Gamma Radiation Effects on Nestling Tree Swallows

Abstract

The sensitivity of Tree Swallows (Tachycineta bicolor) to the stress of ionizing radiation was investigated with growth analysis. Freshly hatched nestings were temporality removed from nests, taken to the laboratory and acutely exposed to 0.9, 2.7, or 4.5 Gy gamma radiation. Some of the unirradiated control nestlings were also taken to the laboratory, whereas other were left in the nests. Growth of all the nestlings was measured daily and analyzed by fitting growth models. There was no detectable radiation—induced mortality up to fledging, °20 after irradiation. Radiation exposure did not affect the basic growth pattern; the logistic growth model was most suitable for body mass and foot length, and the von Bertalanffy model for primary—feather length, irrespective of treatment. Parameter values from these models indicated pronounced growth depression in the 2.7—Gy and 4.5—Gy groups, particularly for body mass. Radiation also affected the timing of development. The growth depression of the 2.7—Gy group was similar to that cause by hatching asynchrony in unirradiated nestlings. The 4.5—Gy nestlings grew as well as unexposed nestlings that died from natural causes. Chronic irradiation at °1.0 Gy/d caused more severe growth effects than acute exposure to 4.5 Gy and may have caused permanent stunting. Growth analysis is a potent tool for assessing man—made environmental stresses. Observed body—mass statistics and model parameters seem to be most sensitive to environmental stresses, but coefficients of variation are not necessarily correlated with seabirds. Unfortunately, growth analysis may fail to assess the full impact of the stress, because stress factors can have effects far beyond the initial growing period.

Ecotoxicity literature review of selected Hanford Site contaminants

“…The adult mortality rate approached 100% at about 2000 R at a dose rate of up to 150 R/d (Wagner and Marples 1966). External exposure to gamma-radiation of up to 600 R did not result in the mortality of embryos or nestlings of passerine species (Zach and Mayoh 1984, 1986a, 1986b. Chronic irradiation with 960 rad over 20 days reduced hatchability in domestic chicken (Gallus domesticus) and black-headed gull (Larus ridibundus) eggs (Phillips and Coggle 1988).…”

“…Willard (1963) calculated that a chronic dose LD50 of 21,700 mGy would be needed to kill 50% of bluebird (Sialia sialis) nestlings over a 16-day period of irradiation with cesium-137. Growth of tree swallows was significantly affected by acute doses of 2700 to 4500 mGy (Zach and Mayoh 1984). Hatching success was reduced by chronic doses of 100 mGy/d (Zach and Mayoh 1984).…”

Growth dynamics in the American alligator (Alligator mississippiensis)

“…The choice between the two therefore becomes a theoretical and practical matter. GMSVL reflects better the variable growth rate that actually occurs within capture intervals and has been used in critical studies of growth curve analysis (Kaufmann, 1981;Zach & Mayoh, 1984). Other measures of central tendency might also be used (e.g.…”

“…The relative importance of genetic and environmental constraints and growth dynamics appears to differ among species. For some, growth appears to proceed at a physiological maximum; for others, especially those having long growth periods, it appears that external constraints can be crucial determinants of growth dynamics (Dunn, 1975;Fendley & Brisbin, 1977;Zach & Mayoh, 1984;Ricklefs, 1984). Among poikilotherms, temperature and energetics seem important factors controlling growth (Hawkins, 1986;Sweeney & Vannote, 1986).…”

“…They may be used to estimate such population parameters as maximum size, age or size at maturity, or environmentally-related variability in growth rates. However, many models can fit a data set, and comparisons among populations have been hampered by a priori choice of model and by a failure to evaluate objectively goodness of fit relative to alternative models (Zach & Mayoh, 1984). If all populations of a species were to grow according to the same theoretical model, model parameters could be compared among populations to detect localized effects of environmental conditions.…”