text
stringlengths 0
7.06k
|
|---|
In May 2009 , the IUPAC / IUPAP Joint Working Party reported on the discovery of copernicium and acknowledged the discovery of the isotope 283Cn . This implied the de facto discovery of the livermorium @-@ 291 isotope , from the acknowledgment of the data relating to its granddaughter 283Cn , although the livermorium data was not absolutely critical for the demonstration of copernicium 's discovery . Also in 2009 , confirmation from Berkeley and the Gesellschaft fΓΌr Schwerionenforschung ( GSI ) in Germany came for the flerovium isotopes 286 to 289 , immediate daughters of the four known livermorium isotopes . In 2011 , IUPAC evaluated the Dubna team experiments of 2000 β 2006 . Whereas they found the earliest data ( not involving 291Lv and 283Cn ) inconclusive , the results of 2004 β 2006 were accepted as identification of livermorium , and the element was officially recognized as having been discovered .
|
In recent years , the synthesis of livermorium has been separately confirmed in two other laboratories .
|
= = = Naming = = =
|
Using Mendeleev 's nomenclature for unnamed and undiscovered elements , livermorium is sometimes called eka @-@ polonium . In 1979 IUPAC recommended that the placeholder systematic element name <unk> ( with the corresponding symbol of <unk> ) be used until the discovery of the element was confirmed and a name was decided . Although widely used in the chemical community on all levels , from chemistry classrooms to advanced textbooks , the recommendations were mostly ignored among scientists in the field , who called it " element 116 " , with the symbol of ( 116 ) or even simply 116 .
|
According to IUPAC recommendations , the discoverer or discoverers of a new element have the right to suggest a name . The discovery of livermorium was recognized by the Joint Working Party ( JWP ) of IUPAC on 1 June 2011 , along with that of flerovium . According to the vice @-@ director of JINR , the Dubna team originally wanted to name element 116 moscovium , after the Moscow Oblast in which Dubna is located . The name livermorium and the symbol Lv were adopted on May 23 , 2012 after an approval process by the IUPAC . The name recognises the Lawrence Livermore National Laboratory , within the city of Livermore , California , USA , which collaborated with JINR on the discovery . The city in turn is named after the American rancher Robert Livermore , a naturalized Mexican citizen of English birth .
|
= = Predicted properties = =
|
= = = Nuclear stability and isotopes = = =
|
Livermorium is expected to be near an island of stability centered on copernicium ( element 112 ) and flerovium ( element 114 ) . The reasons for the presence of this island are still not well understood . Due to the expected high fission barriers , any nucleus within this island of stability exclusively decays by alpha decay and perhaps some electron capture and beta decay . While the known isotopes of livermorium do not actually have enough neutrons to be on the island of stability , they can be seen to approach the island as in general , the heavier isotopes are the longer @-@ lived ones .
|
Superheavy elements are produced by nuclear fusion . These fusion reactions can be divided into " hot " and " cold " fusion , depending on the excitation energy of the compound nucleus produced . In hot fusion reactions , very light , high @-@ energy projectiles are accelerated toward very heavy targets ( actinides ) , giving rise to compound nuclei at high excitation energy ( ~ 40 β 50 MeV ) that may either fission or evaporate several ( 3 to 5 ) neutrons . In cold fusion reactions ( which use heavier projectiles , typically from the fourth period , and lighter targets , usually lead and bismuth ) , the produced fused nuclei have a relatively low excitation energy ( ~ 10 β 20 MeV ) , which decreases the probability that these products will undergo fission reactions . As the fused nuclei cool to the ground state , they require emission of only one or two neutrons . Hot fusion reactions tend to produce more neutron @-@ rich products because the actinides have the highest neutron @-@ to @-@ proton ratios of any elements that can presently be made in macroscopic quantities .
|
Important information could be gained regarding the properties of superheavy nuclei by the synthesis of more livermorium isotopes , specifically those with a few neutrons more or less than the known ones β <unk> , <unk> , <unk> , <unk> , <unk> , and 295Lv . This is possible because there are many reasonably long @-@ lived isotopes of curium that can be used to make a target . The light isotopes can be made by fusing curium @-@ 243 with calcium @-@ 48 . They would undergo a chain of alpha decays , ending at transactinide isotopes that are too light to achieve by hot fusion and too heavy to be produced by cold fusion .
