Birds of Indian Subcontinent

Influence of Site Fidelity on Mate Switching in Urban-Breeding Merlins (Falco columbarius)

Publication Type:Journal Article
Year of Publication:1991
Authors:Warkentin, IG, James, PC, Oliphant, LW
Journal:The Auk
Date Published:1991
ISBN Number:00048038
Keywords:Aesalon, Aesalon columbarius, Canada, Falco, Falco columbarius, Falconidae
Abstract:From 1985 to 1989, we examined 120 nesting attempts by urban-breeding Merlins (Falco columbarius) in Saskatoon, Saskatchewan, Canada. Males showed significantly higher levels of site fidelity from year to year than females. Males returned to the same nesting area 61% of the time (n = 28), while females returned to the same nesting area a second year only 28% of the time (n = 39). Mate fidelity was low among Merlins in this population (only 20% of 60 pairings contained the same birds for two successive years), and it appeared largely related to the degree of site fidelity. The rate of interyear mate switching in this population (change of mate when both members of a pair were known to be alive the second year) was >68% (n = 19). Among males, mate and site fidelity were statistically independent. Thus, when males maintained the same nesting area between years, the probability of retaining the same mate was no better than by chance (58% of 12 males found retaining the same nesting area were paired with a different mate the second year, compared with 85% of 7 males who moved to a different nesting area and acquired a different mate). In contrast, among females, mate and site fidelity were not independent. Females who changed nesting area were unlikely to have the same mate (91% of 11 females), but those that remained on the same site were more likely to have the same mate (71% of 7 females). There was no apparent benefit of site or mate fidelity to Merlin productivity, measured as the number of young produced per nesting attempt. Birds that had been paired for two or more years did not have significantly higher productivity than those pairs that remained together for only one year. Likewise, previous experience on a site did not significantly improve an individuals' productivity when both birds were the same or only one of the pair was the same, compared with that of pairs where both birds were new to the site. Low site and mate fidelity within this population may reflect the absence of selective pressure favoring fidelity.
Short Title:The Auk
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith