J.R. Maestrelli | USGS Science

USGS1986

DDE, DDT + dieldrin: Residues in American kestrels and relations to reproduction

Captive American kestrels (Falco sparverius) given long-term dietary dosages of DDT and dieldrin in combination, at low and high rates, were compared with controls to determine the effects of the toxicants on reproductive success and eggshell thickness. Additional kestrels were dosed with DDE to determine its effect on shell thickness. Tissues of birds that died or were sacrificed, and eggs, were analyzed for DDE, DDD, DDT, and dieldrin. Eight paired birds, mostly males, given a high dosage of DDT + dieldrin died of dieldrin poisoning. Three periods of heavy mortality involving only dosed birds, which occurred in summer 1966, fall 1967, and spring 1968, followed temperature declines and other stress factors. Organochlorine concentrations in tissues of sacrificed birds and eggs in all units of the DDT + dieldrin study were significantly different among treatments. Residue concentrations in tissues of birds on high dosage of DDT + dieldrin were about 3 times higher than those on low dosage, a difference similar to the relative magnitude of the dose rates. Concentrations of some toxicants, especially DDE, were significantly higher in tissues of males than females, although these differences were difficult to interpret because males generally were sacrificed later than females. Concentrations in tissues and eggs of dosed yearlings, placed on clean food 7 to 9 weeks before pairing, were often significantly lower than in those yearlings that remained on dosage. Concentrations of each toxicant were usually highly correlated (r > 0.85) among tissues, especially for DDE and dieldrin. Organochlorine concentrations in brains and eggs could be predicted from concentrations in carcasses. DDE and dieldrin concentrations in eggs were about one-half those in carcasses, DDD about one-seventh, and DDT 1.5 to 2 times higher in eggs than carcasses. Eggshells of DDT + dieldrin-dosed kestrels were 6-23% thinner than eggshells of corresponding controls in different groups and years. Organochlorine concentrations in eggs and tissues of females were poorly correlated with shell thickness. Of the four toxicants in eggs, DDE was significantly and most closely correlated with fledging success. Interpretation of direct comparisons between our DDT + dieldrin studies and most current field situations are difficult because contaminant profiles in our birds are unlike those in most field samples.

Fish and Wildlife Technical Report↗

USGS1975

Breeding bald eagles in captivity

A 7-year-old female Bald Eagle from Alabama was paired with a 4-year-old Alaskan male in a large flight pen during December 1969. Both birds were free of physical defects when originally placed in the pen but the female was blind in one eye prior to the 1973 breeding season.....Nesting first occurred during 1971 when at least two eggs were laid; all but one, which showed no sign of embryonic development after being incubated for 56 days, were broken by the adult birds. Two of three eggs laid in 1972 hatched. Both young died a few days after hatching following a period of inclement weather. Three eggs were laid and hatched during 1973. Antagonism between the nestlings was observed soon after hatching and may have been responsible for the unobserved death of one nestling, two days after the third young hatched. The two remaining young were raised by the adult birds and eventually left the nest 85 days after the first egg hatched. Incubation periods for the 1972-73 clutches averaged 35 days. No renesting attempts were made by the eagles during the 3.year period.

The Wilson Bulletin↗

USGS1973

Propagation of barn owls in captivity

Some aspects of the biology and life history of native birds often are more readily obtained in captivity than in the field. This is particularly true in evaluating the effects of pesticides or other pollutants on birds, because establishing cause-and-effect relationships requires experimental studies. Few wild species have been bred in captivity with sufficient success to permit the large-scale studies that are needed. This paper reports successful efforts to breed Barn Owls ( Tyto alba prolinicol a) in captivity and presents biological data concerning reproduction.

The Auk↗