92 STUDIES IN A VIAN BIOLOGY NO. 2

on high-quality habitat throughout the br eding ea. on (e.g., ar a Z in Fig. 41 b) a a re ult of increased tolerance by breeder given unusually abundant acorn into the um­mer month .

During the year, floater earch for and fill available breeding vacancie as hown in Figure 41. Although breeding vacancie ari. e from breeder death throughout uitable habitat, floater have the greate t probability of gaining a breeding vacancy either in poor quality habitat where breeder turnover may be greater or in high-quality habitat where breeder den ity ha been reduced by an acorn crop failure. Al o as hown in Figure 41, there is movement of breeder from one territory to another, often from lower to higher quality habitat. Not illu trated are the relatively rare regional acorn crop failures that may re ult in breeder den ity decline and ub equent low reproducti e output over a broad area providing increa ed opportunity for di per ing off pring and older floater to gain a territory and breeding status.

The e pattern of habitat quality and acorn production, the varied behavior floater. employ to acquire breeding pace and exploit re ource , the behavioral interaction be­tween territorial jay and floater , and the ability of breeder to move and impro e the quality of their territorie all promote election for early disper al and floating in . crub­jays in central coastal California, and election again t cooperative breeding.

ACKNOWLEDGMENTS

Fanny Hastings Arnold, through her continuou genero. ity, and the Mu. eum of Vertebrate Zoology, provided the exqui ite Hasting Natural History Re ervation where this research was done. Financial a. sistance was provided by the Department of Fore ·try and Re. ource onservation (Oliver Lyman Fund), the merican Mu. eum of Natural History (Frank M. Chapman Memorial Fund), Sigma Xi, the American Acad my of Sciences (0. C. Marsh und), and the Museum of Vertebrate Zoology (Kellogg Fund). I was also supported by University Fellowships, Graduate Minority Fellowships, and a Betty . Davis M morial Fellowship.

l am especially grateful to Walt K enig and Ron Mumme for their companionship at Hastings and their ideas con erning cooperative breeding. Frank Pitelka and Dal McCullough continu­ally sent me back to the field with new ideas and rekindled enthusiasm. Numerous field assis­tants worked on the study: Greg shcroft, Bob Beffy, Clay Clifton, haron Dough rty, Len re Feinburg, and Jim iegel , all of whom braved long hours and certain exposure to poison oak in . earch of s rub-jay nests.

Frank Pitelka, Walter Koenig, Ron Mumme. Glen Woolf nd n, John itzpatrick, P t r Sta ey, and Dale Mc ullough made numerous helpful criticisms of earlier drafts. Jo eph Jehl and John Rotenberry provided long-term editorial support. Karen J. Nardi pro ided love and understanding and both the finan ial and moral support needed to complete the study. To all of these individuals I give my sincere thanks.

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