NOTES

OBSERVATIONS ON THE NEST BEHAVIOR OF THE SCRUB

To our knowledge no one has reported sustainedobservations of the nest behavior of the California Scrub Jay ( coemlescens).Incomplete observationsof one nest were reportedby Michenerand Michener(1945). On 28 March 1972 we found a completednest on a steepravine about five feet from the ground in a Toyon (Heteromeles arbu•folia) on the Point Reyes National Seashorein Marin Co., California. We watched the nest from a blind 30 feet away for 61 hoursand 53 minuteson the 2nd, 5th, 6th, 7th, 8th, 10th, 11th, and 17th days after the first egg hatchedand once during the incubationperiod. Sincethe parents had been color bandedpreviously we knew that the female was 4 years old and the male at least 3. The female laid $ eggsand incubationlasted 18 days. Bent (1946) reported that incubationwas 14 to 16 days.The malewas not observedincubating. During the only sustainedobservation of adults during the incubationperiod, the female sat on the eggsfor 3 hours and 7 minutesbefore leaving the nest. During the 51 minutesshe was off the nest sheranged over most of the defendedterritory. The young hatched one at a time during a two-day period. The night after the last young hatched it rained and the next morning at 0600 the female was observed taking a dead nestlingfrom the nest. The last nestlingto hatch was noticeably smaller than the earlier ones;we assume,therefore, that becauseof the rain and becausethe youngestnestling was probably the weakest,that this nestlingdied. When the eggshatched the male began to bring food to the female and the nestlings.Upon arrivingat the nest he would poke hisbeak asfar ashe couldinto the female's mouth transferring some of his food to her. Then usually both parents fed the nestlings.The number of trips made by the male was •elatively constant until day 10 but increased after that (Figure 1). The female began bringingfood to the nest for the youngon day 7. The increasein feedingtrips to the nest by the female on day 11 coincidedwith her cessationof broodin• the young (Figures1 and 2). At this time the male stoppedfeeding the femaleat the nest. Some time between day 14 and 16 another nestling died. When we color bandedthe nestlingson day 10 this nestlinghad the least developedplumage so we assumethe nestlingthat died wasthe youngestin the nestat that time. The first young jay left the nest during the afternoon of day 24. Bent (1946) reported that young are able to leavethe nest in 18 days. His behaviorduring the previous2 days suggestedthat he was ready to leave.He would jump hack and forth acrossthe nest when the parentscame to feed, occasionallyhopping out when the parentsleft, but returningeiich time to snuggleinto the nest with the other young. When he f'mally left the nest for food, one of the other nestlings stoodin the nestlooking in his directionand makingcrying sounds. This behavior continuedfor sometime. The secondremaining nestling, on the otherhand, just sat in the nest with no apparent concern.The next day these two nestlingsalso left (day 25), but a small pile of young jay feathersfound later about 15 feet from the undisturbednest •uggested that one youngwas killed by a predatorafter leaving.It appears,therefore, that two of the originalfive youngsurvived. Throughoutthe nestingperiod the parent vigorouslydefended their territory againstall other Scrub Jaysand they were the only adultswe observed Calif. Birds 3: 93-95, 1972 93 NOTES

3.0 770 I•J Male .•65 2.5 k•{ Female

795 415 165 140 120 705

1.0

0.,5

II II II 2 5 6 7 8 I0 II 17 Days after hatching

Figure 1. Averagenumber of feedingtrips to nestby ScrubJay pair. Numbers abovethe bars representminutes of observation.

IOO

415

80- 795 165

60-

705 120 40- 140

20-

770 0 / / 2 5 6 7 8 I0 II 17 Days after hatching

Figure 2. Percentof time femaleScrub Jay broodedyoung. Numbers above the bars representminutes of observation. 94 NOTES feedingthe nestlings. We thank Kate Darling, Sharon Long, Keller McDonald and Jim Higbeefor their observationsat the nest and Nick Story for drawing the figttres. This is Contribution $ 7 of the Point ReyesBird Observatory.

LITERATURE CITED

Bent, A. C. 1946. Life histories of North American jays, crowsand titmice. Nat. Mus. Bull. 191. Michener,H. and J. Michener.1945. Californiajays, their storageand recoveryof food, and observationsat one nest. Condor 47:206-210.

Robert M. Stewart, Stephen M. Long and Meryl Stewart, Point Reyes Observatory,P.O. Box 321, Bolinas,Cah•fornia 94924. •

Sketch by Tim Manolis

95 BACK ISSUES AND FIELD LISTS AVAILABLE

Back issuesof California Birds are available at $6.00 for Volume i (1970) and $5.00 for Volume 2 (1971). The CFO Field List of the Birds of California (1972), a 16 page checklist designed for recording 10 field trips, can be obtainedat a cost of $1.00 for 4 copies(additional copies 25c each), including tax and postage.Back issuesand field lists may be ordered from Clifford R. Lyons, Treasurer,Post Office Box 369, Del Mar, California 92014. Make checks payableto California Field Ornithologists.

Membership dues and changesof addressshould be sent to Clifford R. Lyons, Treasurer, Post Office Box 369, De1 Mar, California 92014. Classesof member- ship (all include subscriptionto California Birds): Patron, $1000; Life, $150; Supporting, $20 annually; Contributing, $10 annually; Regular, $5 annually. Make checkspayable to California Birds.

Manuscriptsshould be sent to California Birds, Post Office Box 369, Del Mar, California 92014. Use of the CBE Style Manual, 3rd ed., 1972, is suggestedas a guide in preparingmanuscripts. It is availablefrom the AmericanInstitute of Biological Sciences,3900 WisconsinAvenue, NW; Washington,D.C. 20016 for $6.00. Fifty reprints of each article ate provided free of charge.Arrangements for additional reprints may be made at the time manuscriptsare submitted;the additional cost will be borne by the contributor.

Rate bird reports shouldbe sent to Jon Winter, Secretary,Rare Bird Commit- tee, Point Reyes Bird Observatory, Mesa Rd., Bolinas. California 94924.

Layout and cover designby Virginia P. Johnson

96