Personality traits of pair members predict pair compatibility and reproductive success in a socially monogamous parrot breeding in captivity.

While pair behavioral compatibility seems to be a determinant of reproductive success in at least some species of monogamous birds, the specific factors underlying among-pair variation in behavioral compatibility remain poorly understood. However, recent research on the relationship between personality traits and reproductive success in several species of socially monogamous birds suggests that the fit between mates' personality traits might play a role in determining behavioral compatibility. To test this hypothesis, we used ten pairs formed by free choice from a captive population of cockatiels (Nymphicus hollandicus) to investigate whether personality ratings could be used to predict pair compatibility and reproductive success in pairs breeding for the first time. We found that pairs that ultimately hatched eggs paired disassortatively for agreeableness (an aggregate measure of social style which measures birds' tendency to be aggressive vs. gentle, submissive, and tolerant of others' behavior), and, as predicted, showed lower intrapair aggression and better coordination during incubation. Conversely, unsuccessful pairs paired assortatively for agreeableness, showed higher levels of intrapair aggression, and showed poorer coordination during incubation. Our results suggest that personality measurements may provide a useful adjunct to other information currently used in selecting mates for birds breeding in captivity.

Tuberal hypothalamic expression of the glial intermediate filaments, glial fibrillary acidic protein and vimentin across the turkey hen (Meleagris gallopavo) reproductive cycle: Further evidence for a role of glial structural plasticity in seasonal reproduction.

Glia regulate the hypothalamic-pituitary-gonadal (HPG) axis in birds and mammals. This is accomplished mechanically by ensheathing gonadotrophin-releasing hormone I (GnRH) nerve terminals thereby blocking access to the pituitary blood supply, or chemically in a paracrine manner. Such regulation requires appropriate spatial associations between glia and nerve terminals. Female turkeys (Meleagris gallopavo) use day length as a primary breeding cue. Long days activate the HPG-axis until the hen enters a photorefractory state when previously stimulatory day lengths no longer support HPG-axis activity. Hens must then be exposed to short days before reactivation of the reproductive axis occurs. As adult hens have discrete inactive reproductive states in addition to a fertile state, they are useful for examining the glial contribution to reproductive function. We immunostained tuberal hypothalami from short and long-day photosensitive hens, plus long-day photorefractory hens to examine expression of two intermediate filaments that affect glial morphology: glial fibrillary acidic protein (GFAP) and vimentin. GFAP expression was drastically reduced in the central median eminence of long day photosensitive hens, especially within the internal zone. Vimentin expression was similar among groups. However, vimentin-immunoreactive fibers abutting the portal vasculature were significantly negatively correlated with GFAP expression in the median eminence, which is consistent with our hypothesis for a reciprocal relationship between GFAP and vimentin expression. It appears that up-regulation of GFAP expression in the central median eminence of turkey hens is associated with periods of reproductive quiescence and that photofractoriness is associated with the lack of a glial cytoskeletal response to long days.

2,3-cis-2R,3R-(-)-epiafzelechin-3-O-p-coumarate, a novel flavan-3-ol isolated from Fallopia convolvulus seed, is an estrogen receptor agonist in human cell lines.

BACKGROUND: The plant genus Fallopia is well-known in Chinese traditional medicine and includes many species that contain bioactive compounds, namely phytoestrogens. Consumption of phytoestrogens may be linked to decreased incidence of breast and prostate cancers therefore discovery of novel phytoestrogens and novel sources of phytoestrogens is of interest. Although phytoestrogen content has been analyzed in the rhizomes of various Fallopia sp., seeds of a Fallopia sp. have never been examined for phytoestrogen presence. METHODS: Analytical chemistry techniques were used with guidance from an in vitro estrogen receptor bioassay (a stably transfected human ovarian carcinoma cell line) to isolate and identify estrogenic components from seeds of Fallopia convolvulus. A transiently transfected human breast carcinoma cell line was used to characterize the biological activity of the isolated compounds on estrogen receptors (ER) α and ß. RESULTS: Two compounds, emodin and the novel flavan-3-ol, (-)-epiafzelechin-3-O-p-coumarate (rhodoeosein), were identified to be responsible for estrogenic activity of F. convolvulus seed extract. Absolute stereochemistry of rhodoeosein was determined by 1 and 2D NMR, optical rotation and circular dichroism. Emodin was identified by HPLC/DAD, LC/MS/MS, and FT/ICR-MS. When characterizing the ER specificity in biological activity of rhodoeosein and emodin, rhodoeosein was able to exhibit a four-fold greater relative estrogenic potency (REP) in breast cells transiently-transfected with ERß as compared to those transfected with ERα, and emodin exhibited a six-fold greater REP in ERß-transfected breast cells. Cell type-specific differences were observed with rhodoeosein but not emodin; rhodoeosein produced superinduction of reporter gene activity in the human ovarian cell line (> 400% of maximum estradiol [E2] induction) but not in the breast cell line. CONCLUSION: This study is the first to characterize the novel flavan-3-ol compound, rhodoeosein, and its ability to induce estrogenic activity in human cell lines. Rhodoeosein and emodin may have potential therapeutic applications as natural products activating ERß, and further characterization of rhodoeosein is necessary to evaluate its selectivity as a cell type-specific ER agonist.

