Destruction Of Eggs Research Articles

Efeito da quimioterapia sobre os ovos do Schistosoma mansoni

Praziquantel administered to mice with Schistosoma mansoni infection (50 cercarias/8 weeks) was observed to cause death of adult worms and disintegration of the eggs trapped within granulomas, sometimes with calcification, after the 4th day of treatment. Combined administration of oxamniquine/hycanthone to animals similarly infected, although quite effective in killing adult worms, did not interfere with the eggs in the tissue. The miracidium eclosion test was positive up to the 15th day after the curative treatment of these animals. Since praziquantel treatment causes a rapid destruction of eggs, possible serological and pathogenic effects are expected that may enable a faster reabsorption of granulomas by the host tissues than that produced by other equally effective drugs.

Intraspecific egg destruction in marsh wrens: a study of mechanisms preventing filial ovicide

Marsh wrens, Cistothorus palustris, attack the nests of other birds, including conspecifics. The tendency of wrens to attack conspecific nests raises the question: what prevents breeding individuals from destroying their own offspring? In this study the mechanisms that prevent filial ovicide (i.e. the destruction of eggs by parents) are examined. The results suggest that male filial ovicide is prevented by the presence of a female in the nest area, which presumably inhibits the male's ovicidal tendencies. In addition, incubating females aggressively exclude males from their breeding area, thereby further reducing the threat to their nest. Female filial ovicide is prevented through the inhibition of intraspecific nest-destroying behaviour in breeding females and through the ability of individual females to recognize their own nest site and nest. Differences between the intraspecific nest-destroying behaviour of male and female marsh wrens may reflect different reproductive strategies of the two sexes.

Dominance and Mating in a Communal Polygynandrous Bird: Cooperation or Indifference towards Mating Competitors?

AbstractThe effect of dominance on the mating behaviour of both females and males was investigated for the communally breeding pukeko (Porphyrio porphyrio melanotus). Pukeko are polygynandrous with most groups consisting of three to 7 breeding males and one or two breeding females that lay eggs in a single nest. Linear dominance hierarchies are well established within breeding groups.Alpha females were involved in more copulations than beta females, but this difference did not appear to be a result of dominance status. There was also no evidence of egg tossing or egg destruction by breeding females. There was no positive correspondence between dominance rank of males and their frequency of sexual activity or copulations during the prelaying or laying periods. Dominants did interrupt matings by subordinates, but both qualitative and quantitative analyses of behaviour found no evidence of mate guarding. Furthermore dominants were no more likely to interrupt a copulation involving a subordinate male than they were to passively observe it or not react at all. This led us to suggest that males tended to behave indifferently toward mating competitors. As a result, multiple paternity is predicted to be high in pukeko groups. We also question the standard interpretation that males are behaving cooperatively in communal groups rather than coactively.

Immunoglobulins inside Schistosoma japonicum Eggs from the Livers of Mice

Using fluorescent antibody techniques, immunoglobulins (Ig's), mainly IgG class, were detected inside Schistosoma japonicum eggs lodged in mouse liver. Ig's were observed as a focal pattern between the miracidium and the eggshell during early infection (5-7 wk), particularly in lightly infected mice (20 cercariae). With advancement of time of infection (8-18 wk), a diffuse pattern of staining over the miracidial body developed and became predominant. The diffuse pattern of staining could be observed in the eggs taken from heavily infected mice (50 cercariae), during early stage. Eggs showing the focal pattern in a restricted area appeared to be morphologically intact, whereas eggs showing the diffuse pattern exhibited some types of eggshell destruction. We conclude that the focal pattern reflects disintegration of eggs in the initial stage and the diffuse pattern in the advanced stage. This spatial relationship between Ig's and eggs is discussed in relation to destruction of eggs.

Survival of strongyle nematode eggs and larvae in wastelage and fermented liquid dung

Wastelage and fermented liquid dung (FLD) were inoculated with strongyle eggs or L 3 larvae at 500 eggs or larvae g −1 of premix. Complete destruction of eggs and larvae was detected after 20 days of wastelage fermentation. FLD was inoculated only with L 3 larvae and these were destroyed within 24 h of fermentation.

