Examination of nocturnal activity and behaviour in resident white-crowned sparrows (Zonotrichia leucophrys nuttalli)

摘要

Observations of nocturnal activity in resident species held in captivity are often attributed to migratory restlessness (MR). Previous publications investigating migratory white-crowned sparrows (Zonotrichia leucophrys gambelii) provided a distinct set of traits characteristic of MR, which we used to test the expression of activity and behaviour in the resident subspecies (Z. l. nuttalli). Under a winter photocycle, the 24-h activity profile of Z. l. nuttalli closely resembled that of migrant relatives. Following photostimulation, most birds expressed some activity during the dark phase; however, the diel pattern differed greatly from that of migrants. Unlike Z. l. gambelii, peak activity levels during the light phase remained greater than those expressed during the dark phase. Furthermore, birds did not express a quiescent phase prior to the initiation of the dark phase, nor did photostimulation result in increases in body mass or fat deposits. However, two birds did exhibit migration-specific behaviours (beak-up and beak-up flight) coupled with intense dark phase locomotor activity, which is consistent with MR expression. The suite of contrasts between conspecifics however, may suggest a different context of nocturnal behaviour, perhaps representing an underlying ancestral migratory phenotype that may now be associated with territorial or reproductive activities.