Darvell H

Hohtola E

Lange CH

Longmoor GK

Orell M

Rytkönen S

Smulders TV

Vatka E

Walker L

In most species of seasonally breeding songbirds studied to date, the brain areas that control singing (the song control system: SCS) are larger during the breeding season than at other times of the year. In the family of titmice and chickadees (Paridae), one species (the blue tit, Cyanistes caeruleus) shows the “traditional” pattern of seasonal changes, while another species (the black-capped chickadee, Poecile atricapillus) shows at best much reduced seasonal changes in the SCS. To test whether this pattern holds up in the two Parid lineages to which these two species belong, and to rule out that the differences in seasonal patterns observed were due to differences in geography or in laboratory, we compared the seasonal patterns in two song system nuclei volumes (HVC and Area X) in willow tits (Poecile montanus; closely related to black-capped chickadees) and great tits (Parusmajor; more closely related to blue tits) from the same area around Oulu, Finland. Both species had larger gonads in the spring than during the rest of the year. Great tit males had a larger HVC in the spring than at other times of the year, but their Area X did not change in size. Willow tits showed no seasonal change in HVC or Area X size, despite having much larger gonads in the spring than the great tits. Our findings suggest that the song system of willow tits and their relatives may be involved in learning and producing non-song social vocalizations. Since these vocalisations are used year round, there may be year-round demand on the song system. The great tit and blue tit HVC may change seasonally because demand is only placed on the song system during the breeding season, since they only produce learned vocalisations during this time. We suggest that changes were not observed in Area X because its main role is in song learning, and there is evidence that great tits do not learn new songs after their first year of life. Further study is required to determine whether our hypothesis about the role of the song system in the learned, non-song vocalisations of the willow tit and chickadee is correct, and to test our hypothesis about the role of Area X in the great tit song system

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Different seasonal patterns in song system volume in willow tits and great tits

Different seasonal patterns in song system volume in willow tits and great tits

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