The Fecundity of Schistosoma mansoni in Baboons, with Evidence for a Sex Ratio Effect

The average daily egg output of Schistosoma mansoni females in rodents has been estimated by several investigators to fall within the range of 234-380 eggs per day per female (Moore and Sandground, 1956, Am. J. Trop. Med. Hyg. 5: 831-840; Weinmann and Hunter, 1961, Exp. Parasitol. 11: 56-62; Cheever and Anderson, 1971, Am. J. Trop. Med. Hyg. 20: 62-68). These values were determined for Puerto Rican stocks of the parasite in hamsters or mice. Cheever and Anderson (1971, loc. cit.) called attention to the probability that fecundity was underestimated in these studies, because only tissue egg loads and fecal egg outputs were considered, and egg destruction in the tissues was not. Later, Cheever and Duvall (1974, Am. J. Trop. Med. Hyg. 23: 884-894), taking into account rates of destruction of eggs in tissues, examined fecundity of the NIH Puerto Rican strain of S. mansoni in grivet monkeys (Cercopithecus aethiops aethiops). They used an earlier, experimentally determined, tissue egg half-life of 8 days, derived for the same S. mansoni strain in rhesus monkeys, Macaca mulatta (Cheever and Powers, 1971, Am. J. Trop. Med. Hyg. 20: 69-76). Use of the rhesus monkeyderived half-life value with grivet monkey tissue and fecal egg load data was justified on the basis of evidence for the common rapid occurrence of a steady state in tissue egg burdens and a high proportion of living to dead eggs in the tissues of both host species. Applying a steady state equation analogous to the radioactive decay equation to their data, they determined the daily oviposition rate of female S. mansoni to be 529658 eggs, in single infections of varying durations, a figure about twice that of the earlier estimates. Unfortunately, the old fecundity value of about 300 eggs/day/female continues to be cited in many current textbooks and other sources. As a basis for studies on fecundity suppression in experimental schistosomiasis in nonhuman primates, we derived an equation to express the average rate of egg production by the population f mature female worms within a single host. The necessary data are: (1) the number of mature females present in that host, as determined by perfusion, inspection, and dissection; (2) the total number of eggs in the tissues, as determined by KOH digestion (Cheever, 1968, Bull. W.H.0. 39: 328-331) of affected organs, including intestines, liver, lungs, etc.; (3) the average, 24-hr egg output in the feces; and (4) the half-life of eggs in the tissues. We determined the first three values in a s ries of singly-exposed, captivity-born baboons (Papio cynocephalus), infected with a Kenyan strain of S. mansoni, by methods as described (Damian et al., 1972, Am. J. Trop. Med. Hyg., 21: 951-958). Because baboons also evidenced rapid development of a steady state amount of tissue eggs, which included a high proportion of live eggs (Damian et al., 1976, Am. J. Trop. Med. Hyg. 25: 299-306), we too employed Cheever and Powers' (1971, loc. cit.) tissue egg half-life estimate of 8 days in our calculations. Other assumptions that we made, in addition to the half-life value of tissue eggs, included the following: (1) female worms do not die at an appreciable rate in baboons (Damian et al., 1976, loc. cit.); (2) all females within a single host produce eggs at the same rate; and (3) eggs in the intestinal wall are subject to destruction at the same rate as those elsewhere in the tissues (Cheever and Anderson, 1971, loc. cit.). The fecundity value, F, or average number of eggs produced per day per female may be obtained from the equation

Role of host granulomatous response in murine schistosomiasis mansoni. eosinophil-mediated destruction of eggs.

Eosinophils form 50% of cells in the host granulomatous response to Schistosoma mansoni eggs, but their functional role in these granulomas and their relation to egg destruction is unknown. We have studied the course of S. mansoni infection in mice treated with normal rabbit serum (NRS) or depleted of their eosinophils by monospecific anti-eosinophil serum (AES). At 6-wk of infection (after 2 wk of egg deposition) the AES-treated animals were similar to NRS-treated controls with the exception that hepatic granulomas in the AES-treated animals were 50% smaller and devoid of eosinophils. At 8 wk of infection, AES-treated mice had significantly higher mortality, spleen weight, portal pressure, and 80% more eggs retained in their livers. These data suggest that eosinophil depletion delayed egg destruction. We subsequently studied destruction of eggs injected into the pulmonary microvasculature of sensitized mice. 2,000 S. mansoni eggs were intravenously injected into the tail veins of mice treated with NRS, anti-neutrophil serum, AES or ATG (anti-thymocyte globulin); at time intervals the remaining eggs were recovered from the lungs by tissue digestion. Egg recovery from NRS- or anti-neutrophil serum-treated mice began to decrease by day 16 and the percent recovery of eggs at day 24 was 55 and 52%, respectively. In contrast, animals treated with AES had smaller lung granulomas that were devoid of eosinophils and a marked delay of egg destruction was seen. It took until day 44 for 50% of the eggs to be destroyed. In ATG-treated animals smaller granulomas were seen that had diminished lymphocytes and also 75% less eosinophils. ATG treatment apparently slowed egg destruction but was not statistically significant. Our data define the role of the eosinophils in destruction of schistosome eggs in vivo and delineates the protective function of these cells within the host granulomatous response.

