Breeding on the leading edge of a northward range expansion: differences in morphology and the stress response in the arctic Gambel’s white-crowned sparrow

Abstract

Individuals at the forefront of a range shift are likely to exhibit phenotypic traits that distinguish them from the population breeding within the historic range. Recent studies have examined morphological, physiological and behavioral phenotypes of individuals at the edge of their range. Several studies have found differences in the hypothalamic–pituitary–adrenal (HPA) axis activity in response to acute restraint stress in individuals at the range limits. HPA axis activation leads to elevations in glucocorticoids that regulate physiology and behavior. Here we compare the hormonal profiles and morphometrics from Gambel’s white-crowned sparrows (Zonotrichia leucophrys gambelii) breeding at the northern limit of the population’s range to those birds breeding within the historic population range. Birds breeding at the northern limit experienced a harsher environment with colder temperatures; however, we found no differences in arthropod prey biomass between the northern limit and more southern (historic) sites. Males at the northern limit had higher body condition scores (mass corrected for body size) compared to individuals within the historic range, but no differences were found in beak and tarsus lengths, wing chord, muscle profile or fat stores. In males during the pre-parental stage, before breeding commenced, HPA axis activity was elevated in birds at the northern limit of the range, but no differences were found during the parental or molt stages. Females showed no differences in HPA axis activity during the parental stage. This study suggests that “pioneering” individuals at the limits of their breeding range exhibit physiology and morphology that are distinct from individuals within the historic range.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-015-3447-7) contains supplementary material, which is available to authorized users.

How birds cope physiologically and behaviourally with extreme climatic events

“…Lapland longspurs responding to an extreme weather event had elevated levels of corticosterone when tested with a standardized stressor (capture, handling and restraint) whereas baseline levels were not different [24,26]. Similar results were obtained for white-crowned sparrows breeding at the northern edge of their range in Alaska and in a more harsh environment (see [53]). There may be numerous reasons to explain these apparent anomalies given that corticosterone receptors can change, as can blood levels of a binding protein, corticosterone-binding globulin [14].…”

Behavioral and physiological traits of migrant and resident White-crowned Sparrows: a common garden approach

“…Comparing the local habitats for each subspecies -coastal versus the Central Valley -each differs in terms of structure, floral and faunal communities, as well as climate, all of which likely contribute to differential demands and responses of the HPA axis. Furthermore, stress-induced levels are elevated upon arrival in spring and onset of breeding in free-living Z. l. gambelii, whereas Z. l. nuttalli show a more muted response at the outset of their breeding stage (Addis et al, 2011;Krause et al, 2015aKrause et al, , 2016. However, under our common garden conditions without the imposition of natural environmental demands, birds showed similar baseline and stress-induced responses.…”

Species’ traits as predictors of range shifts under contemporary climate change: A review and meta‐analysis

“…The growing coverage of global trait databases, such as TraitNet (traitnet.ecoinformatics.org), Elton Traits (Wilman et al., ), and the TRYplant trait database (http://www.try-db.org), will facilitate standardization of trait data, but future analyses should also include trait sets that are comparable to other studies. Further complications in quantifying traits may arise due to trait variation within a population, particularly if individuals at an expanding range edge have different traits than individuals in the range center (Bowler & Benton, ; Chuang & Peterson, ; Krause et al., ).…”

“…Further complications in quantifying traits may arise due to trait variation within a population, particularly if individuals at an expanding range edge have different traits than individuals in the range center (Bowler & Benton, 2005;Chuang & Peterson, 2016;Krause et al, 2016).…”