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1 March 2011 Seasonal Fecundity and Source-Sink Status of Shrub-Nesting Birds in a Southwestern Riparian Corridor
L. Arriana Brand, Barry R. Noon
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Saltcedar (Tamarix spp.) has increasingly dominated riparian floodplains relative to native forests in the southwestern U.S., but little is known about its impacts on avian productivity or population status. We monitored 86 Arizona Bell's Vireo (Vireo bellii arizonae), 147 Abert's Towhee (Melozone aberti), and 154 Yellow-breasted Chat (Icteria virens) nests to assess reproductive parameters in cottonwood-willow (Populus-Salix), saltcedar, and mesquite (Prosopis spp.) stands along the San Pedro River, Arizona during 1999–2001. We also assessed source-sink status for each species in each vegetation type using field data combined with data from the literature. There were no significant differences in reproductive parameters between vegetation types for Abert's Towhee or Yellow-breasted Chat, although seasonal fecundity was quite low across vegetation types for the latter (0.75 ± 0.14; mean ± SE). Bell's Vireo had extremely low seasonal fecundity in saltcedar (0.10 ± 0.09) and significantly fewer fledglings per nest in saltcedar (0.09 ± 0.09) compared with cottonwood (1.07 ± 0.32). Point estimates of λ were substantially <1 for all three focal species in all habitats indicating the entire study area may be performing as a sink; 90% CI of i1559-4491-123-1-48-e01.gif included 1 only for Abert's Towhee across vegetation types and Bell's Vireo in cottonwood vegetation. These results are surprising given the San Pedro is considered to be one of the best remaining occurrences of lowland native riparian vegetation in the southwestern United States.

L. Arriana Brand and Barry R. Noon "Seasonal Fecundity and Source-Sink Status of Shrub-Nesting Birds in a Southwestern Riparian Corridor," The Wilson Journal of Ornithology 123(1), 48-58, (1 March 2011).
Received: 15 April 2010; Accepted: 1 October 2010; Published: 1 March 2011
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