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Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight
It is demonstrated that birds show wingtip path coherence when flying in V positions, flapping spatially in phase and thus enabling upwash capture to be maximized throughout the entire flap cycle, and suggested that birds in V formation have phasing strategies to cope with the dynamic wakes produced by flapping wings.
Annual changes in body mass and resting metabolism in captive barnacle geese (Branta leucopsis): the importance of wing moult
- S. Portugal, Jonathan A. Green, P. Butler
- Biology, Environmental ScienceJournal of Experimental Biology
- 15 April 2007
It is concluded that the increase in metabolism led to the use of endogenous energy reserves because the birds reduced rather than increased their food intake rates, and as a result, the barnacle geese lost body mass during wing moult.
Visual fields, foraging and collision vulnerability in Gyps vultures
It is concluded that by erecting structures such as wind turbines, which extend into open airspace, humans have provided a perceptual challenge that the vision of foraging vultures cannot overcome.
Miniaturization of biologgers is not alleviating the 5% rule
Applying a metaanalytical approach, recent studies of birds have shown that externally attached devices can have negative effects on nesting productivity, clutch, and the “rule” is often broken.
Matching times of leading and following suggest cooperation through direct reciprocity during V-formation flight in ibis
- B. Voelkl, S. Portugal, M. Unsöld, J. Usherwood, Alan M. Wilson, J. Fritz
- BiologyProceedings of the National Academy of Sciences
- 2 February 2015
This study studied the flight behavior of a flock of juvenile Northern bald ibis (Geronticus eremita) during a human-guided autumn migration and shows that direct reciprocation can enable cooperation between animals in a natural context.
Review: an embryo's eye view of avian eggshell pigmentation
Seven hypotheses are identified, which address how the interaction of eggshell pigments and the light environment may influence embryonic development, including thermo-regulation; UV-B protection; photo-acceleration; lateralization; circadian rhythm;photo-reactivation; and antimicrobial defence.
Why are birds' eggs colourful? Eggshell pigments co‐vary with life‐history and nesting ecology among British breeding non‐passerine birds
The breeding ecology and life history-dependence of eggshell pigment concentrations in these comparative analyses implies that related species share pigment strategies, and that those strategies relate to broad adaptive roles in the evolution of variation in avian eggshell coloration and its underlying mechanisms.
Avian eggshell pigments are not consistently correlated with colour measurements or egg constituents in two Turdus thrushes
The results reveal that it is not appropriate to simply assume in these two avian species that refl ectancebased eggshell colour measures are a suitable proxy for eggshell pigment concentrations or can be used as consistent predictors of maternal reproductive investment, and the need to assess and validate the strength and direction of the statistical relationships between egg shell colour measures, pigment concentrations, and maternal resource deposition in the egg for other species of birds.
Implantation reduces the negative effects of bio-logging devices on birds
- C. R. White, P. Cassey, N. Schimpf, L. Halsey, Jonathan A. Green, S. Portugal
- BiologyJournal of Experimental Biology
- 15 February 2013
A meta-analysis of 183 estimates of device impact from 39 studies of 36 species of bird designed to explicitly compare the effects of externally attached and surgically implanted devices on a range of traits, including condition, energy expenditure and reproduction concludes that device implantation is preferable to external attachment.
The origin and maintenance of metabolic allometry in animals
The authors identify a strong positive relationship between mass and metabolic rate among insects, fish, amphibians, reptiles, birds and mammals, and show that the genetic and interspecific correlations between these traits are consistent with a pattern of multivariate selection.