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Citation:
Hayes, M. A., and J. A. Barzen. 2016. Timing of family dissociation does not affect long-term survival estimates of sandhill crane chicks. Proceedings of the North American Crane Workshop 13:33-41.
Abstract:
Sandhill crane (Grus canadensis) chicks depend on their parents beyond fledging, but timing of chick separation from their parents has rarely been quantified and reported. We color-banded and radio-tagged sandhill crane chicks on known natal territories in south-central Wisconsin and monitored family groups to determine age of chick independence. Using a Cormack-Jolly-Seber open population model in program MARK, we estimated survival for chicks that dissociated from their parents prior to fall migration, over winter (including migration), and following spring migration. Of 96 chicks with a known timing of dissociation from their parents, 11 (12%) became independent from their parents in the fall before migration during their hatch year, 76 (79%) became independent over winter, and 9 (9%) returned from spring migration with their parents and then became independent. Mean age (±1 SE) at independence varied from 146 ± 7 days (fall) to 248 ± 14 days (off breeding areas) to 335 ± 11 days (spring). Season of chick dissociation did not affect whether a chick was philopatric or dispersive in its first year. Lifetime survival estimates were high (92%) and did not generally differ based on marking scheme (radio-tagged vs. color-banded), sex (male or female), or timing of dissociation (fall, off breeding areas, or spring). Chicks that did not migrate with their parents likely learned migratory routes and behaviors from conspecifics. More research on interactions between parents, their offspring, and other conspecifics off breeding areas (winter and migratory stopover areas) could provide insight into dissociation patterns and the mechanism of separation.
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© 2016 North American Crane Working Group
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