My
research seeks to better understand animal movement
decisions in habitats of varying quality and to create
empirically derived individual based models of survivorship
in a landscape context. Movement is a component of
nearly all animal behaviors and is often incorporated
into life history strategy and population level models
but there have been relatively few hypothesis driven
studies about the effects of movement decisions on
individuals. There are three primary reasons why stopover
during migration is well suited to studying the relationship
between avian movement ecology and habitat: 1) Migrants
are often new to the landscapes they stopover in because
the migratory route is influenced by extrinsic factors
such as weather, so they are less likely to rely on
information from a previous season for habitat selection.
2) Migrants are often energetically constrained when
they stopover mid-route so the consequences of decisions
about resources are more likely to be expressed in
a short time period. 3) Stopover is temporally restricted
so it is more realistic to make the assumption of resource
constancy during the period of study and decisions
are more likely to be based on immediate costs and
benefits.
I propose to use
translocation experiments of nocturnal migrants into
a novel landscape to create empirically derived
models of migrant-habitat relations during stopover.
To create individual based models the following three
questions
regarding the movement ecology of nocturnal migrants
during stopover must be addressed:
1) Do within habitat
movements
for resource acquisition vary with habitat quality?
2) Do migrants move
between habitat types to select habitat after landing
in a novel landscape?
3) Does movement
both within and between habitat types
vary with the energetic
condition of the bird?
The
resulting models can be used to predict survivorship to
continue
migration
in
landscapes
across the region and with projected
land use changes.
Survival, Habitat Use and Movements of Fledgling
White-throated Robins in Tropical Agricultural Habitats
I used radio-telemetry to study the behavior
of White-throated Robins (Turdus assimilis) during the
postfledging dependent
period. The study was conducted in a mixed agricultural
and forested landscape in southern Costa Rica from March
through August of 2001 and 2002. A transmitter was attached
to one fledgling per brood (n = 53). Each bird was located
daily prior to dispersal. I compared survivorship, habitat
use, and movements for fledglings from nests in coffee
plantations and cattle pastures. The probability of surviving
the first three weeks out of the nest was 0.67 ±?0.07
(SE) for fledglings from nests in all habitats, 0.58 ± ?0.10
for fledglings from nests in coffee, and 0.74 ± ?0.26
for fledglings from nests in pasture. Fledglings from nests
in pasture left their nesting habitat type at younger ages
than did birds from nests in coffee and most birds from
both habitats moved into forest when they left their nesting
habitat. Pasture was rarely used during the postfledging
period while coffee plantations were used extensively.
Fledglings that remained in agricultural habitats (coffee
or pasture) were less likely to survive until dispersal
than were those that moved into forested areas. Average
daily distances from the nest gradually increased until
fledglings dispersed away from the natal area, always into
forest, and were not different for birds from pasture or
coffee. White-throated Robins can nest successfully in
agricultural habitats but the use of forest positively
influenced survivorship of young during the postfledging
dependent period.
Cohen, E. B., and C. A. Lindell. 2005. Habitat use of
White-throated Robins (Turdus assimilis) during
the breeding season in a mosaic landscape in Costa Rica.
Journal of
Field Ornithology 76:279-286.
Cohen, E. B., and C. A. Lindell. 2004.
Survival, habitat use, and movements of fledgling White-throated
Robins (Turdus
assimilis) in a Costa Rican agricultural landscape.
Auk 121:404-414.
Lindell, C. A., E. B. Cohen, and J. S.
Fritz. 2004. Are daily mortality rates for real and artificial
clutches
comparable? Ornithologia Neotropical 15: 201-208.
Woodworth, B.L., J. T. Nelson, E.J. Tweed,
S.G. Fancy, M.P. Moore, E. B. Cohen, and M. S. Collins.
2001. Demography
of the endangered Hawai’i Creeper in a wet forest
refuge on Mauna Kea, Hawai’i. In The Status, Ecology,
and Conservation of the Hawiian Avifauna. Studies in Avian
Biology. 22: 164-172.
Whitfield, M. J., E. B. Cohen, and C. D.
Otahal. 1999. Southwestern Willow Flycatcher (Empidonax
traillii extimus)
surveys, nest monitoring, and removal of Brown-headed Cowbirds
on the South Fork Kern River, California in 1999. Report
submitted to California Dept. of Fish and Game and U.S.
Army Corps. of Engineers, Sacramento District, Purchase
Order: DACW05-99-P-0374.
Department of Biological Sciences
The University of Southern Mississippi
118 College Drive # 5018
Hattiesburg, MS 39406-0001
601-266-4394 (lab)
601-266-5797 (fax) emlcohen@hotmail.com
My
research seeks to better understand animal movement
decisions in habitats of varying quality and to create
empirically derived individual based models of survivorship
in a landscape context. Movement is a component of
nearly all animal behaviors and is often incorporated
into life history strategy and population level models
but there have been relatively few hypothesis driven
studies about the effects of movement decisions on
individuals. There are three primary reasons why stopover
during migration is well suited to studying the relationship
between avian movement ecology and habitat: 1) Migrants
are often new to the landscapes they stopover in because
the migratory route is influenced by extrinsic factors
such as weather, so they are less likely to rely on
information from a previous season for habitat selection.
2) Migrants are often energetically constrained when
they stopover mid-route so the consequences of decisions
about resources are more likely to be expressed in
a short time period. 3) Stopover is temporally restricted
so it is more realistic to make the assumption of resource
constancy during the period of study and decisions
are more likely to be based on immediate costs and
benefits. 