North American Crane Working Group

 

Date of this Version

2008

Document Type

Article

Citation

Hayes, M.A., J.A. Barzen, and H.B. Britten. Mate fidelity in a dense breeding population of sandhill cranes. In: Folk, MJ and SA Nesbitt, eds. 2008. Proceedings of the Tenth North American Crane Workshop, Feb. 7-10, 2006, Zacatecas City, Zacatecas, Mexico: North American Crane Working Group. p. 168.

Comments

Reproduced by permission of the North American Crane Working Group.

Abstract

The objective of this study was to investigate mate switches observed in a dense breeding population of banded Sandhill Cranes (Grus canadensis). Over a 14-year period, 50 of 70 breeding pairs switched mates (71%), with 45 pairs switching permanently (64%). Mean mate retention between years was 83%, with an average pair bond lasting 5.7 years (range 1-13 years). Most permanent switches occurred following the death or disappearance of a mate, and overall permanent divorce (19%; 13 of 70 pairs) and annual divorce rates (6%) were low. Territory retention following mate switches was high. Males and females did not differ in their ability to retain their original territory. Retaining their original territory after a mate switch, however, did not increase reproductive fitness for either sex. Previous reproductive success was not a significant cause of divorce, nor did an individual crane’s reproductive success significantly increase following divorce. Five of the 13 divorced pairs (38%) fledged at least one chick to fall migration prior to divorcing. Also, 10 of 57 pairs that did not divorce went 5-8 years without fledging chicks without observation of divorce. There was evidence to suggest that sandhill cranes may choose to divorce in response to an opening on a nearby territory. Having a breeding territory may take precedence over reproductive success experienced by a pair. If a nearby territory becomes available, a breeding adult sandhill crane in this population may have to choose between staying with a current mate (possibly weighing reproductive history) and changing mates and perhaps territories to increase reproductive success.