| an analysis of sex and breeding stage differences in prolactin binding activity in brain and hypothalamic gnrh concentration in wilson's phalarope, a sex role-reversed species. | wilson's phalarope (phalaropus tricolor) is a sex role-reversed species in which incubation of eggs and care of young is performed exclusively by the male. plasma levels of prolactin (prl), the hormone most associated with parental care in birds, are higher in incubating males than in nonincubating males or females. conversely, plasma testosterone levels are reduced in males during incubation. in an attempt to characterize the physiological basis of this unusual parental care system we used quan ... | 1998 | 9446729 |
| proximate and landscape factors influence grassland bird distributions. | ecologists increasingly recognize that birds can respond to features well beyond their normal areas of activity, but little is known about the relative importance of landscapes and proximate factors or about the scales of landscapes that influence bird distributions. we examined the influences of tree cover at both proximate and landscape scales on grassland birds, a group of birds of high conservation concern, in the sheyenne national grassland in north dakota, usa. the grassland contains a div ... | 2006 | 16827003 |
| first records of chewing lice (phthiraptera: menoponidae) in pacific migratory shorebirds wintering in ecuador. | chewing lice were collected from small shorebirds (charadriformes: scolopacidae) overwintering in foraging grounds of coastal ecuador. on 27 occasions at least one louse (3.7%) was collected from six host species. based on external morphological characters, at least two species of chewing lice could be preliminary identified (family: menoponidae), including actornithophilus umbrinus (burmeister, 1842) and austromenopon sp. a. umbrinus was found in the western sandpiper (calidris mauri), least sa ... | 2014 | 25054510 |
| [distribution of aquatic and raptor birds in a freshwater artificial pond of baja california sur, mexico]. | we determined the taxonomic composition and spatial-temporal distribution of aquatic and raptor birds in a freshwater artificial pond of el centenario, baja california sur, méxico, during 24 biweekly censuses (april, 1998 to march, 1999). the pond is particularly attractive for birds because of its variety of food items. a total 25,563 records of 69 species were done, among them the first report of chlidonias niger and phalaropus tricolor for the region. species richness and abundance were deter ... | 2006 | 12189794 |
| sex-role reversal and the absence of extra-pair fertilization in wilson's phalaropes. | extra-pair fertilizations are common in birds, which has led to great interest in how this phenomenon is regulated at a proximate level and how extra-pair fertilizations, and extra-pair fertilization avoidance, shape avian social systems. in wilson's phalaropes, phalaropus tricolor, incubation and brood-rearing is performed exclusively by males. males are able to rear only a single brood of four during a breeding season. this suggests that males have a high level of paternity in clutches and bro ... | 1998 | 9632484 |
| aromatase, 5 alpha- and 5 beta-reductase in brain, pituitary and skin of the sex-role reversed wilson's phalarope. | while intrasexual competition for mates is generally considered to be an androgen-dependent characteristic of reproductively active males, in the wilson's phalarope (phalaropus tricolor) it is the female that acquires the brighter nuptial plumage and aggressively competes for access to the less aggressive males. despite this pronounced sex-role reversal, circulating sex steroid hormones of breeding phalaropes are similar to those of avian species displaying traditional male-female reproductive r ... | 1989 | 2769170 |
| hormonal changes associated with natural and manipulated incubation in the sex-role reversed wilson's phalarope. | wilson's phalarope (phalaropus tricolor) is characterized by intense female intrasexual competition and exclusive male parental care. females occasionally are polyandrous and no territories are defended. prolactin (prl) and testosterone (t) were analyzed from plasma samples obtained from individuals of different reproductive stages. males tended to have higher plasma prl levels than females throughout the breeding season. prolactin levels of males declined posthatch, reaching baseline levels whe ... | 1988 | 3197945 |
| plasma steroid hormone levels in free-living wilson's phalaropes, phalaropus tricolor. | blood samples collected from free-living wilson's phalaropes during the reproductive season were analyzed for testosterone, dihydrotestosterone, estradiol-17 beta, and progesterone. levels of testosterone were seven times greater in nonincubating males than in females. during incubation males underwent a reduction in testosterone and dihydrotestosterone to levels similar to those of females. estradiol-17 beta values were higher in females than in incubating males and comparable to values reporte ... | 1986 | 3781211 |