Eosinophils as effector cells in the destruction of Schistosoma mansoni eggs in granulomas.

Histopathological sections of wedge-biopsied liver and surgically removed gallbladder of a schistosomiasis mansoni patient were studied for the eosinophil-mediated destruction of eggs in granulomas. Apparent degranulation of eosinophils on the eggs in the granulomas and concomittant deterioration of miracidia were observed. It was construed that granule-associated enzymes may be released upon the degranulation of eosinophils, pass through the micropores of the egg shell and cause death of the miracidium inside the egg.

Stages of infection and ecological effects of a fungal epidemic on the eggs of a limnetic copepod

SUMMARY. Fungal infection of calanoid copepod (Diaptomus novamexicanus) eggs was observed in each of three years in an alpine lake (Castle Lake, California, U.S.A.). Stages in the infection process were examined by light and scanning electron microscopy and evidence was obtained that the Lagenidium‐like fungus concerned was a virulent parasite. Fungal destruction of eggs varied in timing and severity from year to year. The maximum impact of the disease was an estimated 48.4% decrease in potential copepod recruitment in 1976 due to the onset of a severe epidemic early in the summer growing season. The minimum impact, a 5.6% decrease in potential recruitment, was recorded in 1975. In this year the proportion of infected eggs was reduced and large numbers of juveniles had been released before the fungal disease began. The 1974 epidemic was intermediate in severity. The effect of these epidemics on Castle Lake calanoid populations is discussed in relation to temperature, food availability and predation.

Eosinophil-mediated destruction of S. mansoni eggs : IV. Effects of several inhibitory substances on eosinophil function

The destruction of isolated Schistosoma mansoni eggs in vitro by eosinophil-rich peritoneal exudative cells obtained from S. mansoni-infected mice is known to involve both specific anti-egg antibody and non-specific activation of the cells by lymphokine(s). The current study reports the effects of various metabolic inhibitors and other reagents known to alter cell function. The addition of inhibitors of glycolysis (Iodoacetate, 2 deoxy- d glucose) ablated the egg-destructive activity of eosinophils, but also resulted in considerable cell mortality during the 24 hr incubation period. Antimycin A, an inhibitor of aerobic respiration, also inhibited egg destruction. The presence of divalent cations, Ca 2+ in particular, was found to be essential for eosinophil-mediated egg destruction to occur. Cytochalasin B also inhibited this eosinophil-dependent activity. Tosyl-lysine-chloromethyl ketone decreased the extent of egg destruction, but when used at non-cytotoxic concentrations this effect was marginal. The metabolic requirements for eosinophils, and other cell types, in this and other systems are compared.

Eosinophil-mediated destruction of Schistosoma mansoni eggs : III. Lymphokine involvement in the induction of eosinophil functional abilities

Granulomas isolated from the livers of CBA/J mice infected for 8 weeks with Schistosoma mansoni produced a chemotactic activity for eosinophils, in a manner which correlated with the production of the lymphokine eosinophil stimulation promoter (ESP). ESP and chemotactic activities were also produced when eosinophilrich peritoneal exudative cells from S. mansoni-infected mice were cultured with S. mansoni eggs. These S. mansoni-related eosinophils destroyed approximately 20% of the eggs whereas eosinophils from normal (uninfected) mice did not have this ability. However, normal cells exposed to ESP-containing fluids in the co-cultivation system actively participated in egg destruction. Eosinophil-rich peritoneal exudative cells obtained from Trichinella spiralis-infected mice were incapable of destroying S. mansoni eggs during the normal 24 hr co-cultivation period, but did achieve destruction if the incubation period was extended to 48 hr. Marginal levels of chemotactic activity for eosinophils were detected in the co-cultivation fluids from T. spiralis-related cells and S. mansoni eggs, although these fluids did not contain demonstrable levels of ESP. Together, these data indicate that ESP/chemotactic factor-containing culture fluids can induce in normal, unreactive eosinophils the functional ability to destroy S. mansoni eggs in vitro. This may account for the ability of T. spiralis-related eosinophils to do so upon extended incubation.