|
The synthesis of <unk> and 295Lv could be accomplished by fusing the heavy curium isotope curium @-@ 250 with calcium @-@ 48 . The cross section of this nuclear reaction would be about 1 <unk> . After a few alpha decays , these livermorium isotopes would reach nuclides at the line of beta stability . Additionally , electron capture may also become an important decay mode in this region , allowing affected nuclei to reach the middle of the island . For example , 295Lv would alpha decay to 291Fl , which would undergo successive electron capture to <unk> and then 291Cn which is expected to be in the middle of the island of stability and have a half @-@ life of about 1200 years , affording the most likely hope of reaching the middle of the island using current technology . A drawback is that the decay properties of superheavy nuclei this close to the line of beta stability are largely unexplored .
|
Other possibilities to synthesize nuclei on the island of stability include quasifission ( partial fusion followed by fission ) of a massive nucleus . Such nuclei tend to fission , expelling doubly magic or nearly doubly magic fragments such as calcium @-@ 40 , tin @-@ 132 , lead @-@ 208 , or bismuth @-@ 209 . Recently it has been shown that the multi @-@ nucleon transfer reactions in collisions of actinide nuclei ( such as uranium and curium ) might be used to synthesize the neutron @-@ rich superheavy nuclei located at the island of stability , although formation of the lighter elements nobelium or seaborgium is more favored . One last possibility to synthesize isotopes near the island is to use controlled nuclear explosions to create a neutron flux high enough to bypass the gaps of instability at 258 β 260Fm and at mass number 275 ( atomic numbers 104 to 108 ) , mimicking the r @-@ process in which the actinides were first produced in nature and the gap of instability around radon bypassed . Some such isotopes ( especially 291Cn and 293Cn ) may even have been synthesized in nature , but would have decayed away far too quickly ( with half @-@ lives of only thousands of years ) and be produced in far too small quantities ( about 10 β 12 the abundance of lead ) to be detectable as primordial nuclides today outside cosmic rays .
|
= = = Physical and atomic = = =
|
In the periodic table , livermorium is a member of group 16 , the chalcogens , in the periodic table , below oxygen , sulfur , selenium , tellurium , and polonium . Every previous chalcogen has six electrons in its valence shell , forming a valence electron configuration of <unk> . In livermorium 's case , the trend should be continued and the valence electron configuration is predicted to be <unk> ; therefore , livermorium will have some similarities to its lighter congeners . Differences are likely to arise ; a large contributing effect is the spin β orbit ( SO ) interaction β the mutual interaction between the electrons ' motion and spin . It is especially strong for the superheavy elements , because their electrons move much faster than in lighter atoms , at velocities comparable to the speed of light . In relation to livermorium atoms , it lowers the 7s and the 7p electron energy levels ( stabilizing the corresponding electrons ) , but two of the 7p electron energy levels are stabilized more than the other four . The stabilization of the 7s electrons is called the inert pair effect , and the effect " tearing " the 7p subshell into the more stabilized and the less stabilized parts is called subshell splitting . Computation chemists see the split as a change of the second ( azimuthal ) quantum number l from 1 to 1 β 2 and 3 β 2 for the more stabilized and less stabilized parts of the 7p subshell , respectively : the 7p1 / 2 subshell acts as a second inert pair , though not as inert as the 7s electrons , while the 7p3 / 2 subshell can easily participate in chemistry . For many theoretical purposes , the valence electron configuration may be represented to reflect the 7p subshell split as 7s27p2
|
1 / <unk>
|
3 / 2 .
|
The inert pair effects in livermorium should be even stronger than for polonium and hence the + 2 oxidation state becomes more stable than the + 4 state , which would be stabilized only by the most electronegative ligands ; this is reflected in the expected ionization energies of livermorium , where there are large gaps between the second and third ionization energies ( corresponding to the breaching of the unreactive 7p1 / 2 shell ) and fourth and fifth ionization energies . Indeed , the 7s electrons are expected to be so inert that the + 6 state will not be possible to attain . The melting and boiling points of livermorium are expected to continue the trends down the chalcogens ; thus livermorium should melt at a higher temperature than polonium , but boil at a lower temperature . It should also be denser than polonium ( Lv : 12 @.@ 9 g / cm3 ; Ξ± @-@ Po : 9 @.@ 2 g / cm3 ) . The electron of the hydrogen @-@ like livermorium atom ( oxidized so that it only has one electron , <unk> + ) is expected to move so fast that it has a mass 1 @.@ 86 times that of a stationary electron , due to relativistic effects . For comparison , the figures for hydrogen @-@ like polonium and tellurium are expected to be 1 @.@ 26 and 1 @.@ 080 respectively .
