Liana Zanette
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Associate Professor Department of Biology Phone: (519) 661-2111 ext. 88317 |
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Killam PDF, UBC, 1999-2001
Ph.D., University of New England, 1999
M.Sc., Queen's University, 1990
B.Sc., University of Toronto, 1988
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Website last updated 01 June, 2010
Overview
Dozens of species of songbirds have declined in abundance or disappeared
altogether
from much of their historical range in association with large-scale habitat
destruction,
and changes in land use, on every inhabited continent. Rachel Carson’s
warnings in the
early 1960’s that excessive pesticide use could result in a ‘silent spring’
highlighted the
effects of persistent toxic chemicals as a potential mechanism in these
songbird declines.
By identifying a particular mechanism, Carson’s work was instrumental in
changing
agricultural practices and thereby averting the disaster she foresaw.
Unfortunately, the
pattern of decline has continued. Surprisingly, the mechanisms
responsible for these
continued declines are not well understood. The long-term goal of my
research program
is to identify the mechanisms responsible for the global declines in songbird
abundance.
Through a series of rigorously designed, large-scale, controlled field
experiments, I am
testing the various mechanisms hypothesized to be responsible for these
declines.
This research is already being cited as a model for the experimental approach
to the study
of ecology and will have broad implications for the conservation of
biodiversity. As in
medicine, an accurate diagnosis is indispensable for both prevention and
recovery.
Synergistic effects of food and predators on the population viability of songbirds.
Most animals must continually balance the need for food against becoming
food. Hence,
food and predators are unlikely to have independent effects on demography.
Because
population level experiments on terrestrial vertebrates are rare, and
bifactorial
experiments are rarer still, synergistic effects of food and predators on
demography have
only recently been shown in mammals and have never before been demonstrated in
birds.
My current research provides the first evidence of just such synergistic
effects in birds.
These results confirm conclusions from my earlier work on the respective
roles of
forest fragmentation, and Brown-headed
Cowbirds, in songbird declines, and help to
explain why declines are both so common and so precipitous. Since
anthropogenic
disturbance both reduces food availability and increases predation, it follows
that natural
systems must generally possess both more food and fewer predators. When
these natural
systems are disturbed, precipitous declines are to be expected if a there is a negative
synergism between food shortage and increased predation, and either food
or predation
changes. A fuller understanding of such synergistic effects is essential
if we hope to
prevent further declines, and reverse existing ones.
Graduate student Marc Travers commutes to work
My current major research program involves an ongoing 2x2, manipulative food
addition
plus natural predator reduction experiment on 14 populations of Song Sparrows
(Melospiza melodia). Each site is home to about 7 territorial
pairs. Six sites are located
in Victoria, B.C., where predators are abundant, and the remaining 8 are
located on
several small islands (in the adjacent Haro Strait), where predators are rare
or absent.
From Feb.-Aug. food is added ad libitum to half (3) of the high predator
and half (4) of
the low predator sites. A single gravity fed feeder filled with a mixture
of millet seed and
high protein pellets is located in the middle of each territory at the food
supplemented
sites. All 14 Song Sparrow populations are intensively monitored
throughout the 7 mo.
breeding season. Breeding success is established by finding every nest
built by every
territorial pair as early as possible in the nesting cycle and conducting
frequent nest
checks thereafter to accurately determine the pattern of nest failures and the
proximate cause (abandonment, starvation or predation).
Fed and control sites in low (Portland Isl.) and
high (Victoria) predator areas
On average territories subject to the combined food addition + low
predator treatment
fledge almost twice (1.7 times) as many young as would be expected if the
effects of
food and predators were independent and additive. This effect (1.7 >
additive)
is similar in scale to those (1.5-1.9 > additive) recently shown in mammals.
Balancing food and predator pressure induces chronic stress in songbirds.
Chronic physiological stress induced by the never-ending tension between
finding food
and avoiding predators appears to be the proximate mechanism underlying the
above
synergistic effects on demography. The ‘chronic stress’ hypothesis
predicts: 1) an
animal’s stress profile will be a simultaneous function of food and predator
pressures
given the aforementioned tension; and 2) these inseparable effects on
physiology will
produce inseparable effects on demography due to the resulting adverse health
effects.
Working with Prof. Michael Clinchy
(UVIC), Prof. Rudy
Boonstra (U of T) and Prof.
John Wingfield
(U Washington) we have now documented the simultaneous
food and
predator effects on measures of chronic stress predicted by the 'chronic
stress'
hypothesis. Chronic stress appears to provide the missing link between
immediate
behavioural and longer-term demographic processes.
This work was featured in the Globe and
Mail, National Post and on CBC webnews.
Professors Mike Clinchy and Rudy Boonstra
stressing out on the Gulf Islands
Mobile Solar Video (MSV) systems for wildlife surveillance.
