*Birds as Intrinsic Bio-Indicators for Probing Heavy Metal Contamination Signatures in Polluted… DOI: http://dx.doi.org/10.5772/intechopen.110449*

equilibrium. Contaminants are the main type of environmental contaminant that harms our ecosystem. Pests, condensates, and other materials can carry bacteria, chemicals, and particulate contaminants. While adulteration brought on by environmental microbes causes content to decay and disease, chemical pollutants frequently induce harmful reactions. Heavy metals are metallic elements that are denser than water in comparison [14–16] asserts that arsenic, a metalloid, is hazardous when exposed at low levels and draws the assumption that toxicity and mass are related. A few of the environmental sources of heavy metals are the atmosphere, industries agriculture, geological pollution, pharmaceuticals, and home effluents [17].

Mine tailings, emissions from industrial regions, deposition of elemental waste produced by the paint, fertiliser, and pesticide industries, sewage, thermal power plant residues, petrochemical spillage, and atmospheric deposition are the principal sources of heavy metals and metalloids in soils. Regardless of where they come from, heavy metals are mostly absorbed by the soil. While inorganic contaminants like metals do not go through the oxidation process described above and stay relatively persistent in soils even after introduction, several organic contaminants do so as a result of microbial activity [18, 19].

Industrial, agricultural, and other anthropogenic activities harm aquatic ecology [20]. Metals continue to biomagnify in aquatic environments through the food chain

**Figure 1.**

*Illustration of heavy metals and other toxic compounds which impacts avifauna, revering them as "bio-indicators."*

and cause biological harm that poses a concern to humankind [21]. According to Canli and Atli [22], aquatic species occasionally accumulate heavy metals inside of them that is higher than ambient levels. Industrial discharges cause freshwater habitats to become more contaminated than other environments over time [23]. Numerous aquatic ecosystems may be able to withstand large levels of pollution, according to studies, however, those ecosystems may also suffer harm from the resulting living populations.

### **4. Bio-indicators**

Bioindicators (**Figure 1**) are species that are used to assess the health of an ecosystem or the environment. They can assess the integrity of the environment based on their populations and functions. Monitoring the state of several ecological unit constituents is essential for protecting and managing the natural environment. Ecologists have utilised wild birds as indicators of heavy metal contamination over the years because they can gauge the impact of environmental heavy metal concentrations. In ecology and conservation science, surrogate species have been employed over time to ascertain the relationship between plants and animals in a particular geographic location [24]. Because managing ecosystems is challenging and there are few scientific tools available, conservation biologists have also employed target species as desirable shortcuts.
