phylogeny contribute to the evolution of specialization in diet and trophic structures.