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At least 793 records · Page 44Linked to original sources
PubMed2006

Testosterone and corticosterone during the breeding cycle of equatorial and European stonechats (Saxicola torquata axillaris and S. t. rubicola).

Northern-temperate male birds show seasonal changes in testosterone concentrations with a peak during the breeding season. Many tropical birds express much lower concentrations of testosterone with slight elevations during breeding. Here we describe testosterone and corticosterone concentrations of male stonechats from equatorial Kenya during different substages of breeding and molt. This tropical species has a short breeding season of approximately 3 months. We compare their hormone concentrations to previously published data of males of a northern-temperate relative, the European stonechat, also a seasonal breeder but with a breeding season of approximately 5 months. Equatorial stonechats show a pronounced peak of testosterone during the nest-building and laying stage. During all other stages, testosterone concentrations are low, similar to other year-round territorial tropical bird species. Corticosterone concentrations peak also during the nest-building and laying stage suggesting that this period of maximum female fecundity is a demanding period for the male. Equatorial stonechats have significantly lower concentrations of testosterone than European stonechats during all stages, except during the nest-building and laying stage. During this stage of maximum female fertility, testosterone levels tend to be higher in equatorial than in European stonechats. Our results suggest that equatorial stonechats belong to a group of tropical bird species that are characterized by a short breeding season and a brief high peak of testosterone during the female's fertile period. Such brief, but substantial peaks of testosterone may be common in tropical birds, but they may easily be missed if the exact breeding stage of individual birds is not known.

Animals↗
PubMed2006

A phylogeny for the Cisticolidae (Aves: Passeriformes) based on nuclear and mitochondrial DNA sequence data, and a re-interpretation of an unique nest-building specialization.

Based on some general similarities in feeding adaptations, a large number of Old World passerine birds were in the past lumped in one broad family, the Sylviidae. Recent molecular studies, starting with the DNA-DNA hybridization work by Sibley et al. [Sibley, C.G., Ahlquist, J.E., 1990. Phylogeny and Classification of Birds: A Study in Molecular Evolution, Yale University Press, New Haven, CT], have revealed that this group is in fact a paraphyletic assemblage, mainly in the superfamily Sylvioidea, and within this assemblage a distinct group (the Cisticolidae) can be identified around the genus Cisticola. In this study we try to define natural lineages within it, based on DNA sequence data from 35 ingroup taxa representing 12 putative genera. Both nuclear myoglobin intron II (630 bp in our study) and mitochondrial ND2 (1041 bp) genes were sequenced, and 1671 bp were aligned and subjected to parsimony, maximum likelihood and Bayesian analyses. The results strongly support the monophyly of a cisticolid clade, with the Malagasy warblers Neomixis constituting the deepest branch within the clade. Three major clades receive statistical support, but not all relationships between and within these are well resolved. All species of the genus Bathmocercus belong to the Cisticolidae but in two different clades. The tailorbirds appear also polyphyletic with most species of the genus Orthotomus (but O. cucullatus falling in the outgroup) and the African metopias being in two different clades. Also the genus Apalis is polyphyletic, but all other included genera seem to be confirmed as natural units. Based on these findings we resurrect the genera Scepomycter and Artisornis. Calamonastes is confirmed to be in the Cisticolidae and grouped with Camaroptera. Main basic nest types do not follow the phylogenetic branching, and notably the peculiar "tailorbird" technique of stitching leaves together around the nest is found in different parts of the phylogeny. The basic types of nests seem to be found in particular environments, and the sewing may therefore have evolved in some ancestor of the Cisticolidae and was later lost or modified in some genera or species following the spread of drier habitats from the mid-Miocene.

Animals↗
PubMed2006

Phylogeny of Palaearctic wheatears (genus Oenanthe)--congruence between morphometric and molecular data.

Wheatears of the genus Oenanthe are birds specialized to desert ecosystems in the Palaearctic region from Morocco to China. Although they have been the subject of many morphological and ecological studies, no molecular data have been used to elucidate their phylogenetic relationships, and, their relationships are still debated. Here we use DNA sequences of 1180 bp of two mitochondrial genes, 16S rRNA and cytochrome oxidase subunit I, from 32 individuals from Middle East and North Africa, and Bayesian methods to derive a phylogeny for 11 species of Oenanthe. The resulting tree supported three major clades: (A) O. alboniger, O. chrysopygia, O. lugens, O. finschii, O. leucopyga, O. picata, O. moesta, (B) O. deserti and O. pleschanka; and (C) O. isabellina and O. oenanthe. These results largely differ from previous hypotheses based on analysis of morphological and chromatic characters. However, the two clades (B) and (C) were also supported by a phenetic analysis of new morphometric data presented here, indicating that characters related to colouration and ecology in Oenanthe are more strongly influenced by homoplasy than those of body shape.

