Tiger census : In Indian national parks and tiger reserves, the tiger population is often estimated by counting pugmarks (footprints) and fecal pellets (scat). These are non-biological markers that provide a reliable estimate of the population without the need to physically see every tiger.

Fish density : This is typically measured using relative density, such as the number of fish caught per trap. While this is an indirect method, it still relies on the physical capture of the biological organism itself.

Bacteria : Density in a culture plate is usually determined by counting colonies or measuring total biomass, which are biological parameters.

Siberian cranes : These are usually counted through direct visual observation or biological tracking, as they are large and congregate in specific areas like the Bharatpur wetlands.

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