|
= = = Chemical = = =
|
Livermorium is projected to be the fourth member of the 7p series of chemical elements and the heaviest member of group 16 ( VIA ) in the Periodic Table , below polonium . While it is the least theoretically studied of the 7p elements , its chemistry is expected to be quite similar to that of polonium . The group oxidation state of + 6 is known for all the chalcogens apart from oxygen which lacks available d @-@ orbitals for expansion of its octet and is itself one of the strongest oxidizing agents among the chemical elements . Oxygen is thus limited to a maximum + 2 state , exhibited in the fluoride <unk> . The + 4 state is known for sulfur , selenium , tellurium , and polonium , undergoing a shift in stability from reducing for sulfur ( IV ) and selenium ( IV ) through being the most stable state for tellurium ( IV ) to being oxidizing in polonium ( IV ) . This suggests a decreasing stability for the higher oxidation states as the group is descended due to the increasing importance of relativistic effects , especially the inert pair effect . The most stable oxidation state of livermorium should thus be + 2 , with a rather unstable + 4 state . The + 2 state should be about as easy to form as it is for beryllium and magnesium , and the + 4 state should only be achieved with strongly electronegative ligands , such as in livermorium ( IV ) fluoride ( <unk> ) . The + 6 state should not exist at all due to the very strong stabilization of the 7s electrons , making the valence core of livermorium only four electrons . The lighter chalcogens are also known to form a β 2 state as oxide , sulfide , selenide , telluride , and <unk> ; due to the destabilization of livermorium 's 7p3 / 2 subshell , the β 2 state should be very unstable for livermorium , whose chemistry should be essentially cationic , though the larger subshell and spinor energy <unk> of livermorium as compared to polonium should stabilize <unk> β slightly .
|
<unk> ( LvH2 ) would be the heaviest chalcogen hydride and the heaviest homolog of water ( the lighter ones being H2S , H2Se , <unk> , and PoH2 ) . <unk> ( polonium hydride ) is a more covalent compound than most metal hydrides because polonium straddles the border between metals and metalloids and has some nonmetallic properties : it is intermediate between a hydrogen halide like hydrogen chloride ( HCl ) and a metal hydride like <unk> ( <unk> ) . <unk> should continue this trend : it should be a hydride rather than a <unk> , but would still be a covalent molecular compound . Spin @-@ orbit interactions are expected to make the Lv β H bond longer than expected simply from periodic trends alone , and make the H β Lv β H bond angle larger than expected : this is theorized to be because the unoccupied 8s orbitals are relatively low in energy and can hybridize with the valence 7p orbitals of livermorium . This is the first molecule to be studied in detail to display this phenomenon , dubbed " <unk> hybridization " , although it was earlier predicted that the same phenomenon would occur with elements 156 β 164 , which would use 7d β 9s β <unk> / 2 hybridizations despite only the 7d ( and occasionally 9s ) orbitals being partially filled . The heavier livermorium dihalides are predicted to be linear , but the lighter ones are predicted to be bent .
|
= = Experimental chemistry = =
|
Unambiguous determination of the chemical characteristics of livermorium has not yet been established . In 2011 , experiments were conducted to create ununtrium , flerovium , and ununpentium isotopes in the reactions between calcium @-@ 48 projectiles and targets of americium @-@ 243 and plutonium @-@ 244 . The targets included lead and bismuth impurities and hence some isotopes of bismuth and polonium were generated in nucleon transfer reactions . This , while an unforeseen complication , could give information that would help in the future chemical investigation of the heavier homologs of bismuth and polonium , which are respectively ununpentium and livermorium . The produced nuclides bismuth @-@ 213 and polonium @-@ <unk> were transported as the hydrides <unk> and <unk> at 850 Β° C through a quartz wool filter unit held with tantalum , showing that these hydrides were surprisingly thermally stable , although their heavier congeners UupH3 and LvH2 would be expected to be less thermally stable from simple extrapolation of periodic trends in the p @-@ block . Further calculations on the stability and electronic structure of <unk> , UupH3 , PoH2 , and LvH2 are needed before chemical investigations take place . Ununpentium and livermorium are expected to be volatile enough as pure elements for them to be chemically investigated in the near future , a property livermorium would then share with its lighter congener polonium . The chief barrier to their chemical investigation at present is the lack of known isotopes of these elements which are long @-@ lived enough .
