In 2011 we began highlighting articles that we believe deserve special attention from our members and hopefully increase interest in the journal in readers who are not members now. Below are my choices for this issue of The Auk.
One species but two patterns: Populations of the Hudsonian Godwit (Limosa haemastica) differ in spring migration timing
Nathan R. Senner
Hudsonian Godwits (Limosa haemastica) annually migrate between Argentina and Chile and Arctic and subarctic breeding grounds in an elliptical route down the Atlantic flyway in fall, to then return north along midcontinental and Pacific coastal routes in spring. Timing is critical and climate change has the potential to alter phenologies and lead to mistimed arrival dates. Senner used 37 and 23 years of data from Alaskan and Manitoban breeding populations, respectively, to show that climate change produced entirely different effects at the two sites. Alaskan godwits arrived 9 days earlier whereas godwits in Manitoba arrived nearly 11 days later than they did in the 1970s. The coastal Alaskan site creates greater predictability and buffering against climate change and godwits appear to use information from the previous year to accurately time their arrival. By contrast, midcontinental populations can closely approach the breeding grounds and use local cues to time their arrival, but increasingly poor weather in early spring associated with climate change has led to a progressive delay in arrival. Senner’s results highlight the role of ecological constraints in limiting migratory timing, and that not all populations of the same species respond identically to the earth’s changing climate.
El Niño–Southern Oscillation influences annual survival of a migratory songbird at a regional scale
Joseph A. LaManna, T. Luke George, James F. Saracco, M. Philip Nott, and David F. DeSante
LaManna and colleagues use records from nearly 11,000 Swainson’s Thrushes (Catharus ustulatus) banded through the MAPS program along the Pacific coast states to evaluate the extent to which adult survival varies with large-scale climatic events, including El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation, and Pacific Decadal Oscillation. Survival did not vary with geographic origin of the bird, or with any of the regional climate processes other than ENSO. The authors examined several alternative mechanisms for the effect of ENSO on survival. Survival increased with increasing dry-season precipitation along the spring migration route of thrushes in western Mexico and southern California, presumably because rainfall increased primary productivity and food supplies for migrants. Survival increased by as much as 15–20% over the observed range of spring rainfall, and thus the potential for ENSO to influence demography of west coast populations was substantial. Numerous passerine species travel the same route as Swainson’s Thrushes, which suggests that other species may be affected by the same large-scale weather phenomena.
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