Wildlife exposure factors handbook

Survival rates in relation to body weight in European birds

ABSTRACr.--Counts migrating hawks were initiated in 1934 at Hawk Mountain and, except for 1943-1945, have continued to the present. We analyzed the data from 1934-1986 by a standardized sample period appropriate for each species. Counts of several species known to be susceptible to detrimental effects of organochlorine pesticides crashed between 19461971. All of these populations recovered subsequently. The immature-age classes and the species with the shortest generation times recovered first after DDT use diminished in North America. These observations mostly conform to predictions made on the basis of the adverse effects of DDT and metabolites on raptors. We suggest that standardized migration counts reflect qualitative trends of most raptor populations that pass over Hawk Mountain in the autumn. Currently, populations of many species appear to be either stable or recovering from the effects of organochlorines. Possible exceptions are eastern populations of the Red-tailed Hawk (Buteo jamaicensis), American Kestrel (Falco sparverius), Broad-winged Hawk (B. platypterus), Red-shouldered Hawk (B. lineatus), and Golden Eagle (Aquila chrysaetos), which may be decreasing. Received 15 November 1988, accepted 28 July 1989. ANALYSIS of the population trends of birds has received attention recently because of observed and predicted regional or global changes in the environment and the availability of data suitable for long-term trend assessment (e.g.

http://www.globalraptors.org/grin/researchers/uploads/409/migration_counts_1990.pdf

Migration Counts of Raptors at Hawk Mountain, Pennsylvania, as Indicators of Population Trends, 1934-1986

In the United States, many fish and wildlife species have been used nationwide to monitor environmental contaminant exposure and effects, including carcasses of the bald eagle (Haliaeetus leucocephalus), the only top avian predator regularly used in the past. Unfortunately, bald eagles are sensitive to investigator intrusion at the nest. Thus, the osprey (Pandion haliaetus) is evaluated as a potential sentinel species for aquatic ecosystems. Several characteristics support the choice of the osprey as a sentinel species, including: (1) fish-eating diet atop the aquatic food web, (2) long-lived with strong nest fidelity, (3) adapts to human landscapes (potentially the most contaminated), (4) tolerates short-term nest disturbance, (5) nests spatially distributed at regular intervals, (6) highly visible nests easily located for study, (7) ability to accumulate most, if not all, lipophilic contaminants, (8) known sensitivity to many contaminants, and (9) nearly a worldwide distribution. These osprey traits have been instrumental in successfully using the species to understand population distribution, abundance, and changes over time; the effects of various contaminants on reproductive success; how contaminants in prey (fish on biomass basis) contribute to egg concentrations (i.e., biomagnification factors); and spatial residue patterns. Data summarized include nesting population surveys, detailed nesting studies, and chemical analyses of osprey egg, organ, blood, and feather samples for contaminants that bioaccumulate and/or biomagnify in aquatic food webs; and biochemical evaluations of blood and various organs. Studies in the United States, Canada, Mexico, Europe, and elsewhere have shown the osprey to be a useful sentinel species for monitoring selected environmental contaminants, including some emerging contaminants in lakes, reservoirs, rivers, and estuaries.

Osprey: Worldwide Sentinel Species for Assessing and Monitoring Environmental Contamination in Rivers, Lakes, Reservoirs, and Estuaries

Nesting success of ospreys (Pandion haliaetus) breeding in the Connecticut--Long Island area has increased since 1973 and is now approaching the levels recorded prior to the 1950's. Simultaneously, DDE and dieldrin residues have declined in unhatched eggs. Levels of polychorinated biphenyls have shown no changes over the period 1969 to 1976. The increase in productivity is attributed primarily to lower levels of DDE contamination. Detrimental effects in the past on ospreys in the Connecticut River estuary are attributed to local contamination with dieldrin.

http://science.sciencemag.org/content/sci/202/4365/333.full.pdf

Productivity of ospreys in connecticut-long island increases as DDE residues decline

MANY ornithologists have noted declines in Osprey (Pandion haliatus carolinensis) populations in the United States since the beginning of the twentieth century (Bent, 1937; Stone, 1937; Kenyon, 1947; Ames and Mersereau, 1964; Schmid, 1966; and others). The acceleration of these declines in the last 15 to 20 years is causing much concern among conservationists. It is axiomatic that, assuming no permanent emigration, a decline in population size results from (1) increased mortality, (2) decreased productivity, or (3) a combination of both of these. This paper reports on estimates of mortality rates derived from reports of band recoveries from a segment of the northeastern population of Ospreys banded in New York and New Jersey from 1926 to 1961. Although these estimates do not necessarily reflect the mortality rates now being sustained by this population, they show the amount of production per nest needed to maintain the population and bring into focus the dynamics of the decline that has taken place.

https://www.jstor.org/stable/info/4083495

Howard M. Wight

Papers

An Endangered Osprey Population: Estimates of Mortality and Production

Allopreening in Owls: What Are Its Functions?