Extrapair paternity in hooded warblers

We examined the role of extrapair fertilizations (EPFs) in themating system of the hooded warbler (Wilsonia citrina), a monogamoussongbird. DNA fingerprinting revealed that 8 of 17 (47%) femaleshad extrapair young in their first or second brood, and 23 of78 (29%) nestlings were the result of EPFs. Extrapair youngwere signifkandy more likely to occur in first broods than insecond broods. The proportion of EPFs within a brood was stronglybirnodal among broods: nests had 50% or more extrapair youngor none. In seven of eight broods where EPFs occurred, an adjacentmale neighbor was identified as the actual father. Male-likecoloration in females did not reduce the likelihood of havingextrapair young. Females with extrapair young did not receiveless parental care from their mates. All males who obtainedEPFs were mated to fertile females or were feeding offspringat the time they most likely mated with the extrapair female.Our results are consistent with the female control hypothesis,which predicts that females benefit from extrapair copulations(EPCs) and have some control over which males, if any, obtainEPCs. However, we could not reject the alternative hypothesisthat some male neighbors are particularly dominant and aggressiveduring EPC attempts, so females accept these EPCs to minimizecosts.     

Prototype symbolization in hooded crows

The ability in prototype symbolization was studied in four crows trained in matching concept. The experimental approach was characterized by the absence of direct training providing an association between the pictured arrays and Arabic numerals. Experimental sessions were divided into demonstrative and test phases. In the demonstrative phases, the sample and the reinforced stimulus belonged to the same category: if the sample was a pictured array, the reinforced stimulus was also the pictured array, if the sample was a numeral, the reinforced stimulus was likewise a numeral. Matching-to-sample competence was sufficient to perform this task successfully. In case of a correct choice a crow received some mealworms, their number was equal to the number of items in the pictured array or the Arabic numeral. In the test phases, the sample and the comparison stimuli were of different categories. If the sample was a pictured array, the comparison stimuli were numerals; if the sample was a numeral, the comparisons were the pictured arrays. Such tests required the birds to choose a numeric symbol corresponding to the pictured array or to choose the array of pictured items numerically equal to the Arabic symbol. All four crows performed this task successfully. Birds were able to set up a correspondence between the Arabic numeral from 1 to 4 and the number of elements in pictured arrays by way of mental juxtaposition of the earlier received information. Similar experiments showed that crows are likely to be able to perform mental operations with numerals analogous to simple arithmetic addition.     

Genetics of barley hooded suppression

The molecular basis of the barley dominant Hooded (K) mutant is a duplication of 305 bp in intron IV of the homeobox gene Bkn3. A chemical mutagenesis screen was carried out to identify genetical factors that participate in Bkn3 intron-mediated gene regulation. Plants from recurrently mutagenized KK seeds were examined for the suppression of the hooded awn phenotype induced by the K allele and, in total, 41 suK (suppressor of K) recessive mutants were identified. Complementation tests established the existence of five suK loci, and alleles suKB-4, suKC-33, suKD-25, suKE-74, and suKF-76 were studied in detail. All K-suppressed mutants showed a short-awn phenotype. The suK loci have been mapped by bulked segregant analysis nested in a standard mapping procedure based on AFLP markers. K suppressor loci suKB, B, E, and F all map in a short interval of chromosome 7H, while the locus suKD is assigned to chromosome 5H. A complementation test between the four suK mutants mapping on chromosome 7H and the short-awn mutant lks2, located nearby, excluded the allelism between suK loci and lks2. The last experiment made clear that the short-awn phenotype of suK mutants is due to a specific dominant function of the K allele, a function that is independent from the control on hood formation. The suK loci are discussed as candidate participants in the regulation of Bkn3 expression.     

The diet of coastal breeding hooded crows corvus corone comix

Three methods of analysis were used to determine the diet of territorial hooded crows at Lough Hyne Marine Reserve, Co Cork, Ireland The regular collection of prey Items from these sites at Lough Hyne was integrated with pellet and stomach analysis to determine diet Intertidal organisms occurred in over 80% of pellets and 43% of stomachs and occupied over 77% of the total wet weight of foods identified in pellets All prey items recovered from drop sites originated from the intertidal habitat, involved either large-sized species or larger individuals of smaller-sized species, and were only dropped during October to February Twenty-five intertidal species were identified but only a few of these species contributed to the bulk of the diet Hooded crows were shown to consume a wide range of intertidal species throughout the year, though the species composition in the diet was seasonally influenced Depletion and weight loss of intertidal molluscs through the winter was shown to have a minimal effect on selection suggesting that prey switching was driven by the birds nutritional requirements     