|
= American white ibis =
|
The American white ibis ( Eudocimus albus ) is a species of bird in the ibis family , <unk> . It is found from North Carolina via the Gulf Coast of the United States south through most of the coastal New World tropics . This particular ibis is a medium @-@ sized bird with an overall white plumage , bright red @-@ orange down @-@ curved bill and long legs , and black wing tips that are usually only visible in flight . Males are larger and have longer bills than females . The breeding range runs along the Gulf and Atlantic Coast , and the coasts of Mexico and Central America . Outside the breeding period , the range extends further inland in North America and also includes the Caribbean . It is also found along the northwestern South American coastline in Colombia and Venezuela . Populations in central Venezuela overlap and interbreed with the scarlet ibis . The two have been classified by some authorities as a single species .
|
Their diet consists primarily of small aquatic prey , such as insects and small fishes . Crayfish are its preferred food in most regions , but it can adjust its diet according to the habitat and prey abundance . Its main foraging behavior is probing with its beak at the bottom of shallow water to feel for and capture its prey . It does not see the prey .
|
During the breeding season , the American white ibis gathers in huge colonies near water . Pairs are predominantly monogamous and both parents care for the young , although males tend to engage in extra @-@ pair copulation with other females to increase their reproductive success . Males have also been found to pirate food from unmated females and juveniles during the breeding season .
|
Human pollution has affected the behavior of the American white ibis via an increase in the concentrations of methylmercury , which is released into the environment from untreated waste . Exposure to methylmercury alters the hormone levels of American white ibis , affecting their mating and nesting behavior and leading to lower reproduction rates .
|
= = Taxonomy = =
|
The American white ibis was one of the many bird species originally described by Carl Linnaeus in the 1758 10th edition of his Systema Naturae , where it was given the binomial name of <unk> albus . The species name is the Latin adjective albus " white " . Alternative common names that have been used include Spanish curlew and white curlew . English naturalist Mark Catesby mistook immature birds for a separate species , which he called the brown curlew . Local creole names in Louisiana include bec <unk> and petit <unk> .
|
Johann Georg Wagler gave the species its current binomial name in 1832 when he erected the new genus Eudocimus , whose only other species is the scarlet ibis ( E. ruber ) . There has long been debate on whether the two should be considered subspecies or closely related species , and the American Ornithologists ' Union considers the two to be a superspecies as they are parapatric . The lack of observed hybrids was a large factor in the view that the species were separate .
|
However , in a field study published in 1987 , researchers Cristina Ramo and Benjamin Busto found evidence of interbreeding in a population where the ranges of the scarlet and white ibises overlap along the coast and in the Llanos region of Colombia and Venezuela . They observed individuals of the two species mating and pairing , as well as hybrid ibises with pale orange plumage , or white plumage with occasional orange feathers ; their proposal that these birds be classified as a single species , has been followed by least one field guide . Hybrid ibises have also been recorded in Florida , where the scarlet ibis has been introduced into wild populations of American white ibis . Birds of intermediate to red plumage have persisted for generations .
|
Ornithologists James Hancock and Jim <unk> also consider the two to be a single species , with the differences in plumage , size , skin coloration and degree of bill darkening during breeding season forming the diagnostic characters . They have proposed the populations <unk> in northwestern South America after a period of separation , and that the color difference is likely due to the presence of an enzyme that allows uptake of pigment in the diet . They have questioned whether white @-@ plumaged birds of South America are in fact part of the ruber rather than the albus taxon , and acknowledge that more investigation is needed to determine this .
|
= = Description = =
|
The white plumage and pink facial skin of adult American white ibises are distinctive . Adults have black wingtips that are usually only visible in flight . In non @-@ breeding condition the long downcurved bill and long legs are bright red @-@ orange . During the first ten days of the breeding season , the skin darkens to a deep pink on the bill and an almost purple @-@ tinted red on the legs . It then fades to a paler pink , and the tip of the bill becomes blackish . It is difficult to determine the sex of an adult American white ibis from its external appearance , since the sexes have similar plumage . However , there is sexual dimorphism in size and proportion as males are significantly larger and heavier than females and have longer and stouter bills . A study of the American white ibis in southern Florida yielded weight ranges of 872 @.@ 9 to 1 @,@ 261 g ( 1 @.@ 924 to 2 @.@ 780 lb ) for males and 592 @.@ 7 to 861 @.@ 3 g ( 1 @.@ 307 to 1 @.@ 899 lb ) for females , with average weights of 1 @,@ 036 @.@ 4 g ( 2 @.@ 285 lb ) for males and 764 @.@ 5 g ( 1 @.@ 685 lb ) for females . The length of adult female and male birds ranges from 53 to 70 cm ( 21 to 28 in ) with a 90 to 105 cm ( 35 to 41 in ) wingspan . Among standard measurements , American white ibis measure 20 @.@ 5 β 31 cm ( 8 @.@ 1 β 12 @.@ 2 in ) along each wing , have a tail measurement of 9 @.@ 3 β 12 @.@ 2 cm ( 3 @.@ 7 β 4 @.@ 8 in ) , a tarsus of 6 @.@ 75 β 11 @.@ 3 cm ( 2 @.@ 66 β 4 @.@ 45 in ) and a culmen of 11 β 16 @.@ 9 cm ( 4 @.@ 3 β 6 @.@ 7 in ) .
