| ecological factors affecting the adrenocortical response to stress in chestnut-collared and mccown's longspurs (calcarius ornatus, calcarius mccownii). | secretion of the steroid hormone corticosterone (cort) in response to perturbations results in behavior patterns that can maximize survival. three commonly cited hypotheses suggest that during breeding, there are advantages associated with suppressed (cort) secretion in (1) the sex that is most important for parental care, (2) individuals in good body condition, and (3) species with a short breeding season and limited renesting opportunities. we addressed these hypotheses in two midlatitude bree ... | 2013 | 13130435 |
| songbird response to rest-rotation and season-long cattle grazing in a grassland sagebrush ecosystem. | grazing on natural rangelands, which are areas dominated by native vegetation that are used for livestock grazing, can achieve desired vegetation outcomes, preserve native habitat, and economically benefit multiple stakeholders. it is a powerful tool that can be manipulated to reduce wildlife declines and benefit ecosystems. however, the benefits of conservation grazing systems on many wildlife communities remain relatively unexplored. we compared songbird communities between two grazing systems ... | 2017 | 28946000 |
| a phylogenetically controlled test of hypotheses for behavioral insensitivity to testosterone in birds. | in most male birds that exhibit paternal care, extending the spring testosterone (t) peak throughout the breeding season reduces nestling provisioning. however, in some species, this trade-off between high t and expression of paternal care is absent. for example, during some or all of the nestling period, t did not affect paternal behavior in male lapland longspurs (calcarius lapponicus), chestnut-collared longspurs (calcarius ornatus), and great tits (parus major). two ecological constraints ha ... | 2005 | 15664020 |
| dissociation of testosterone and aggressive behavior during the breeding season in male chestnut-collared longspurs, calcarius ornatus. | in many species of birds, expression of male-male aggression during breeding elicits increased secretion of testosterone. elevations in testosterone in turn enhance expression of aggressive behavior in appropriate contexts. however, in other species, the relationship between elevated plasma testosterone and aggressive behavior is subtle or nonexistent. we examined the relationship between high testosterone and male-male aggression in the chestnut-collared longspur, a species in which males exhib ... | 2008 | 18275961 |
| effects of shallow natural gas well structures and associated roads on grassland songbird reproductive success in alberta, canada. | grassland songbird populations across north america have experienced dramatic population declines due to habitat loss and degradation. in canada, energy development continues to fragment and disturb prairie habitat, but effects of oil and gas development on reproductive success of songbirds in north american mixed-grass prairies remains largely unknown. from 2010-2012, in southeastern alberta, canada, we monitored 257 nests of two ground-nesting grassland songbird species, savannah sparrow (pass ... | 2017 | 28355241 |