Destruction of eggs by the long-billed marsh wren (Telmatodytes palustris palustris)

The frequency of nest destruction by the long-billed marsh wren (Telmatodytes palustris palustris) and the stimuli eliciting it were examined by experimentally offering marsh wrens different nests with eggs or nestlings. Marsh wrens of both sexes, as well as juveniles, attacked any type of eggs in any type of nest, including those of conspecifics; they attacked them regardless of where the nests were placed. Nestlings of redwing blackbirds and marsh wrens were also attacked.It is suggested that nest destruction by marsh wrens has evolved as an interference mechanism to reduce possible interspecific competition. Through this behaviour marsh wrens most likely exclude redwing blackbirds and possibly some other marsh nesting species from certain parts of marsh nesting areas.

Influence of Temperature and Wind on the Survival of Early Stages of Yellow Perch, Perca flavescens

Survival from the egg to larval stage was estimated for the 1969–75 year-classes of yellow perch, Perca flavescens, in Oneida Lake. Egg production was determined from mark-and-recapture estimates of adult stock and measurements of fecundity, and abundance of the resulting cohort was estimated from annual larval surveys. Early survival, which varied from 1.6 to 18.4% was correlated positively with temperature and negatively with wind. Two variables, mean daily air temperature during the 3 wk prior to the date the larvae attained a mean length of 8 mm and mean daily wind velocity for 4 wk prior to this date, accounted for 87% of the variability in survival of perch. Physical destruction and movement of eggs by high winds and greater mortality of prolarvae caused by low temperature could account for the differences in survival between years, but do not appear severe enough to account for the 80+% base mortality that occurred in all years. The low year-to-year variation in survival suggests that temperature and wind influenced year-class size through a complex of many relatively minor mortality factors, rather than through one catastrophic event.

Mortality of the Immature Stages of Rhinocyllus conicus , 1 a Thistle Head Weevil, in Virginia 2

Mortality of pre-adult Rhinocyllus conicus Froelich on musk thistle ( Carduus nutans L.) at Pulaski, Va., in 1972 was 68.0%. The range in mortality at 11 sampling sites was 56.6–95.8%; greater losses occurred in open, unsheltered pasture. Egg and early instar larval mortality (58.3%) resulted primarily from egg destruction by wind and rain. Mortality of late instar larvae and pupae (9.7%) was partially attributable to parasitism (3.6%) by Aliolus curculionis (Fitch), Bracon mellitor (Say), and Campoplex polychrosidis Viereck. Some loss of larvae and pupae was caused by crowding.

The Toxicity of p,p prime -DDT to the Clapper Rail

The LC5o (concentration of toxicant in the diet expected to kill half of the test birds in 5 days) for p,p'-DDT in clapper rails (Rallus longirostris) was found to be 1,612 ppm for males and 1,896 ppm for females. Amounts of DDT + DDD in the brains of birds that died were significantly greater (P < 0.01) than those in the brains of survivors. Thirty ppm DDT + DDD approximated the lower limit of these compounds in the brains of rails diagnostic of death from DDT poisoning. Residues in livers and carcasses are reported. Considering the relatively high resistance of the clapper rail to DDT poisoning, we concluded that exposure to this pesticide in marshes is not likely to be a significant factor in mortality of adult rails. Effects other than direct mortality were not evaluated in this study. J. WILDL. MANAGE. 39(2):305-309 During an 11-year study (1955-65) of the population dynamics of the clapper rail in New Jersey marshes, Ferrigno (1966) noted that a occurred in 1959 and again in 1965. He attributed the severe (62.2 percent) drop in production in 1959 to overpopulation in 1958 which resulted in fighting, in nest and egg destruction, and in greatly increased predation. He could not, however, attribute the observed decline (74.4 percent) in production from 1963 through 1965 to those factors alone and recommended that future investigations be designed to determine whether the poorer survival of young in the crash years was due to weather, other natural conditions, over-harvest, or pesticides. Years of spraying DDT against the salt marsh mosquito in many of the marshes along the eastern coast of the United States have led to very high levels of residues of the compound in the soils of those marshes. For example, Woodwell et al. (1967:821) found that DDT residues in the soil of an extensive salt marsh on the shore of Long Island averaged 15 kg/ha; the maximum was 36 kg/ha. Under such conditions the clapper rail, a salt marsh inhabitant, scarcely could avoid prolonged exposure to that compound. The experiment reported here was designed and conducted in 1967-68 to determine the toxicity of DDT to the clapper rail and residues in the brains diagnostic of death. Toxicity was measured by determining the LCo50 of DDT (defined as the concentration of chemical in the feed expected to kill 50 percent of the test birds in 5 days). We wish to express our appreciation to R. G. Heath for his advice on the statistical treatment of our data.