Post-hatch oral estrogen in zebra finches (Taeniopygia guttata): is infertility due to disrupted testes morphology or reduced copulatory behavior?

Previous studies show that post-hatch oral exposure of zebra finches to estradiol benzoate compromises male fertility, but the basis of the infertility is not clear. In this study, zebra finch nestlings were orally dosed with estradiol benzoate (at 1, 10, or 100 nmol/g BW per day, post-hatch days 5 to 11 [EB1, EB10, and EB100, respectively]). EB10 and EB100 males exhibited no significant differences in the frequency of mounting behavior (compared to canola oil [vehicle]-treated controls), when observed for six weeks as adults in communal breeding cages with similarly treated females; EB1 males showed reduced mounting behavior compared to controls (p<0.05). EB- and control-treated adult pairs were subsequently co-housed in a communal breeding trial to determine the extent of parentage outside the established pair-bond. Microsatellite analysis was consistent with EB-treated males having lower success than controls in obtaining paternity outside the established pair-bond. Histological examination of testes revealed dose-related disruption of normal morphology: disrupted basal-to-lumen laminarity of spermatogenesis stages, increased vacuolization within seminiferous tubules, decreased sperm aggregation and decreased spermatid density. Additionally, EB100 and control males were housed individually, implanted with testosterone propionate (TP) and presented with a female 3, 5, 9, and 11 days post-implantation for assessment of male sexual behavior. EB-treated, TP-implanted birds showed a slight decrease in mounting and singing behavior on day 5 after implantation; other male courtship behaviors (display, solicitation) were unaffected. Taken together, these results suggest that infertility in male zebra finches resulting from early oral estrogen exposure is more likely due to disrupted testicular morphology than altered sexual behavior.

Phytoestrogens and avian reproduction: Exploring the evolution and function of phytoestrogens and possible role of plant compounds in the breeding ecology of wild birds.

Phytoestrogens are secondary plant compounds, which can act to mimic estrogen and cause the disruption of estrogenic responses in organisms. Although there is a substantial body of research studying phytoestrogens, including their mechanisms of estrogenic effects, evolution, and detection in biological systems, little is known about their ecological significance. There is evidence, however, that an ecological relationship involving phytoestrogens exists between plants and animals-plants may produce phytoestrogens to reduce fecundity of organisms that eat them. Birds and other vertebrates may also exploit phytoestrogens to regulate their own reproduction-there are well known examples of phytoestrogens inhibiting reproduction in higher vertebrates, including birds. Also, common plant stressors (e.g., high temperature) increase the production of secondary plant compounds, and, as evidence suggests, also induce phytoestrogen biosynthesis. These observations are consistent with the single study ever done on phytoestrogens and reproduction in wild birds [Leopold, A.S., Erwin, M., Oh, J., Browning, B., 1976. Phytoestrogens adverse effects on reproduction in California quail. Science 191, 98-100.], which found that drought stress correlated with increased levels of phytoestrogens in plants, and that increased phytoestrogen levels correlated with decreased young. This review discusses the hypothesis that plants may have an effect on the reproduction of avian species by producing phytoestrogens as a plant defense against herbivory, and that birds may "use" changing levels of phytoestrogens in the vegetation to ensure that food resources will support potential young produced. Evidence from our laboratory and others appear to support this hypothesis.