A chronic problem facing anyone
studying the 90 % of vertebrates that are small and
secretive is that while the effect of predation is easily measured we rarely
actually know
who the principal predators are. The development in just the past few
years of
miniaturized systems that allow us to ‘catch predators in the act’ is as
significant an
innovation for ecology as the development of the microscope was for the study
of
disease. Technical constraints, however, have so limited the use of these
systems that
only one study has generated enough data for statistical analyses. While
working with
me as a post-doc, and using funds from a Canada Foundation for Innovation (CFI)
grant
on which I acted as PI, Prof. Michael
Clinchy (UVIC) developed 8 Mobile Solar Video
(MSV) systems designed to permit 24 hr/day, continuous video surveillance of
wildlife,
over a 20 ha area, at remote locations anywhere in Canada. The
picture below is from a
video clip you can watch using
Windows Media Player. In this video the song sparrow
mom tries to defend her nest against a female brown-headed
cowbird. There are 2 eggs
to start with, 1 of which the cowbird tries to toss.
When the cowbird leaves, there are
3 eggs. So in less than 10 seconds the cowbird has
punctured a sparrow egg and laid
her own all while being attacked by the song sparrow mom.
Song sparrow mom attacking brown-headed cowbird
Cowbird Research
Brown-headed Cowbirds skew host offspring sex ratios
Brown-headed Cowbirds (Molothrus ater) do not build their own nests
but instead
lay their eggs in the nests of other species. Because Cowbirds often
destroy the
eggs or nestlings of the host to ensure that their own young has fewer
competitors in
the nest, they may have the same effect on host numbers as other more
conventional
predators. Continentally, Cowbird numbers have increased in association
with land
clearance for agriculture. Many U.S. states presently invest millions in
Cowbird
eradication. Debate over the efficacy of these programs has persisted
because the
evidence to date has all been correlational and circumstantial. I
collaborated in
conducting the very first large-scale, spatially and temporally replicated,
controlled
Cowbird removal experiment in North America. This
research showed that adult
Cowbirds can reduce the annual reproductive success of their hosts by 50
%. New
research in my lab has shown that the presence of Cowbird nestlings causes a
further 50 % loss of female host nestlings! This new research was
featured in Science
(immediately below) and I was interviewed concerning it by Bob McDonald on the
21 May, 2005, broadcast of CBC's radio's Quirks and Quarks.
Feature item in the Editor's Choice section of Science
(2005, Vol. 308, p. 927).
Forest Fragmentation Research
Food supply, nest predation and songbird demography in forest fragments.
Many species of songbirds that do well when occupying only a few hectares
within an
intact forest decline and disappear from similarly sized remnants. Such
‘area-sensitive’
species often only persist in remnants that are much larger than would be
expected given
their habitat requirements within intact forests. I conducted a
large-scale, spatially and
temporally replicated, mensurative experiment designed to test the joint
effects of food
and predation on the demography of an area-sensitive songbird inhabiting forest
fragments of different size. I compared three independent indices of food
availability,
and three measures of predation, as well as monitoring seasonal fecundity and
adult
female survival among Eastern Yellow Robins breeding in two small, and two
large
forest fragments, set within an agricultural landscape in southeastern
Australia. All three
indices of food availability were indicative of food shortage in smaller
fragments. These
novel results have attracted considerable attention (see links to E.N.N.
Report below).
Environmental News Network Report: "Deforestation may be starving songbirds"
Eastern Yellow Robin (Eopsaltria australis)
I am looking for both Ph.D. and M.Sc. students to work on a variety of
projects within
the context of my current major research program.
If you find the kinds of questions my
research addresses compelling, please fill in my Potential
Grad Student Questionnaire
and forward it to me (via e-mail) together with a brief (up to 2 page) outline
of the kind
of research you envisage conducting in my lab. Please also send your
transcripts as an
attachment. Transcripts from the web are fine (i.e., I do not require
official transcripts).
View from Shell Beach (Control, bottom left
Portland Isl. map)
Travers, M., Clinchy, M., Zanette, L., Boonstra, R, and Williams,
T. D. 2010.
Indirect predator effects on clutch size
and the cost of egg production.
Ecology
Letters (early view online).
Zanette, L., Clinchy, M. and H.-C. Sung.
2009. Food supplementing parents
reduces their sons’ song repertoire
size. Proc. R. Soc. B, 276: 2855-2860.
(Quirks and Quarks
interview with Bob MacDonald, 30 May 2009).
Pagnucco, K., Zanette, L., Clinchy, M., and Leonard, M.
L. 2008. Sheep in wolf's
clothing: host nestling vocalizations resemble their
cowbird competitors. Proc. R.
Soc. B, 275: 1061-1065.
