| a stable-isotope approach to delineate geographical catchment areas of avian migration monitoring stations in north america. | migration monitoring stations (mmss) were established to provide information on population trends of north american passerines. however, apart from inferring general origins of birds, there has been no way to delineate geographical catchment areas sampled by mmss. the ability to resolve mms catchment areas would greatly enhance our ability to link and constrain population declines to specific geographical areas and thereby focus conservation efforts. here, we utilize stable-hydrogen (delta d) an ... | 2001 | 11355202 |
| on the recovery of photosensitivity in two passerine species, american tree sparrows (spizella arborea) and harris' sparrows (zonotrichia querula). | to test the hypothesis that a spontaneous increase in plasma luteinizing hormone (lh) signals recovery of photosensitivity in castrated passerine birds, lh concentrations were measured weekly in intact and in castrated photorefractory tree sparrows and harris' sparrows transferred to short days. after 7 weeks on short days (experiment 1) or after 1, 3, 5, 7, and 10 weeks (experiment 2) were challenged with long days (1 week) to determine if photosensitivity had been restored. as evidenced by a s ... | 1990 | 2391029 |
| photorefractory harris' sparrows (zonotrichia querula) exposed to a winter-like daylength gradually regain photosensitivity after a lag. | the time course of regaining photosensitivity was monitored in intact and in castrated harris' sparrows (zonotrichia querula) held on short days. measured endpoints, assumed to be equivalent indicators of the photosensitive state, were photoinduced testicular growth in intact males and a photoinduced elevation in plasma lh (luteinizing hormone) concentration in castrated males. intact males were initially photorefractory when they were moved from long days to short days, and they remained so for ... | 1992 | 1426942 |
| changes in the blood and plasma volume of harris' sparrows during postnuptial molt. | in captive harris' sparrows (zonotrichia querula), plasma and blood volume increased significantly during stages 2 and 3 of postnuptial molt, when extensive feather replacement was taking place in the wings, tail and body tracts. erythrocyte number did not increase significantly until molt was essentially complete. consequently the 6% mean maximum reduction in hematocrit that was observed during molt appeared to be largely the result of plasma volume expansion. this plasma volume expansion was n ... | 1985 | 2863078 |