|
The newly hatched American white ibis is covered with purple down feathers , deepening to dark brown or black on the head and wings . The chest is often bare and there can be a white tuft on the head . The irises are brown . The exposed skin is pinkish initially , apart from the tip of the bill which is dark gray , but turns gray within a few days of hatching . The bill is short and straight at birth and has an egg tooth which falls off between days five and nine , and develops three black rings from around day six , before turning gray by around six weeks of age . The gray to sandy gray brown juvenile plumage appears between weeks two and six , and face and bill become pink a few weeks later , while the legs remain gray . The irises have turned slate @-@ gray by this stage . Once fledged , the juvenile American white ibis has largely brown plumage and only the rump , underwing and underparts are white . The legs become light orange . As it matures , white feathers begin appearing on the back and it undergoes a gradual molt to obtain the white adult plumage . This is mostly complete by the end of the second year , although some brown feathers persist on the head and neck until the end of the third year . Juvenile birds take around two years to reach adult size and weight .
|
Like other species of ibis , the American white ibis flies with neck and legs outstretched , often in long loose lines or V formations β a 1986 field study in North Carolina noted over 80 % of adult ibis doing so , while juveniles rapidly took up the practice over the course of the summer . The resulting improvement in aerodynamics may lower energy expenditure . These lines fly in an undulating pattern as they alternately flap and glide . Soaring in a circular pattern is also seen . Heights of 500 to 1 @,@ 000 m ( 1 @,@ 600 to 3 @,@ 300 ft ) may be reached as birds glide over flights of 20 km ( 12 mi ) or more . More commonly , birds fly between 60 and 100 m ( 200 and 330 ft ) above the ground , gliding or flapping at a rate of around 3 @.@ 3 wingbeats a second .
|
The main call of the American white ibis is a honking sound , transcribed as <unk> , <unk> , or hunk , hunk . The call is used in flight , courtship or when disturbed . Birds also utter a muted huu @-@ huu @-@ huu call while foraging , and make a squealing call in courtship . Young in the nest give a high @-@ pitched <unk> as a begging call .
|
= = = Similar species = = =
|
Immature American white and scarlet ibises are very difficult to tell apart , although scarlet ibises tend to have darker legs and bare skin around the face . An immature American white ibis could be mistaken for an immature glossy ibis , but the latter is wholly dark brown and lacks the white belly and rump . The adult is distinguishable from the wood stork , which is much larger and its wings have more black on them .
|
= = Distribution and habitat = =
|
The American white ibis is most common in Florida , where over 30 @,@ 000 have been counted in a single breeding colony . It also occurs throughout the Caribbean , on both coasts of Mexico ( from Baja California southwards ) and Central America , and as far south as Columbia and Venezuela . The non @-@ breeding range extends further inland , reaching north to Virginia , and west to eastern Texas .
|
The species is known to wander , and has been sighted , sometimes in small flocks , in states far out of its usual range .
|
In North America , breeding takes place along the Atlantic coast , from the Carolinas south to Florida and thence west along the Gulf Coast . Laguna CuyutlΓ‘n is an isolated and regionally important wetland in the state of Colima on MΓ©xico 's west coast where a breeding colony has been recorded . American white ibises are not faithful to the sites where they breed , and large breeding colonies composed of ten thousand birds or more can congregate and disband in one or two breeding seasons . Breeding populations across its range have fluctuated greatly with wholesale movement between states . Until the 1940s , the species only bred in large numbers in Florida , mostly within the Everglades . Drought conditions elsewhere in the United States led to over 400 @,@ 000 American white ibis breeding there in the 1930s . In the 1950s and 1960s , large colonies appeared in Alabama , Louisiana , and then North and South Carolina and the Gulf Coast of Florida , and finally Texas in the 1970s . Then , between the 1970s and early 1990s , breeding colonies declined and disappeared in South Carolina and Florida , and greatly increased in Louisiana , and North Carolina . Colonies last between one and seventeen years , their longevity related to size and quality of nearby wetlands . The longest @-@ lasting are associated with wetlands over 800 km2 ( 310 sq mi ) in size . Degradation of wetland or breeding sites are reasons for abandonment . The population of American white ibises in a colony at Pumpkinseed Island in Georgetown County , South Carolina dropped from 10 @,@ 000 to zero between 1989 and 1990 as Hurricane Hugo had inundated nearby freshwater foraging areas with salt water .
