The Effects of Climate
and Winter
Habitat on Fitness Correlates in a Differential Migrant
Differences
between the sexes in dispersal behavior and winter habitat preference
can cause
males and females to settle at different winter latitudes giving rise
to a
pattern of distribution known differential migration. In many avian
species,
recent warming events have resulted in changes in migratory schedules
and
earlier arrival on the breeding grounds.
Far less is known about the effect of climate change on autumn
migratory
schedules or winter distributions. For
differential migrants, changes in climate and potentially distribution
may be
especially important, as relaxation in segregation may impact one sex
more than
the other, resulting in significant changes in demography, population
dynamics
and possibly population declines. My
dissertation will evaluate the effects of sex and wintering latitude on
fitness
correlates and
compare
current demography to data collected 30 years ago to assess whether
warming is
detectable in a change in population structure.
Specifically I ask:
- Have recent warming
events altered patterns of differential migration in the junco?
- Are there negative
consequences for female juncos that winter at northern latitudes where
male abundance is high?
- Does junco immune
function (i.e. susceptibility to disease and the ability to mount a
response to infection) vary with latitude and is it correlated with
latitudinal differences in winter climate?
All of
these topics deal with the effect of climate on wintering birds and
their
decisions regarding choice of winter location and the effects of this
choice on
winter health and survival. Climate
change, or global warming, is therefore of background importance to all
topics
including the natural latitudinal variation in winter climate as
measured by
temperature, snowfall, and precipitation.
Results of these studies will be the first to assess the effects
of
milder winter climate on the behavior and physiology of a differential
migrant. Understanding the effects of
climate warming on differential migration can not only give insight
into the
evolution of sex differences, but also into factors influencing
population
dynamics and ultimately the conservation of biodiversity.
Additionally, since many migratory birds,
including the junco, have the potential to transport several avian
vector
diseases such as Lyme disease and the West Nile Virus, discerning the
effects
of winter climate on immune function becomes even more important in
terms of
managing this potential mechanism of disease spread.
Presented
Papers
Impact
of
Winter Sex Ratio on Winter Physiology in a Differential Migrant the
Dark-eyed
junco. Society for Integrative and Comparative Biology. January
2008.
Poster
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