Abstract
Patterns of migration including connectivity between breeding and non-breeding populations and intraspecific variation in the distance travelled are important to study because they can affect individual fitness and population dynamics. Using data from 182 band recoveries across North America and 17 light-level geolocators, we examined the migration patterns of the northern flicker (Colaptes auratus), a migratory woodpecker. This species is unusual among birds because males invest more in parental care than females. Breeding latitude was positively correlated to migration distance because populations in the north appeared to travel farther distances than southern populations to find wintering locations with little snow cover. Connectivity was strong for populations west and east of the Continental Divide. Contrary to the three main hypotheses for intraspecific variation in migration distance, females wintered, on average, farther north than males, although there was overlap throughout their non-breeding range. This pattern contradicts those of other species found to date and is most consistent with the fasting endurance hypothesis if investment in parental care depletes the energy reserves of male flickers more than females. We thus propose a new factor, parental effort, which may influence optimal wintering areas and migration strategies within birds, and encourage future experimental studies to test the relationship between parental care roles and migration strategies of the sexes.
Highlights
Birds exhibit diverse strategies for migrating between their breeding and wintering sites, such as variation in routes, timing and distances travelled
We propose a revision to the fasting endurance hypothesis that if parental care is energetically costly, providing parental care drains energy reserves so that the sex which provides more care should be more willing to travel to a favourable wintering habitat in order to recoup body condition
We study the northern flicker (Colaptes auratus), a woodpecker with partly reversed sex roles in which males do most of the excavation of nesting cavities [16], do more incubation and brooding of the young than females [17], feed the young slightly more [18] and provide care for a longer time [19]
Summary
Birds exhibit diverse strategies for migrating between their breeding and wintering sites, such as variation in routes, timing and distances travelled. Many individuals in 2 the Northern Hemisphere show roughly north–south parallel movements meaning that westernbreeding populations winter farther west than eastern-breeding populations, on a continental scale [2,3,4,5]. Populations may differ in their propensity to migrate based on latitude. In other cases ‘leapfrog’ migrations may occur where northern-breeding populations winter at more southerly latitudes than do the southern-breeding populations [8]. In contrast to ‘leapfrog’ migration, occurs when winter populations occur in the same north–south sequence as breeding populations [1]
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