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    Author(s): Yvette K. Ortega; Leigh F. Greenwood; Ragan M. Callaway; Dean E. Pearson
    Date: 2014
    Source: Biological Invasions. 16: 1757-1767.
    Publication Series: Scientific Journal (JRNL)
    Station: Rocky Mountain Research Station
    PDF: Download Publication  (374.37 KB)


    Exotic species can provide abundant food resources for native consumers, but predicting which native species will respond positively remains a challenge. We studied the foraging behavior of blackcapped (Poecile atricapillus) andmountain (P. gambeli) chickadees in westernMontana to compare the degree to which these congeric and syntopic consumers exploited larvae of Urophora, an exotic biological control insect living within the seedheads of the invasive forb, spotted knapweed (Centaurea stoebe). Chickadees typically forage within tree or shrub cover, whereas knapweed and hence Urophora larvae thrive in open grassland away from cover. We found that black-capped chickadeesweremuchmore likely thanmountain chickadees to forage for Urophora. Black-capped chickadees strategically minimized time spent in open habitats by flying out from cover to retrieve knapweed seedheads and immediately returning to cover to extract the larvae. Black-capped chickadees also employed an atypical hovering technique nearly twice as often as their congeners did, particularly when foraging away from cover. Via this hovering technique, birds were able to gather knapweed seedheads from erect plants rather than searching for seedheads on the ground. These shifts in foraging behavior allowed black-capped chickadees to exploit Urophora larvae to amuch greater degree than their congeners while minimizing exposure to a highrisk habitat, an outcome with potentially important community-wide consequences. Behavioral flexibility has been used to predict the success of invading species. We suggest that behavioral flexibility may also be used to predict how native species will respond to invasions, particularly the availability of exotic food resources.

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    Ortega, Yvette K.; Greenwood, Leigh F.; Callaway, Ragan M.; Pearson, Dean E. 2014. Different responses of congeneric consumers to an exotic food resource: Who gets the novel resource prize? Biological Invasions. 16: 1757-1767.


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    behavioral plasticity, biological control agent, food subsidy, foraging behavior, Urophora

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