Head-bobbing patterns, while walking, of Black-winged Stilts Himantopus himantopus and various herons

Head-bobbing in the Ring-billed Gull (<i>Larus delawarensis</i>)

“…A comparison of walking speeds (calculated by dividing the total distance travelled by the body marker by the time of the film sequence and expressed in head lengths/s) revealed that walking speeds during head-bobbing were slower (2.56 ± 0.66 head lengths/s, n = 11) than during non-head-bobbing (3.98 ± 1.48 head lengths/s, n = 11). Our finding that head-bobbing only occurs at slow walking speeds in Ring-billed Gulls is consistent with previous results for Black-headed Gulls (Fujita 2006), Bar-tailed Godwits (Limosa lapponica;Dagg 1977), and Japanese Nightherons (Gorsachius goisagi; Fujita and Kawakami 2003). Moreover, Little Grebes (Tachybaptus ruficollis), a species that head-bobs when diving under water, tend to head-bob only when swimming slowly (Gunji et al 2013).…”

“…There are other examples of birds originally thought to be non-head-bobbers, but reclassified as more evidence became available. For example, herons and stilts, initially classified as non-head-bobbers by Dagg (1977), have since been shown to head-bob commonly as they walk (Fujita 2003;Fujita and Kawakami 2003). Therefore, we recommend that the walking behaviour of other gulls (and indeed other birds currently considered to be non-bobbers) be subjected to greater scrutiny to determine whether they truly are non-headbobbing species.…”

“…Films were downloaded to a computer and edited so that only sequences showing birds walking in an approximately horizontal direction perpendicular to the optical axis of the camera were used for analysis (Fujita 2006). Using ImageJ (Wayne Rasband, Research Services Branch, National Institute of Mental Health, Bethesda, Maryland, USA), landmark positions on the head (the eye) and body (e.g., the anterior or posterior tip of the wing, the tip of the tail feathers, or a prominent wing colour patch) were digitized for each frame (Fujita 2003(Fujita , 2006Fujita and Kawakami 2003). In addition to the head and body landmarks, the position of a static environmental landmark, such as a rock or piece of vegetation, in approximately the same plane as the bird was also digitized (Fujita 2006), allowing us to correct for displacements in the positions of the head and body landmarks resulting from panning movements of the camera.…”

“…Head-bobbing is presumed to be beneficial because it requires energy and because this behaviour is present in a wide variety of avian species (Dagg 1977). If head-bobbing is advantageous in terms of visual perception or in some other way, then it remains a puzzle why some species of bird head-bob while others apparently do not (Dagg 1977;Fujita and Kawakami 2003;Necker 2007). To identify ecological and behavioural correlates of head-bobbing across species, which in turn may help us understand the functional significance of this behaviour, it is important to determine which bird species head-bob and which do not, and also under what circumstances head-bobbing occurs (Fujita and Kawakami 2003;Fujita 2006;Necker 2007).…”

Head-bobbing behavior in walking whooping cranes (Grus americana) and sandhill cranes (Grus canadensis)

“…This is misleading, as the head might bob more than once each step (e.g. Fujita and Kawakami 2003), might not bob at all on occasion (Fujita 2006;Fujita and Kawakami 2003), or can bob when the bird is not walking at all (e.g. Fig.…”