(Quirks and
Quarks interview with Bob MacDonald, 05 April 2008).
Pfaff, J. A., Zanette, L.,
MacDougall-Shackleton, S. A., and MacDougall-Shackleton,
E.
A. 2007. Song
repertoire size varies with HVC volume and is indicative of male
quality in song sparrows (Melospiza melodia).
Proc. R. Soc. B, 274: 2035-2040.
(Guardian [UK] feature
"Big song repetoire makes male sparrows sexier")
Zanette, L., Haydon, D.
T., Smith, J. N. M, Taitt, M. J., and Clinchy, M. 2007.
Reassessing the cowbird threat. Auk, 124:
210-223.
Kempster, B., Zanette, L.,
Longstaffe, F., MacDougall-Shackleton, S. A., Wingfield,
J. C., and Clinchy, M. 2007. Do stable
isotopes reflect nutritional stress? Results
from a laboratory experiment on song sparrows. Oecologia,
151: 365-371.
Zanette, L., Clinchy, M., and Smith, J. N.
M. 2006. Food and predators affect egg
production in song sparrows. Ecology, 87:
2459-2467.
Zanette, L., Clinchy, M., and Smith, J. N.
M. 2006. Combined food and predator
effects on songbird nest survival and annual reproductive
success: results from a
bi-factorial experiment. Oecologia, 147:
632-640.
MacDonald, I. F., Kempster,
B., Zanette, L., and MacDougall-Shackleton, S. A. 2006.
Early nutritional stress impairs development of a
song-control brain region in both male
and female juvenile song sparrows (Melospiza
melodia) at the onset of song learning.
Proc. R. Soc. B, 273: 2559-2564.
(New
Scientist feature "Hungry sparrows sing the saddest songs")
Duncan-Rastogi, A., Zanette,
L., and Clinchy,
M. 2006. Food availability affects
diurnal nest predation and adult antipredator behaviour in
song sparrows, Melospiza
melodia. Animal Behaviour, 72:
933-940.
Zanette,
L., MacDougall-Shakleton,
E., Clinchy, M., and Smith, J. N. M. 2005.
Brown-headed cowbirds skew host offspring sex ratios.
Ecology, 86: 815-820.
(Quirks
and Quarks interview with Bob McDonald, 21 May 2005)
Clinchy, M., Zanette,
L., Boonstra, R., Wingfield, J. C., and Smith, J. N. M. 2004.
Balancing food and predator pressure induces chronic
stress in songbirds.
Proc. R. Soc. B, 271: 2473-2479.
(See features in the Globe and Mail, National Post and on CBC webnews).
Zanette, L.,
Smith, J. N. M., van Oort, H., and Clinchy, M. 2003.
Synergistic
effects of food and predators on annual reproductive
success in song sparrows.
Proc. R. Soc. B, 270: 799-803.
Smith, J. N. M., Taitt, M. J. and Zanette,
L., and Myers-Smith, I. H. 2003. How do
Brown-headed Cowbirds (Molothrus ater) cause
nest failures in Song Sparrows
(Melospiza melodia)? A removal experiment. Auk,
120: 772-783.
Smith, J. N. M.,
Taitt, M. J. and Zanette, L. 2002. Removing Brown-headed
Cowbirds increases seasonal fecundity and population
growth in Song Sparrows.
Ecology, 83: 3037-3047.
Zanette, L. 2001.
What do artificial nests tell us about nest predation?
Biological Conservation, 103: 323-329.
Zanette, L. 2001.
Indicators of habitat quality and the reproductive output of a forest
songbird in small and large fragments. Journal of
Avian Biology, 32: 38-46.
Zanette, L. 2000.
Fragment size and the demography of an area-sensitive songbird.
Journal of Animal Ecology, 69: 458-470.
Zanette, L., and Jenkins, B. 2000.
Nesting success and nest predators in forest
fragments: a study using real and artificial nests. Auk,
117: 445-454.
Zanette, L., Doyle, P.,
and Tremont, S. M. 2000. Food shortage in small fragments:
evidence from an area-sensitive passerine. Ecology,
81: 1654-1666.
(E.S.A. Press
Release)
Leonard, M. L., and Zanette, L.
1998. Female mate choice and male behaviour
in domestic fowl. Animal Behaviour, 56:
1099-1105.
(Nature
Science Update)
Zanette, L., and Ratcliffe, L.
M. 1994. Social rank influences conspicuous behaviour
by black-capped chickadees, Parus atricapillus.
Animal Behaviour, 48: 119-127.
("Watching
the hunted", Bird Watcher's Digest)
Herz, R. S., Zanette, L., and
Sherry, D. F. 1994. Spatial cues for cache retrieval in
black-capped chickadees. Animal Behaviour,
48: 343-351.