Rabies in hooded and striped skunks in Arizona

Arizona is home to four species of skunks, and rabies is enzootic in the region in which their ranges overlap. Examination of state health data from 1985 to 2004 revealed an irregular 4-10 yr periodicity in the number of cases annually, which may be related to past precipitation patterns. The number of rabid skunks peaked during springtime. Locations of rabies epizootics changed over time, but there was no evidence of a large-scale geographic spread. Skunks live-trapped during 1996-2002 had a low prevalence of rabies-virus neutralizing antibodies. This study was the first to document rabies in hooded skunks (Mephitis macroura).     

The eye of the hooded seal,Cystophora cristata,in air and water

Summary Multiple refractive state measurements were made on a male and female hooded seal (Cystophora cristata) when the eyes were exposed to air and to water. The measures, made by conventional retinoscopy and by photorefraction, show that the seals are moderately hyperopic (2–3 diopters) in water and moderately myopic (2–4 diopters) in air. No significant astigmatism was noted in either medium. The absence of refractive state variation over time suggests that an accommodative mechanism is insignificant or absent, although histological study indicates that the ciliary muscle is well developed.Photokeratoscopy, carried out on two animals with two keratoscopic instruments, show that the cornea is relatively flat (30 mm, or about one-half the diameter of the eye). Furthermore the cornea is only slightly astigmatic (less than 1 diopter). The refractive power of the external corneal surface (in air), calculated from a measurement of corneal refractive index of 1.378, amounts to only 10 or 11 diopters.As in the typical fish eye, hooded seal lenses are spherical or nearly spherical in shape (24–23 mm), and have short focal lengths (30–32 mm). Focal measures for rays at varying distances from the lens center indicate that spherical aberration is well corrected.There is no indication in this seal species, of a previously reported adaptation involving a highly astigmatic cornea which together with a slit pupil can minimize the optical effect of movement from water to air.     

Seasonal movements of hooded seals tagged in the Gulf of St. Lawrence,Canada

Hooded seals were tagged as pups (N = 1186) in the Gulf of St. Lawrence between 1975 and 1984. A total of 76 tags have been recovered or resighted. These recoveries indicate a dispersal from the Gulf in the spring to Greenland waters during the summer, and confirm that some seals marked as pups in the Gulf return as adults to this area during the whelping season.     

Spontaneous arthritis in nude rats of Rowett hooded strain

Spontaneous arthritis was found in 19 of 55 Rowett hooded strain rats with rnu gene. Most cases were in the male rnu/rnu (15/19) but a few occurred in the male rnu/+ (3/10) and female rnu/rnu (1/8). The lesions were first noted as reddened swelling due to exudative inflammation of periarticular soft tissues including synovial membranes in the tarsal and/or carpal joints. Most of the affected animals cured leaving slight induration but in a few male rnu/rnu ankylosis with pannus formation and exostosis developed. No sign of mycoplasmal or bacterial infection was noticed in the colony.     

Covert extraterritorial behavior of female hooded warblers

Extraterritorial forays are one specialized tactic that femalesuse to obtain extrapair copulations (EPCs). By radio-trackingfemale hooded warblers (Wilionia citrina) during the breedingseason, we found that females made covert forays onto neighboringterritories. Almost 80% of females made extraterritorial foraysduring their fertile stages, but none visited territories duringthe nonfertile (incubation) stage, which is consistent withthe extraterritorial foray hypothesis. Females that left theirterritories visited from one to four neighboring territories,and they intruded at a rate of 0.6 territories/h. The propensityof females to foray from their territory did not correlate withbody size or age of the social mate. One female that left herterritory obtained an extrapair fertilization. Females may useforays to assess male quality as well as participate in extrapaircopulations. An alternative hypothesis for extra-territorialforays is that females may foray onto neighboring territoriesto obtain food during the energetically stressful period ofegg production. The extraterritorial foray hypothesis and foraginghypothesis may not be mutually exclusive. Females may obtainbenefits of foraging while at the same time assessing malesfor EPCs. Extraterritorial behavior of female birds may be morecommon than previously believed and in many cases may only beruled out through radio-tracking     

