Egyik előző bejegyzésben említett kéziratunkat egy javításokat kérő bírálati kör után véglegesen elfogadták közlésre. A cikk jelenleg szerkesztés alatt áll, így annak hivatalos oldalát nem tudom megadni. Ellenben lentebb közzé teszem a cikk kivonatát, grafikus kivonatát és népszerűsítő kivonatát olyan formában, ahogy a Functional Ecology is közölni fogja (mindhárom angol nyelven).
Pap PL, Osváth G, Sándor K, Vincze O, Bărbos L, Marton A, Nudds RL and Vágási CI
2015. Interspecific variation in the structural properties of flight
feathers in birds indicates adaptation to flight requirements and
habitat. Functional Ecology (in press).
Summary
1. The functional
significance of intra- and inter-specific structural variations in the
flight feathers of birds is poorly understood. Here, a phylogenetic
comparative analysis of four structural features (rachis width, barb and
barbule density, and porosity) of proximal and distal primary feathers
of 137 European bird species was conducted.
2. Flight type (flapping
and soaring, flapping and gliding, continuous flapping or passerine
type), habitat (terrestrial, riparian or aquatic), wing characteristics
(wing area, S and aspect ratio, AR), and moult strategy were all found
to affect feather structure to some extent. Species characterized by low
wing-beat frequency flight (soaring and gliding) have broader feather
rachises (shafts) and feather vanes with lower barb density than birds
associated with more active flapping modes of flight. However, the
effect of flying mode on rachis width disappeared after controlling for S
and AR, suggesting that rachis width is primarily determined by wing
morphology.
3. Rachis width and
feather vane density are likely related to differences in force
distribution across the wingspan during different flight modes. An
increase in shaft diameter, barb density and porosity from the proximal
to distal wing feathers was found, and was highest in species with
flapping flight indicating that aerodynamic forces are more biased
toward the distal feathers in flapping flyers than soarers, and gliders.
4. Habitat affected barb
and barbule density, which was greatest in aquatic species, and within
this group, barb density was greater in divers than non-divers,
suggesting that the need for water repellency and resistance to water
penetration may influence feather structure. However, we found little
support for the importance of porosity in water repellency and water
penetration, because porosity was similar in aquatic, riparian and
terrestrial species, and among the aquatic birds (divers and
non-divers). We also found that barb density was affected by moult
pattern.
5. Our results have
broad implications for the understanding of the selection pressures
driving flight feather functional morphology. Specifically, the large
sample size relative to any previous studies has emphasised that the
morphology of flight feathers is the result of a suite of selection
pressures. As well as routine flight needs, nutrition, habitat
(particularly aquatic) and migratory requirements also affect flight
feather morphology. Identifying the exact nature of these trade-offs
will perhaps inform the reconstruction of the flying modes of extinct
birds.
Key-words: barb density,
barbule density, flight feathers, flight, functional morphology, moult,
vane porosity, rachis width, water repellence, wing morphology
Graphical abstract
Four representatives of the entire species pool: common rosefinch Carpodacus erythrinus (a), red-footed falcon Falco vespertinus (b), Eurasian wryneck Jynx torquilla (c), and common kingfisher Alcedo atthis (d). Photographs by Csongor I. Vágási.
Lay summary
The size and structure of primary
feathers appears to vary greatly between species. The primary feathers
form the outer wing and are used to propel birds through the air.
Feathers consist of a central shaft called the rachis. Attached to and
aligned perpendicular to the rachis are the barbs and attached to, and,
again perpendicular to the barbs, are the barbules. Barbs and barbules
together make the feather vane, which gives the feather its shape and
surface area. Feathers become damaged over time so birds replace them
through a process called moult, replacing old feathers with new ones.
Birds differ in the way they fly
(different flight types), particularly in how much and how fast they
beat their wings. Birds also have differing life history traits, i.e.
living in different habitats, moulting feathers at different times of
year and some migrate over long distances. Also, wing shape differs
between species (e.g. long and narrow versus short, and broad wings). In
this study, we examined the primary feathers of 137 European species to
determine whether feather structure was related to life history traits
and wing shape.
Flight type, habitat, wing morphology,
and moult strategy all affected feather structure. Species characterized
by low wing-beat frequency flight (soaring and gliding flight) had
broader rachises and feathers with a lower density of barbs than birds
associated with more active flapping flight types (high wing-beat
frequency). Rachis width was primarily determined by wing shape. Our
results suggest that species that flap their wings most vigorously
during flight require denser feather vanes. The forces created by the
air increase with flapping frequency and more dense feathers are likely
to reduce the chance of air being forced through the feathers.
Barb and barbule density was highest in
aquatic species, peaking within diving birds. Hence, the need for water
repellency and resistance to water penetration may also influence
feather structure.
In conclusion, the optimum feather
morphology for flight and habitat for some species may conflict
resulting in a compromise structure, for example, gliding and soaring
flight selects for low barb density, while aquatic habitats select for
high density.
