WINTERING YELLOW-IIUMPED WARBLERS (DENDROICA CORONATA) TRACK MANIPULATED ABUNDANCE OF MYRlCA CERIFERA FRUITS

A s s m c r -Food ava~labihty during wmter may determme habitat use and limit populahens of ovenvintenng birds, yet its unportance is difficult to judge because few stud~es habc c.xperimentally tested the response of nonbreedlng birds to changes in resource abundance 'i41c expenmentally exammed the link between f ru~t avadability and habttat u.;r by manlpulat~ng wlnter abundance of Myrrca cenfcra L. (h4yncaceae) fruits in managed longleaf ( P l i ~ u s paiustrzs) and loblolly (P. taeda) pme stands in South Carohna Myrica crrlfera 1s a common understory shrub in the southeastern Umted States and provides lipid-nch frult ~n late winter (February and March), when Insects and other fru~ts are scarce. On treatment plots, we covered frulting M cerifera shrubs with netting in early winter to prevent blrds from eattng their fruits In late February, when M cerrfera fruit crops were largely depleted elsewhere on our study site, we uncovered the shmbs and documented the response of the btrd commuruty to those patches of h ~ g h frult availability. Relative to control plots, total bxd abundance (exdudmg the most common speues, Yellow-rumped Warbler [Dendrotcn coronafa]) and spenes richness did not change after net removal Yellow-rumped Warblers, however, became slgnihcantly more abundant on treatment plots after net removal, whtch suggests that they track M cenfera frult abundance We quggest that M r~tlfEra plays a role m determvllng the local dtstribuhon of ~mntering Ycllow-rumped Warblers at our study site. To put these results into a management context, we also exam~ned the effect of prescnbed fire frequencies on M cerlfera fruit production Across pme stands wlth different fire reglmes, M. cenfera frult abundance Increased with the number of years since burmng It takes 4 4 years for lndlvlduals to recover suff~uently from a burn to produce lmge quanbties of fnut Thus, shorter mtervals between burns will reduce wnter fruit availabihty Taken together, these results suggest that w~thm those plne plantahons, the local winter distribution of at least one common m~gratory blrd is closely bed to f ru~t abundance, which m turn is hed to the frequei1cy of prescnbed fires Recezved 22 October 2002, accepted 15 September 2003