Extraterritorial forays and male parental care in hooded warblers

Extrapair paternity is common among many songbird species yet few studies have quantified male extraterritorial foray (ETF) effort and examined potential trade-offs. One potentially important constraint for males is the need to provide parental care. Current models of male extrapair mating tactics propose that males reduce extraterritorial foray effort later in the breeding season because they face a trade-off between feeding nestlings versus pursuing extrapair matings. However, detailed field studies examining the trade-off between paternal care and male extraterritorial forays are lacking. We used radiotelemetry to quantify male extraterritorial foray effort in hooded warblers, Wilsonia citrina, to test the widely held predictions that: (1) males make significantly fewer and shorter forays during the nestling stage relative to other stages (i.e. fertile and incubating stages); and (2) male extraterritorial foray effort is negatively correlated with parental effort. Males made 0.87+/-0.09 forays/h and spent on average 12.2% of their time foraying off territory. Results were equivocal; some data suggested male foray effort decreased in relation to parental care, while other data suggested otherwise. Pairwise tests controlling for (1) extrapair mating opportunity among males and (2) male, territory and social mate quality revealed a possible trade-off between the mean duration and percentage of time in extraterritorial foray versus providing parental care. Conversely, results also revealed (1) no difference in foray rate, foray duration or percentage of time spent off territory over the various stages of the breeding season, (2) no relationship between male foray effort and male feeding rate, and (3) no difference in foray rate in pairwise comparisons, controlling for variability in extrapair mating opportunity and male quality. Overall, the trade-off between providing male parental care and pursuing alternative mating tactics may not be as strong for male hooded warblers as once hypothesized because males dedicated relatively little time to seeking extrapair copulations off territory. Copyright 2000 The Association for the Study of Animal Behaviour.     

Endothelum-dependent and-independent relaxations in aortic rings obtained from hypertensive hooded (Aguti) rats.

Experimental hypertension studies are few in the hooded (Aguti) rat. The present study was designed to investigate the usefulness of this rat strain for experimental hypertension studies and to test the hypothesis that the hypertension may be associated with a diminution of endothelium dependent and independent relaxations. Hypertension was induced in inbred hooded rats (n=8 each) by administering 8% salt in the diet and /or 100 mg/kg/day Nomega-nitro-L-arginine-methyl-ester (L-NAME) in the drinking water for six and/or four weeks respectively. The rats were anaesthetized using a 25% urethane and 1% chloralose mixture given intraperitoneally at a dose of 5 mg/kg. Their blood pressure was measured invasively. Thereafter, relaxations of rat aortic preparations to acetylcholine, histamine and sodium nitroprusside (SNP) were assessed using standard organ bath conditions. Probabiliity level of 0.05 was taken as statistically significant. The mean arterial pressure (MAP;mm Hg) rose significantly in all test groups (Salt: 148.3 +/- 4.6; L-NAME: 181.7 +/-8.3; Salt+L-NAME:154.9 +/-8.7) compared with control (94.2 +/-6.8; [P < 0.05]. The MAP was significantly [P < 0.05] higher in the L-NAME group than in all the other groups. The heart rate fell significantly in the salt + L-NAME group compared to control [P <0.05].The IC50 of acetylcholine in aortic rings from L-NAME rats (7.9 x 10(-1) +/- 6.0 x 10(-3)) was significantly higher than in rings from control (9.4 x 10(-8) +/- 2.8 x 10(-8)), salt (7.8 x 10(-7) +/- 4.7 x 10(-7)) and salt + L-NAME (3.3 x 10 (-7) +/- 2.1 x 10(-7)) rats [P < 0.05]. The IC50 of histamine and SNP in the rings from the test groups of rats showed no significant difference from control. Also, endothelium dependent and independent relaxations were preserved in the various forms of hypertension studied except in chronic NOS inhibition where the former was attenuated in response to acetylcholine.     

The production of chimeric rats and their use in the analysis of the hooded pigmentation pattern

New, improved media and procedures for making rat chimeric embryos and culturing them in vitro have been developed. We have produced 27 rat chimeras: 20 males and 7 females. This ratio of males to females is consistent with that seen in mouse chimeras, suggesting that rat sex chimeras develop as phenotypic males. By aggregating embryos containing appropriate genetic markers for pigment cell differentiation, it is possible to produce chimeras that elucidate the site of action of the hooded gene. The coat color patterns of black ? black hooded chimeras display a white belly spot. In black ? albino hooded chimeras, small patches of white hair appear on the head and a large white spot occurs on the belly. Black ? agouti hooded chimeras display both agouti and nonagouti pigmentation over the entire surface of the chimera. These animals are fully pigmented with no white spots. In black ? albino non-hooded chimeras, rather small irregular patches of black and white hairs are distributed throughout the pelage. Histological examination of sections of hair follicles obtained from the white areas in the head of black ? albino hooded chimeras revealed amelanotic melanocytes. On the other hand, hair bulbs from the white belly spots do not contain any such melanocytes. Thus the white hairs of the head are due to the presence of albino melanocytes, but the white hairs of the belly are due to the total absence of melanocytes. All these observations are consistent with the conclusion that the hooded gene acts within melanoblasts, probably to retard their migration from the neural crest and/or to prevent their entrance into the hair follicles of the white areas of hooded rats.     