|
The American white ibis is found in a variety of habitats , although shallow coastal marshes , wetlands and mangrove swamps are preferred . It is also commonly found in muddy pools , on mudflats and even wet lawns . Populations that are away from the coast and shoreline , particularly in southern Florida , often reside in other forms of wetlands such as marshes , ponds and flooded fields . In summer , these move to more coastal and estuarine habitats as inland waterways become flooded with summer rains and the ibis find the water levels too deep to forage effectively .
|
= = = Fossil record = = =
|
Remains similar to the American white ibis have been found in Middle Pliocene deposits of the Bone Valley formation in central Florida , and Lower Pliocene deposits of the Yorktown Formation at Lee Creek in North Carolina . Two species , one living and one extinct , have been recovered from the Talara Tar <unk> in northern coastal Peru . Eudocimus peruvianus was described from a tarsometatarsus that differed slightly from E. albus , whose remains were also found there . Remains of neither species are common in the beds . The tar seeps have been dated at 13 @,@ 900 years old . The American white ibis is still found in Peru .
|
= = Behavior = =
|
A field study late in the Florida nesting season revealed that on an average day , adult American white ibis spent 10 @.@ 25 hours looking for food , 0 @.@ 75 hours flying , 13 hours resting , roosting , and attending to their nests . Much of the time roosting is spent preening , biting and working their feathers with their long bills , as well as rubbing the oil glands on the sides of their heads on back plumage . American white ibis generally only preen themselves , not engaging in allopreening unless part of courtship behavior . Bathing often takes place before preening ; ibis squat in water 5 β 20 cm ( 2 @.@ 0 β 7 @.@ 9 in ) deep and flick water over themselves with each wing in succession . Hundreds of birds may bathe together around the time of courtship .
|
The American white ibis is territorial , defending the nesting and display sites against intruders . Agonistic or threat displays include lunging forward with the bill in a horizontal posture , and standing upright and snapping the bill opposite another bird engaging in the same display . Birds also lunge and bite , often holding onto an opponent 's head or wings .
|
= = = Breeding and lifespan = = =
|
The American white ibis pairs up in spring and breeds in huge colonies , often with other waterbird species . Nesting begins as soon as suitable foraging and nesting habitat is available . The female selects the site , usually in the branches of a tree or shrub , which is often over water , and builds the nest , and males assist by bringing nest material . Anywhere from one to five eggs are typically laid , with two or three being the most common . The eggs are matt pale blue @-@ green in color with brown splotches and measure 5 @.@ 8 cm Γ 3 @.@ 9 cm ( 2 @.@ 3 in Γ 1 @.@ 5 in ) and weigh on average 50 @.@ 8 g ( 1 @.@ 79 oz ) . Clutch sizes are usually lower in coastal colonies as compared to inland colonies , although there are no statistically significant differences in the fledging rate of both colonies . Throughout the mating and incubation period , the male undergoes a period of starvation to stay close to the nest and aggressively defend his nest and mate from both predators and other ibises in preference to foraging for food . In the 2006 breeding season , a non @-@ breeding adult female was observed to be tending to multiple nests that belonged to other American white ibises β the first time the behavior has been documented for this species .
|
Although the American white ibis is predominantly monogamous and both sexes provide parental care to their young , the male often flies off to engage in extra pair copulation with other nesting females after mating with its primary female partner . These extra @-@ pair copulations are usually done after the within @-@ pair copulations , and make up about 45 % of all total matings , although only about 15 % of all extra @-@ pair copulations are successful . By not restricting the number of females it copulates with , the male is able to increase its reproductive success considerably . Although females are receptive towards extra @-@ pair copulations , male mate @-@ guarding greatly reduces the rate of successful female involvement in attempted extra @-@ pair copulations by other males .