Rabbit Destruction of Tern Eggs

Rabbit Destruction of Tern Eggs

Egg Destruction as a Response to Reduced Living Space in Japanese Quail

Japanese quail, housed one to a cage, were exposed to reduced living areas caused by an accumulation of their own eggs. After an average of 14 eggs had accumulated, these birds began to destroy their eggs at the same rate they laid them. The effect was to maintain about .026 m.2 of clear floor area. No changes in egg production were found. Behavioral control of living space is suggested by these results.

Eggshell Breakage by Incubating Black Ducks Fed DDE

Black duck (Anas rubripes) hens fed 10 ppm dry weight (approximately 3 ppm wet weight) of p,p'-DDE in the diet laid eggs with shells 22 percent thinner at the equator, 30 percent thinner at the cap, and 33 percent thinner at the apex than those of controls. Natural incubation increased shell cracking more than fourfold as compared with mechanical incubation. Hens removed cracked eggs from nests, and one hen terminated incubation. Hens fed DDE produced one-fifth as many ducklings as controls. DDE in eggs of dosed hens averaged 64.9 ppm wet weight. J. WILDL. MANAGE. 37(3):390-394 Field observers have reported that eggs of raptors, gulls, and pelicans have been cracked, crushed, and sometimes eaten by parent birds (Ratcliffe 1958, 1960; Ludwig and Tomoff 1966, Jehl 1969, Keith et al. 1970). A close association between egg destruction and organochlorine residues has usually been noted (Ratcliffe 1967, Hickey and Anderson 1968, Fyfe et al. 1969, Cade et al. 1971, Blus et al. 1972). Eggs of kestrels (Falco sparverius) fed dieldrin and DDT in combination disappeared from nests in greater proportion than eggs of controls (Porter and Wiemeyer 1969). Egg loss was attributed to breakage of thin-shelled eggs and egg eating by the adults. Black ducks fed either 10 or 30 ppm of DDE (dry weight) in the diet laid eggs which had thinner shells and cracked more readily than controls (Longcore et al. 1971). Since eggs were gathered daily and placed in mechanical incubators, the effects of natural incubation were not evaluated. In the present study, black ducks were allowed to nest as pairs in individual pens to approximate a natural nesting cycle and to compare shell cracking and hatching success of eggs incubated by nesting hens and those incubated mechanically. We acknowledge R. J. Diebolt for his care of these ducks; R. G. Heath advised on statistical procedures; R. Andrews and L. F. Stickel reviewed the manuscript; and E. H. Dustman contributed to initial study design. MATERIALS AND METHODS The black ducks used in this study were 2-year olds that had bred successfully in 1970 (Longcore et al. 1971). Ten pairs had received dietary dosage of 10 ppm of p,p'DDE (approximately 3 ppm wet weight) from mid-November 1969 to mid-June 1970 and untreated food from mid-June 1970 to mid-November 1970, when dosage was resumed. Ten pairs of controls received untreated commercial duck breeder mash throughout. Details of pen facilities and food preparation are discussed by Longcore et al. (1971). At the onset of egg laying about 5 months after initiation of dosage, nests were visited daily and eggs were numbered and examined for cracks. After completion of laying, eggs were examined for cracks at weekly intervals. Hens were allowed to incubate until they had exceeded the normal incubation period. Eggs were then removed and examined to ascertain development. The third egg laid by each hen was removed from the clutch to obtain shell measurements and residue analysis. Shells 1 Present address: Department of Zoology, Utah State University, Logan 84321. 390 J. Wildl. Manage. 37(3):1973 This content downloaded from 40.77.167.7 on Sat, 16 Jul 2016 05:28:11 UTC All use subject to http://about.jstor.org/terms EGGSHELL BREAKAGE BY BLACK DUCKS * Longcore and Samson 391 were washed while maintaining membranes intact and air-dried to constant weight. Shell thickness was measured at the shell equator, cap, and apex with a micrometer graduated in 0.01 mm units. Shell surface area was determined by the methods of Romanoff and Romanoff (1949:110), and shell weight per unit area was calculated. Egg contents were analyzed for organochlorine pesticides and PCB's by WARF Institute, Inc., using gas chromatography. Egg contents were dried and ground with sodium sulphate; extracted with a mixture of ethyl ether and petroleum ether (70:170) for 8 hours in Soxhlet apparatus; cleaned and separated by two elutions through a Florisil column with ethyl ether and petroleum ether (3:97; 15:85). Analysis was by gas chromatography, using a Barber-Coleman Pesticide Analyzer Model 5360. Columns were glass, 1.219 m x 4 mm. For the first elution, the column packing was 5 percent DC 200 Gas Chrom Q (60/80 mesh); temperatures were: injector 230 C, column 200 C, and detector 240 C. For the second elution, packing was 3 percent OV-17 on Gas Chrom Q (80/100 mesh); and temperatures were: injector 230 C, column 200 C, and detector 240 C. Nitrogen flow rates were such that p,p'-DDT had a retention of 6-8 minutes. For PCB separation an aliquot of the first elution was placed on silicic acid-Celite column (Armour and Burke 1970). Typical elutions were petroleum ether followed by 1:19:80 solution of acetonitrile:hexane:di-