Reproduction in a population of the hooded crow Corvus cornix

Nest density was stable during the 8-year study period. The mean clutch size was 4.3, and the production of fledglings was 2.0 per pair. Incubation started, on average, when there were still two eggs to be laid and lasted for 18 days. Few eggs were lost but 23% of all broods of nestlings were lost to predators. Single nestlings in a brood were not lost to predators but often starved to death, this applied to 25% of all nestlings. A large proportion of the nestlings were probably infected by Syngamus tracheae , and some of these succumbed during the first weeks after fledging. A comparison with other studies of crow populations shows that the major causes of breeding failure are different in different populations. The causes of variation in breeding success between populations are discussed, especially considering the role of nonbreeding crows.     

Peroxidase activity in hooded and awned barley at successive stages of development

The hooded (KK) and awned (kk) genotypes of barley differ in the amount of peroxidase activity at various stages of development. In hooded, this activity is at most stages higher than in awned, but it varies more from one stage to another, so that at certain stages, particularly the first leaf stages of young plants, it is lower. The peroxidase enzymes of the two genotypes are alike in electrophoretic mobility. Since peroxidase activity is particularly high in meristems of hooded at the beginning of their transition from the vegetative to the flowering condition, which is shortly before the first effects on morphogenesis can be observed, a connection between high peroxidase activity and the morphogenetic effects appears likely.     

Sexual shape dimorphism in the skull of the hooded seal Cystophora cristata

Multiple-group principal component analysis was used to investigate morphological differences between skulls of male and female hooded seals. The scores on the first principal axis (PCI), calculated from the variance-covariance matrix of log-transformed data, were highly correlated with age and the component was interpreted as a general growth axis. The other components had correlations between dimensions and component scores of different signs and magnitude and were interpreted as shape axes. The standardized component scores were subjected to analyses of variance and discriminant analyses. Sexual dimorphism was disclosed on eight of the components including PCI, and was functionally related mostly to the hood of the males.     

Panmictic population structure in the hooded seal (Cystophora cristata)

Two putative populations of hooded seals (Cystophora cristata) occur in the North Atlantic. The Greenland Sea population pup and breed on the pack ice near Jan Mayen ('West Ice') while the Northwest Atlantic population is thought to pup in the Davis Strait, in the Gulf of St. Lawrence (the 'Gulf'), and off southern Labrador or northeast Newfoundland (the 'Front'). We used microsatellite profiling of 300 individuals at 13 loci and mitochondrial DNA sequencing of the control region of 123 individuals to test for genetic differentiation between these four breeding herds. We found no significant genetic differences between breeding areas, nor evidence for cryptic nor higher level genetic structure in this species. The Greenland Sea breeding herd was genetically most distant from the Northwest Atlantic breeding areas; however, the differences were statistically nonsignificant. Our data therefore suggest that the world's hooded seals comprise a single panmictic genetic population.     

Partial albinism and natural selection in the hooded crow Corvus corone cornix

We studied the frequency of partial albinism amongst hooded crows in Norway, mostly in a population at Trondheim. A total of 3461 birds were collected from the field. About 5% of fledged young showed albinoid markings on their third right-hand primary; the frequency decreased to 2% among yearling birds and to only 1% among birds that had acquired their adult plumage. No significant difference was found in relation to sex. The partially albinoid birds were typically small-sized, both as regards their bone structure (ulna, tibia, tarsus) and feathers (wing, tail). Their feathers bore more defective markings than those of birds of normal plumage coloration. A study of the plumage of preserved specimens of hooded crows in the collections of Natural History museums in Norway also indicated that a differential mortality takes place in the wild, such albinoid birds disappearing rapidly from the population.
Experimental interchanges of eggs and hatchlings between nests indicated that the occurrence of partial albinism may be related to the feeding conditions during the nestling stage, rather than to any genetical differences. It is not known, however, whether the former was due to starvation, to an unbalanced diet, or to eating poisonous food.