|
The breeding success of the American white ibis is sensitive to the hydrological conditions of the ecosystem such as rainfall and water levels . Low and decreasing water levels predict good prey accessibility . Water level reversals , where levels rise in the breeding season , disperse prey and impact on foraging success . Nest numbers and average clutch sizes are smaller in periods of reduced prey availability . The success rate of parents raising one or more young to 20 days of age ranges widely from 5 to 70 % of nests , and varies greatly between nearby colonies . American white ibis parents have been known to supplement their chicks ' diet with items such as cockroaches and rotting food from human garbage in poorer years , when fish and crayfish are more scarce . Studies have also shown that years with higher nesting numbers had significantly faster spring drying rates of water bodies than years with low nesting numbers . This is because faster drying rates means that there are fewer fish and increased available area where crayfish can be hunted . This highlights the fact that American white ibises do not use probability of nesting failure as a key factor in determining nesting sites but instead , rely on other criteria such as prey availability and nest @-@ site predation rates . The draining of wetlands in south Florida has also impacted on species that forage in shallow water such as the American white ibis , and its increase in numbers is a key indicator of restoration of habitat within the Everglades .
|
The main cause of nest failure among the species is due to nest abandonment , the leading cause of which is inundation from extremely high tides . Parents abandoned 61 % of all nesting starts either during or immediately after extremely high tides . The eggs float out of the flooded nests , or get washed out into the sea by wave action . <unk> parents usually abandon the nest when the water or tidal levels reaches 3 to 8 cm ( 1 @.@ 2 to 3 @.@ 1 in ) above the bottom of the nest cup . Nevertheless , there have been instances where the parents have been observed to transport their eggs to another nest in an attempt to salvage some eggs . However , despite the fact that some nesting sites face high chance of tidal damage every breeding season , American white ibises still continue to nest in these areas because of other favorable conditions such as abundant nearby food sources and low egg predation rates .
|
The eggs hatch after about three weeks and the young are attended by both parents . Males are present around the nest for most of the day , and females most of the night . The parents exchange nest duties in the morning and in the evening . Most of the feeding of the chicks occurs during the period where they swap nesting duties . Little feeding is done in the period of the day that is between the two duty swaps and no feeding is done between midnight and 6 a.m. Chick mortality is highest in the first twenty days post hatching , with anywhere from 37 to 83 % of hatchlings surviving to three weeks of age in the Everglades . During periods of food limitations and starvation events , the American white ibis tends to exhibit sex @-@ dependent pre @-@ fledgling mortality . For many bird species that have sexually dimorphic nestlings , mortality rates are higher for larger @-@ sized male nestlings as a result of the parents ' inability to meet its greater nutritional needs . However , in the case of the American white ibis , the male nestlings actually have a lower mortality rate as compared to the females despite being on average 15 % greater in mass as compared to its female counterparts . Although current research has yet to discover the underlying factors to why the males tend to have better survival rates under such conditions , it is suspected that the parents tend to feed the larger male nestlings first because they are either perceived by the parents to have a higher chance of survival , or , being generally larger , the male nestlings simply out @-@ compete the small females for food .
|
Bird predators may seize anywhere from 7 % to 75 % of the progeny in a breeding colony . The fish crow ( Corvus ossifragus ) is common raider of American white ibis nests , accounting for up to 44 % of egg loss in a field study at Battery Island , North Carolina . Other predators of eggs and young include the boat @-@ tailed grackle ( <unk> major ) , black @-@ crowned night heron ( Nycticorax nycticorax ) , gulls , and possibly vultures , as well as the common opossum ( Didelphis marsupialis ) , raccoon ( Procyon lotor ) , and rat snakes ( <unk> species ) . Egg predation rates of the American white ibis decline with nest age owing to increased nest attentiveness by the parents , especially during the last week of incubation . High nest densities and reduced synchrony increase egg predation rates because of the increased opportunities afforded by the longer incubation times , as well as the greater availability of nests available for predation .
|
The American white ibis begins breeding in its third summer , although birds in captivity may breed as young as nine or ten months of age . The oldest member of the species recorded in captivity was over 20 years of age , and a wild bird has been picked up 16 years and 4 months after being banded .
