Emily Beth Cohen

 
 


Red-eyed Vireo with transmitterMy 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 HabitatsEmily radiotracking

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

 

The University of Southern Mississippi. Last modified: 11 June, 2009 . Questions and Comments?
URL: http://www.usm.edu/mbrg/Emily.htm
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