Dietary red clover (Trifolium pratense) induces oviduct growth and decreases ovary and testes growth in Japanese quail chicks.

To determine whether drought-stress alters phytoestrogens in red clover and whether red clover in the diet influences sexual development in Japanese quail, we fed chicks diets containing irrigated or non-irrigated clover. Irrigation altered phytoestrogenic activity of red clover (determined using an in vitro bioassay), with extracts of irrigated clover diet containing more estrogenic activity than extracts of non-irrigated clover diet. Chick growth was negatively correlated with the amount of irrigated or non-irrigated clover in the diet. Dietary red clover also depressed both absolute and relative gonad weights; however, relative oviduct weight was increased by the irrigated diet. Diets did not affect serum vitellogenin. These results reveal a negative influence of drought-stress on phytoestrogenic potency of clover, and that red clover in the diet can inhibit avian growth and development independent of irrigation state. Thus, phytoestrogens may affect reproductive development in wild birds, and environmental stressors may influence levels of phytoestrogens in the field.

Post-hatch oral estrogen exposure reduces oviduct and egg mass and alters nest-building behavior in adult zebra finches (Taeniopygia guttata).

In addition to well recognized effects on the zebra finch song system, we previously showed that post-hatch oral estrogen and xenoestrogen exposure disrupts reproduction by increasing eggshell breakage in females and decreasing fertility in males. Here we show that post-hatch exposure to estradiol benzoate (by oral gavage on days 5 to 11) at a 100 nmol EB per g body mass dose (EB100) also reduces adult oviduct mass. Further, EB100 and doses two orders of magnitude lower (EB10, EB1) reduce egg mass and length. Similar to the induction of song-control nuclei in females, dosing with EB10 and EB100 increased and masculinized another highly differentiated behavior: nest-building. Zebra finches orally exposed as chicks were observed during reproductive trials in communal breeding cages for 4 or 6weeks duration. EB100 males and females and EB10 males showed increased nest-building behaviors. Further, EB10 and EB100 birds had larger nests than canola oil-treated controls, and EB100 birds had faster rates of nest-building than controls, while EB1 birds had significantly slower rates of nest-building than controls. Additionally, EB100 males and females also showed an increased preference for a coarser male-typical nest-building material (jute) over a finer, female-typical material (wool), suggesting a masculinization of nest-building behavior at the higher doses. The change in zebra finch nest-building behavior induced by early EB exposure suggests that nest size and quality, in addition to egg mass and length, may provide new endpoints for assessing avian exposure to xeno- and phyto-estrogens in wild birds.

Digit ratio unaffected by estradiol treatment of zebra finch nestlings.

There is rapidly growing evidence that the relative length of the second to fourth digit (digit ratio) in human hands is correlated with a large number of physiological and behavioral traits that are influenced by sex hormones. However, it is still unclear why these correlations exist. Very recently, similar correlations with relative toe lengths have been found in other vertebrate species including the zebra finch (Taeniopygia guttata). These non-human study organisms allow us to test experimentally various hypotheses regarding the mechanisms responsible for these patterns. In the present paper we first attempt to clarify the various hypotheses that have been proposed regarding the pleiotropic factor that is thought to affect both, the digits and the sex-hormone dependent physiology and behavior. We then present an experimental test of one specific hypothesis, namely that high levels of estradiol during the main growth period affect the relative size of the second vs. fourth toe. Twenty-three zebra finch nestlings from nine different families were treated daily (days 5-11 posthatch) with a high oral dose of estradiol benzoate administered by gavage. While the treatment had clear effects on the birds' reproductive physiology in adulthood (shown elsewhere), we found no significant effect on their digit ratio compared to control birds. At best, the effect could have been very small or restricted to certain genotypes. Hence, it seems unlikely that the estradiol level during the main growth phase is the pleiotropic agent that causes digit ratio to correlate with sex-hormone dependent behavioral and physiological traits.

Effects of perchlorate on growth and behavior of a granivorous passerine, the zebra finch (Taeniopygia guttata).

