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Publications - Bird ecology
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Sylvain
Allombert, Anthony J. Gaston, Jean-Louis Martin, 2005, A natural experiment on the impact of
overabundant deer on songbird populations, Biological Conservation 126
(2005) 1–13 – PDF
Abstract: Declines in
songbird populations have been identified both in North America and in Europe. Several explanations have been proposed
but few studies have evaluated the possibility that deer overabundance might
affect songbird populations, and none have identified general rules to predict
such an impact. We used a group of islands in the Haida Gwaii archipelago
(British Columbia, Canada), where islands without deer co-exist near islands
with deer, as a natural experiment to test if the dependence of each species on
understorey vegetation was a good predictor of deer impact. Forest bird assemblages were compared on
six islands that either had no deer, had deer for less than 20 years or for
more than 50 years, and on an enlarged set of 31 islands for which vegetation
data and an index of deer impact were available. In the six islands data-set,
songbird abundance on islands browsed for more than 50 years was 55–70% lower
than on deer-free islands. There was a significant decrease in alpha diversity
on islands browsed by deer, but gamma diversity remained unchanged. Bird
species with the highest dependence on understorey vegetation were most
affected and their abundance decreased by 93%. Bird communities flipped from
being 73% dependant on understory vegetation on deer-free islands to 79% not
dependant on understory vegetation on islands with deer for more than 50 years.
A canonical correspondence analysis on the 31 island data-set allowed us to
further separate the interactions between bird abundance and distribution,
vegetation features and deer presence. We propose that deer overabundance
results in a decrease in songbird habitat quality through decreased food
resources and nest site quality and may explain part of current
continental-scale decreases in songbird populations.
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Sylvain
Allombert, Anthony J. Gaston, Jean-Louis Martin, 2005,
Sea Surface Temperatures Mediated by the El
Niño-Southern Oscillation Affect Birds Breeding in Temperate Coastal Rain Forests,
Avian Conservation and Ecology - Écologie et
conservation des oiseaux 1(1): 4 http://www.ace-eco.org/vol1/iss1/art4/ - PDF
Abstract: We studied the timing of
breeding and juvenile/adult ratios among songbirds in temperate rain forests
over four years on the Haida Gwaii (Queen Charlotte Islands) archipelago, British Columbia. In May 1998, air temperatures in
Haida Gwaii were above average, whereas in 1999 they were the lowest in 20 yr:
temperatures in the other two years were closer to normal, although 2001 was
almost as cold as 1999. Temperatures closely followed the patterns of sea
surface temperatures created by the 1997–1998 El Niño, i.e., warm, event and
the subsequent strong La Niña, i.e., cool, event. Timing of breeding, as
measured by the first capture of
juveniles or by direct observations of hatching, varied by approximately19 d
between the earliest (1998) and latest (1999) years. In 1998, the proportion of
juveniles among birds trapped increased steeply as soon as young birds began to
appear. In other years, the rate of increase was slower. In 1999, the peak
proportions of hatching-year individuals among the foliage-gleaning
insectivores, i.e., the Orange-crowned Warbler (Vermivora celata),
Townsend’s Warbler (Dendroica townsendi), and the Golden-crowned Kinglet
(Regulus satrapa), were lower than in other years, with almost no young Orange-crowned
Warblers captured at all. The pattern of variation in the timing of breeding
and in the
proportion of hatching-year
individuals trapped fitted the temperature data well, although rainfall may
also have contributed. We concluded that changes mediated by El Niño-Southern
Oscillation (ENSO) in sea surface temperatures off northern British Columbia, through their effects on air
temperatures, had a strong effect on the breeding of forest birds, to the point
of causing nearly complete reproductive failure for one species in 1999. An
intensification of the ENSO cycle could lead to more erratic reproduction for
some species.
