FACTORS INFLUENCING REPRODUCTIVE SUCCESS AND NESTING STRATEGIES IN BLACK TERNS

摘要: Factors which might influence reproductive success, coloniality and the timing of breeding in Black Terns (Chlidonias niger) were examined. The most important factors influencing hatching success (overall average 73%) rising water levels wind wave action (average 15.4%). second largest temperature precipitation. Predation was only responsible for 8.6% overall losses. factor fledging 61%) that last chick to hatch grew significantly more slowly, showed signs starvation eventually died, independent clutch size. Tern young ate 55% odonates, 35% other insects, 10% fish. Peaks odonate emergence differed by as much 15 weeks between years rate decreased from 1981-1984. Foraging adults 5.09 items/min b when catching 0.82 fish 2.03 insects simultaneously. preferred nest areas with 33% open water, 42% matted vegetation 25% standing stalks occupied 10-50 cm2/m2 at surface. Water level fluctuations variable over years, but greatest early season. Changes 2 cm destroyed some nests. Experimental evidence nests surrounded or on a platform suffered least fluctuating levels. Nests ~halaris habitats survived better than those habitat types. low this study. Observations potentially predatory species corvids mobbed equally during egg phases Great Blue Herons mainly phase. abundance did not vary throughout Coloniality can be explained are usually invoked species. terns loose colonies benefit joint mobbing, scattered enough permit food obtained near nest. More precise synchronization season is favored because unpredictable. ACKNOWLEDGEMENTS I would like thank my senior supervisor, Dr. Nicolaas A. M. Verbeek always being available willing discuss provide feedback project, including design, results conclusions, well editorial comments manuscript. My thanks also go committee members Brian Hartwick Mark Winston providing useful project manuscript . staff Creston Valley Wildlife Management Area, namely Dwight Moore, Stushnoff, Harold Casemore, Sandra Hopcraft Carmen Wood very helpful terms access study moving large pieces equipment. am particularly grateful Moore allowing use Area equipment facilities. Many Stushnoff help identification plant following gratefully acknowledged assistance field: Ingrid Bonsel, Scott Forbes, Penny Ohanjanian, Terry Parsons Margaret Shamlock. thankful many people discussions Howie Richardson, Craig Orr, Rob Butler Ron Ydenberg. This research funded NSERC grant (A0239) N.A.M. Verbeek. extremely Santo financial writing stage project. Lastly, husband, Fred Mosher, assisting work Elizabeth Lake, moral support final stages so positive, supportive understanding had return Vancouver extensive periods prepare defense. TABLE QF CONTENTS Approval ii ABSTRACT iii v List Figures x Tables xi GENERAL INTRODUCTION ..l REPRODUCTIVE SUCCESS NESTING STRATEGIES .. 3 A) COLONIALITY B) TIMING OF BREEDING 7 I1 STUDY AREA AND SEASONAL CHRONOLOGY 12 CRESTON VALLEY WILDLIFE MANAGEMENT ELIZABETH LAKE 16 I11 17 METHODS 18 RESULTS 0 Number nesting birds 20 Laying dates 1 ~eproductive 23 6 DISCUSSION 28 IV HABITAT AVAILABILITY NEST DISPERSION 33 35