Predator birds

The risk posed to predators eating contaminated fish is determined by comparing the estimated daily intake (EDI) of fish predators (birds or mammals) with the predicted no-effect concentration in these predatory species. If adequate data are missing, the latter value was estimated from laboratory rodent or meat-eating animals (Table 3.3). 

Fat will store toxins such as the polyhalogenated pesticides DDT, Dieldrin and Aldrin. The now banned plasticizers PCBs and PBBs are also polyhalogenated. It was DDT which caused a problem with certain species of predator birds. The pesticide accumulated in waterways where it was taken in by microorganisms and then by fish... 

Sometimes animals can be harmed when they feed on plants or animals that have pesticide residues on or in them. A special concern is for predator birds or mammals that feed on animals that have been killed by pesticides. The predators may be harmed by the pesticide residues remaining on or in the bodies of the dead animals. 

It has been proposed that capsaicin serves chili peppers by selectively deterring predators. Birds, productive vectors for seed dispersion, do not respond to capsaicin. In contrast, mammals are predatory but are deterred by the capsaicin (with the exception of humans) [26], The molecular basis of the differential capsaicin sensitivity between birds and mammals can be traced to VR1 [27]. The avian homolog of VR1, like its mammalian counterpart, is responsive to heat but unlike its mammalian counterpart, avian VR1 does not respond to capsaicin. 

The pesticide DDT is also an endocrine disrupter, and concentrates in predator birds at the highest levels of the food pyramid. DDT causes eggshell thinning and other developmental abnormalities. Eggs in the nest break, and reproduction suffers. 

DDE, fatty tissues of predator birds such as osprey that feed on fish contaminated with DDT. When DDE and DDT concentration is high, mother osprey produce eggs with very thin shells that are easily crushed, so fewer osprey chicks hatch. In Chapter 8, we learn about elimination reactions, the second general reaction of alkyl halides, which form alkenes like DDE. 

One of the most mysterious observations in Nature is the appearance of a single parameter that determines the macroscopic structure of a large variety of apparently unrelated objects, such as the distribution of florets in a composite seed head [1], the periodic table of the elements [2], the flight path of a predator bird in pursuit of its prey, the curvature of a kudu horn [1] and the surface features of a nanoparticle [3], This ubiquitous parameter, known as the golden ratio, has also been called the divine proportion and for millennia has been used in architectural design, as a measure of human anatomical features, in works of art and in musical composition [1],... 

The effects of pollution can be direct, such as toxic emissions providing a fatal dose of toxicant to fish, animal life, and even human beings. The effects also can be indirect. Toxic materials which are nonbiodegradable, such as waste from the manufacture of insecticides and pesticides, if released to the environment, are absorbed by bacteria and enter the food chain. These compounds can remain in the environment for long periods of time, slowly being concentrated at each stage in the food chain until ultimately they prove fatal, generally to predators at the top of the food chain such as fish or birds. 

Later evidence suggested that merlins (Falco columbarius) also declined in parts of Britain during the late 1950s or early 1960s as the result of exposure to cyclodienes (Newton, Meek, and Little 1978). The merlin, like the peregrine and sparrow hawk, is a bird-eating predator. 

In comparison to the situation in birds, there is far less evidence of dieldrin having had harmful effects in the field in mammals. It has been suggested that this is a reflection of the fact that mammals tend to be more reclusive and therefore more difficult to observe, catch, or count (Shore and Rattner 2001). That said, at the time when cyclodienes were widely used in Western Europe and North America, there were a fair number of reports of mammals being poisoned by them on agricultural land. Such animals included predators such as the fox (Vulpes vulpes) and badger (Meles meles), which had evidently acquired lethal doses from their prey. 

Brodifacoum, difenacoum, flocoumafen, and other superwarfarins bind strongly to proteins of the hepatic endoplasmic reticulum and consequently have long half-lives in vertebrates, often exceeding 100 days. Thus, they present a hazard to predators and scavengers that feed on rodents which have been exposed to superwarfarins. A number of species of predatory and scavenging birds have died as a consequence... 

For threatened or endangered species, or species of special concern, it is often necessary to analyze specimens that have died of causes not directly attributable to mercury. Bird eggs that have been abandoned or flooded out may be used for analyses. However, if the eggs were pushed out of the nest by parents that are incnbating the rest of the clntch, the reason for rejection of the egg must be considered in order to properly interpret mercury residue levels. Similarly, birds killed by predators may be suitable for analysis, but the internal tissues of sick or emaciated birds should not be nsed for residue analysis because in some studies, error has resulted from remobilization of mercury (Ensor etal. 1992 Sundlof etal. 1994). 

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