Predation of Gasteracantha cancriformis (Arachnidae: Araneidae) Eggs in Florida Citrus Groves by Phalacrotophora epeirae (Insecta: Phoridae) and Arachnophaga ferruginea (Insecta: Eupelmidae)

Predation of 216 egg cases of Gasteracantha cancriformis (L.) collected from more than 20 groves involved 48.2% of the cases: 43.7% by the phorid, Phalacrotophora epeirae (Brues), 3.2% by the eupelmid, Arachnophaga ferruginea Gahan, and 1.3% by unidentifiable predators. The phorid completed development in 2 to 4 weeks with a mean attack rate of 17 larvae per egg case. The eupelmid completed development in 3 to 6 weeks with a mean attack rate of 12 larvae per egg case. A hyperparasitic eulophid, Tetrastichus sp., emerged from the pupae of the phorid. The attack rate of this hyperparasite was not determined but 70% of the spider egg cases attacked by the phorid also produced the eulophid. Spider egg destruction was not always complete in predated cases but the predator-parasite complex unquestionably reduces populations of this spider.

Changes Attributable to Pesticides in Egg Breakage Frequency and Eggshell Thickness in Some British Birds

Before the late 1940s it was a rare event for broken eggs to be found in the nests of peregrine (Falco peregrinus) and sparrowhawk (Accipiter nisus), but from 1951 onwards, both species have shown a high frequency of clutch depletions in which eggs were either found broken, or disappeared in circumstances where human interference was not indicated as the cause. In most instances it appeared that the parent birds destroyed their own eggs, either by eating or by breaking and/or ejecting them (Ratcliffe 1958, 1960). Scottish golden eagles (Aquila chrysaetos) also showed an unusually high frequency of egg breakage, again attributable to parental destruction, during 1960-63 (Lockie & Ratcliffe 1964). Although golden eagle egg breakage evidently became frequent before 1960 (Ratcliffe 1960), lack of earlier observations made accurate dating of the change difficult. An examination of the eggshells of peregrine and sparrowhawk has recently disclosed that a highly significant decrease in weight (thickness) occurred in both during 1946-50, and has been maintained ever since; golden eagle eggshells showed a less marked but still highly significant decrease in weight (thickness), dating from around 1951 and continuing up to 1966 (Ratcliffe 1967a). The present paper sets out in greater detail the evidence for egg destruction and change in eggshell weight, and discusses the correlation between these phenomena; relationships to the well-established decline in population status and breeding success* in these three species are examined, together with the environmental changes believed to be responsible. The study has been extended to other raptors and a wider range of other bird types.