1. Locate a dimensionless-point target at a centre of a circle of a specified sight distance (radii) which constitutes the centre of a circle. This point target (dimensionless) is represented by the intersection of the upper arc of a tennis ball (with ~7 cm diameter) and the right or left side (depending on which eye is closed) of a vertical staff on which the ball is mounted. Position them in randomly chosen points in the plots (usually in the bushes in my case, since that’s where the two species are usually found).

Sight distance can be based on the most visible stratum (height). Minimal area empirically determined and reported by Mueller-Dombois and Ellenberg (1974) converted to plot radii (sight distances) shows that for forest understorey, it is between 4.0 to 8.0 metres. Four metres was found to be the most suitable in my study (for visibility and precision in plantations) and hence, it was adopted as the sight radii. Use two 2m PVC pipes (cut into two and joint by connectors for easier transportation purpose and easy use in the field) with a 0.75 inch diameter as a viewing pole (for viewing the point target) and one as the pole where the tennis ball is kept (in the center).

2. Locate the point at a specific height above the ground. This height was selected as 1.25 m due to the common occurrence of both the species around this height (*S.albiventris* are usually found a little lower (on the ground) and *M.fairbanki*, a little higher; but they are variable as *S.albiventris* have been spotted upto 8 m (while singing) whereas *M.fairbanki* have been spotted upto 3 m during the study period). Heights of 0.5 m and 1.5 m were also tested before selection. The fact that 1.25 m is often taken as a standard height for horizontal cover measurement (Collins and Becker, 2001) gives weight to the decision.

3. Observe this non-dimensional point from equally-spaced points systematically distributed in the circle (6 points for the 4 m radii). This was derived from the example quoted in the Collins and Becker (2001) study. Since it is a circle, aligning in the correct orientation is difficult and a source of error. This is due to the fact that the rope used in the original technique for tracing the sight radii - from the centre of centre of the circle where the pole with the ball is kept - is not utilized due to the large amount of vegetation in the selected study area.

Instead, align positions by taking 15o angle deviation away from the normal with a protractor (line parallel to the point target fixed - arbitrary since any line can be parallel to a point, but irrelevant as long as all other positions for viewing are referenced to this normal) with the 2 m pole and another 15o deviation towards the point, like the two sides of an isosceles triangle (with 2 sides = 2 m each) or an inverted V.

4. Sight each observation with 1 eye to avoid parallax error (with eye corresponding to the side of the point target, open). To avoid biasing the location of your (observer's) eye when each of the succeeding observation points is reached, assume a stationary posture (repeatedly) before viewing the target. Adjust the height of the eye according to the marks on the staff-pole held by you (the observer) that is the same as height of the target (1.25 m) being observed.

5. All 6 observations within the circle are considered as a single observation. The percentage of points around the target from where the target is visually obstructed by vegetation indicates the percent cover, i.e. Percent cover = (No. of points at which target is no sighted/No. of total points along the circumference of the circle) × 100. Eg: In three along the perimeter of the imaginary circle, the non-dimensional point is visible, the visibility is (3/6)×100 = 50% percent horizontal cover/visibility.