Diurnal Rhythm of Attentiveness of Incubating Female Tree Sparrows (Spizella Arborea) at a Northern Latitude

Weeden, J

Nest attentiveness was studied in Alaska (65°25' N, 145°32' E) by using photo-resistors mounted in the nests to indicate the presence or absence of the female by the amount of light striking the photo-resistor. The pattern of activity of incubation became gradually established during the egg-laying stage. The first attentive interval was the night rest spent on the nest as soon as laying began, followed on the second last day of laying by the establishment of attentive periods preceding and succeeding the night rest, and finally on the day of clutch completion by the establishment of daytime attentiveness. During incubation the rhythmic alternation of attentive and inattentive periods varied throughout the day. The attentive periods were significantly longer in the intervals preceding and succeeding the night rest than during midday. The mean length of attentive periods preceding and succeeding the night rest varied between 23 and 30 minutes, while the mean daytime intervals varied between 12 and 17 minutes. The mean length of inattentive periods varied between 6.7 and 9.4 minutes throughout the day. No change in this pattern was observed as incubation progressed. Total daytime activity of female Tree Sparrows during the incubation period in continuous daylight was 16 to 17 hours, a value similar to that of passerine species in temperature regions. The total daytime activity of females at Eagle Creek was three to four hours shorter than that of male Tree-Sparrows. During the nestling stage the attentive periods were shorter but the total length of attentiveness throughout the day was greater. The interval preceding the night rest during the nestling stage continued to have short attentive intervals similar to those during midday. Temperature apparently did not influence the length of the attentive or inattentive periods. It did, however, influence the total daytime activity. On warm days, when the birds had a good feeding opportunity, they tended to retire earlier t

Diurnal Rhythm of Attentiveness of Incubating Female Tree Sparrows (Spizella Arborea) at a Northern Latitude

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