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

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

The diagnostic value of a single measurement of superior vena cava flow in the first 24 h of life in very preterm infants

Low superior vena cava (SVC) flow has been associated with intraventricular haemorrhage (IVH) in very preterm infants. We studied the diagnostic value of a single measurement of SVC flow within the first 24 h of life in very preterm infants and its association with occurrence or extension of IVH in a setting of limited availability of neonatal echocardiography. Preterm infants who were born at less than 30 weeks gestation and who had an echocardiogram within 24 h after birth were eligible. Baseline, clinical and ultrasound data were collected. A total of 165 preterm infants were included. Low SVC flow (<41 ml/kg/min) occurred in six infants and was associated with severe IVH and extension of IVH, although this was not significant after adjusting for confounders. The only independently associated variable with low SVC flow was admission temperature (odds ratio 0.27, p = 0.001). A review of SVC flow values shows that these are higher now than initially reported. This study does not show an association of low SVC flow and severe IVH or extension of IVH after adjusting for confounders as a single measurement of SVC flow did not add any diagnostic value in this cohort. Thus, the exact role of SVC flow measurements in the circulatory assessment of preterm infants remains to be elucidated. However, admission temperature may have an effect on systemic blood flow in very preterm infants

Arrival date and territorial behavior are associated with corticosterone metabolite levels in a migratory bird

International audienceGlucocorticoids promote the mobilization of energy stores and they may facilitate the expression of energetically expensive functions. Early arrival on the breeding grounds in migratory species and territorial competition are energetically demanding activities that may be supported by elevated baseline glucocorticoid levels. Here, we evaluated the associations between the baseline levels of excreted corticosterone (CORT) metabolites of male Pied Flycatchers () just after arriving on their breeding area and timing of arrival, considering ornamental traits indicative of social status, like forehead patch size and black plumage coloration, as well as heat shock protein levels (HSP60). We observed a positive association of CORT metabolites with HSP60 levels, which are synthesized under several environmental challenges affecting cell homeostasis. Our data showed a negative association between arrival date and CORT metabolite levels, possibly as a result of the higher energetic demands imposed by the hard environmental conditions experienced at the time of an early arrival after migration. We observed a negative relationship of forehead patch dimensions and CORT metabolite levels, suggesting that dominance is associated with low baseline CORT metabolites. Also, males that expressed a higher degree of territorial behaviour when exposed to a playback song of a conspecific at their nest-box showed higher CORT metabolites upon arrival than males that expressed a lower degree of territorial behavior. This may indicate that elevated baseline CORT metabolite levels may facilitate an intense territorial competition in males. Thus, male–male competition may be a factor affecting observed baseline glucocorticoid levels in migratory birds