Perchlorate (ClO (4)(-) ) is a thyroid hormone inhibitor and persistent environmental contaminant that has been shown to impair thyroid function and growth in ground-dwelling birds. In this study, we used the zebra finch (Taeniopygia guttata) as a model to examine the effects of environmentally relevant perchlorate concentrations on growth and behavior of a granivorous passerine. On post-hatch days (PHDs) 3-14, finch chicks were orally dosed once per day with either 0, 10, 100, or 1000 microg sodium perchlorate/g body mass, and multiple endpoints of growth and behavior were examined in birds up to 72 days of age. Mean (+/-SE) body mass and tibiotarsal length were significantly reduced in the 100 and 1000 microg/g dose groups from PHDs 3-14, and this reduction persisted until PHD 40. Mean liver mass (PHD 15) in the 100 and 1000 microg/g dose groups were significantly greater than controls. Mean brain mass and mean nuclear volume of the song control nucleus area X in brains of 72-day-old males did not differ among dose groups. All endpoints of finch behavior were significantly influenced by perchlorate exposure at the highest dose level. Compared to controls, birds in this dose group exhibited a greater begging intensity, decreased motivation for spontaneous movement (e.g., attempts to fly), and reduced capacity to wean themselves from parental care. On PHD 15, flight attempts were also significantly reduced in the 10 and 100 microg/g dose groups, and the proportion of perchlorate-dosed birds attempting flight was less than half that in the control group. This study demonstrates a dose-dependent alteration of multiple growth and behavioral endpoints in zebra finches exposed to environmentally relevant concentrations of perchlorate. Comparable exposures in the wild may also affect normal development and behavior in similarly sensitive avian granivores.

Expression of hypothalamic GnRH-I mRNA in the female turkey at different reproductive states and following photostimulation.

In birds, changes in hypothalamic gonadotropin-releasing hormone-I (GnRH-I) content and release are correlated with reproductive stages. This study examined the distribution and expression level of GnRH-I mRNA in anatomically discrete hypothalamic nuclei throughout the turkey reproductive cycle and following photostimulation. GnRH-I mRNA expression was determined using in situ hybridization in non-photostimulated (NPS), egg-laying (LAY), incubating (INC) and photorefractory (REF) hens. Overall, GnRH-I mRNA expression was greatest in the nucleus commissurae pallii (nCPa) and around the organum vasculosum lamina terminalis (OVLT), with less expression observed in the nucleus septalis lateralis (SL), cortico-habenula cortico-septum area, and within the nucleus preopticus medialis. GnRH-I mRNA expression was significantly increased in nCPa, OVLT, and SL after NPS hens (6L:18D) were exposed to a 30 or 90 min pulse of light beginning 14 h after first light (dawn). GnRH-I mRNA abundance within nCPa, OVLT and SL was greater in LAY than in NPS and INC hens, while mRNA expression was least in REF hens. These results indicate that GnRH-I mRNA expression in birds is sensitive to light stimulation during the photosensitive period and can be used to more precisely characterize their different reproductive stages.

Distribution of interleukin-1 receptor in chicken and quail brain.

Interleukin 1 isoforms (IL-1) are major regulators of vertebrate immune responses. In the mammalian CNS, this function is reflected in physiological and anatomical evidence implicating IL-1 in a suite of behaviors associated with sickness. Although birds show sickness behavior, a parallel role of IL-1 in birds has not been investigated. As proinflammatory effects of IL-1 are mediated via the IL-1 type I receptor (IL-1RI), we investigated the distribution of IL-1RI protein and mRNA after lipopolysaccharide challenge in brains of two avian species, the chicken and Japanese quail. In some respects, the neuroanatomic distribution of IL-1R mRNA and protein in chicken and Japanese quail resembled that reported in mammals and was consistent with its putative role in the physiology and behavior of sickness. For example, we found IL-1RI mRNA or IL-1RI immunoreactivity in lemnothalamic visual projection areas of the pallium, surrounding blood vessels in pallial areas, in the dorsomedial nucleus of the hypothalamus, in the nucleus taenia, in cerebeller Purkinje cells and the motor components of the trigeminal and vagus nuclei. However, in contrast to mammals, we did not find evidence of IL1-RI receptors in medial or lateral pallial structures, paraventricular nucleus, areas homologous to the arcuate nucleus, the choroid plexus, organum vasculosum of the lamina terminalis or the reticular activating system. The distribution of IL-1RI suggests that a role for IL-1 in sickness behavior is conserved in birds, but that roles in other putative mammalian functions (e.g. hypothalamic-pituitary-adrenal and gonadal axes regulation, transport through barrier-related tissues, arousal) may differ.

