North American Osprey Populations and Contaminants: Historic and Contemporary Perspectives

Abstract

Osprey (Pandion haliaetus) populations were adversely affected by DDT and perhaps other contaminants in the United States and elsewhere. Reduced productivity, eggshell thinning, and high DDE concentrations in eggs were the signs associated with declining osprey populations in the 1950s, 1960s, and 1970s. The species was one of the first studied on a large scale to bring contaminant issues into focus. Although few quantitative population data were available prior to the 1960s, many osprey populations in North America were studied during the 1960s and 1970s with much learned about basic life history and biology. This article reviews the historical and current effects of contaminants on regional osprey populations. Breeding populations in many regions of North America showed post-DDT-era (1972) population increases of varying magnitudes, with many populations now appearing to stabilize at much higher numbers than initially reported in the 1970s and 1980s. However, the magnitude of regional population increases in the United States between 1981 (first Nationwide Survey, ∼8,000 pairs), when some recovery had already occurred, 1994 (second survey, ∼14,200), and 2001 (third survey, ∼16,000-19,000), or any other years, is likely not a simple response to the release from earlier contaminant effects, but a response to multi-factorial effects. This indirect "contaminant effects" measurement comparing changes (i.e., recovery) in post-DDT-era population numbers over time is probably confounded by changing human attitudes toward birds of prey (shooting, destroying nests, etc.), changing habitats, changing fish populations, and perhaps competition from other species. The species' adaptation to newly created reservoirs and its increasing use of artificial nesting structures (power poles, nesting platforms, cell towers, channel markers, offshore duck blinds, etc.) are two important factors. The timing of the initial use of artificial nesting structures, which replaced declining numbers of suitable trees at many locations, varied regionally (much later in the western United States and Mexico). Because of the increasing use of artificial nesting structures, there may be more ospreys nesting in North America now than ever before. Now, with the impact of most legacy organic contaminants (DDT, other organochlorine [OC] pesticides, polychlorinated biphenyls [PCB], polychlorinated dibenzo-p-dioxins [PCDD], polychlorinated dibenzofurans (PCDF]) greatly reduced or eliminated, and some osprey populations showing evidence of stabilizing, the species was proposed as a Worldwide Sentinel Species for evaluating emerging contaminants. Several emerging contaminants are already being studied, such as polybrominated diphenyl ethers (PBDE) and perfluorinated acids and sulfonate compounds (PFC). The many advantages for continued contaminant investigations using the osprey include a good understanding of its biology and ecology, its known distribution and abundance, and its ability to habituate to humans and their activities, which permits nesting in...

Avian predators transmit fear along the air–water interface influencing prey and their parental care

“…Ospreys are one of the greatest examples of conservation success in North America because their populations have recovered following decades of decline due to habitat loss and pollution from pesticide (Henny et al 2010). Previously, little was known about the effects these raptorial birds have on prey and the greater food web (Bierregaard et al 2014).…”

Recent impact of DDT contamination on Black Stork eggs

“…And eggshell thinning and subsequent breakage have been described as the major cause of low breeding success in many predatory species, Brown Pelican, and Herons (e.g. Ratcliffe 1970;Cooke 1973;Burger et al 1995;Henny et al 2010). In many cases, the reduced strength of eggshells has been associated with changes in egg structure (Gould 1972;Peakall et al 1973;Reynolds and Perrins 2010), but at least in several tern species embryo mortality in DDT-contaminated eggs was not caused by changes in eggshell structure (Nisbet and Fox 2009).…”

Mercury and Other Mining-Related Contaminants in Ospreys Along the Upper Clark Fork River, Montana, USA

“…We focused on osprey chicks because virtually all of their biomass grew from consumption of local fish, thus reflecting local environmental conditions. This is compared with adult ospreys, which can accumulate considerable concentrations of contaminants on their wintering grounds (Henny et al 2010;Rivera-Rodríguez and Rodríguez-Estrella 2011). Our objective was to determine and compare source contaminant levels in river sediments and in osprey chicks as a representative predator at the top of the local aquatic food web.…”

“…This is because ospreys eat almost exclusively fish, are top trophic-level predators in aquatic food chains and thus potentially at risk from environmental contamination, nest readily on manmade nest platforms, and habituate quickly to human activity and other disturbance (Grove et al 2009;Henny et al 2010).…”