|
= = = Diet = = =
|
The American white ibis prefers to eat crayfish and other crustaceans , but also takes aquatic insects and small fish . Outside the nesting season , the diet is highly variable , as abundance and types of prey depend on the both region and habitat . In Los Llanos , located on the border of Columbia and Venezuela , the most frequent prey are insects , such as fly larvae and beetles . Generally in North America the main prey are crustaceans , mostly crayfish . In the Everglades and cypress swamps , the diet is primarily made up of crayfish , while those that feed in willow ponds eat predominantly fish . American white ibises that feed in mangrove swamps focus on crabs . The tactile nature of the ibis 's probing for food in mud means that it catches prey that are too slow to evade the ibis once located by its bill . In the Everglades , this means that crayfish make up a large part of the diet , but a more diverse array of invertebrates are taken in coastal areas . Although crayfish are sought by foraging ibises , prey switching to fish does occur if fish are found in great abundance . It is unclear whether the fish are more easily caught if overcrowded , or whether sheer numbers of fish mean that ibises are catching them instead of crayfish β normally , fish are more agile than crayfish and hence elude the ibis 's bill more easily . Fish are a more energy @-@ rich source of food for the American white ibis . In the breeding season , American white ibises in a colony at Pumpkinseed Island travelled further to forage in freshwater wetlands and catch crayfish , than nearby saltwater areas where fiddler crabs predominated , indicating their benefit was worth the extra energy expended in fetching them for their young . This travel results in the wholesale transport of nutrients across the landscape by the colony ; in a successful breeding year the colony at Pumpkinseed Island was estimated to have contributed a third as much phosphorus to the neighboring estuary as other environmental processes .
|
The American white ibis is found in mixed @-@ species foraging flocks with the glossy ibis ( Plegadis falcinellus ) in flooded fields , and the two species select different food items with little overlap ; the former foraging for crabs and aquatic insects and the latter feeding mainly on grain . The wood stork is also found in the same habitat in Florida , but hunts larger prey and a higher percentage of fish , so there is little overlap . In the Llanos , where American white ibis coexist with the scarlet ibis , their diets differ , the former consuming more bugs , fish and crustaceans , while the latter eat a much higher proportion of beetles . The <unk> ( Tringa <unk> ) has been observed trailing American white ibis and catching prey disturbed by them , and even <unk> ( stealing ) from them , in J. N. " Ding " Darling National Wildlife Refuge on Sanibel Island in Florida . An isolated event of intraspecific predation in juvenile American white ibis has been observed , where a juvenile attacked and consumed a chick from another nest .
|
= = = Foraging = = =
|
During the summer , the American white ibis roams along the coast of tidal flats and mangrove swamps as the inland marshes are usually flooded . However , as the water level recedes in the fall , populations at the coast shift their foraging area inland , to inland marshes and swamplands . It has become more common in urban landscapes in Florida since the late 1990s , and is one of a number of wetland @-@ dependent bird species which forages in man @-@ made ponds on golf courses in the southwest of the state .
|
The American white ibis is a tactile , <unk> forager , which limits its ability to choose from a wide variety of prey . For the most part , the American white ibis forages for food by tactile probing . It wades slowly through shallow water and sticks its long , downcurved bill into the substrate of the water body with its bill held at around 1 to 2 cm ( 0 @.@ 39 to 0 @.@ 79 in ) agape at the tip , and sweeps its long bill back and forth across the bottom to pick out suitable food items . Birds may also probe when standing still . <unk> with a wide open bill is a technique used by ibis in deeper water when alone , as is head swinging , in which the ibis swings its wide open bill widely in open water . Others copy this type of foraging if they see one ibis doing it . On land , the American white ibis locates prey by sight and pecks , and does not have to insert its bill into the substrate . The American white ibis seeks small prey when other birds are around , as it needs time to break up larger food items into smaller pieces to eat , and other predators such as herons and egrets often take the opportunity to rob the ibis of its catch . Along with the scarlet ibis , the species coexists with another five species of ibis in the Llanos in Venezuela . American white ibis males are aggressive to and take prey items from smaller ibises , but the smaller females are more often the victims of this behavior .
|
Juveniles have lower foraging efficiency compared to adults and in most feeding flocks , the juveniles are usually outnumbered by the adults . They usually tend to stay close to one another and forage for food together at the peripheral region of the group . During the breeding season , adult male ibises have been recorded raiding other parent ibises who are feeding their young in the colony . The raiders force their bill down the throat of the victim β either the parent about to disgorge their food or recently fed young β and extract the ball of food . This behavior allows the otherwise starving adult males to obtain food without having to spend long periods of time away from the nest , and prevent its female mate copulating with another male ibis , which would reduce its own reproductive success . Females and juveniles almost never try to drive off the larger and more aggressive pirating males , but instead try to avoid or move away from them . This pirating behavior is less common between two male ibises as the males will actively fight off the pirate . The explanation of the species ' sexual dimorphism of body size is unclear , because no differences between the sexes in feeding success rates or the foraging behavior have been observed and , as males are larger , they need more food than females .
|
= = Parasites and mortality = =
|
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.