An avian bioassay for environmental estrogens: the growth response of zebra finch (Taeniopygia guttata) chick oviduct to oral estrogens.

The rat uterotrophic assay is a recommended tier 1 screening assay for environmental estrogens, but no comparable assay exists for altricial birds. We orally dosed zebra finch chicks daily during their linear growth phase (days 5-11) with estradiol benzoate (EB), genistein, methoxychlor, or octylphenol, all dissolved or suspended in canola oil, or canola oil alone, as a vehicle control. On day 12, oviducts were removed, weighed and examined histologically. All doses of EB (0.1-1,000 nmol/g body wt), genistein at 100 nmol/g. and methoxychlor and octylphenol at 1,000 nmol/g, markedly increased oviduct weight, with the highest dose of EB inducing a 60-fold increase over controls. Oviducts were differentiated in a dose-depedent manner to the point of having tubular glands and a pseudostratified, ciliated epithelium at the higher doses of EB. Our earlier results show that EB at 100 and 1,000 nmol/g impairs reproductive performance of zebra finches. Thus, the zebra finch oviduct bioassay measures estrogenicity over a wide dose range and, for EB exposure, can predict impairment in adult reproductive performance. The responsiveness of chick oviducts to estrogen stimulation may serve as a useful marker of estrogen exposure in wild populations of songbirds.

Oral estrogen masculinizes female zebra finch song system.

It is well established that parenteral treatment of female zebra finch chicks with estradiol masculinizes their song control nuclei and that as adults they are capable of song. Concern over the widespread use of putative environmental estrogens caused us to ask whether oral exposure to estrogens (a natural route of exposure) could produce similar effects. We dosed chicks orally with estradiol benzoate (EB; 1, 10, 100, and 1000 nmol/g of body mass per day, days 5-11 posthatch), the non-ionic surfactant octylphenol (100 and 1000 nmol/g), or the pesticides methoxychlor (100 and 1000 nmol/g) and dicofol (100 nmol/g) and measured their song control nuclei as adults. EB treatment produced increases in song nuclei comparable to that induced by parenteral administration of estrogens. This is the first study of which we are aware to use an oral route of administration, which simulates the natural process of parent birds feeding their nestlings. We conclude that oral exposure to estradiol alters song control nuclei and we report in a related paper (Millam et al., 2001) that such exposure severely disrupts reproductive performance. Although we detected no influence of xenobiotics on induction of song control nuclei the possibility remains that oral exposure to xenoestrogens in high enough doses could affect development.

Thresholds for sweet, salt, and sour taste stimuli in cockatiels (Nymphicus hollandicus).

Little is known about avian taste perception and how taste affects food choice. We designed a study to determine the concentrations of aqueous solutions of common chemical taste stimuli that result in altered consumption patterns. Using two-choice taste-preference tests, we studied the taste thresholds of caged cockatiels (Nymphicus hollandicus) for aqueous solutions of potassium chloride, a phosphate buffer (to test pH), fructose, and glucose. First, the preferred and nonpreferred bottle locations were determined for each bird. Then, depending on the compound, the test solutions were placed in bottles in either the preferred or the nonpreferred locations and water was placed in the opposite bottle. Four parameters were measured at the end of 3-day test periods (total consumption, consumption from water side, consumption from test solution side, and proportion of nonpreferred side consumption to total consumption). Experiments were repeated with increasing concentrations of test flavors until intake variables were significantly affected (P < 0.05). Cockatiels distinguished (P < 0.05) between purified water and 0.16 mol L(-1) potassium chloride, 0.40 mol L(-1) fructose, or 0.16 mol L(-1) glucose. The test birds did not distinguish between water and 0.05 mol L(-1) mono- and dibasic sodium phosphate buffer solution at any tested pH within the range of 4.9-7.7. When these findings are compared to previous experiments with the same birds, it becomes clear that the gustatory reactions of cockatiels for two different stimuli (e.g., NaCl and KCl) from the same general taste category (salt, sweet, sour) can vary widely. This variation in the responses to related stimuli could be the result of a number of factors including anion effects (for salts and acids) as well as nongustatory physiological processes (e.g., as renal control of blood osmolarity). Zoo Biol 20:1-13, 2001. Copyright 2001 Wiley-Liss, Inc.