Using the bird class from the examples in 3D > transform > birds,
would this be the correct way to do it?
currently experimenting with it and apparently no birds are coming out ...

1.   columns = a.width / cellsize;  // Calculate # of columns
     rows = a.height / cellsize;  // Calculate # of rows
        image(a, 75, 50,width/2,height/1.5);
       for ( int i = 0; i < columns; i++) {
       // Begin loop for rows
       for ( int j = 0; j < rows; j++) {
         int h = i*cellsize + cellsize/2;  // x position
         int v = j*cellsize + cellsize/2;  // y position
         int loc = h + v*a.width;  // Pixel array location
         float r = red(a.pixels[loc]);  // Grab the color
         float g = green(a.pixels[loc]);
         float b = blue(a.pixels[loc]);
         if ((r+g+b)= 0){
   
           birdCount =k;
               birds[k] = new Bird(h, v,
               0, random(5, 30), random(5, 30));
         x[k] = random(20, 340);
         y[k] = random(30, 350);
         z[k] = random(1000, 4800);
         rx[k] = random(-160, 160);
         ry[k] = random(-55, 55);
         rz[k] = random(-20, 20);
         spd[k] = random(.1, 3.75);
         rot[k] = random(.025, .15);
               birdCount++;
         }
       }
       }