Africa, Northern↗
PubMed2006

Sexual dimorphism, female reproduction and egg incubation in the oriental leaf-toed gecko (Hemidactylus bowringii) from southern China.

We studied sexual dimorphism, female reproduction and egg incubation of the oriental leaf-toed gecko (Hemidactylus bowringii) from a population in southern China. The largest male and female in our sample were 60 and 57 mm snout-vent length (SVL), respectively. Males are the larger sex; sexual dimorphism in head size and tail length (TL) is evident in juveniles and adults, with males having larger heads as well as longer tails than females. Oviposition occurred between late May and late July. Females switched from laying two eggs early in the breeding season to 1-2 eggs later in the season. Clutch mass and egg mass were both independent of female SVL, whereas relative clutch mass was negatively correlated with female SVL. The previous conclusion that female H. bowringii lay a single clutch of eggs per breeding season is unlikely to be true. Thermal environments experienced by H. bowringii eggs affect incubation length as well as morphological and locomotor phenotypes of hatchlings. Hatchlings from eggs incubated at 30 degrees C were larger (SVL, tail length and body mass) and performed better in the racetrack than their counterparts from eggs incubated at 24 degrees C. Temperatures suitable for embryonic development are relatively high in H. bowringii, primarily as a consequence of the adaptive response to warm environments in southern China.

Animals↗
PubMed2003

Seasonal variation in plasma catecholamines and adipose tissue lipolysis in adult female green sea turtles (Chelonia mydas).

We investigated three aspects of potential interrenal regulation of reproduction in female green sea turtles, Chelonia mydas. First, seasonal trends in plasma catecholamines were examined from female C. mydas at different stages of their reproductive cycles. Second, variation in catecholamine levels during a nesting season were analysed in relation to restraint time, and ecological variables such as nesting habitat, body size, and reproductive investment. Third, catecholamine and corticosterone (CORT) induced lipolysis was investigated with adipose tissue collected from gravid green turtles, using in vitro incubations. Plasma epinephrine (EPI) was lowest in non-vitellogenic (1.55 +/- 0.26 ng/ml) and post-breeding (1.57 +/- 0.22 ng/ml) females, and highest in courting females (2.87 +/- 0.28). Concentrations of norepinephrine (NE) and EPI were relatively constant throughout a nesting season, and not significantly related to restraint time, reproductive investment or nesting habitat. In vitro concentrations of CORT (>3 ng/ml) and NE (2 ng/ml) induced significant release of glycerol after 6h of incubation. Epinephrine tended to induce an antilipolytic affect at low concentrations (0.25 ng/ml) and a net lipolytic response at higher concentrations (>1 ng/ml). Our data suggest that EPI may play a role in regulating body condition during vitellogenesis, and maintaining energy stores during prolonged aphagia during courtship and nesting in female green sea turtles. Furthermore, we provide preliminary evidence that suggests that catecholamine production may be either down regulated or de-sensitised in gravid female C. mydas.

Adipose Tissue↗
PubMed2003

Comparative analysis of male androgen responsiveness to social environment in birds: the effects of mating system and paternal incubation.

Male androgen responses to social challenges have been predicted to vary with mating system, male-male aggressiveness, and the degree of paternal investment in birds ("challenge hypothesis," Am. Nat. 136 (1990), 829). This study focused on the interspecific predictions of the challenge hypothesis. Comparative methods were used to control for effects of the phylogenetic relatedness among the sampled species. Male androgen data of 84 bird species were collected from literature records on seasonal androgen patterns. From these, the androgen responsiveness (AR) was calculated as described in the original challenge hypothesis (i.e., maximum physiological level/breeding baseline). Scatterplots of AR versus mating strategy, male-male aggressiveness, and the degree of paternal care confirmed the expected interspecific patterns. When phylogenetic analyses were performed among all of the sampled species, the effects of paternal investment disappeared while the AR remained covarying to a high degree with mating system and male-male aggressiveness. Although these mechanisms may be different at the intraspecific level, this suggests that interspecific differences of AR in male birds may have evolved in response to changes of mating strategies, rather than in response to altered paternal duties. However, control for phylogeny among the subsample of 32 passerine species revealed that if any paternal investment contributed to the observed variance in AR, then the change from "no male incubation" to "male shares incubation duties" represented the most effective, whereas the male's contribution to feeding offspring did not explain the observed variation of AR.

