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[[circled page number]] 20

[[Sitt]]i and the Blue and Orange Tanager do when their are no mixed flocks around? Especially early in the morning? (It seems likely that mixed flocks do not form until some time after dawn.)
   Presumably Blue & Black's are not very "successful" as passive nuclear species (i.e. are not always followed by other species) simply because they often take [[underline]] long [[/underline]] flights. (The BCBT's in Chiriqui may be so "successful" because their flights are always or almost always short. Their flights do not cause them to "disappear" suddenly. Their companions probably can usually hear and/or see them, still, after they have flown.
[[margin, in red]] Gen [[/margin]]      My observations here, this year and in 1962, [[underline]] indicate that every single one of the local species [[/underline]], belonging to the groups in which I am interested (i.e. honeycreepers, tanagers, Whitestarts, and bush finches), [[underline]] occurs in mixed flocks at least occasionally [[/underline]]. The only possible exception is [[underline]] Atlapetes brunnei-nucha [[/underline]].
    This is really quite incredible!
    The behavior of many of the birds here is excellent evidence that the principal advantage of joining mixed flocks is protection against predators. Certainly many of the birds in mixed flocks are not feeding on insects while with the flocks. Only attendant flycatchers make flycatching flights. GT's certainly spend all or most of their time getting fruit. So, in all probability, do many of the other tanagers (I have yet to see [[underline]] Buthraupis [[/underline]] take anything but fruit)
    I am not sure that there is anything like a [[underline]] purely[[/underline]] treetop mixed flock here. I think that all the flocks I have seen, so far, have included at least one member who occasionally came down into at least moderately low scrub.