1,569 research outputs found
Greater flamingos Phoenicopterus roseus are partial capital breeders
Capital breeding refers to a strategy in which birds use body stores for egg formation, whereas income breeders obtain all resources for egg formation at breeding sites. Capital breeding should occur more in large-bodied species because the relative cost of carrying stores for egg formation becomes smaller with increasing body size. Based on a comparison between stable isotopes of carbon and nitrogen in potential prey at wintering sites and eggs, we examined whether greater flamingos use nutrients stored earlier in the year for egg production. Our results suggest that the greater flamingo is a partial income breeder, since prey for egg formation were obtained both in overwintering sites and at the breeding site. This may be because there are selective pressures for nesting females to lay soon after arriving at the breeding site, which may be facilitated by arriving at the breeding site with developed ovarian follicles. © 2011 The Authors.Peer Reviewe
Manifestation of the Roughness-Square-Gradient Scattering in Surface-Corrugated Waveguides
We study a new mechanism of wave/electron scattering in multi-mode
surface-corrugated waveguides/wires. This mechanism is due to specific
square-gradient terms in an effective Hamiltonian describing the surface
scattering, that were neglected in all previous studies. With a careful
analysis of the role of roughness slopes in a surface profile, we show that
these terms strongly contribute to the expression for the inverse attenuation
length (mean free path), provided the correlation length of corrugations is
relatively small. The analytical results are illustrated by numerical data.Comment: 13 pages, 3 figure
Spatial, environmental and human influences on the distribution of otter (Lutra lutra) in the Spanish provinces
In a previous survey of otters
(
Lutra lutra
L. 1758) in Spain, different causes
were invoked to explain the frequency of the
species in each province. To find common causes
of the distribution of the otter in Spain, we
recorded a number of spatial, environmental and
human variables in each Spanish province. We
then performed a stepwise linear multiple regression
of the proportion of positive sites of otter in
the Spanish provinces separately on each of the
three groups of variables. Geographic longitude,
January air humidity, soil permeability and highway
density were the variables selected. A linear
regression of the proportion of otter presence on
these variables explained 62.4% of the variance.
We then used the selected variables in a partial
regression analysis to specify which proportions
of the variation are explained exclusively by
spatial, environmental and human factors, and
which proportions are attributable to interactions
between these components. Pure environmental
effects accounted for only 5.5% of the variation,
while pure spatial and pure human effects
explained 18% and 9.7%, respectively. Shared
variation among the components totalled 29.2%,
of which 10.9% was explained by the interaction
between environmental and spatial factors.
Human factors explained globally less variance
than spatial and environmental ones, but the
pure human influence was higher than the pure
environmental one. We concluded that most of
the variation in the proportion of occurrences of
otter in Spanish provinces is spatially structured,
and that environmental factors have more influence
on otter presence than human ones; however,
the human influence on otter distribution is
less structured in space, and thus can be more
disruptive. This effect of large infrastructures on
wild populations must be taken into account
when planning large-scale conservation policie
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