| 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 |
| glutamatergic stimulation of luteinising hormone secretion in relatively refractory male songbirds. | seasonal breeding in two sonoran desert passerines, the cassin's (aimophila cassinii) and rufous-crowned (aimophila ruficeps) sparrows is thought to be terminated by the development of a decrease in responsiveness to photostimulation, a condition known as relative photorefractoriness. it was predicted that the development of relative refractoriness is a consequence of a decrease in gonadotrophin-releasing hormone (gnrh) synthesis and associated stores of releasable gnrh. this hypothesis was test ... | 2008 | 18673412 |
| avian reproductive failure in response to an extreme climatic event. | recently, climate change research has emphasized the potential increase in the frequency and severity of climatic extremes. we compared the reproductive effort and output among four species of passerine birds in coastal southern california, usa, a semi-arid region, during a normal precipitation year (2001) and the driest year in a 150-year climate record (2002). both reproductive effort and output differed dramatically between years. mean reproductive output among the four species was 2.37 fledg ... | 2005 | 15549403 |
| a phylogenetic analysis of the emberizid sparrows based on three mitochondrial genes. | previous molecular phylogenetic studies have examined the taxonomic relationships among a number of typical emberizid sparrow genera. to help clarify these relationships, we sequenced a 1673 base pair fragment for the complete sequence of three mitochondrial genes: adenosine triphosphatase (atp8 and atp6) and cytochrome oxidase subunit iii (coiii) for 38 sparrow species, along with passerina amoena (cardinalidae) and piranga ludoviciana (thraupidae) which were selected as the outgroups. our anal ... | 2003 | 12967606 |
| variation in a sparrow's reproductive success with rainfall: food and predator-mediated processes. | from 1997 to 1999, we monitored the reproductive success of individual rufous-crowned sparrows (aimophila ruficeps) in coastal sage scrub habitat of southern california, usa. annual reproductive output of this ground-nesting species varied strongly with annual variation in rainfall, attributed to the el niño-southern oscillation. birds fledged 3.0 young per breeding pair in 1997, when rainfall was near the long-term mean, 5.1 offspring per pair in 1998, a wet el niño year, and 0.8 fledglings per ... | 2002 | 28466220 |