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Jean-Louis Martin, Mathieu Joron, 2003, Nest predation in forest birds: influence of predator type and predator’s
habitat quality, OIKOS 102:
641–653, 2003 – PDF
Abstract: We used the
introduction of a generalist nest predator, the red squirrel Tamiasciurus
hudsonicus, and of a large herbivore, the
Sitka black-tailed deer Odocoileus
hemionus sitkensis,
to the islands of Haida Gwaii (Queen Charlotte Islands, British Columbia,Canada) to study how predator assemblage
and habitat quality and structure influenced nest predation in forest birds. We
compared losses of natural nests to predators on islands with and without
squirrels. We selected nine islands with or without squirrel or deer and used
506 artificial nests put on the ground or in shrubs to further analyse
variation of nest predation with predator assemblage and habitat quality for
the predators. For both natural and artificial nests predation risk was higher
in presence of squirrels. But predation risk varied within island categories. In
presence of squirrels it was highest in stands with mature conifers where it
fluctuated from year to year, in response to fluctuations in squirrel
abundance. Vegetation cover around the nest had little effect on nest predation
by squirrels. Where squirrels were
absent,
nest predation concentrated near predictable food sources for corvids, the main
native predators, and increased with decreasing vegetation cover, suggesting that
removal of the vegetation by deer increased the risk of predation by native
avian nest predators that use visual cues. Predation risk in these forests
therefore varies in space and time with predator composition and with quality
of the habitat from the predators’ perspective. This temporal and spatial
variation in predation risk should promote trade-offs in the response of birds
to nest predation, rather than fine-tuned adaptations to a given predation
pattern.
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Bruno Walther, Jean-Louis Martin, 2001, Species richness estimation of birds
communities: how to control for sampling effort? British
ornithologists’ union, Ibis 143 413:419 – PDF
Abstract: Since
estimates of total species richness increase with sampling effort, methods to
control for this sapling effect need to be tested and used We present seven
non-parametric and 12 accumulation curve methods that have been used recently
in the ecological literature. To test their performance, we used data from bird
communities in the Queen Charlotte Islands, Canada. The performance of each method was
evaluated by calculating the bias and precision of its estimates against the
known total species richness. For our data set, the two Chao estimators were
the overall least biased and most precise estimation methods, followed by the
two jackknife estimators, thus supporting results of previous studies.
Non-parametric estimators tended to perform better than accumulation curve
models. Most estimations methods had the problem that they tended to underestimate
species richness for early samples, but slightly overestimated it for late
samples. We briefly discuss the practical use of these methods which may
greatly increase our ability to answer ecological questions and to guide
conservation decisions, especially fr species-rich tropical bird communities.
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Jean-Louis Martin, Anthony J. Gaston, Simon Hitier, 1995, The effect of island size
and isolation on old growth forest habitat and diversity in Gwaii Haanas (Queen
Charlotte Islands, Canada), OIKOS 72 115:131 – PDF
Abstract: We surveyed
the vegetation and birds faunas of forests on 65 islands in the Gwaii Haanas archipelago
of British
Columbia, Canada, ranging in size from 1 to > 100 000
ha, using point counts at a uniform distance from the shore. Variation in
habitat structure was correlated with variation in area and isolation. Only
among the smaller islands did the number of birds species decrease with area.
As some species became rarer with decreasing island size, others became more
common. The distribution of bird species among the islands was correlated with
the distribution of habitat features that were consistent with the biology and
ecology of each species. In only a minority of species was their distribution
related to area and isolation per se rather than to habitat features correlated
with island size and isolation. Hence, we considered that variation in habitat
structure mediated by area and isolation was the key factor involved in
determining the local composition of the bird community. Only for a few species
restricted to the largest islands, or missing from the very small islands, were
high rates of extinction related to small population size the most parsimonious
hypothesis explaining species distribution patterns. Our results emphasise how
considering only the relationship between numbers of species and island area
can mask all but the roughest species distribution patterns and prevent a
deeper understanding of the biology of islands.
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Daniel Simberloff, Jean-Louis Martin, 1991, Nestedness of insular avifaunas: simple summary statistics masking complex
species patterns, Ornis fennica 68 178:192 – PDF
Abstract: Nestedness
patterns have been recommended as a guide in designing refuges. The birds of
three island archipelagos and one set of mainland quadrats display strongly
nested patterns, exactly as do most systems studied in this way. Nestedness may
be expressed by several statistics, which are likely to be highly correlated,
and may be viewed from either the community-wide or individual species
vantagepoint. The latter is more informative. Individual species’ nestedness
scores can be similar even though the ecological forces generating them differ
greatly. Nestedness scores based on island or site area are not directly comparable
to those based on species richness. It is neither intuitively apparent nor
empirically demonstrated that extinction would produce characteristically
different nestedness scores than would colonization. Nestedness statistics are
closely related to incidence functions in the ecological literature and to
SLOSS comparisons in the conservation literature. None of these statistics is
likely to provide much insight into refuge design.
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