| interspecific differences in hematozoan infection in sonoran desert aimophila sparrows. | numerous studies have identified factors that control avian hematozoan infections, but the mechanisms that account for host differences in parasitemia remain largely speculative. to address this issue, we compared the prevalence of these parasites in stained blood smears from four conspecific sonoran desert aimophila sparrow species sampled during their breeding season: rufous-winged (aimophila carpalis; rwsp), rufous-crowned (aimophila ruficeps; rcsp), cassin's (aimophila cassinii, casp), and b ... | 2005 | 16244063 |
| control of luteinizing hormone and testosterone secretion in a flexibly breeding male passerine, the rufous-winged sparrow, aimophila carpalis. | rufous-winged sparrows, aimophila carpalis, reside in the sonoran desert and although testicular development is initiated in the spring under the influence of increasing day length, breeding occurs opportunistically in summer in association with heavy rainfall or "monsoon". the aim of this study in free-living male rufous-winged sparrows was to establish the relationship between concentrations of plasma luteinizing hormone (lh) and testosterone (t), and breeding associated with heavy rainfall, a ... | 2006 | 16876798 |
| acute stress rapidly decreases plasma testosterone in a free-ranging male songbird: potential site of action and mechanism. | we used a free-ranging, seasonally breeding adult male songbird, the rufous-winged sparrow, aimophila carpalis, to investigate the effects of acute stress-induced by capture followed by restraint, on the hypothalamo-pituitary-testicular axis. intra- and interindividual comparisons revealed that males decreased their plasma testosterone (t) by 37-52% in response to acute stress. the decrease occurred within 15 min of capture and persisted for at least another 15 min. within 15 min, the decrease i ... | 2010 | 20691650 |
| relative photorefractoriness, prolactin, and reproductive regression in a flexibly breeding sonoran desert passerine, the rufous-winged sparrow, aimophila carpalis. | we tested the hypothesis that adult male rufous-winged sparrows, aimophila carpalis, exhibit relative photorefractoriness. this condition results in partial loss of sensitivity to photoperiod as a reproductive stimulus after prolonged exposure to long photoperiods and is similar to the mammalian condition called photoperiodic memory. captive birds were exposed either to 8 h of light/16 h of dark per day (8l) or to 16l for 11 weeks and were then exposed either to 8l, 13l, 14l, or 16l. testicular ... | 2008 | 18258759 |
| photoperiod-independent hypothalamic regulation of luteinizing hormone secretion in a free-living sonoran desert bird, the rufous-winged sparrow (aimophila carpalis). | we investigated the regulation of luteinizing hormone (lh) in the male rufous-winged sparrow,aimophila carpalis, a resident of the sonoran desert that breeds after irregular summer rains. although the testes develop in march due to increasing photoperiod and regress in september due to decreasing photoperiod, lh does not consistently increase in the spring as in other photoperiodic birds. however, throughout the year increased plasma lh is correlated with rainfall. to investigate this rainfall-a ... | 2008 | 18032888 |
| auditory stimulation of reproductive function in male rufous-winged sparrows, aimophila carpalis. | prolonged exposure to conspecific song stimulates gonadal function and reproductive hormone secretion in female birds but few studies have investigated the physiological effects of conspecific song exposure on males outside of short-term, aggressive interactions. we exposed male rufous-winged sparrows, aimophila carpalis, either to conspecific song (cs song), to heterospecific song (black-throated sparrow, amphispiza bilineata; hs song), or to no recorded song (no song) for 59 consecutive days ( ... | 2008 | 17920598 |
| plasticity of the rufous-winged sparrow, aimophila carpalis, song control regions during the monsoon-associated summer breeding period. | in most temperate zone songbirds, exposure to increasing photoperiod in the spring stimulates the reproductive system and induces reproductive behaviors. additionally, the brain regions that control singing (song control regions; scrs) are larger during the breeding season, thus paralleling changes in the activity of the reproductive system. however, in some birds, environmental factors other than photoperiod initiate breeding. for example, free-living male rufous-winged sparrows develop their t ... | 2007 | 17673216 |
| environmental regulation of the reproductive system in a flexibly breeding sonoran desert bird, the rufous-winged sparrow, aimophila carpalis. | we investigated reproductive regulation in male rufous-winged sparrows, aimophila carpalis, a sonoran desert passerine that breeds after irregular summer rains. field and captive data demonstrate that increased photoperiod stimulates testicular development in march and maintains it until early september. free-living birds caught in july and placed on captive long days (16l: 8d) maintained developed testes for up to 7 months, and free-living birds caught in september, during testicular regression ... | 2007 | 17321527 |