Advanced departure dates in long-distance migratory raptors

Auteurs: Ondine Filippi-Codaccioni, Jean-Pierre Moussus, Jean-Paul Urcun, Frédéric Jiguet
Bron: JOURNAL OF ORNITHOLOGY, online DOI 10.1007/s10336-010-0500-5
Abstract: Evidences for phenological changes in response to climate change are now
numerous. One of the most documented changes has
been the advance of spring arrival dates in migratory birds. However,
the effects of climate change on subsequent events of
the annual cycle remain poorly studied and understood. Moreover, the
rare studies on autumn migration have mainly concerned
passerines. Here, we investigated whether raptor species have changed
their autumn migratory phenology during the past 30
years at one of the most important convergent points of western
European migration routes in France, the Organbidexka pass,
in the Western Pyrenees. Eight out of the 14 studied raptor species
showed significant phenological shifts during 1981–2008.
Long-distance migrants displayed stronger phenological responses than
short-distance migrants, and advanced their mean passage
dates significantly. As only some short-distance migrants were found to
delay their autumn migration and as their trends in
breeding and migrating numbers were not significantly negative, we were
not able to show any possible settling process of
raptor populations. Negative trends in numbers of migrating raptors
were found to be related to weaker phenological responses.
Further studies using data from other migration sites are necessary to
investigate eventual changes in migration routes and
possible settling process.

Territorial reactions of male Yellowhammers (Emberiza citrinella) toward a specific song structure

Auteurs: Thibaud Gruber, Laurent Nagle
Bron: JOURNAL OF ORNITHOLOGY, Online, DOI 10.1007/s10336-010-0502-3
Abstract: Male songbirds assess their rivals by listening to their songs and, in some species, are especially sensitive to certain parts of the song. Yellowhammers (Emberiza citrinella) sing songs with different structures consisting of an initial phrase of stereotyped and repeated notes in a trill, and a terminal phrase, present or not, which consists of low or high frequency whistles that we called elements. We analyzed 1,055 songs from 25 different males and found that four different structures could be distinguished in a French Yellowhammer population. We found that the frequency ranges of the elements were more constant across individuals than the ranges of the notes, and among them, the low frequency element was nearly twice as conserved as the high frequency element. Then, in the wild, we tested the territorial responses of males to the four different structures and found that the full song structure, which is composed of the initial phrase followed by a high frequency element and a low frequency element, induced stronger territory defence responses from the males than any of the other structures. As only the structure containing the initial phrase and the low frequency element also induced a strong response, we propose that the main element responsible for the enhanced reaction of the males is the low frequency element, which is consistent with the fact that it is more conserved than the other constituents.

Why don't female purple sandpipers perform brood care? A removal experiment

Auteurs: Elin P. Pierce, Lewis W. Oring, Eivin Røskaft, Jan T. Lifjeld
Bron: BEHAVIORAL ECOLOGY, Volume 21, Number 2, p. 275-283
Abstract: In most monogamous sandpiper species, females share parental care
but leave the brood earlier than males, a feature unusual among
birds in general. In the purple sandpiper (Calidris maritima),
females almost always leave the brood at hatching and never share
brood care. Males perform uniparental brood care from hatching
until well after fledging. In this paper, we report the
results of a mate-removal experiment conducted on the purple sandpiper
in high Arctic Svalbard and discuss the implications for the
evolution of their mate desertion strategy. By removing males
from nests near hatching, we tested 2 hypotheses: 1) Males assume
brood care because females, who always have a net benefit from
deserting, have a fixed brood desertion strategy, whereas males
do not; 2) females desert the brood because they cannot perform
uniparental brood care as well as males and/or because they
are under physiological stress at hatching due to egg laying and
incubation activities hypothesis). We found that when experimentally
deserted, most female purple sandpipers assumed brood care. Parental
behavior and the growth and survival of the chicks suggested
that the attending females were not under physiological stress
after hatching and did not seem less able than males to
perform brood care. Thus, we found no support for either hypothesis.
We suggest that uniparental brood desertion is a consequence
of strong selection for uniparental brood care in this
species and that the actual sex roles may result from rather marginal
differences between the sexes in the fitness consequences of
care and desertion.

Do Highly Modified Landscapes Favour Generalists at the Expense of Specialists? An Example using Woodland Birds.

Auteurs: Hinsley Shelley A., Hill Ross A., Bellamy Paul, Broughton Richard K., Harrison Nancy M., Mackenzie Julia A., Speakman John R., Ferns Peter N.
Bron: Landscape Research Oct2009, Vol. 34 Issue 5, p509-526
Abstract: Demands on land use in heavily populated landscapes create mosaic
structures where semi-natural habitat patches are generally small and
dominated by edges. Small patches are also more exposed and thus more
vulnerable to adverse weather and potential effects of climate change.
These conditions may be less problematic for generalist species than for
specialists. Using insectivorous woodland birds (great tits and blue
tits) as an example, we demonstrate that even generalists suffer reduced
breeding success (in particular, rearing fewer and poorer-quality
young) and increased parental costs (daily energy expenditure) when
living in such highly modified secondary habitats (small woods, parks,
farmland). Within-habitat heterogeneity (using the example of Monks Wood
NNR) is generally associated with greater species diversity, but to
benefit from heterogeneity at a landscape scale may require both high
mobility and the ability to thrive in small habitat patches. Modern
landscapes, dominated by small, modified and scattered habitat patches,
may fail to provide specialists, especially sedentary ones, with access
to sufficient quantity and quality of resources, while simultaneously
increasing the potential for competition from generalists

Predators and bird declines

The findings of a new study on the impact of predators on bird prey, which looks at declining species, shows that for most there is no link between increasing predator numbers and falling populations.

The biggest ever analysis of songbirds and their predators, published today (8 March) in the Journal of Applied Ecology, looked at the role of predators in the decline of species such as Bullfinch and Yellowhammer.

The results show that while a small number of associations may suggest significant negative effects between predator and prey species, for the majority of the songbird species examined there is no evidence that increases in common avian predators or Grey Squirrels are associated with large-scale population declines.

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Bird wing shapes changing

New research suggests that the shape of birds’ wings can change over time in response to changes in the environment, especially the fragmentation of forest habitats.

André Desrochers of the Center for Forest Research at Laval University, Quebec has found that as Canada’s vast boreal forest has been cut down over the past century, birds that live in the mature woodlands have developed more pointed wing tips.

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