Aggression↗
PubMed2003

Plasma corticosterone in American kestrel siblings: effects of age, hatching order, and hatching asynchrony.

Although it is well documented that hatching asynchrony in birds can lead to competitive and developmental hierarchies, potentially greatly affecting growth and survival of nestlings, hatching asynchrony may also precipitate modulations in neuroendocrine development or function. Here we examine sibling variation in adrenocortical function in postnatally developing, asynchronously hatching American kestrels (Falco sparverius) by measurements of baseline and stress-induced levels of corticosterone at ages 10, 16, 22, and 28 days posthatching. There was a significant effect of hatching order on both baseline and stress-induced corticosterone levels during development and these effects grew stronger through development. First-hatched chicks exhibited higher baseline levels than later-hatched chicks throughout development and higher stress-induced levels during the latter half of development. Furthermore, there was significant hatching span (difference in days between first- and last-hatched chicks) x hatching order interaction on both baseline and stress-induced corticosterone levels during development. Hatching span was also positively correlated with both measures of corticosterone and body mass in first-hatched chicks, but was negatively correlated with these factors through most of the development in last-hatched chicks. It is known that hatching asynchrony creates mass and size hierarchies within kestrel broods and we suggest that hierarchies in adrenocortical function among siblings may be one physiological mechanism by which these competitive hierarchies are maintained.

Acute Disease↗
PubMed1991

Seasonal siderosis in female eider nesting in Svalbard.

Specimens of female and male eider (Somateria mollissima) were collected in Svalbard. Atomic absorption analyses revealed mean hepatic iron concentrations of 280 micrograms per g wet weight 2 to 3 weeks before egg laying, 2620 micrograms per g after 2 to 3 weeks brooding and 800 micrograms per g 2 weeks after hatching. At the highest concentration, there was massive siderosis with the iron located in both parenchymal and non-parenchymal cells. No signs of liver injury were seen. The female eider fasts completely from the start of egg laying to the end of hatching. The non-parenchymal iron deposits are probably the result of catabolism of blood and lean tissue, i.e., translocation of body iron. The parenchymal siderosis can hardly be explained by liver weight loss alone. An increased iron absorption preceding the egg laying is suggested.

Animals↗
PubMedDate not supplied

Effects of ovariohysterectomy on prostaglandin F2alpha-induced nesting behaviour in pigs.

Exogenously administered prostaglandin (PG) F2alpha induces behaviour similar to prepartum nest building in pregnant, pseudopregnant and nonpregnant female postpubescent pigs (Sus scrofa). These effects may be regulated by PGF2alpha-induced endocrine changes within the reproductive tract, such as those that initiate luteolysis. This study investigated the short-term effects of ovariohysterectomy on PGF2alpha-induced nesting behaviour in nonpregnant females. Cyclic 9-month-old virgin female pigs (gilts) received an oral dose (20 mg/day) of a synthetic progestogen (altrenogest; Regumate porcine, Hoechst, Milton Keynes, UK) for 18-21 days to synchronize oestrus. The gilts were then ovariohysterectomized (n=8) or sham-operated (n=7) on Days 3-8 after oestrus. They were housed individually and initially subjected to a series of control behavioural tests to establish the effect of ovariohysterectomy on their responses to the experimenters, novel objects, straw bedding and space restriction. Ovariohysterectomized gilts had a shorter latency to approach the experimenters than sham-operated animals, but there were no differences in their responses to a novel object, straw bedding or space restriction. Twelve to 16 days after oestrus, corresponding to the midluteal phase in sham-operated gilts, they were treated intramuscularly with 15 mg PGF2alpha (0.12 mg/kg, dinoprost; Lutalyse, Upjohn, Crawley, UK). PGF2alpha treatment induced a significant increase in straw gathering in ovariohysterectomized but not in sham-operated gilts. Other nesting behaviours, including rooting and pawing at straw, were induced in all animals. These results show that the uterus and ovaries are not required for the expression of PGF2alpha-induced nesting behaviour and the removal of the reproductive tract appears to have facilitated increased levels of gathering. This suggests that PGF2alpha induces luteolysis and nest building separately, and that PGF2alpha or a metabolite, may act centrally to mediate directly its effects on prepartum nest building in the pig.

Animals↗
PubMed1997

Prostaglandin F2alpha-induced nest-building in pseudopregnant pigs. II. Space restriction stress does not influence secretion of oxytocin, prolactin, oestradiol or progesterone.

