In an effort to assess ties between birds' feeding habits and the spread of nonnative invasive plants, researchers provided ornithologists from four U.S. states with questionnaires on daily bird-plant encounters. The 1,143 unique interactions reported by the birders laid the groundwork for a study on the role of native birds in the seed dispersal of invasive plants throughout the U.S.
Clare Aslan and Marcel Rejmnek of the University of California, Davis mailed questionnaires to more than 1,000 members of the Ornithological Societies of North America in the states of California, Florida, New York and Washington. The questionnaires addressed daily birding activities, experience level of the birder, bird-plant interactions and any additional comments. The answers were analyzed by the researchers and compared with pre-existing empirical data and/or follow-up field observations.
From the 179 birders who responded, the researchers gathered 1,143 interactionsof those interactions, 539 (47 percent) involved birds feeding on fruits or seeds of nonnative plants. As birds feed on seed-bearing fruit or the seeds of plants themselves, they inadvertently drop leftovers in nearby soil or carry them greater distances in their plumage. The birders' reports suggest that--through their feeding and habitat preferences--specific birds are contributing to the spread of certain nonnative invasive plant species.
"The spread of invasive plants is tricky to keep track of," said Aslan. "Even if scientists are able to pin-point the site of introduction, it's very difficult to untangle the method, frequency and route of dispersal. In the case of fruit-eating migratory birds, this can be even more challenging as the seed dispersal is more widespread. The goal is to link specific birds with their new-found preferences for certain invasive plant species."
For example, the common North American bird the Yellow-rumped Warbler (Dendroica coronata) was reporte
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Ecological Society of America