We have previously shown that prostaglandin F2alpha (PG) is capable of inducing nest-building behaviour in pseudopregnant gilts and established a protocol. This experiment examined which reproductive endocrine systems might mediate these behavioural responses, in the presence or absence of a space restriction stress. Pseudopregnancy was induced with 5 mg/day i.m. (intramuscular) injections of oestradiol valerate (OV) on Days 11-15 of the oestrous cycle, jugular vein catheters were placed on Day 39 of pseudopregnancy, and blood samples were collected daily from Day 40 to Day 48. On Day 42, gilts were either space restricted to farrowing crates 1.6 x 0.6 m (C: n = 11) or left in pens 2.8 x 1.74 m (P: n = 11). On Day 47, blood samples were collected from all animals every 15 min from 90 min prior to a single i.m. injection of 15 mg of prostaglandin F2alpha (PG: Lutalyse, Upjohn, Crowley, West Sussex) to 120 min post-PG and then hourly for 4 h and assayed for oxytocin, prolactin, progesterone, and oestradiol. Results showed that mean daily concentrations of prolactin and progesterone were significantly lower (p < 0.05 respectively) in C than P gilts from Day 42 to Day 46 of pseudopregnancy. There were no significant differences in mean daily concentrations of oxytocin and oestradiol between C and P gilts during this time. For both groups, oxytocin, prolactin, and progesterone concentrations increased significantly (p < 0.05) post-PG when compared to their respective pre-PG values. However, for both groups, oestradiol concentrations were unaffected by PG injection. The prostaglandin-induced increases in oxytocin, prolactin, and progesterone concentrations did not differ between groups. We conclude that coincident changes in oestradiol secretion does not influence nesting behaviour and that space restriction stress associated with nest-building does not influence secretion of oxytocin, prolactin, oestradiol, or progesterone.

Animals↗
PubMed1997

Prostaglandin F2alpha-induced nest-building in pseudopregnant pigs. I. Effects of environment on behaviour and cortisol secretion.

Pigs may be susceptible to stress when they are strongly motivated to nest-build in a space-restricted environment. This study aimed to explore whether nest-building behaviour could be induced by prostaglandin F2alpha (PG) administration to pseudopregnant gilts and to determine whether induced behaviour and cortisol output differed between animals chronically placed in either farrowing crates or pens. Jugular vein catheters were placed on Day 39 of pseudopregnancy and blood samples collected daily from Day 40 to Day 48. On Day 42, gilts were either restricted to farrowing crates 1.6 x 0.6 m with no straw (C: n = 11) or left in pens 2.8 x 1.74 m with straw (P: n = 11). On Day 47, blood and behaviour sampling was from 90 min pre-PG (Dinoprost; Lutalyse, Upjohn, Kalamazoo, MI) to 6 h post-PG. PG injection successfully induced nest-building behaviour in P gilts within 15 min of injection. Penned gilts engaged in more straw/floor-directed behaviour than C gilts (p < 0.01), whereas attempts in C gilts seemed partial or incomplete. Conversely, C gilts showed increased (p < 0.05) amounts of fixture-directed behaviour, whereas P gilts did not post-PG. For both groups, cortisol increased significantly (p < 0.05) post-PG compared to pre-PG values. Cortisol concentrations in C gilts were significantly greater than in P gilts prior to and after PG (p < 0.05) on Day 47, whereas there were no significant differences in concentrations of cortisol between C and P on other days. These results demonstrate that PG can induce nest-building behaviour in the absence of foetal signals. Whereas the pseudopregnant gilt seemed to chronically adapt to the imposition of a farrowing crate, gilts subsequently attempting to nest-build showed increases in cortisol output when compared to their penned counterparts, suggesting that a stress was imposed by the space-restricted environment.

Animals↗
PubMed2001

Lead and cadmium in eggs of colonially nesting waterbirds of different position in the food chain of Greek wetlands of international importance.

Lead and cadmium concentrations were measured in eggs of collonially nesting waterbirds with different position in the food chains of Greek wetlands of international importance. Differences were found between species in the levels of both lead and cadmium in the Evros and Axios Deltas attributable to their different diets. Nevertheless, the concentration in eggs was unrelated to the position of each species studied in its food chain. There was no significant difference in lead levels among four wetlands sampled for the cormorant and in Cd levels among three wetlands sampled for the Mediterranean gull, probably implying species-specific accumulation patterns. A higher lead pollution of the Axios Delta area was only reflected in the eggs of the Mediterranean gull. The very low concentrations of both metals found in the eggs may either suggest low environmental inputs or lack of sensitivity in using eggs as lead and cadmium biomonitors, thus a more sensitive bioindicator still remains to be found.

Animals↗